A Technical Case Study of a 7.5 kW Variable-Frequency Drive and Three-Phase Induction Motor

Introduction

Variable-frequency drives are widely used in fans, pumps, conveyors, mixers, machine tools, packaging machinery, and many other industrial systems. Their main functions include motor speed control, soft starting, torque regulation, energy saving, and electrical protection.

When a drive displays a fault code, the correct response is not to replace the drive immediately, repeatedly reset the fault, or disable the protection function. A reliable diagnosis must consider the fault code, motor nameplate data, drive capacity, operating current, load characteristics, parameter settings, wiring condition, and the exact stage at which the fault occurs.

This article analyzes an actual case involving an Inovance MD310T7.5B variable-frequency drive operating a 7.5 kW three-phase induction motor. The drive displayed the fault code Err10.

The main equipment data are as follows:

• Drive model: Inovance MD310T7.5B
• Rated drive power: 7.5 kW
• Drive input: Three-phase AC 380–440 V
• Rated drive output current: Approximately 17 A
• Motor rated power: 7.5 kW
• Motor rated voltage: 380 V
• Motor rated current: 15 A
• Motor rated frequency: 50 Hz
• Motor rated speed: 1440 r/min
• Drive fault code: Err10

Based on the rated power and current, the drive and motor are generally matched. Therefore, the fault should not be attributed immediately to insufficient drive capacity. The actual cause may be related to mechanical overload, motor stall, incorrect motor parameters, improper wiring, poor cooling, abnormal power supply, or a defect in the drive’s current-detection circuit.

The following sections present a complete diagnostic method that can also be applied to many other induction-motor systems.

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1. Meaning of Err10 on an Inovance MD310 Drive

On the Inovance MD310 series, Err10 means drive overload.

Typical causes include:

1. Excessive mechanical load
2. Motor stall
3. Undersized drive capacity

The corresponding corrective actions are generally:

• Reduce the mechanical load
• Inspect the motor and driven equipment
• Use a drive with a larger capacity when necessary

A drive-overload fault is not exactly the same as an instantaneous overcurrent fault.

An overcurrent fault usually means that the output current has exceeded a hardware protection threshold within a very short period. A drive-overload fault normally indicates that the drive has carried excessive current for a certain duration, causing its internal thermal model or overload calculation to reach the protection limit.

For example, a brief current peak during acceleration may not trigger Err10. However, if the motor remains in a high-current condition for several seconds or minutes because of heavy load, slow acceleration, low-speed stalling, or mechanical blockage, the drive may eventually trip on overload.

Therefore, Err10 essentially means:

The drive has detected that its output current and overload duration have exceeded the permitted operating range.

This does not automatically mean that the drive is damaged. It means that the drive is protecting itself from prolonged electrical and thermal stress.

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2. Why a 7.5 kW Drive Can Overload a 7.5 kW Motor

A common misunderstanding is that a 7.5 kW drive can always operate a 7.5 kW motor without overload. In practice, drive selection cannot be based on power alone.

The following factors must also be considered:

• Motor rated current
• Drive rated output current
• Motor starting torque
• Load torque characteristics
• Acceleration time
• Operating frequency
• Duty cycle
• Ambient temperature
• Installation altitude
• Frequency of starting and stopping
• Frequency of forward and reverse operation
• Mechanical inertia
• Shock-load conditions

In this case, the motor rated current is 15 A and the drive rated output current is approximately 17 A. The current margin is therefore only about 2 A.

If the motor normally operates at 15–16 A, even a relatively small increase in load may push the drive beyond its continuous current capability. This can happen because of:

• Increased mechanical friction
• Reduced supply voltage
• Short acceleration time
• Incorrect motor parameters
• Partial brake engagement
• Bearing deterioration
• Product buildup in the machine
• Improper motor connection

For constant-torque or impact-load applications, a drive with the same nominal power as the motor may not provide sufficient overload margin.

Applications that require particular attention include:

• Mixers
• Crushers
• Extruders
• Hoists
• Fully loaded conveyors
• Compressors
• Centrifuges
• Large-inertia rotating machinery
• Machines with frequent reversing
• Equipment that cannot start unloaded

Fans and centrifugal pumps usually have relatively favorable starting characteristics, but conveyors, mixers, hoists, and crushers may require considerably more starting torque.

Therefore, the correct selection principle is:

Compare both rated power and rated current, and evaluate the actual load profile rather than relying on the kW rating alone.

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3. Difference Between Err10 and Err11

On the MD310 series:

• Err10: Drive overload
• Err11: Motor overload

The distinction is important.

Err10 protects the drive power section and its internal overload model. Err11 mainly protects the motor according to motor rated current and electronic thermal protection settings.

If a motor rated at 15 A is incorrectly configured as a 9 A motor, motor overload protection may operate too early. If the motor rated current is configured excessively high, the motor may not receive adequate protection and could overheat.

Therefore, technicians should confirm the exact fault code before starting diagnosis.

For Err10, the main concerns are:

• Excessive drive output current
• Mechanical overload
• Motor stall
• Insufficient drive capacity
• Current-measurement error

For Err11, the main concerns are:

• Motor electronic thermal protection
• Motor rated current setting
• Motor cooling
• Motor overload duration

The two faults may be caused by similar field conditions, but their protection targets and parameter relationships are different.

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4. Determine When the Fault Occurs

The timing of the Err10 fault is one of the most useful diagnostic clues.

