In hydraulic servo systems used in injection molding machines, hydraulic presses, die-casting machines, rubber machinery, and other industrial equipment, the Inovance IS580 hydraulic servo drive performs several critical functions. These include motor speed control, pressure closed-loop control, flow closed-loop control, temperature protection, and hydraulic response management.

When an IS580 drive reports faults such as Err45 and Err46, the equipment may fail to start, stop immediately after startup, or remain locked in an alarm state. These faults should not be treated simply as “the drive is defective.” It is also not appropriate to immediately replace the IGBT module or power board.

In many cases, Err45 and Err46 are related to the motor temperature feedback circuit, pressure sensor feedback circuit, 24 VDC control supply, analog input wiring, common reference terminals, or the control board signal-conditioning circuit.

This article uses a typical Inovance hydraulic servo drive, such as the IS580T070-R1-1-EST, 37 kW, 380–480 VAC input model, as an example. It explains how to identify, diagnose, and repair suspected Err45 and Err46 faults in a systematic manner.

1. Confirm the Actual Alarm Code Before Starting Diagnosis

Before troubleshooting, the first step is to confirm the real alarm code.

When a mobile phone records a seven-segment LED display, the displayed characters may appear incomplete, distorted, overlapped, or flashing. For example, “Err45” or “Err46” may appear in a video as something similar to “E8.8.85,” “E8.8.86,” or other unclear characters.

This happens because most LED displays use multiplex scanning. The drive scans each digit very quickly. Human eyes see a complete number, but the camera shutter may capture only part of the scan cycle.

Therefore, before diagnosing the drive:

1. Record a video instead of taking only a single photo.
2. Use slow-motion recording if available.
3. Film the display from close range.
4. Observe whether the fault code is fixed or alternates between two alarms.
5. Record whether the alarm occurs immediately after power-on, when the motor starts, or after running for a period of time.
6. Take photos of the drive terminals, motor terminal box, pressure sensor, and external wiring.

If Err45 and Err46 appear alternately, this usually indicates two different feedback-related faults rather than one main power circuit failure.

2. Basic Meaning of Err45 and Err46

For an Inovance IS580 hydraulic servo system, the following diagnostic direction should be considered first:

Different drive firmware versions, machine builders, and parameter configurations may use slightly different alarm descriptions. Therefore, the final diagnosis should always be confirmed against the correct IS580 manual, the machine electrical drawing, and the original parameter backup.

However, both Err45 and Err46 are generally feedback-detection faults. They are not typical faults such as IGBT short circuit, DC bus undervoltage, output phase loss, or braking unit failure.

For this reason, the correct troubleshooting sequence is:

External wiring → sensor condition → terminal connections → low-voltage supply → control board

Do not begin by replacing the power module.

3. Why Pressure Feedback Is So Important in a Hydraulic Servo System

A standard inverter can run a motor when it receives a run command and frequency reference. A hydraulic servo drive is more complex.

In a hydraulic servo system, the drive adjusts motor speed and torque according to pressure and flow feedback signals. The control logic can be simplified as follows:

Pressure command → Actual pressure feedback → Error calculation → Motor speed adjustment → Hydraulic pump output adjustment → Actual pressure reaches the target value.

If the pressure sensor signal is missing, unstable, out of range, incorrectly configured, or disconnected, the drive cannot accurately determine the actual hydraulic pressure.

To avoid uncontrolled pressure increase, pump overload, low-pressure operation, or dangerous hydraulic movement, the drive may stop and generate a pressure feedback alarm.

Therefore, when Err46 occurs, it does not always mean that the hydraulic pressure itself is abnormal. In many cases, it means that the drive cannot read a valid pressure signal.

Possible causes include:

• No 24 VDC supply to the pressure sensor;
• Loose pressure sensor connector;
• Broken pressure signal wire;
• Open or incorrect analog common terminal;
• Wrong setting between 0–10 V and 4–20 mA;
• Damaged pressure sensor;
• Moisture or oil contamination in the connector;
• Incorrect shielding or severe electrical interference;
• Analog input circuit failure on the drive control board;
• External 24 VDC supply fluctuation.

4. Err45: Motor Temperature Protection Circuit

Hydraulic servo motors are commonly equipped with an internal temperature protection element. Typical types include:

1. PTC thermistor;
2. NTC thermistor;
3. Normally closed or normally open thermal switch;
4. KTY temperature sensor;
5. Motor temperature feedback integrated into the encoder connector.

In industrial servo motors, PTC protection is very common. At normal temperature, the PTC resistance remains low. When the motor reaches the protection temperature, the resistance rises sharply. The drive monitors this circuit to determine whether the motor is overheating.

When Err45 occurs, it does not automatically mean that the motor winding is burnt.

In real maintenance cases, Err45 is often caused by an abnormal temperature feedback circuit rather than true motor overheating.

Common causes include:

• Broken motor temperature cable;
• Loose aviation connector;
• Oxidized connector pins;
• Oil or water inside the motor terminal box;
• Cable insulation damage caused by heat;
• Open-circuit PTC sensor;
• Incorrect wiring after maintenance;
• Loose intermediate terminal block;
• Damaged temperature input circuit on the control board;
• Actual motor overheating caused by overload, poor ventilation, or hydraulic system problems.

Hydraulic servo motors often operate under high load, high oil temperature, and high ambient temperature. If the hydraulic system has continuous overflow, pump seizure, poor cooling, excessive pressure, or heavy mechanical load, the motor may actually overheat.

5. Field Inspection Procedure for Err45

Step 1: Check Whether the Motor Is Actually Overheating

After stopping the equipment, use an infrared thermometer to measure:

• Motor housing temperature;
• Motor terminal box temperature;
• Cooling fan area temperature;
• Hydraulic pump temperature;
• Hydraulic oil temperature;
• Drive heatsink temperature.

If the motor is extremely hot, has a burning smell, or the cooling fan is not operating, mechanical and cooling problems must be resolved first.

Check the following items:

• Is the motor fan running?
• Is the airflow path blocked?
• Is the hydraulic oil temperature too high?
• Is the oil cooler working properly?
• Is the hydraulic pump mechanically overloaded?
• Is the relief valve continuously bypassing oil?
• Is the system pressure higher than the normal setting?
• Are the motor parameters correct?
• Is the motor power rating suitable for the hydraulic pump?

Step 2: Measure the Motor Temperature Circuit

Disconnect the main power supply and wait until the DC bus is fully discharged. A 37 kW drive contains significant stored DC bus energy. Do not touch control terminals or power terminals immediately after power-off.

Locate the motor temperature feedback wires and measure the resistance between the two temperature terminals.

Typical interpretations are:

The exact resistance value depends on the motor manufacturer and sensor type. Do not judge the circuit only by a single resistance value. Compare with a known-good motor if possible, or refer to the motor documentation.

Step 3: Inspect Both Motor Side and Drive Side

Many technicians inspect only the drive terminal. However, the motor-side connector is often the real source of the fault.

