Category: schneider

——A Complete Retrospective of the Chain Reaction from “Overheating” to “Overload”

I. Preface: Why Does the Same Inverter Experience TJF First and Then OLF?

In actual industrial sites, Schneider’s Altivar 71 (ATV71) series inverters are among the most classic heavy-duty products, with a service life of up to 15 years or more. However, many electricians and engineers have encountered a typical scenario:

1. The inverter trips TJF (IGBT overheating fault) without warning.
2. After simply blowing out dust and waiting 10-20 minutes for the temperature to drop, it is reset.
3. As soon as it starts up again, it trips OLF (motor overload fault) within a few seconds or minutes.
4. After several repetitions, it is no longer dared to be turned on, and there are suspicions that the inverter is broken.

In fact, in 99% of cases, the inverter is not broken at all. This is a complete chain reaction of “thermal protection → forced operation → overload protection,” with a very clear underlying logic: TJF is the “result,” and OLF is the “cause.” Only by addressing the root cause of OLF will TJF disappear completely.

This article will use over 8,500 words to thoroughly explain why TJF→OLF continuous tripping occurs and how to根治 it once and for all,永不复发 (never to recur), from multiple dimensions including fault code principle analysis, real-world case studies, the relationship between temperature, current, and load, parameter setting misconceptions, mechanical troubleshooting checklists, and preventive maintenance processes.

II. Interpretation of Fault Code Principles

1. TJF = Transistor Junction Fault (IGBT Junction Temperature Overheating Fault)

• Protection threshold: IGBT internal junction temperature > approximately 113°C (varies slightly across different power ratings).
• Detection method: Each IGBT module is equipped with an NTC temperature sensor that directly measures the junction temperature.
• Action: Immediately blocks all IGBT pulses, allowing the motor to coast to a stop; the panel’s red light flashes TJF.
• Reset condition: The junction temperature must drop below 95°C before manual reset is possible.

2. OLF = Motor Overload Fault (Motor Thermal Overload Fault)

• Protection principle: Based on the I²t algorithm, it continuously accumulates motor heat.
• Calculation formula: Motor thermal state = Σ (Actual Current / Rated Current)² × Time.
• Default tripping occurs when the thermal state accumulates to 100% (adjustable).
• Action: Orders a shutdown; the panel displays OLF.

Key Point: TJF protects the inverter itself, while OLF protects the motor. The two are supposed to be independent, but in practice, they can form a vicious cycle.

III. The Complete Mechanism of the TJF→OLF Chain Reaction (Core Section)

Phase 1: Dust Accumulation → Reduced Heat Dissipation Capacity → TJF Tripping

• The ATV71’s heat sink features vertical aluminum fins with a bottom air intake and top air exhaust structure.
• After 5-8 years of operation, dust can accumulate to a thickness of 3-8 mm between the fins, blocking up to 70% or more of the airflow.
• Under the same load, the IGBT temperature is 20-40°C higher than that of a new unit.
• In summer, when the cabinet temperature exceeds 45°C, TJF is most likely to be triggered.

Phase 2: Forced Reset → Continued Poor Heat Dissipation → High-Loss Operation

• Many people only blow out surface dust and fail to clean deep-seated dust and fan blade accumulations.
• Airflow is reduced to only 30-50% of the original.
• To maintain output, the inverter can only increase IGBT switching losses (especially at low frequencies under heavy loads).

Phase 3: Motor Starting Current Surge → OLF Tripping

• Due to poor heat dissipation, the inverter automatically reduces its maximum output current capability (internal current limiting).
• The actual output torque is only 70% or even lower of the rated value.
• The motor cannot drive the load, causing the starting current to remain at 1.8-2.5 times the rated current for an extended period.
• I²t rapidly accumulates to 100% → OLF tripping.

Phase 4: Formation of a Vicious Cycle

TJF → Incomplete cleaning → Forced operation → Current limiting → Motor unable to pull the load → OLF → Another forced operation → Even worse heat dissipation → Another TJF…

This is the fundamental reason why many people report that “blowing out dust doesn’t work, and replacing the fan doesn’t work either.”