Before changing any parameter, determine whether the fault occurs:

• Immediately after power-up
• Immediately after pressing RUN
• During acceleration
• After reaching the commanded frequency
• After several minutes of operation
• Only under load
• Even under no-load conditions
• Every time or only intermittently

The operator should also be asked whether there was:

• Abnormal noise
• Reduced speed
• Vibration
• Burning smell
• Mechanical jamming
• Product buildup
• Recent motor replacement
• Recent drive replacement
• Recent parameter modification
• Recent maintenance on the gearbox or driven machine

4.1 Err10 Appears Immediately After RUN

If the drive trips almost immediately after receiving the run command, the likely causes include:

• Motor shaft locked
• Mechanical equipment jammed
• Electromagnetic brake not released
• Motor wiring short circuit
• Motor winding fault
• Incorrect star/delta connection
• Severe motor parameter error
• Drive current-detection fault

If the motor does not rotate and the current rises rapidly, the system is probably in a stalled condition.

4.2 Err10 Appears During Acceleration

If the motor starts but trips while increasing speed, inspect:

• Acceleration time
• Load inertia
• Starting load
• Motor torque capability
• Mechanical resistance
• Brake release
• Motor parameter identification
• Control mode
• V/f curve

A short acceleration time forces the motor to produce both load torque and acceleration torque. If the load inertia is high, the drive must supply excessive current for an extended period.

This is common in:

• Conveyors
• Centrifuges
• Large fans
• Mixers
• High-inertia rollers
• Heavy rotating tables

4.3 Err10 Appears After Several Minutes

If the machine starts and reaches full speed normally but trips after operating for several minutes, the likely causes are:

• Continuous overload
• Mechanical load gradually increasing
• Bearing temperature increasing
• Gearbox resistance increasing
• Product accumulation
• Drive cooling fan failure
• Blocked ventilation
• High cabinet temperature
• Low supply voltage
• Long-term operation close to the current limit

Although inadequate cooling may more commonly produce an overtemperature fault, poor cooling reduces the drive’s practical overload capability and can contribute to Err10.

4.4 Err10 Occurs Mainly at Low Frequency

Low-speed, high-torque operation is demanding for both the motor and the drive.

At low frequency:

• The motor’s shaft-mounted cooling fan turns slowly
• Motor cooling is reduced
• High current may be required to produce torque
• Incorrect motor parameters can cause weak torque
• The drive may remain in current limiting
• The motor may rotate slowly or stall

If the process requires continuous low-speed, high-torque operation, consider:

• An inverter-duty motor
• Forced external motor cooling
• A larger motor
• A larger drive
• Closed-loop vector control
• A mechanical reduction ratio change

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5. Use the Fault History Data

The MD310 stores fault information and operating conditions at the time of the fault.

Useful parameters include:

• F9-14: First previous fault type
• F9-15: Second previous fault type
• F9-16: Most recent fault type
• F9-17: Output frequency at the most recent fault
• F9-18: Output current at the most recent fault
• F9-19: DC bus voltage at the most recent fault
• F9-20: Input terminal status at the most recent fault

Among these, F9-18 is especially important.

5.1 Fault Current Clearly Above 17 A

If the recorded current is significantly higher than the drive rated current, the overload is probably real.

Check:

• Mechanical blockage
• Excessive load
• Brake not released
• Motor stall
• Incorrect motor connection
• Short acceleration time
• High load inertia

5.2 Low Frequency and High Current

For example:

• Fault frequency: 5 Hz
• Fault current: 22 A
• Motor speed: Very low or zero

This strongly indicates:

• Motor stall
• Mechanical jamming
• Insufficient low-speed torque
• Incorrect motor parameters
• Brake engagement
• Incorrect star/delta connection

5.3 Near-Rated Frequency and High Current

If the fault occurs at 40–50 Hz and the current remains high, the machine is probably running under excessive working load.

Typical causes include:

• Conveyor overload
• Pump blockage
• High-viscosity material
• Fan impeller friction
• Tight belt
• Damaged bearing
• Gearbox problem
• Excessive production rate

5.4 Recorded Current Is Low but Err10 Still Occurs

If the stored current is not high and Err10 occurs repeatedly, inspect the drive itself.

Possible causes include:

• Current-sensor offset
• Hall sensor drift
• Current-sampling circuit fault
• Operational amplifier fault
• Control-board ADC error
• Internal connector fault
• Software or parameter corruption

Compare the drive display current with an external true-RMS clamp meter suitable for variable-frequency drive output.

If the drive displays 20 A while the external meter measures only 6 A, the current-detection circuit is likely inaccurate.

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6. Check the Motor Nameplate Parameters

Accurate motor data are essential, especially in vector-control modes.

For this motor, the recommended basic values are:

Parameter	Description	Recommended value
F1-00	Motor type	Standard induction motor
F1-01	Rated motor power	7.5 kW
F1-02	Rated motor voltage	380 V
F1-03	Rated motor current	15.0 A
F1-04	Rated motor frequency	50.00 Hz
F1-05	Rated motor speed	1440 r/min

6.1 Effect of Incorrect Rated Current

If F1-03 is set too low:

• Motor control may be inaccurate
• Torque may be insufficient
• Motor protection may operate too early
• Low-speed performance may be poor

If F1-03 is set too high:

• The motor may not be properly protected
• The control model may be inaccurate
• Motor temperature may rise excessively
• A real overload may be hidden

The rated current must not be increased simply to suppress an alarm.

6.2 Effect of Incorrect Rated Speed

A 1440 r/min motor at 50 Hz is typically a four-pole induction motor.