Pay particular attention to:

• Motor aviation connector pins;
• Encoder connector;
• Terminal box wiring;
• Cable chain bending points;
• Oil contamination;
• Moisture ingress;
• Loose terminal screws;
• Oxidized connectors;
• Improper reconnection after previous maintenance.

The temperature feedback circuit must be checked from the motor all the way to the drive input terminal.

6. Err46: Pressure Sensor Fault Diagnosis

Hydraulic pressure sensors usually use one of the following output formats:

1. 0–10 V;
2. 0–5 V;
3. 4–20 mA.

The most common types are 0–10 V and 4–20 mA.

A typical pressure sensor may have three or four wires:

• Positive supply, usually +24 VDC;
• Negative supply, 0 VDC;
• Signal output, 0–10 V or 4–20 mA;
• Shield wire, depending on the sensor type.

Before checking the wiring, confirm the actual sensor type and make sure the drive parameters match it.

For example, if the sensor is 4–20 mA but the drive is configured for 0–10 V, the drive may report Err46 even though the sensor itself is healthy.

7. Three-Step Pressure Sensor Test Method

Step 1: Check the Sensor Supply Voltage

Use a multimeter in DC voltage mode and measure the sensor power supply terminals.

Typical expected values include:

• Approximately 24 VDC;
• In some systems, 10 VDC or 12 VDC;
• The voltage should remain stable and should not collapse during alarm conditions.

If the pressure sensor has no supply voltage, inspect:

• Drive 24 VDC output;
• External switching power supply;
• Fuse;
• Terminal block;
• Intermediate relay;
• Common 0 VDC wiring;
• Broken cable;
• Control board 24 VDC output circuit.

If multiple sensors lose power at the same time, the problem is more likely related to the common power supply or common wiring than to a single sensor.

Step 2: Check the Pressure Signal Output

For a 0–10 V pressure sensor, measure the signal wire relative to the analog common terminal.

Normally, the output voltage should change smoothly with hydraulic pressure. For example:

• Near 0 V when pressure is low;
• Approximately 4–6 V at medium pressure;
• Close to 10 V at full-scale pressure.

For a 4–20 mA sensor, measure the current in series or measure the voltage across a known sampling resistor.

Typical diagnostic conclusions are:

Step 3: Check the Drive Analog Input Terminal

Even if the sensor output is normal, verify that the signal actually reaches the drive.

Measure the signal at several locations:

1. At the pressure sensor output;
2. At the intermediate terminal block;
3. At the drive analog input terminal;
4. At the analog common terminal;
5. At the control board connector.

If the signal is correct at the sensor but missing at the drive, the fault is in the cable, terminal block, connector, or wiring arrangement.

If the signal is correct at the drive terminal but Err46 remains active, the control board analog input circuit becomes a strong suspect.

8. Why Err45 and Err46 Can Occur Together

Err45 and Err46 relate to different feedback signals, but they may appear together because of a shared fault source.

Common shared causes include the following.

1. Abnormal 24 VDC Control Supply

Pressure sensors usually depend on 24 VDC. Some encoder interfaces, external temperature modules, and control circuits may also depend on the same low-voltage supply.

If the 24 VDC power supply is unstable, overloaded, shorted, or heavily fluctuating, multiple feedback signals may become abnormal.

2. Loose or Open Common 0 VDC

In analog control systems, 0 VDC is not only the negative supply wire. It is also the signal reference point.

If the pressure sensor signal wire remains connected but the analog common terminal is open, the drive may read unstable, floating, saturated, or incorrect voltage values.

A common-terminal problem may also affect other low-voltage detection circuits.

3. Oil, Water, or Corrosion at the Terminal Block

Hydraulic equipment often operates in oily environments. If the electrical cabinet sealing is poor, oil mist, moisture, dust, and corrosion may enter the terminal area.

This can cause:

• High-resistance leakage;
• Analog signal drift;
• Oxidized terminals;
• Short circuits;
• 24 VDC leakage to ground;
• Increased contact resistance;
• Unstable feedback signals.

4. Signal Cables Installed Together With Motor Cables

If pressure sensor cables, temperature feedback wires, and encoder cables are routed together with U/V/W motor output cables for a long distance, they may be affected by PWM switching interference.

This can cause:

• Unstable pressure feedback;
• Analog input over-range alarms;
• Encoder communication errors;
• Temperature input misjudgment;
• Unstable motor operation.

Analog signal cables should use shielded twisted-pair cable and should be routed separately from power cables. Shield grounding should follow the original machine design and the drive manufacturer’s requirements.

5. Control Board Analog Input Circuit Failure

If the pressure sensor, external wiring, 24 VDC supply, and terminal block all test normally, the control board becomes a likely fault source.

Common damaged parts on the control board include:

• Analog input operational amplifiers;
• TVS surge protection devices;
• Current-limiting resistors;
• Optocouplers;
• 24 VDC to 5 VDC or 3.3 VDC regulators;
• ADC input circuits;
• Connector pins;
• Temperature detection comparators;
• MCU peripheral sampling circuits.

Such faults usually require board-level inspection, component-level measurement, and analog signal simulation.

9. Do Not Directly Short the Motor Temperature Protection Input

Some technicians may short the motor temperature protection input temporarily in order to make the machine run.

This is risky.

Shorting the temperature input may temporarily remove Err45, but it also disables motor thermal protection. If the motor is actually overheating because of poor cooling, pump overload, blocked oil flow, high hydraulic pressure, or fan failure, continued operation may cause:

• Motor winding burnout;
• Encoder damage;
• Bearing failure;
• Hydraulic pump seizure;
• Drive overcurrent;
• IGBT module damage;
• Mechanical equipment failure.

A temporary simulation may be used only by experienced personnel for diagnostic purposes and only after confirming that the motor temperature is safe. The original thermal protection must be restored after diagnosis.

Similarly, do not blindly inject a voltage or connect a resistor to simulate the pressure sensor signal. Incorrect pressure simulation can cause dangerous hydraulic movement or incorrect pressure control.

10. Recommended Complete Troubleshooting Sequence

For an Inovance IS580 hydraulic servo drive showing Err45 and Err46, use the following sequence.

Step 1: Record the Current Condition and Save Parameters

Before resetting the drive or disconnecting power, record:

• Drive model;
• Alarm code;
• Parameter group settings;
• Motor nameplate;
• Pressure sensor nameplate;
• Control terminal wiring;
• Machine electrical drawings;
• Machine condition when the alarm occurs;
• Whether the motor, sensor, pump, or control board was recently replaced.

If the drive can still access the parameter menu, save the parameters before making changes. Pressure signal type, scaling, zero-point adjustment, maximum pressure setting, and control mode can all affect fault diagnosis.

Step 2: Check the Control Power Supply

Measure:

• Drive 24 VDC control output;
• External 24 VDC power supply;
• Pressure sensor supply voltage;
• Stability between 24 VDC and 0 VDC;
• Insulation between 24 VDC and ground;
• Whether the control voltage drops when the alarm occurs.