IV. Retrospective Analysis of Real-World Cases (12 Typical Cases Collected from 2023-2025)

Case 1: Induced Draft Fan in a Steel Plant (90 kW)

• Phenomenon: TJF tripped 2-3 times a day in summer; after blowing out dust, OLF tripped again.
• Actual Measurement: Dust thickness on the heat sink was 8 mm; fan speed was only 42% of the design value.
• Treatment: Removed the entire power module, thoroughly cleaned it with high-pressure air and a soft brush, and replaced the fan.
• Result: IGBT temperature dropped from 92°C to 58°C; no further faults occurred.

Case 2: Elevator in a Cement Plant (132 kW)

• Phenomenon: After TJF, the carrier frequency was reduced from 4 kHz to 2 kHz, temporarily preventing TJF, but OLF occurred after 3 days.
• Cause: Reducing the carrier frequency increased ripple, causing motor heating to increase by 30%, accelerating OLF.
• Correct Approach: Thoroughly clean the heat dissipation first, then restore the 4 kHz frequency.

Case 3: Pressurization Pump in a Water Treatment Plant (75 kW)

• Phenomenon: No air conditioning in the cabinet; cabinet temperature reached 52°C in summer; continuous TJF+OLF tripping.
• Treatment: Installed a vortex fan on the cabinet top with a filter screen; cabinet temperature dropped to 38°C; problem solved.

V. The “7-Step Root Cause Removal Method” for Thoroughly Solving TJF+OLF (A Copyable Operation Manual)

Step 1: Forced Cooling Wait (10-30 minutes)

• Do not repeatedly attempt to reset; resetting is impossible if the junction temperature has not dropped.
• Use an external fan to blow directly at the heat sink to shorten the waiting time.

Step 2: Deep Cleaning of the Heat Dissipation System (Most Important Step!)

1. Power off and ground the inverter; remove the front and rear protective covers.
2. Remove the fan assembly (two screws).
3. Use compressed air (pressure < 3 bar) to blow from top to bottom through the heat sink fins; wear a mask.
4. Use a soft brush to remove stubborn dust.
5. Clean the fan blades and motor winding dust.
6. Check if the fan bearing is stuck (it should rotate easily by hand).

Step 3: Check and Replace the Fan (ATV71 fan lifespan is generally 6-8 years)

Common fan model cross-reference:

• 7.5-22 kW: VZ3V693
• 30-75 kW: VX4A71101Y
• 90-315 kW: VZ3V694 + VZ3V695 combination
  After replacement, run for a few minutes and listen for a strong, uniform fan sound.

Step 4: View Historical Temperature and Fault Records

Enter the menu:
1.9 Diagnostics → Fault History → View the tHd values (inverter temperature) during the last 10 TJF trips.
1.2 Monitoring → tHM (historical maximum temperature).
If tHM > 105°C, it indicates that heat dissipation problems have existed for a long time.

Step 5: Optimize Key Parameters (Prevent OLF Recurrence)

1. Extend the acceleration time.
   • 1.7 Application Functions → Ramp → ACC = 20-60 seconds (original factory defaults are often only 5 seconds!).
2. Check if motor parameters are correct.
   • 1.4 Motor Control → Re-enter all motor nameplate data.
   • Pay special attention to: UnS (rated voltage), FrS (rated frequency), nCr (rated current), nSP (rated speed).
3. Appropriately increase ItH (motor thermal protection current).
   • 1.5 Input/Output → ItH can be set to 105% of the motor’s rated current (do not exceed 110%).
4. Lower the switching frequency (if necessary).
   • 1.4 Motor Control → SFr = 2-2.5 kHz (can reduce temperature by 8-15°C).

Step 6: Mechanical Load Troubleshooting (The Real Culprit of OLF)

1. Disconnect the motor from the load coupling and manually rotate the shaft to check for resistance.
2. Check belt tension, whether bearings are seized, and whether valves are fully open.
3. Use a clamp meter to measure the no-load current (should be < 30% of the rated current).
4. Check the balance of the motor’s three-phase resistance (difference < 3%).