A four-pole motor has a synchronous speed of 1500 r/min at 50 Hz. The lower rated speed is normal because induction motors require slip to produce torque.

If the motor rated speed is incorrectly entered as:

• 960 r/min
• 1500 r/min
• 2900 r/min

The vector-control model may calculate slip and torque incorrectly.

6.3 Effect of Incorrect Rated Frequency

If a 50 Hz motor is configured as a 60 Hz motor, the voltage-to-frequency relationship may become incorrect.

This can cause:

• Reduced magnetic flux
• Insufficient torque
• Overexcitation
• Excessive current
• Poor motor performance

Every nameplate parameter should therefore be checked individually.

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7. Perform Motor Parameter Identification

Motor auto-tuning or parameter identification is important when using sensorless vector control.

The drive may identify or estimate:

• Stator resistance
• Rotor resistance
• Leakage inductance
• Mutual inductance
• No-load current

7.1 Full Rotational Auto-Tuning

Where possible, disconnect the motor from the mechanical load.

Recommended procedure:

1. Isolate the power supply.
2. Disconnect the motor from the gearbox, belt, pump, or other driven equipment.
3. Confirm that the motor shaft can rotate freely.
4. Restore power.
5. Select keypad control.
6. Enter the correct motor nameplate parameters.
7. Select full rotational identification.
8. Press RUN.
9. Keep personnel away from the motor.
10. Wait until identification is completed.

During rotational identification, the motor may accelerate, decelerate, or change direction.

Safety precautions are essential:

• The motor must be firmly mounted.
• The shaft must not carry loose components.
• The machine must be mechanically disconnected.
• The brake must be released.
• Personnel must stay clear.

7.2 Static Identification

If the motor cannot be disconnected from the machine, static identification can be used.

This may be suitable for:

• Integrated pump units
• Large machinery
• Equipment where coupling removal is difficult
• Applications where motor rotation is not permitted during tuning

Static identification is useful, but full rotational identification usually provides more accurate control data.

7.3 Do Not Auto-Tune Before Basic Electrical Checks

Do not perform auto-tuning if:

• The motor winding resistance is unbalanced
• The motor insulation is poor
• The motor shaft is locked
• The brake is engaged
• The output cable is shorted
• The drive has an output-phase fault

Basic electrical and mechanical checks must be completed first.

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8. Check the Motor Star/Delta Connection

Incorrect motor connection is a common cause of low torque, high current, and overload trips.

A standard three-phase motor normally has six terminals and can be connected in star or delta.

The correct connection depends on the voltage combination shown on the motor nameplate.

8.1 Motor Marked 220/380 V

This generally means:

• 220 V: Delta connection
• 380 V: Star connection

If such a motor is incorrectly connected in delta on a 380 V supply, each winding receives excessive voltage. The motor may draw very high current and overheat rapidly.

8.2 Motor Marked 380/660 V

This generally means:

• 380 V: Delta connection
• 660 V: Star connection

If such a motor is connected in star on a 380 V system, each winding receives insufficient voltage.

The motor may:

• Run under no load
• Produce weak torque
• Fail to accelerate under load
• Draw high current while stalled
• Trigger Err10

Therefore, a complete diagnosis requires inspection of:

• The full motor nameplate
• The six-terminal connection box
• The position of the terminal links

The rated voltage “380 V” alone is not enough to determine the correct connection.

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9. Mechanical Inspection

In field service, mechanical problems are among the most common causes of Err10.

9.1 Check Whether the Motor Shaft Turns Freely

After isolating the power, manually rotate the motor shaft or coupling.

Abnormal findings include:

• Shaft cannot rotate
• One position feels locked
• Rotation is unusually heavy
• Metal scraping noise
• Excessive radial movement
• Excessive axial play
• Periodic sticking

9.2 Inspect the Gearbox

Common gearbox problems include:

• Insufficient lubrication
• Degraded lubricant
• Damaged gears
• Seized bearings
• Misalignment
• Excessive output load
• Broken internal components

A gearbox may still operate while developing excessive resistance. As temperature increases, the problem may become more severe and cause intermittent overload trips.

9.3 Inspect Belts and Chains

Belts or chains that are too tight can increase bearing load and mechanical friction.

Typical symptoms include:

• High no-load current
• Bearing overheating
• Slow acceleration
• Low-frequency stalling
• Heavy operating sound

Also check:

• Pulley alignment
• Chain condition
• Sprocket alignment
• Belt damage
• Eccentric pulleys
• Seized rollers

9.4 Inspect Pump Loads

For pump applications, check:

• Pump shaft condition
• Impeller blockage
• Mechanical seal seizure
• Bearing damage
• Incorrect rotation
• Valve position
• Process-fluid viscosity
• Pipe blockage
• Operation outside the pump design point

Different pump types respond differently to valve position. A closed discharge valve may overload some positive-displacement pumps, while centrifugal pumps behave differently. The actual pump type must be considered.

9.5 Inspect Fan Loads

For fans, check:

• Impeller rubbing
• Dust buildup
• Bearing condition
• Damper position
• Belt tension
• Impeller deformation
• Direction of rotation
• Operation above rated frequency

Fan power rises rapidly with speed. Increasing frequency beyond 50 Hz may increase motor load significantly.

9.6 Inspect Conveyor Loads

For conveyors, inspect:

• Belt misalignment
• Roller seizure
• Material accumulation
• Excessive belt tension
• Loaded starting
• Chain or gearbox resistance
• Coupling condition
• Frequent start-stop operation

Where possible, conveyors should start unloaded and receive material only after reaching stable speed.