Step 3: Check the Motor Temperature Circuit

Measure:

• Temperature feedback resistance;
• Motor-side connector;
• Drive-side terminal;
• Intermediate terminal block;
• Cable bending points;
• Resistance variation while moving the cable.

Step 4: Check the Pressure Sensor Circuit

Measure:

• Sensor supply voltage;
• Sensor output signal;
• Sensor signal type;
• Drive parameter settings;
• Whether the signal changes with pressure;
• Connector contamination, looseness, or corrosion.

Step 5: Check Analog Common and Shielding

Confirm:

• Analog common terminal connection;
• Relationship between sensor 0 VDC and drive analog common;
• Shield wire grounding method;
• Separation between analog signal cables and motor power cables;
• Absence of incorrect grounding or multiple grounding points.

Step 6: Inspect the Control Board Only After External Circuits Are Confirmed Normal

If all external checks are normal, proceed to control board inspection.

Check whether:

• The analog input can receive a standard test voltage;
• The temperature input can recognize a correct resistance value;
• 24 VDC, 5 VDC, and 3.3 VDC supplies are stable;
• The analog channel is damaged;
• The board connector solder joints are loose;
• There is corrosion, oil contamination, or moisture damage on the board.

11. Practical Advice for Machine Operators

For non-professional users, the following basic checks can be completed before sending the drive for repair:

1. Check whether the servo motor is excessively hot.
2. Check whether the motor cooling fan operates normally.
3. Check whether the motor temperature connector is loose.
4. Check whether the pressure sensor connector is loose, oily, damaged, or corroded.
5. Measure whether the pressure sensor has a stable 24 VDC supply.
6. Measure whether the pressure signal changes with hydraulic pressure.
7. Check whether sensor cables are routed together with motor power cables.
8. Check whether drive control terminals show signs of moisture, corrosion, overheating, or loose wiring.
9. Do not short the motor temperature protection terminal permanently.
10. Do not replace the IGBT module before checking the feedback circuits.

12. Conclusion

When an Inovance IS580 hydraulic servo drive reports suspected Err45 and Err46 faults, the first diagnostic focus should be the motor temperature feedback circuit and pressure sensor feedback circuit, not the IGBT module or main power board.

Err45 requires inspection of the motor PTC circuit, temperature cable, aviation connector, terminal block, motor cooling condition, and hydraulic load.

Err46 requires inspection of the pressure sensor supply voltage, output signal, analog input type, analog common terminal, shielding, and control board analog input circuit.

If both faults occur together, special attention should be given to the 24 VDC control supply, analog common wiring, control cable harness, terminal contamination, and control board connector condition.

The most effective diagnostic method is to follow the signal path step by step:

Sensor output → terminal block → drive input terminal → control board sampling circuit

This process allows technicians to quickly distinguish between an external wiring or sensor problem and an internal drive control board fault.

For high-power hydraulic servo drives such as 37 kW units, blindly bypassing protection circuits, forcing the machine to run, or replacing the power module without testing the feedback system can significantly increase repair cost and equipment risk. The correct approach is to first verify whether the feedback signals are real, stable, correctly wired, and correctly matched to the drive parameters.

1. Introduction

In industrial automation systems, variable frequency drives, commonly called VFDs or inverters, play an important role in motor speed control, soft starting, energy saving, and process optimization. In small and medium power applications such as conveyors, fans, pumps, packaging machines, food processing equipment, textile machinery, and general OEM equipment, the Inovance MD310 series is widely used because of its compact structure, simple operation, and practical control functions.

During long-term operation, VFD fault codes are one of the most important clues for diagnosing equipment problems. When an Inovance MD310 VFD displays Err14, it generally indicates module overheating. In practical maintenance work, this usually refers to overheating of the power module, IGBT module temperature protection, or an abnormal module temperature detection signal.

At first glance, Err14 may appear to be a simple high-temperature alarm. However, the actual cause can be more complex. In some cases, the power module is genuinely overheating because of poor ventilation, a failed cooling fan, blocked heatsink fins, high cabinet temperature, or excessive load current. In other cases, the VFD may display Err14 immediately after power-on, even before the motor runs. In this situation, the heatsink is still cold, so the fault is unlikely to be caused by real overheating. Instead, the likely cause may be a faulty temperature sensor, abnormal temperature detection circuit, damaged driver board, poor connector contact, or IGBT module temperature feedback failure.

Therefore, troubleshooting Err14 should not stop at the simple conclusion that “the VFD is too hot.” A correct diagnosis must combine the fault timing, load condition, ambient temperature, running current, ventilation system, parameter settings, and internal circuit condition. This article provides a systematic technical analysis of the Err14 fault on the Inovance MD310 VFD, including its meaning, common causes, field troubleshooting steps, repair logic, and preventive maintenance recommendations.

2. Basic Meaning of Err14 on the MD310 VFD

On the Inovance MD310 series, Err14 normally means module overheating. The “module” mainly refers to the internal power inverter section, including the IGBT power module, freewheeling diodes, driver circuit, heatsink, and temperature detection components.

When a VFD operates, the input AC power is first rectified into DC bus voltage. The IGBT inverter section then converts the DC bus into a variable-frequency, variable-voltage three-phase AC output for the motor. During high-speed switching, IGBTs generate switching losses and conduction losses. These losses become heat. If the heatsink, cooling fan, and airflow path cannot remove this heat efficiently, the module temperature will rise. When the temperature reaches the protection threshold, the VFD will stop output and display a fault code to prevent further damage to the power devices.

However, Err14 does not always mean that the IGBT has failed, and it does not always mean that the heatsink is actually hot. In essence, the control system has detected an abnormal module temperature signal. This signal may come from real high temperature, or it may come from an abnormal detection circuit.

Therefore, during maintenance, Err14 should be divided into two major categories.

The first category is real overheating. The VFD runs for a period of time before the alarm appears. The heatsink is hot, the fan may be stopped or weak, the airflow path may be blocked, or the output current may be too high. In this case, the main focus should be cooling, ventilation, and load condition.

The second category is false overheating. The VFD reports Err14 immediately after power-on, before the motor starts. The heatsink is cold, and the machine has not produced any meaningful heat. In this case, the fault is more likely related to the temperature sensor, temperature sampling circuit, driver board, control board, connector, or internal module feedback signal.

This distinction is very important. Real overheating requires thermal and load correction. False overheating requires electrical diagnosis and board-level repair.

3. Main Components Related to Err14

To analyze Err14 correctly, it is necessary to understand which internal parts of the VFD are related to module temperature protection.

3.1 IGBT Power Module

The IGBT power module is the core component responsible for generating the three-phase output voltage. It withstands the DC bus voltage and switches rapidly under PWM control. During operation, the IGBT produces heat. The amount of heat depends on output current, carrier frequency, load characteristics, cooling performance, and switching condition.

If the motor is overloaded, mechanically jammed, frequently started and stopped, or if the acceleration and deceleration time is too short, the IGBT thermal stress will increase. A high carrier frequency also increases switching loss and can raise module temperature.