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10. Perform a No-Load Test

A no-load test is one of the most effective ways to distinguish a drive fault from a motor or mechanical fault.

10.1 Disconnect the Motor From the Machine

Disconnect:

• Coupling
• Belt
• Chain
• Gearbox connection
• Driven shaft

Then run the motor without mechanical load.

10.2 Motor Runs Normally Without Load

If the motor:

• Starts normally
• Reaches 50 Hz
• Draws current well below 15 A
• Runs smoothly
• Does not produce Err10

The drive and motor are probably serviceable, and the fault is most likely mechanical.

10.3 Motor Still Trips Without Load

If Err10 still occurs with the motor mechanically disconnected, check:

• Motor winding
• Motor bearings
• Motor connection
• Output cable
• Motor parameters
• Drive current display
• Drive current-detection circuit
• Power module

10.4 Drive Trips With the Motor Completely Disconnected

If the motor wires are removed from U, V, and W and the drive still reports overload during a brief test, the likely causes are internal:

• Current-sensor fault
• Current-sampling fault
• Driver-board problem
• Control-board problem
• Power-module defect

A no-motor test should be used only as a short diagnostic procedure.

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11. Measure Motor Winding Resistance

After isolating the power, wait for the DC bus voltage to discharge. Allow at least the specified discharge time before touching the terminals.

Disconnect the motor cable from the drive.

Measure:

• U-V
• V-W
• W-U

The three readings should be approximately equal.

For example:

• U-V: 1.2 Ω
• V-W: 1.2 Ω
• W-U: 1.3 Ω

This is generally acceptable.

Abnormal examples include:

• One pair much lower than the others
• One pair open circuit
• Large imbalance between phases

Possible causes include:

• Winding short circuit
• Broken winding
• Loose terminal
• Damaged cable
• Internal motor connection fault

Because a 7.5 kW motor has relatively low winding resistance, a standard multimeter may not provide high accuracy.

A better method is to use:

• A milliohm meter
• A low-resistance ohmmeter
• A Kelvin bridge

When using a standard multimeter, short the test leads first and subtract the lead resistance.

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12. Measure Motor Insulation Resistance

Poor insulation can cause leakage current, ground faults, unstable drive operation, and power-module damage.

Disconnect the motor and motor cable completely from the drive.

Use a 500 V insulation resistance tester to measure:

• U to motor frame
• V to motor frame
• W to motor frame

The insulation resistance should not be lower than the manufacturer’s minimum requirement. In practical maintenance, a healthy dry motor normally shows a value far above the minimum.

Important precautions:

1. Never apply a megohmmeter directly to the drive output terminals.
2. Disconnect all motor wires from the drive.
3. Confirm that the motor is isolated.
4. Discharge the winding after the test.
5. Investigate moisture contamination when the insulation value is low.

If the insulation is poor, dry, clean, repair, or rewind the motor before further operation.

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13. Check Output Current Balance

Use a true-RMS clamp meter suitable for PWM drive output.

Measure the three output phases:

• U
• V
• W

13.1 All Three Phases Balanced but Too High

This usually indicates:

• Mechanical overload
• Motor stall
• Excessive inertia
• Short acceleration time
• Incorrect motor parameters
• Low-speed high-torque operation

13.2 One Phase Is Significantly Different

Possible causes include:

• Unbalanced motor winding
• Loose terminal
• Damaged output cable
• Output module problem
• Current-sensor channel error
• Output-phase loss

13.3 Drive Display and Clamp Meter Differ Greatly

If the drive indicates 20 A but the external meter shows only 5–8 A, investigate:

• Hall current sensor
• Sampling resistor
• Operational amplifier
• Driver-board power supply
• ADC reference
• Internal connector
• Control-board current input

The external meter must be appropriate for variable-frequency drive output, because ordinary meters may not accurately measure PWM waveforms.

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14. Check the Input Power Supply

Low or unbalanced input voltage can contribute to overload conditions.

Measure:

• R-S
• S-T
• T-R

The three line-to-line voltages should be balanced and within the drive’s rated range.

Also inspect:

• Circuit breaker contacts
• Contactor contacts
• Fuse condition
• Cable size
• Terminal tightness
• Input reactor
• Supply transformer capacity

A burned contactor contact may show normal voltage with no load but suffer a large voltage drop under load.

Low input voltage forces the system to draw more current to produce the same output power, especially under heavy-load conditions.

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15. Increase the Acceleration Time for Testing

A short acceleration time is a frequent cause of high current.

During acceleration, the motor must provide:

• Load torque
• Friction torque
• Inertial acceleration torque

The larger the inertia, the greater the required torque and current.

As a diagnostic test, increase the acceleration time to approximately 20–30 seconds and observe the result.

If the fault disappears, the original acceleration time was likely too short for the machine.

However, acceleration time should not be increased indefinitely. If the motor remains in a low-frequency, high-current region for too long, overload may still occur.

The final setting should consider:

• Load inertia
• Starting torque
• Process requirements
• Motor thermal condition
• Mechanical limits

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16. Avoid Continuous Low-Speed, High-Torque Operation

Standard induction motors are often unsuitable for prolonged low-speed, high-load operation without additional cooling.

At low speed:

• The shaft-mounted fan turns slowly
• Cooling is reduced
• Motor temperature increases
• Current may remain high
• Torque performance may become unstable

For demanding low-speed applications, consider:

• Inverter-duty motor
• Forced ventilation
• Larger motor
• Larger drive
• Encoder feedback
• Closed-loop vector control
• Mechanical speed reduction

Do not rely only on increasing torque boost or current limits. Excessive boost may cause magnetic saturation, high current, and overheating.

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17. Inspect Drive Cooling and Installation

The following items should be checked:

• Cooling fan operation
• Fan speed
• Dust accumulation
• Heat-sink cleanliness
• Air inlet blockage
• Air outlet blockage
• Cabinet temperature
• Clearance above and below the drive
• Arrangement of multiple drives
• Cabinet filter condition
• Nearby braking resistors
• Ventilation system

High ambient temperature reduces the drive’s practical continuous-current capability.

Corrective measures may include:

• Cleaning air paths
• Replacing fans
• Adding cabinet ventilation
• Installing an air conditioner
• Increasing mounting clearance
• Relocating heat-generating components
• Derating the drive

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18. When a Larger Drive Is Required

A larger drive may be justified if all of the following are confirmed:

• Mechanical equipment is normal
• Motor parameters are correct
• Motor auto-tuning is complete
• Motor connection is correct
• Input voltage is stable
• Motor winding and insulation are normal
• Current remains close to or above 17 A
• Process load cannot be reduced

If replacing the 7.5 kW drive with an 11 kW drive, the motor protection values must still be based on the actual 7.5 kW motor:

• Rated power: 7.5 kW
• Rated voltage: 380 V
• Rated current: 15 A
• Rated frequency: 50 Hz
• Rated speed: 1440 r/min

A larger drive must not be configured as though the motor were also 11 kW.

Otherwise, the motor may lose proper overload protection.

A larger drive is particularly beneficial for:

• Heavy starting loads
• Large inertia
• Frequent starting
• Frequent reversing
• Shock loads
• Long-term high-current operation

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19. Do Not Defeat the Protection

Unsafe field practices include:

• Increasing the motor rated current without justification
• Disabling overload protection
• Increasing thermal limits excessively
• Repeatedly resetting the fault
• Restarting immediately after each trip
• Increasing torque boost excessively
• Increasing the current limit without diagnosis
• Installing a larger circuit breaker without correcting the cause
• Bypassing fault contacts

Err10 is the protection result, not the root cause.

Repeated forced starting under a stalled condition can damage:

• IGBT module
• Motor winding
• Output cable
• Contactor
• Coupling
• Gearbox
• Mechanical transmission
• Electrical cabinet

The correct approach is to identify why the current is high.

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20. Recommended Standard Diagnostic Procedure

A systematic troubleshooting sequence for an MD310T7.5B driving a 7.5 kW motor is as follows.

Step 1: Record the Fault Condition

Record:

• Operating stage
• Load condition
• Frequency
• Current
• Sound
• Vibration
• Fault recurrence
• Recent maintenance or parameter changes

Step 2: Read Fault History

Check:

• F9-16
• F9-17
• F9-18
• F9-19
• F9-20

Step 3: Confirm Drive and Motor Ratings

Verify:

• Drive: 7.5 kW, approximately 17 A
• Motor: 7.5 kW, 15 A
• Supply: 380 V

Step 4: Check Motor Parameters

Set the motor data according to the nameplate.

Step 5: Inspect the Mechanical System

Check:

• Motor shaft
• Coupling
• Belt
• Chain
• Gearbox
• Bearings
• Brake
• Pump
• Fan
• Conveyor

Step 6: Perform a No-Load Test

Disconnect the mechanical load and run the motor alone.

Step 7: Test the Motor Electrically

Measure:

• Three-phase winding resistance
• Insulation resistance
• Cable continuity
• Star/delta connection

Step 8: Perform Motor Auto-Tuning

Use full rotational identification where possible.

Step 9: Increase Acceleration Time

Temporarily increase acceleration time and repeat the test.

Step 10: Measure Operating Current

Compare:

• Drive display current
• External clamp-meter current
• Motor rated current
• Drive rated current

Step 11: Inspect Cooling

Check fan, ventilation, dust, cabinet temperature, and installation clearance.

Step 12: Evaluate the Drive Hardware

If the motor and mechanics are normal, inspect:

• Current sensor
• Driver board
• Control board
• Sampling circuit
• Power module

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21. Typical Diagnostic Examples

Example 1: Fault at 5 Hz During Starting

Observed condition:

• Motor hums
• Shaft barely moves
• Fault frequency is 5 Hz
• Fault current is 22 A

Likely cause:

• Motor stall
• Mechanical blockage
• Brake not released
• Incorrect motor connection
• Incorrect motor parameters

Example 2: Fault After Several Minutes at 40 Hz

Observed condition:

• Starting is normal
• Current remains at 16–18 A
• Load gradually increases
• Err10 occurs after several minutes

Likely cause:

• Genuine continuous overload
• Increasing process load
• Mechanical resistance
• Insufficient drive margin

Example 3: Motor Runs Normally After Removing the Belt

Observed condition:

• Err10 occurs with the machine connected
• Motor runs normally with the belt removed
• No-load current is approximately 4 A

Conclusion:

• Drive and motor are probably normal
• Mechanical load is the main fault source

Example 4: Err10 With Motor Disconnected

Observed condition:

• Motor cables removed
• Drive still displays abnormal current
• No real output current measured

Likely cause:

• Current-sensor fault
• Current-sampling fault
• Control-board fault
• Driver-board fault

Example 5: Fault After Motor Replacement

Observed condition:

• Original motor operated normally
• New motor has the same rated power
• New motor is marked 380/660 V
• Terminal box is connected in star

Likely cause:

• The motor should normally be connected in delta at 380 V
• Star connection causes insufficient torque
• The motor stalls under load
• Drive overload occurs

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22. Verification After Repair

The repair should not be considered complete merely because the fault no longer appears.