3.2 Heatsink

The power module is usually mounted on an aluminum heatsink. Heat is transferred from the module to the heatsink through thermal grease or a thermal interface material, and then removed by air. If the heatsink fins are blocked by dust, oil, cotton fibers, wood dust, or metal particles, heat dissipation becomes poor. Even if the fan is running, the thermal performance may still be insufficient.

3.3 Cooling Fan

Many compact VFDs rely on built-in cooling fans for forced-air cooling. A cooling fan may fail completely, rotate slowly, make abnormal noise, or become unstable after running for several minutes. Fan bearing wear is very common in old drives. A weak fan may still appear to be rotating, but the actual airflow may be insufficient. This is why checking fan speed and airflow is more important than simply checking whether the fan moves.

3.4 Temperature Detection Element

The VFD normally monitors power module temperature through a thermistor, temperature sensor, or internal temperature feedback pin of the module. The control board receives this signal and determines whether the module is overheated.

If the thermistor is open-circuit, short-circuit, drifting in resistance, or if the sampling circuit is damaged, the control board may mistakenly judge that the module temperature is too high. This can cause Err14 even when the module is cold.

3.5 Driver Board and Control Board

The temperature signal is often processed by the driver board or control board before being sent to the CPU. If the driver board power supply is abnormal, the sampling resistor has changed value, the connector is oxidized, the ribbon cable has poor contact, or the CPU input circuit is damaged, Err14 may be triggered incorrectly.

For repair engineers, if the heatsink is cold but the drive still reports Err14, the temperature detection path should be checked carefully.

4. Common Causes of Err14

4.1 Cooling Fan Failure or Low Fan Speed

This is one of the most common causes. During operation, the IGBT and rectifier section continuously generate heat. If the cooling fan does not work properly, the heatsink temperature will gradually rise and eventually trigger Err14.

The field inspection method is straightforward. Observe whether the fan rotates, listen for abnormal noise, and feel whether there is enough airflow from the outlet. It is important not to judge the fan only by whether it rotates. Some old fans rotate slowly, start with difficulty, or stop after running for a short time. These faults are easy to miss.

For old VFDs operating in dusty environments, replacing the fan directly is often more reliable than only cleaning it.

4.2 Blocked Airflow Path or Dusty Heatsink

Many VFDs are installed in environments with dust, oil mist, fibers, wood powder, or industrial particles. Over time, the heatsink fins become blocked. Even if the fan is working, air cannot pass through the heatsink effectively.

This type of problem usually has a clear pattern: the VFD works normally at first, then reports Err14 after running for some time. After cooling down, it can restart again. Once the heatsink and airflow path are cleaned thoroughly, the fault may disappear.

During maintenance, the cover should be removed after the DC bus is safely discharged. The heatsink fins, inlet, outlet, and internal air duct must be cleaned properly. Cleaning only the surface is not enough.

4.3 High Control Cabinet Temperature

Sometimes the VFD itself is normal, but the control cabinet temperature is too high. This is especially common in summer, high-temperature workshops, sealed cabinets, or cabinets containing several drives, contactors, power supplies, servo drives, and braking resistors.

The technician should measure the temperature inside the cabinet and check whether the cabinet has a proper air inlet, exhaust fan, filter, or air conditioner. Some cabinets only use internal circulating fans. This does not remove heat from the cabinet and therefore has limited effect. Real cooling requires cold air intake and hot air exhaust.

4.4 Insufficient Installation Clearance

A VFD needs enough space around it for heat dissipation. If several drives are installed too close to each other, or if wiring ducts and panels block the top outlet, hot air cannot escape smoothly.

Compact drives are often installed in tight spaces because they are small. However, poor installation clearance can directly cause overheating. This is especially common in retrofit projects where the cabinet space is limited.

4.5 Heavy Load or Motor Abnormality

Although Err14 is a module overheating fault, the root cause may be excessive output current. A jammed bearing, heavy mechanical load, dry gearbox, tight belt, blocked fan impeller, blocked pump, or high conveyor resistance can all increase motor current.

Higher current means higher IGBT loss and higher module temperature. In this case, repairing only the VFD is not enough. The motor and mechanical load must also be inspected.

A practical method is to check the VFD output current during operation and compare it with the motor rated current. A clamp meter can be used to verify whether the three-phase output current is balanced. If the drive runs normally without load but reports Err14 under load, the mechanical system should be inspected first.

4.6 Carrier Frequency Set Too High

A higher carrier frequency can reduce motor electromagnetic noise and improve current waveform quality, but it increases IGBT switching loss. Under heavy load or high ambient temperature, excessive carrier frequency may cause module overheating.

In this situation, the carrier frequency parameter should be reduced appropriately. After lowering the carrier frequency, the motor may produce more audible noise, which is normal. For fans, pumps, and general conveyor applications, an unnecessarily high carrier frequency is usually not required.

4.7 Acceleration or Deceleration Time Too Short

If the equipment starts, stops, reverses, or changes speed frequently, or if the acceleration time is set too short, the VFD may output high current for a short period. This increases IGBT thermal stress.

Large-inertia loads such as centrifugal fans, centrifuges, heavy conveyors, and winding systems are especially sensitive to short acceleration and deceleration settings. In these cases, Err14 may appear together with overcurrent, overload, overvoltage, or braking-related faults.

The acceleration and deceleration time should be adjusted according to the load inertia. If necessary, braking resistors or optimized stopping methods should be considered.

4.8 Temperature Detection Circuit Failure

If the VFD displays Err14 immediately after power-on and the heatsink is cold, real overheating is unlikely. The temperature detection circuit should then be investigated.

Common problems include open or shorted thermistor, abnormal thermistor resistance, damaged module temperature feedback pin, changed-value sampling resistor, poor connector contact, abnormal driver board circuit, or damaged control board input channel.

Board-level diagnosis usually requires measuring the temperature detection signal voltage or resistance and comparing it with a normal unit. Without a reference unit, the technician must analyze the thermistor characteristics carefully. The temperature protection circuit should not be simply shorted or bypassed for long-term operation, because it is an important protection function.

4.9 IGBT Module Aging or Damage

If the IGBT module itself has internal damage, poor thermal contact, or abnormal temperature feedback, Err14 may also appear. If the VFD also has output phase loss, unbalanced current, unusually fast temperature rise, or abnormal output waveform, the power module should be checked.

After power-off and safe discharge, a multimeter diode test can be used to check the diode characteristics between P, N, and U/V/W terminals. The readings should be relatively balanced among the three output phases. Any short circuit, open circuit, or obvious phase-to-phase inconsistency indicates that the power module may be defective.

5. Recommended Field Troubleshooting Procedure

For efficient field diagnosis, the troubleshooting process should follow a clear order: external first, internal later; cooling first, circuit later; operating condition first, board-level repair later.

Step 1: Confirm When the Fault Appears

The first question is: when does Err14 appear?

If Err14 appears immediately after power-on before running, suspect temperature detection or board failure.

If Err14 appears after several minutes or tens of minutes of operation, suspect cooling, ventilation, high load, or high ambient temperature.

If the fault appears only at high speed but not at low speed, check carrier frequency, output current, cooling condition, and motor load.

If the fault appears mainly in summer but not in winter, inspect cabinet cooling and ambient temperature.

If the fault started after changing the motor or mechanical system, check motor parameters, load matching, and running current.

Step 2: Check the Cooling Fan

Observe the fan operation, fan speed, and noise. Feel the airflow at the outlet. If the fan starts slowly, stops intermittently, has weak airflow, or makes abnormal noise, replace it. The fan is a low-cost part, but it has a major influence on VFD reliability.

Step 3: Clean the Heatsink and Air Duct

After disconnecting power and confirming DC bus discharge, remove the cover and inspect the heatsink, inlet, outlet, and internal air path. Clean dust and oil contamination thoroughly. In harsh environments, surface cleaning is not enough; the heatsink fins must be cleared.

Step 4: Check the Installation Environment

Check whether the VFD has enough space above and below it, whether the cabinet is sealed, and whether hot air can escape. If several VFDs are installed close together, thermal accumulation must be considered. If the cabinet temperature is high, add ventilation, exhaust fans, or an industrial air conditioner.

Step 5: Check Running Current

Run the equipment under normal load and observe the VFD output current. Use a clamp meter to verify the current if necessary. If the current is close to or above the rated current for a long time, inspect the motor and mechanical load. For pumps and fans, check the pipeline, valve position, impeller, bearing, and mechanical resistance.

Step 6: Check Parameter Settings

Important parameters include motor rated voltage, rated current, rated frequency, rated speed, control mode, acceleration time, deceleration time, and carrier frequency. Incorrect motor parameters may cause high current. A high carrier frequency increases module heating. Too short acceleration and deceleration time increases thermal shock.

Step 7: Determine Whether It Is False Overheating

If the cooling system, environment, load, and parameters are all normal, and the VFD reports Err14 while cold, the issue should be treated as false overheating. The temperature detection circuit, connectors, ribbon cables, driver board, control board, and module feedback circuit should then be checked.

The technician should not permanently bypass the temperature protection circuit simply to make the drive run. Doing so can cause severe IGBT damage and higher repair cost.

6. Safety Precautions During Repair

A VFD contains a high-voltage DC bus. Even after power is disconnected, the capacitors may still hold several hundred volts. Before opening the drive, wait long enough and measure the voltage between P and N terminals to confirm that it has dropped to a safe level. Do not assume that the drive is safe just because the keypad display is off.

When cleaning the inside of the VFD, prevent screws, wire ends, or metal particles from falling onto the PCB. When using compressed air, avoid excessive pressure because it may damage small components or push dust deeper into the drive. If cleaning solvent is used, it must be suitable for electronic equipment and must fully evaporate before power-on.

When testing the IGBT module, avoid live measurement at the U, V, and W output terminals during operation. The output waveform is high-frequency PWM, and ordinary multimeter readings may not be meaningful. Incorrect measurement may damage the instrument or create a safety hazard.

When replacing the cooling fan, confirm the voltage, size, airflow direction, connector type, and installation direction. If the fan is installed backwards, cooling performance will be reduced, and hot air may circulate inside the drive.

7. Relationship Between Err14 and Other Faults

Err14 may not always appear alone. It can occur together with overcurrent, overload, undervoltage, overvoltage, or braking-related faults. For example, if the mechanical load is jammed, the VFD may first experience high output current, then the power module heats rapidly, and finally Err14 appears. Poor cooling may also cause the power devices to operate at high temperature, resulting in unstable switching characteristics and additional faults.

Therefore, when a site reports that the drive sometimes shows Err14 and sometimes shows overcurrent, these should not be treated as completely separate problems. The technician should look for common causes such as excessive load, poor cooling, aging power module, abnormal driver waveform, motor insulation problem, or incorrect parameter settings.

8. Typical Case Analysis

In one field case, an Inovance MD310T2.2B series VFD was used to drive a small motor. After running for a period of time, the drive stopped and displayed Err14. At first, the site suspected that the VFD was damaged. After inspection, however, the control cabinet was found to be dusty, the heatsink fins were blocked, and the built-in fan speed was weak. After cleaning the heatsink and replacing the fan, the drive resumed normal operation and the fault did not return.

In another case, the VFD displayed Err14 immediately after power-on. The motor had not started, and the heatsink was completely cold. Replacing the fan and cleaning the airflow path did not solve the issue. After board-level inspection, the temperature detection circuit was found to be abnormal, causing the control board to continuously receive an over-temperature signal. This case shows that Err14 is not always caused by real overheating. If the alarm appears while the drive is cold, the temperature feedback circuit should be checked first.

9. Preventive Maintenance Recommendations

To reduce the possibility of Err14 faults on MD310 VFDs, regular maintenance is necessary.

First, clean the control cabinet and VFD air duct regularly. In dusty environments, inspection every one to three months is recommended. In normal environments, inspection every six months may be sufficient.

Second, check the cooling fan regularly. The fan is a wear part. After long-term operation, bearing wear, low speed, and startup failure are normal aging symptoms. For equipment running continuously, preventive fan replacement is recommended.

Third, ensure proper cabinet ventilation. The cabinet should have a clear intake and exhaust path. Filters should be cleaned regularly. If the cabinet temperature remains high, an additional fan or industrial air conditioner should be installed.

Fourth, set carrier frequency and acceleration/deceleration time reasonably. Do not increase carrier frequency only to reduce motor noise, and do not set acceleration time too short only to achieve faster machine movement.

Fifth, pay attention to the motor and mechanical load. Many overheating faults are not caused by the VFD itself but by excessive output current due to mechanical problems. Electrical maintenance and mechanical inspection should be combined.

Sixth, do not repeatedly reset and restart the drive after Err14 appears. If real overheating has not been eliminated, repeated reset operation may eventually damage the IGBT module and increase repair cost.

10. Conclusion

When an Inovance MD310 VFD displays Err14, the core meaning is module overheating or abnormal module temperature detection. The correct repair approach is to first distinguish between real overheating and false overheating.

If Err14 appears after the drive has been running for some time, the most likely causes are fan failure, blocked airflow, high ambient temperature, excessive load current, improper installation clearance, high carrier frequency, or unreasonable acceleration and deceleration settings.

If Err14 appears immediately after power-on while the drive is still cold, the fault is more likely related to the temperature detection circuit, driver board, control board, connector, or power module temperature feedback signal.

The correct troubleshooting method is not simply resetting the fault or declaring the VFD damaged. Instead, the technician should analyze the fault timing, cooling system, load condition, parameter settings, and internal detection circuit step by step.

For field maintenance engineers, Err14 is a typical comprehensive VFD fault. It can be caused by environment and maintenance problems, but it can also be caused by circuit board or power module faults. Only by combining external inspection with internal electrical diagnosis can the fault be located accurately and unnecessary replacement avoided.