22.1 No-Load Test

Confirm:

• Smooth starting
• Balanced current
• Normal sound
• Normal vibration
• Correct frequency and speed relationship

22.2 Gradual Load Test

Increase the load step by step and record:

• Current at 10 Hz
• Current at 20 Hz
• Current at 30 Hz
• Current at 40 Hz
• Current at 50 Hz
• Motor temperature
• Drive temperature

22.3 Continuous Operation Test

Run the equipment continuously for at least 30–60 minutes and monitor:

• Current stability
• Temperature rise
• Cooling fan operation
• Bearing temperature
• Gearbox temperature
• Recurrence of the fault
• Periodic shock loads

22.4 Record Final Parameters

Document:

• Basic frequency parameters
• Motor parameters
• Acceleration and deceleration times
• Control mode
• Frequency command source
• Run command source
• Protection settings
• Fault history

This record is valuable for future maintenance and troubleshooting.

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Conclusion

Err10 on an Inovance MD310 drive means that the drive has entered an overload condition.

In a system using a 7.5 kW MD310T7.5B drive and a 7.5 kW, 380 V, 15 A induction motor, the drive and motor are nominally matched. Therefore, the first conclusion should not be that the drive is undersized.

A correct diagnosis should follow this sequence:

1. Identify the operating stage at which the fault occurs.
2. Read the fault frequency, current, and DC bus voltage.
3. Verify the motor nameplate parameters.
4. Check the star/delta connection.
5. Inspect the mechanical system for blockage or excessive load.
6. Perform a no-load test.
7. Measure winding resistance and insulation resistance.
8. Perform motor parameter identification.
9. Increase acceleration time for testing.
10. Compare the drive current display with actual measured current.
11. Inspect the input power supply and cooling conditions.
12. Investigate the drive current-detection and power circuits only after the motor and mechanical system have been excluded.

Err10 is not usually caused by a single component. It is the result of the interaction between the drive, motor, mechanical load, wiring, parameters, power supply, and thermal conditions.

A reliable repair therefore depends on structured measurement, controlled testing, and elimination of each possible cause. This method prevents unnecessary drive replacement, avoids repeated equipment damage, and provides a technically defensible basis for maintenance decisions.

The Inovance MD605 series compact inverter is a high-performance, cost-effective solution designed for small automation equipment across industries including silicon crystal manufacturing, lithium battery production, woodworking, logistics, cable processing, packaging, and machine tools. This comprehensive guide covers the operation panel functionality, password and parameter access management, external terminal forward/reverse control wiring, and complete fault code troubleshooting procedures based on the official MD605 series manual.

1. Operation Panel Function Overview

1.1 Panel Structure and Display

The MD605 series comes standard with an LED operation panel featuring five 8-segment LED displays and six thin-film keypad buttons. The panel is divided into three functional zones: status display area, function code display area, and keypad control area.

The five-digit LED display shows multiple types of information: set frequency, output frequency, bus voltage, output voltage, output current, output power, output torque, DI input status, DO output status, AI1 voltage value, and fault codes. Status indicators on the panel show running direction (FWD/REV), local/remote mode, torque control mode, alarm status, and running status.

The panel supports a three-level menu structure for parameter configuration:

• Level 1: Function code group (F0, F1, A0, etc.)
• Level 2: Specific function code within the group
• Level 3: Function code value setting

When a digit is flashing in any menu level, the UP and DOWN keys modify that digit’s value, while the SHIFT key moves between digits. Pressing ENTER saves the parameter and moves to the next parameter; pressing the MENU/RETURN key aborts the current edit and returns to the previous menu.

1.2 Parameter Monitoring Configuration

The operation panel supports customizable monitoring displays through parameters A6-03, A6-04 (running state display), and A6-05 (stopped state display). Each parameter uses 16 bits to enable or disable specific monitoring values. For example, setting A6-03 bit0 to 1 displays running frequency, while bit1 shows set frequency.

The MD605 also supports two free-mapping display parameters (A6-07/A6-08 for mapping 0, A6-09/A6-10 for mapping 1), allowing any word connector value to be displayed with custom units and decimal places on the LED panel.

2. Password Setting, Elimination, and Parameter Access Restriction

2.1 Parameter Access Levels

The MD605 implements a four-tier parameter access system to protect critical settings:

Access Level	Code	Description
Standard	0	Default level, accesses basic inverter parameters
Extended	1	Includes user customization parameters and frequency detection functions
Expert	2	Complex motor performance tuning parameters, requires password
Manufacturer	3	Password-locked, reserved for factory service only

Current access level is displayed in parameter A0-10. The target access level is set through A0-11.

2.2 Expert Password Management

To prevent unauthorized modification of expert parameters:

Setting Expert Password:

1. Navigate to parameter A0-16 (Expert Password Setting)
2. Enter a non-zero value (range: 0-65535)
3. The password takes effect immediately; A0-14 shows “Expert password locked”

Unlocking Expert Access:

1. Switch to Extended parameter level (A0-11 = 1)
2. Navigate to A0-15 (Expert Password Input)
3. Enter the correct password matching A0-16
4. A0-14 changes to “Expert password unlocked”
5. Now set A0-11 = 2 to access Expert parameters

Password Timeout: After unlocking, Expert access automatically expires after 1 hour of inactivity. The password can also be cleared by modifying A0-16 or changing A0-11 to a lower level.