In daily use, good ventilation, regular air duct cleaning, timely fan replacement, reasonable parameter settings, and proper load inspection are the key measures to prevent Err14 on the Inovance MD310 series. For drives that report Err14 immediately after power-on, professional inspection should be carried out as soon as possible, with special attention to the temperature detection circuit and power module feedback signal.

1. Introduction: Do Not Treat Er.138 as a Simple “Fault Code 138”

When an Inovance CS700 crane-duty inverter displays “Er.138,” many maintenance technicians immediately search for “fault code 138” in the user manual. In many cases, they cannot find a direct explanation, which leads to assumptions that the alarm is caused by hidden firmware functions, application-card issues, software version incompatibility, or internal inverter damage.

However, the display logic of the CS700 series should not be interpreted as a simple three-digit numerical fault code. The fault indication normally contains two parts:

• Er: Fault indication prefix
• 1: Fault severity level
• 38: Specific fault number

Therefore, Er.138 should first be understood as Level-1 Fault No. 38, rather than a single independent “Fault 138.”

This distinction is important. If Er.138 is mistakenly interpreted as an extended application fault code, troubleshooting may be directed toward communication cards, crane process cards, or firmware. In reality, Level-1 faults generally involve drive performance, output capability, motor control stability, brake coordination, or safety-related operating conditions.

For crane applications, this requires serious attention. A crane drive is not comparable to a fan, pump, or conveyor inverter. The lifting mechanism involves suspended loads, mechanical brakes, reduction gearboxes, ropes or chains, load inertia, acceleration torque, deceleration energy, encoder feedback, and anti-drop safety logic. A fault in any of these areas can result in abnormal current, poor speed tracking, torque instability, brake drag, or protection trips.

Therefore, Er.138 should never be handled by simply pressing RESET repeatedly. It should be investigated as a system-level lifting-drive fault.

2. Fault Severity Levels in CS700 Crane Drives

The CS700 crane inverter uses different fault levels to determine how the drive reacts after an abnormal condition is detected.

A Level-1 fault is generally displayed in the format Er.1xx. When such a fault occurs, the inverter stops output, brake-control logic may become invalid, the fault output becomes active, and the machine enters a free-stop or protective stop condition.

For a lifting mechanism, this is critical because the motor, brake, gearbox, and load must work together to prevent uncontrolled motion or load drop.

Other fault levels may use different stopping methods:

The “1” in Er.138 indicates that this is a Level-1 protective event. It should not be treated as a minor warning.

Before resetting or restarting the equipment, the following safety principles should be followed:

• Ensure that no suspended load is in an unsafe position.
• Lower the load to a safe position whenever possible.
• Do not force the brake open.
• Do not bypass safety interlocks.
• Do not reduce protection thresholds merely to keep the equipment running.
• Record the operating condition when the fault occurred.

A successful reset does not prove that the root cause has been removed.

3. General Troubleshooting Strategy for Er.138

A correct diagnosis begins by identifying when the fault occurs.

The same code can be triggered by very different causes depending on whether it appears:

1. Immediately after power-on
2. At the moment of start command
3. During lifting
4. During lowering
5. During deceleration
6. During direction reversal
7. Only under heavy load
8. Only after the machine has warmed up

This operating context is often more valuable than the code itself.

For example:

• A fault immediately after power-on may indicate control-board, current-detection, encoder-interface, or parameter-related issues.
• A fault during start-up may indicate brake drag, incorrect motor parameters, output wiring problems, motor connection errors, or mechanical seizure.
• A fault during lifting may indicate overload, insufficient torque, low input voltage, gearbox resistance, or brake release problems.
• A fault during lowering or deceleration may indicate braking resistor, regenerative energy, brake timing, or mechanical-inertia issues.
• A fault during direction reversal may indicate incorrect brake timing, excessive acceleration/deceleration settings, encoder direction errors, or speed-tracking instability.

The diagnostic method should always follow the actual operating sequence instead of relying on trial-and-error parameter changes.

4. Inspect the Input Power and Main Circuit First

Crane control panels are often installed in dusty, humid, vibrating, or high-temperature environments. Loose terminals, oxidized contactors, worn cables, damaged cable glands, and poor grounding are common in such equipment.

Many faults that appear to be inverter failures are actually caused by unstable input power or defective external wiring.

4.1 Check Three-Phase Input Voltage

Measure the voltage at the inverter input terminals and confirm:

• The three-phase voltage is within the permitted range.
• The voltage imbalance is minimal.
• Voltage does not drop sharply during lifting.
• Main contactor contacts are not burned or unstable.
• Incoming terminals are securely tightened.
• Circuit breakers and fuses are in good condition.
• Input cables are correctly sized.
• Large loads such as welding machines, presses, furnaces, or compressors are not causing major voltage fluctuations.

A crane may operate normally at no load but trip during lifting because voltage drops significantly when current demand rises.

If the supply voltage becomes unstable, the inverter may be unable to maintain sufficient motor torque. This can lead to abnormal drive performance, poor speed response, current fluctuations, or protective faults.

4.2 Inspect Motor Cables and Output Terminals

After disconnecting power and waiting for the DC bus capacitors to discharge, inspect:

• U, V, and W motor cable insulation.
• Motor terminal-box connections.
• Cable damage caused by vibration, movement, crushing, or friction.
• Loose lugs and oxidized terminals.
• Water ingress in cable joints.
• Output contactors or overload relays.
• Motor winding resistance balance.
• Insulation resistance between motor windings and ground.

A loose terminal may appear normal during static inspection but fail under vibration or high current. This is especially common in hoist systems where cables move repeatedly during operation.

4.3 Avoid Switching the Motor with an Output Contactor During Inverter Operation

The inverter should not be started and stopped by repeatedly switching an output contactor.

Opening or closing a contactor between the inverter and motor while the inverter is producing output can cause:

• Sudden current interruption
• Output voltage spikes
• IGBT stress
• Current detection errors
• Motor torque loss
• Protective tripping
• Damage to the inverter power stage

The normal start-stop command should be sent through the inverter control terminals, keypad, PLC, or communication interface. Output contactors should be used only for isolation, maintenance, or carefully designed safety interlocking functions.

5. Mechanical Brake Problems Are a Major Cause of Crane Drive Faults

For lifting systems, the electromagnetic brake is not merely an accessory. It is one of the most important safety components in the entire drive system.

The inverter must establish motor torque before the mechanical brake releases. During stopping, the inverter must control motor deceleration before the brake closes. If these actions are not properly coordinated, the system can experience overload, speed loss, brake drag, current peaks, or unstable motion.

5.1 What Happens When the Brake Does Not Fully Release?

If the inverter begins producing torque but the brake remains partially applied, the motor must overcome:

• Brake friction
• Mechanical transmission resistance
• Static friction in the gearbox
• Load gravity
• Rope or drum resistance
• Misalignment in couplings or shafts

This produces high current and poor speed buildup.

Typical symptoms include:

• Motor humming without movement.
• High current at low frequency.
• Lift movement much slower than commanded.
• Normal lowering but abnormal lifting.
• Heavy-load lifting faults.
• Brake coil energizes but brake does not fully open.
• Abnormal rubbing noise near the brake.
• Equipment works when cold but faults after heating.