2.3 Parameter Lock Function

For complete parameter protection at the field level:

Setting Parameter Lock:

1. Navigate to A0-31 (Parameter Lock Setting)
2. Enter a non-zero password value (0-65535)
3. All parameter menus are immediately locked

Unlocking Parameter Lock:

1. Enter the correct password when prompted
2. A0-30 shows “Parameter lock unlocked”
3. The lock automatically re-engages after the duration set in A0-32 (default: 3600 seconds)
4. Manual re-locking is possible anytime by setting A0-33 = 1

Removing Password: Set A0-31 = 0 to disable the parameter lock entirely.

3. Restoring Factory Default Settings

Parameter initialization is performed through parameter A0-00 (Parameter Initialization) with three options:

Setting Value	Function
1	Restore factory parameters excluding motor parameters
3	Restore factory parameters including motor parameters
503	Restore factory parameters including motor parameters, and clear all record information

Procedure:

1. Navigate to A0-00
2. Enter the desired initialization code (1, 3, or 503)
3. Press ENTER to confirm
4. The inverter automatically restarts with default parameters

Note: Manufacturer parameters are never restored by any initialization option. For motor parameter preservation during troubleshooting, use setting value 1.

4. External Terminal Forward/Reverse Control

4.1 Control Terminal Wiring

The MD605 control terminals are located on the CN4 12-pin terminal block. Key terminals for external control:

Terminal	Name	Function
DI1	Digital Input 1	Programmable, default: Terminal Start/Stop Module A IN1
DI2	Digital Input 2	Programmable, default: Terminal Start/Stop Module A IN2
DI3	Digital Input 3	Programmable, default: RESET function
DI4	Digital Input 4	High-speed pulse input (HDI), max 20kHz
DI5	Digital Input 5	(MD605A model only) Programmable
OP	DI Power Common	Default connected to internal 24V; switch to external via S4 dip switch
COM	24V Reference Ground	Isolated from GND internally
AI1	Analog Input 1	-10V to +10V or 0-20mA, 12-bit resolution
10V	10V Reference Output	10V +/-5%, max 10mA
GND	Analog Ground	Isolated from COM
TA/TB/TC	Relay Output	Programmable relay contacts

Wiring for External Control:

For the most common sink-type wiring using internal 24V power:

1. Set S4 dip switch to the 24V position (OP connected to internal 24V)
2. Connect an external controller’s 0V/GND to the inverter COM terminal
3. Connect controller output signals to DI1, DI2, etc.
4. When a DI terminal receives 15V-30V (via closed contact), the corresponding function activates

Important: Never short-circuit COM and OP terminals when OP is connected to internal 24V – this will damage the internal power supply.

4.2 Parameter Configuration for Forward/Reverse Control

To enable external terminal control, configure these parameters:

Step 1: Select Terminal Command Source

• Set F0-03 (Control Channel 1 Main Command Source) = 1 [Terminal]
• Alternatively, this is mapped to b1-00 with identical functionality

Step 2: Configure Terminal Mode

Set F0-07 (Terminal Start/Stop Module A Mode) according to your wiring scheme:

• 1: IN1 controls start
• 2: IN1 starts, IN2 controls direction
• 3: IN1 forward start, IN2 reverse start (most common for forward/reverse)
• 4: IN1 pulse start, IN2 stop
• 5: IN1 pulse start, IN2 stop, IN3 direction
• 6: IN1 pulse forward, IN2 pulse reverse, IN3 stop

Step 3: Assign DI Terminal Functions

• F0-10 (DI1 Terminal Function) = 1 [Terminal Module A IN1] – Forward run
• F0-11 (DI2 Terminal Function) = 2 [Terminal Module A IN2] – Reverse run / Direction
• F0-12 (DI3 Terminal Function) = 9 [Fault Reset] – Optional reset function

Example: Independent Forward/Reverse Control

For the most straightforward two-wire forward/reverse setup:

1. F0-03 = 1 (Terminal command source)
2. F0-07 = 3 (IN1 forward, IN2 reverse)
3. F0-10 = 1 (DI1 = IN1, forward start)
4. F0-11 = 2 (DI2 = IN2, reverse start)
5. Wire controller forward contact to DI1-COM
6. Wire controller reverse contact to DI2-COM
7. Ensure both contacts use the same COM reference

When DI1 receives a signal, the motor runs forward. When DI2 receives a signal, the motor runs reverse. If both signals are active simultaneously, the inverter determines priority based on internal logic.

5. Fault Codes and Troubleshooting

The MD605 uses a three-segment fault code format: E-XXX.Y where E indicates fault severity, XXX is the main code, and Y is the sub-code.

5.1 Overcurrent Faults

E002.1 – Hardware Overcurrent
Triggered when instantaneous output current exceeds 4.24 times the inverter rated current (A3-03).

Causes and Solutions:

• Output ground fault: Measure output terminal-to-ground impedance with a megohmmeter; should be mega-ohm level. Replace grounded motor or cable.
• Output phase short: Measure UV, VW, WU resistance with multimeter; values should be symmetrical. Replace shorted components.
• Speed loop parameters too aggressive (SVC): Reduce speed loop Kp (F2-02) by half, set Ti (F2-03) to 2s. Test and repeat if needed.
• Synchronous motor demagnetization: Record back-EMF (F1-12), perform dynamic identification (F1-69=12), compare new value. Analyze root cause before replacing motor.
• Unidentified motor parameters (SVC): Perform accurate parameter identification per manual procedures.
• High carrier frequency needed: For high-speed motors, ensure carrier frequency > 12 x output frequency. Increase A5-01 if necessary.
• Motor rotating at startup: Enable speed tracking startup (d0-02 = 1).
• V/f oscillation: Adjust V/f oscillation suppression gain (d2-23), or switch to SVC control (F0-01 = 0).