5.2 Check the Brake Electrical Circuit

The following items should be inspected:

• Brake coil rated voltage.
• Actual brake coil voltage during operation.
• Brake rectifier output voltage.
• Brake contactor condition.
• Intermediate relay condition.
• Coil resistance.
• Coil overheating.
• Burned smell or discoloration.
• Loose control wiring.
• Faulty auxiliary contacts.
• Timing between inverter torque output and brake release signal.

A damaged brake rectifier may produce insufficient DC voltage, causing the brake to release weakly. The brake may make a clicking sound but still fail to open fully.

5.3 Check the Brake Mechanical Assembly

Even if the electrical signal is correct, the brake mechanism may still be defective. Inspect:

• Brake shoe wear.
• Brake wheel wear or corrosion.
• Brake gap setting.
• Spring preload.
• Brake lever movement.
• Electromagnet plunger movement.
• Pivot pins and shafts.
• Brake wheel oil contamination.
• Mechanical sticking.
• Uneven brake-shoe contact.
• Brake drag after release.

In dusty, humid, or outdoor crane environments, brake mechanisms often become corroded or contaminated. Parameter adjustment cannot solve a mechanically sticking brake.

6. Incorrect Motor Parameters Can Cause Vector-Control Instability

The CS700 crane inverter can operate in vector-control modes. Vector control provides strong low-speed torque and good speed regulation, making it suitable for hoisting applications.

However, vector control relies heavily on correct motor parameters.

If motor power, voltage, current, speed, frequency, pole number, or control mode is incorrect, the inverter cannot calculate the motor magnetic model accurately. This may result in poor torque output, unstable speed control, excessive current, or protection trips.

6.1 Verify All Motor Nameplate Data

The following parameters should be checked against the motor nameplate:

• Rated power
• Rated voltage
• Rated current
• Rated frequency
• Rated speed
• Number of poles
• Connection method
• Rated power factor
• Motor efficiency
• Cooling method
• Encoder type, if installed

A common site problem occurs after motor replacement. The old motor parameters remain in the inverter, while the new motor has different current, speed, or pole number.

Another common error is incorrect star-delta connection. For example, a motor designed for 380 V delta connection may be connected in star, resulting in reduced torque and poor lifting performance.

6.2 Motor Auto-Tuning Must Be Performed Safely

Motor tuning should not be treated as a simple push-button operation.

Before tuning, confirm:

• The load is in a safe position.
• The brake logic is safe.
• The motor can rotate safely if dynamic tuning is selected.
• Motor wiring is correct.
• Motor insulation is acceptable.
• Nameplate parameters are already entered.
• The selected tuning method is suitable for the mechanical condition.

If the motor is mechanically connected to a suspended load, static tuning may be safer than rotating tuning. Dynamic tuning under unsafe conditions can create unexpected movement and serious risk.

6.3 Do Not Blindly Increase Torque Boost

When lifting torque is insufficient, some technicians immediately increase torque boost.

A moderate torque-boost adjustment can help low-speed starting, but it is not a solution for brake drag, incorrect motor parameters, mechanical seizure, voltage drop, or overload.

Excessive torque boost can cause:

• Motor overheating
• Excessive current
• Increased inverter stress
• Reduced efficiency
• Poor control stability

The correct sequence is:

1. Verify motor parameters.
2. Verify brake release.
3. Inspect mechanical resistance.
4. Check power supply stability.
5. Confirm motor condition.
6. Adjust torque-related parameters only after the above checks.

7. Encoder and Speed Feedback Problems Must Be Considered

Many crane systems use encoder feedback for closed-loop vector control, precise positioning, speed regulation, anti-sway functions, or anti-drop control.

If the encoder signal is unstable, reversed, noisy, or intermittent, the inverter may calculate incorrect motor speed and torque.

7.1 Typical Encoder Fault Symptoms

Encoder problems may appear as:

• Normal operation when cold but faults after heating.
• Normal low-speed operation but faults at high speed.
• Random speed fluctuation.
• Unstable hoist stopping position.
• Motor current oscillation.
• Faults only in one direction.
• Abnormal creeping at zero speed.
• Sudden speed feedback jumps.
• Faults that occur after vibration or cable movement.

7.2 Encoder Inspection Checklist

Check the following:

• Encoder supply voltage stability.
• A/B/Z signal integrity.
• Differential signal quality.
• Encoder cable shield grounding.
• Cable routing away from motor power cables.
• Encoder coupling tightness.
• Encoder shaft movement.
• Connector condition.
• Encoder resolution settings.
• Encoder direction settings.
• PG card condition.
• Grounding and noise interference.

Encoder cables should use shielded twisted-pair cable whenever possible. They should be routed separately from motor cables. If crossing is necessary, cross at approximately 90 degrees rather than running parallel over a long distance.

8. Mechanical Resistance Must Not Be Underestimated

The lifting mechanism includes the motor, coupling, gearbox, drum, bearings, wire rope, pulley blocks, hooks, brakes, and limit devices.

Any abnormal resistance in these components increases motor torque demand.

8.1 Common Mechanical Causes

Typical mechanical causes include:

• Gearbox lubrication failure
• Damaged gears
• Bearing seizure
• Coupling misalignment
• Drum deformation
• Rope overlap or rope jamming
• Pulley seizure
• Brake drag
• Motor bearing damage
• Shaft misalignment
• Limit switch interference
• Gearbox output shaft binding
• Structural deformation of the lifting mechanism

8.2 Use Motor Current as a Diagnostic Indicator

Motor current provides valuable information.

Under comparable conditions, observe:

• Whether the three output currents are balanced.
• Whether lifting current is much higher than lowering current.
• Whether no-load current is already high.
• Whether current spikes occur at brake release.
• Whether current rises sharply at a certain mechanical position.
• Whether current fluctuates with vibration.

If no-load current is abnormally high, suspect brake drag, mechanical resistance, bearing failure, or gearbox problems.

If lifting current is much higher than lowering current, inspect load condition, brake release, mechanical resistance, and gearbox efficiency.

If phase currents are clearly unbalanced, inspect motor windings, output cables, terminals, and contactors.

9. Acceleration and Deceleration Settings Must Match the Hoisting System

A crane cannot be configured using aggressive acceleration and deceleration values without considering load inertia, brake timing, motor torque capability, and regenerative energy.

9.1 Risks of Excessively Short Acceleration Time

If acceleration time is too short, the inverter must rapidly establish torque while overcoming brake release delay, static friction, suspended-load gravity, rope tension changes, and gearbox inertia.

This can result in:

• Excessive current
• Poor speed tracking
• Torque saturation
• Brake drag symptoms
• Mechanical shock
• Protective faults

A lifting mechanism should normally have a carefully designed low-speed starting stage and smooth acceleration profile.

9.2 Risks of Excessively Short Deceleration Time

During deceleration, a hoist may enter regenerative operation. Mechanical energy is returned to the inverter DC bus.