E002.2 – Software Overcurrent
Triggered when current exceeds the custom software overcurrent point (A3-54).

Additional causes include:

• Overcurrent suppression misconfigured: Check d2-26=1, adjust d2-27, d2-28, d2-29
• Torque boost too high: Reduce manual torque boost (d2-14), perform static identification (F1-69=1)
• Acceleration/deceleration time too short: Extend ramp times (F0-48, F0-49)
• V/f curve voltage excessive: Reduce voltage/frequency ratio in multi-point V/f settings

5.2 Overvoltage Faults

E005.1 – Bus Overvoltage
Triggered when DC bus voltage exceeds the overvoltage activation point (A3-58).

Causes and Solutions:

• Insufficient braking power: Extend deceleration time, increase braking resistor power, enable overvoltage suppression (d1-54=1 for non-hoisting loads)
• Load dump causing overshoot: Increase speed loop Kp (F2-02), set Ti (F2-03) to 2s, enable S-curve (b7-00=1)
• Deceleration time too short: Extend F0-49 (ramp 1 deceleration time), add braking resistor if needed
• Input voltage too high: Verify input voltage is within rated range (380V-480V for 380V class, 220V-240V for 220V class)
• Braking unit voltage set too high: Lower braking unit activation voltage (A4-00) if needed

E005.2 – Overvoltage Suppression Active
System-level warning; contact technical support if persistent.

5.3 Undervoltage Faults

E009.1 – Undervoltage Fault
Triggered when DC bus voltage falls below the undervoltage activation point (A3-56).

Causes and Solutions:

• Input phase loss: Measure RS, ST, RT line voltages with multimeter AC mode; check for symmetry. Inspect input switches, contactors, and terminals.
• Grid voltage dip (most common cause): Enable undervoltage suppression (d1-63=1) for fan/pump/compressor loads. The inverter converts motor kinetic energy to electrical energy to maintain bus voltage.
• Input voltage too low: Increase input voltage to rated range, ensure upstream breakers/contactors are closed and functional.
• Undervoltage suppression parameters incorrect: Adjust undervoltage suppression Kp/Ki (d1-66/67). Start with smaller values and increase if ineffective.
• Motor oscillation causing undervoltage: Resolve motor oscillation issues by adjusting control parameters.

E009.2 – Undervoltage Suppression Active
System-level warning indicating active suppression. Hardware fault requires technical support.

E009.3 – Pre-Drive Timeout
Bus voltage remains below undervoltage point after startup command within timeout period.

• Check input wiring per manual diagrams
• Verify input voltage is within specification
• If input is confirmed correct, hardware damage likely – contact technical support

5.4 Overload Faults

E0010.1 – Inverter Overload
Inverter cumulative overload coefficient (LC-32) reaches 100%.

Causes and Solutions:

• Load too heavy or motor blocked: Check if load is abnormally heavy, verify brake is releasing properly
• For asynchronous motors at low/mid speed: Increase no-load current (F1-30), decrease mutual inductance (F1-28), maintain their product constant
• For synchronous motors at low/mid speed: Increase MTPA adjustment coefficient (d5-29) for salient-pole motors
• High-speed weak magnetic zone overload: Increase modulation index (A5-06), keep below 108%
• V/f acceleration time too short: Extend F0-48/49, enable overcurrent suppression (d2-26=1)
• Motor parameter error: Verify motor nameplate matches F1-00 through F1-11 settings
• Inverter undersized: Recalculate load requirements and select larger inverter if necessary

E0011.1 – Motor Overload
Motor cumulative overload coefficient (LC-33) reaches 100%.

• Verify load is not mechanically overloaded
• Check motor overload protection coefficient (d1-46); increase if actual motor temperature is low but fault persists
• Confirm motor parameters match nameplate data
• Verify input voltage is within specification
• For prolonged overload, consider upsizing motor or inverter

5.5 Phase Loss Faults

E0012.1 – Input Phase Loss
Detected by hardware circuit when input phase is missing.

• Verify input wiring is correct per manual
• Check input voltage is within range
• If input is confirmed correct and voltage normal, inverter diode damage likely – contact technical support

E0013.1/E0013.2/E0013.3 – U/V/W Phase Loss
Running current in one phase is significantly lower than the other two phases.

• Check output wiring for open circuits
• Verify output contactor is closed (not tripped)
• Test motor: check for line breaks, measure UV/UW/VW resistances for balance
• If resistances are unbalanced, repair or replace motor

5.6 Fault Reset Methods

After resolving the root cause, reset the fault using one of these methods:

1. DI Terminal Reset: Configure any DI terminal (E0-00 through E0-04) to function 9 [Fault Reset], then activate that terminal
2. Panel Reset: Press the RUN/STOP key on the LED panel while in fault state
3. Power Cycle: Disconnect main power, wait until display goes dark, then reconnect power
4. Communication Reset: When in communication control mode (b1-00=2), write value “16” (bit4 fault reset command) to communication address 7321H

For persistent or unclear faults, do not attempt internal repairs. Contact Inovance technical support or an authorized distributor for professional assistance.

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This guide provides the essential procedures for operating the Inovance MD605 series inverter safely and effectively. Always follow safety precautions, verify wiring before energizing, and perform parameter identification when using vector control modes for optimal performance.