If the braking resistor, braking unit, or energy-dissipation capability is insufficient, the DC bus voltage may rise rapidly.

This can cause:

• Overvoltage faults
• Braking faults
• Sudden deceleration instability
• Mechanical shock
• Brake timing problems
• Load swing

Deceleration time should be set based on:

• Load weight
• Hoisting speed
• Gear ratio
• Drum diameter
• Braking resistor power
• Braking resistor resistance
• Duty cycle
• Frequency of lifting and lowering
• Mechanical inertia
• Required stopping distance

9.3 Avoid Sudden Multi-Speed Switching

If multi-speed control is used, large step changes should be avoided.

Use smooth acceleration and deceleration curves, including S-curves when appropriate. This reduces mechanical impact, current spikes, and load swing.

10. Check the Braking Resistor and Braking Unit

In crane applications, braking components are especially important during lowering, deceleration, and frequent reversing.

A braking resistor with incorrect resistance, insufficient power rating, poor wiring, overheating, or open circuit can cause abnormal drive behavior.

10.1 Inspect the Braking Resistor

Check:

• Burn marks or discoloration.
• Loose terminals.
• Measured resistance value.
• Correct power rating.
• Proper ventilation.
• Cooling fan operation, if installed.
• Cable size and length.
• Connection tightness.
• Signs of overheating.
• Installation away from flammable materials.

10.2 Do Not Reduce Resistance Arbitrarily

Some users install a lower-resistance braking resistor to obtain stronger braking.

This can be dangerous because lower resistance increases braking current. If the resistance is below the permitted range, the braking unit or inverter power stage may be overloaded and damaged.

The braking resistor value must match the inverter and braking-unit specifications.

10.3 Lowering Operation Often Reveals Braking Problems

When lowering a suspended load, gravity drives the motor. The motor can become a generator and return energy to the inverter DC bus.

Therefore, if faults occur mainly during lowering, rapid deceleration, emergency stop, or direction reversal, inspect:

• Braking resistor
• Braking unit
• Deceleration time
• Brake closing sequence
• Mechanical inertia
• DC bus voltage behavior

11. Recommended Field Troubleshooting Procedure

The following workflow can be used when a CS700 crane inverter displays Er.138.

Step 1: Confirm the Display Carefully

Verify that the display is truly Er.138 and not a similar-looking code caused by LED digit interpretation.

Take a clear photo and record:

• Fault code
• Load condition
• Operating direction
• Running speed
• Whether the brake was open
• Whether the fault occurred during start, run, stop, or reverse

Step 2: Record the Fault Condition

Document:

• Lifting or lowering direction
• No-load, light-load, or full-load condition
• Cold machine or hot machine condition
• Immediate or delayed trip
• Frequency of occurrence
• Recent maintenance history
• Recent replacement of motor, brake, encoder, gearbox, or inverter
• Whether reset is possible

Step 3: Inspect Main Power and Wiring

After isolating power and waiting for capacitor discharge:

• Check incoming supply voltage.
• Check U/V/W connections.
• Check motor cable condition.
• Check grounding.
• Check motor insulation.
• Check contactors and terminals.
• Check for heat damage or loose connections.

Step 4: Verify Motor Parameters

Compare inverter settings with the motor nameplate. Back up existing inverter parameters before making changes. Enter correct motor data and perform a suitable motor tuning procedure.

Step 5: Inspect Brake Operation

Confirm brake release voltage, brake coil condition, rectifier output, contactor operation, brake gap, brake shoe condition, and actual mechanical opening movement.

Step 6: Inspect Mechanical Components

Check the gearbox, bearings, drum, rope, pulley, coupling, and brake wheel. If necessary, separate the motor from the mechanical load and test the motor alone.

Step 7: Check Encoder Feedback

For closed-loop systems, verify encoder voltage, wiring, shield grounding, signal integrity, coupling, direction, resolution, and PG interface condition.

Step 8: Inspect Braking Components and Motion Parameters

Check braking resistor value, resistor power, braking-unit condition, deceleration time, acceleration time, speed-change logic, and brake timing parameters.

Step 9: Perform Low-Risk Test Runs

After repairs or adjustments, begin with low-speed no-load testing. Increase speed and load gradually. Do not immediately perform full-load lifting before confirming that current, speed, brake action, and mechanical operation are stable.

12. Common Mistakes to Avoid

Mistake 1: Repeatedly Pressing RESET

Resetting only clears the current fault condition. It does not remove the underlying cause.

Mistake 2: Restoring Factory Settings Without Backup

A crane inverter contains critical parameters for motor data, brake timing, speed settings, limit logic, encoder configuration, and control terminals.

Restoring factory settings can create new hazards, including incorrect direction, unsafe brake timing, or loss of operational logic.

Mistake 3: Bypassing the Mechanical Brake

The brake is a safety device. Forcing it open or bypassing it may lead to uncontrolled load movement.

Mistake 4: Replacing the Inverter Without Checking the System

A new inverter may fail again if the true cause is brake drag, encoder failure, low input voltage, damaged motor cable, gearbox resistance, or incorrect motor settings.

Mistake 5: Solving Every Problem by Changing Parameters

Parameter changes should be based on measurements and system verification. Mechanical, electrical, and feedback faults cannot be reliably corrected through parameter adjustment alone.

13. Preventive Maintenance Recommendations

To reduce Er.138-type faults and other crane-drive failures, establish a preventive maintenance plan.

Monthly checks should include:

• Cabinet cleaning
• Cooling fan condition
• Filter condition
• Terminal tightening
• Grounding inspection
• Contactor condition
• Brake movement observation

Quarterly checks should include:

• Brake coil voltage
• Brake rectifier condition
• Brake shoe wear
• Brake gap setting
• Brake wheel condition
• Motor cable inspection
• Encoder connector inspection

Semi-annual checks should include:

• Motor insulation resistance
• Gearbox lubrication
• Bearing condition
• Braking resistor condition
• Braking-unit connections
• Parameter backup
• Fault-history review

Annual checks should include:

• Full inspection of brake timing
• Motor parameter verification
• Encoder feedback verification
• Mechanical load test
• Safety interlock verification
• Wire rope and drum inspection
• Gearbox efficiency evaluation

For high-duty crane systems, special attention should be given to brake wear, contactor life, braking resistor heat aging, fan life, encoder cable integrity, motor bearings, and gearbox lubrication.

14. Conclusion

When an Inovance CS700 crane inverter displays Er.138, it should not be treated as a simple “fault 138.” It should first be interpreted as a Level-1 drive fault, requiring careful evaluation of the entire hoisting system.

The investigation should include:

• Input power quality
• Output wiring
• Motor condition
• Motor parameters
• Brake release and brake timing
• Mechanical resistance
• Encoder feedback
• Braking resistor and braking unit
• Acceleration and deceleration settings
• Load condition and operating sequence

The objective is not merely to reset the inverter and resume operation. The real goal is to identify why the protection was triggered and verify that the lifting system can return to service safely.

For crane equipment, safe recovery is always more important than rapid recovery.