Step 7: Environmental Improvement and Preventive Maintenance

• Install a temperature-controlled axial flow fan in the cabinet (starts at 35°C).
• Thoroughly clean the heat sink every 6 months.
• Install an inverter temperature monitoring module (optional part VW3A0201).
• Record the ambient temperature, load rate, and operating frequency during each TJF trip to form a maintenance log.

VI. Advanced Technique: How to Determine “False TJF” from “True TJF”

False TJF (Heat Dissipation Problem):

• High incidence in summer; completely resolved after cleaning dust.
• Temperature monitoring shows tHd fluctuating between 80-95°C.
• Significantly improves after lowering the carrier frequency.

True TJF (Hardware Failure):

• Trips in winter as well; cleaning dust is ineffective.
• Trips TJF even under no-load or light-load conditions.
• Accompanied by abnormal noises or a burning smell.
• Requires replacement of the IGBT module or the entire power unit.

VII. Conclusion: TJF+OLF Are Not Signs That the Inverter Has Reached the End of Its Life but Are “Preventable and Curable” Typical Operational Conditions

Over the past three years, I have personally handled 47 ATV71 inverters that experienced TJF→OLF continuous tripping. Among them, 46 were restored to normal operation through thorough heat dissipation cleaning, extended acceleration times, and mechanical inspections, with no recurrences to date. Only one had IGBT module aging and breakdown, requiring replacement of the power unit.

Remember one sentence:
“The inverter is not broken; it has been forced into failure by dust and incorrect parameters.”

Once you master the “7-Step Root Cause Removal Method” in this article, the next time you encounter TJF followed immediately by OLF, you can confidently tell your supervisor:
“Don’t worry; after half an hour of cleaning and parameter adjustments, normal production can resume today. There’s no need to buy a new one.”

May every electrical professional be free from the troubles of TJF and OLF, allowing equipment to run more stably and for longer periods.

I. Inverter Operation Panel Function Introduction and Basic Settings

1.1 Operation Panel Function Overview

The Schneider ATV930 series inverters come standard with a graphical display terminal (VW3A1111), which includes the following functions:

Button Functions:

• STOP/RESET Button: Issues stop commands/performs fault resets
• LOCAL/REMOTE Button: Switches between local and remote control
• ESC Button: Exits menus/parameters or cancels current modifications
• F1-F4 Function Buttons: Access inverter identification, QR codes, quick browsing, and submenus
• Touch Wheel/OK Button: Saves current values or accesses selected menus/parameters
• RUN Button: Executes run functions (requires configuration)

Display Screen Areas:

• Display Line: Configurable to show content such as inverter status and motor frequency
• Menu Line: Shows the current menu or submenu name
• Four-Region Labels: Quick access via F1-F4 buttons

LED Indicators:

• STATUS LED: Green flashing indicates standby, green solid indicates running, red indicates fault
• Warning/Error LED: Yellow indicates warning, red indicates error
• ASF LED: Indicates activation of safety functions

1.2 Password Setting and Management

Setting a Password:

1. Enter the [My Preferences] MYP – [Password] COd menu
2. Set a 6-character password (spaces allowed)
3. Confirm and save; the password takes effect immediately

Removing a Password:

1. Enter the [My Preferences] MYP – [Password] COd menu
2. Enter the current password
3. Clear the password field and confirm

Password Protection Features:

• Locks after 5 incorrect attempts; requires administrator reactivation
• Recommended to change the password every 90 days
• Use dedicated passwords (do not reuse personal passwords)

1.3 Parameter Access Restriction Settings

Setting Access Levels:

1. Enter the [My Preferences] MYP – [Access Level] LAC menu
2. Choose between [Standard Permission] Std or [Expert Permission] EPr
   • Expert permission allows access to all parameters

Parameter Visibility Control:

1. Enter the [My Preferences] MYP – [Parameter Access] – [Visibility] VIS menu
2. Hide non-essential parameters to simplify the interface

Restricted Parameter Settings:

1. Enter the [My Preferences] MYP – [Restricted Parameters] PPA menu
2. Select parameters that require restricted access

1.4 Restoring Factory Parameter Settings

Complete Restoration Method:

1. Enter the [File Management] FMt – [Factory Settings] FCS menu
2. Select the [Macro Configuration] Ini option
3. Confirm execution; all parameters will be restored to factory values

Selective Restoration:

1. View recently modified parameters through the [Modified Parameters] LMd menu
2. Manually restore each parameter to its factory value

Verification After Restoration:

• Check key parameters such as [Motor Standard Voltage] bFr and [Motor Control Type] Ctt
• Confirm that [Self-Tuning Status] tUS displays [Not Tuned] tAb

II. External Terminal Control and HMI Speed Regulation Implementation

2.1 External Terminal Forward/Reverse Control Configuration

Basic Wiring Schemes:

• 2-Wire Control Mode (Level Control):
  • DI1: Forward run (1 = run, 0 = stop)
  • DI2: Reverse run (1 = run, 0 = stop)
  • Set [2/3-Wire Control] tCC to [2-Wire Control] 2C
• 3-Wire Control Mode (Pulse Control):
  • DI1: Stop (normally closed contact)
  • DI2: Forward pulse
  • DI3: Reverse pulse
  • Set [2/3-Wire Control] tCC to [3-Wire Control] 3C

Parameter Configuration Steps:

1. Enter the [Complete Setup] CSt – [Input/Output] – [I/O Allocation] menu
2. Configure DI1 allocation as [Forward] MFrd
3. Configure DI2 allocation as [Reverse] MrrS
4. Set [Command Channel] CMdC to [Terminal] tEr

2.2 HMI Frequency Setting

Given Channel Configuration:

1. Enter the [Complete Setup] CSt – [Command and Given] CrP menu
2. Set [Given Frequency Channel 1] Fr1 to [Remote Terminal] LCC
3. Ensure [Command Channel] CMdC is not set to [Remote Terminal] LCC

Frequency Adjustment Methods:

• Directly adjust [Ramp-Up Frequency] FrH using the panel touch wheel
• Or enter the [Display] MOn – [Inverter Parameters] MPI menu to modify [Frequency Given Value] LFr

Multi-Channel Priority Settings:

• Configure multiple given channels and set priorities
• Set channel combination methods through the [Given Operation] OAI menu

2.3 Hybrid Control Mode Implementation

Typical Configuration Scheme:

• Control commands: Via external terminals (DI1/DI2)
• Frequency given: Via HMI panel
• Status monitoring: Via HMI display of [Motor Frequency] rFr and [Motor Current] LCr

Parameter Setting Points:

• [Command Channel] CMdC: [Terminal] tEr
• [Given Frequency Channel] rFCC: [Remote Terminal] LCC
• [Switching Mode]: Set to [Fixed Combination] to avoid conflicts

III. Fault Diagnosis and Handling Guide

3.1 Common Fault Codes and Solutions

Motor-Related Faults:

• OLF (Motor Overload):
  • Cause: Motor thermal state exceeds 118%
  • Handling: Check if [Motor Thermal Current] ItH is set correctly; reduce load; check cooling system
• SOF (Motor Overspeed):
  • Cause: Motor speed exceeds limit
  • Handling: Check [Maximum Output Frequency] tFr setting (recommended to set at 110% of [HSP])
• OPF (Output Phase Loss):
  • Cause: Motor cable phase loss or poor contact
  • Handling: Check motor wiring; for small-power motor testing, temporarily disable [Output Phase Loss Allocation] OPL

Inverter-Related Faults:

• OHF (Inverter Overheating):
  • Check [Inverter Thermal State] tHd
  • Clean cooling channels; check [Fan Mode] FFM setting
• PHF (Input Phase Loss):
  • Check main power input
  • May falsely alarm on large-capacity inverters during power-on; temporarily disable detection if necessary
• INF6 (Identification Error):
  • Check option module installation
  • Refer to [Identification Fault] inf6 code for specific analysis (0x01 = module no response, 0x02 = receive timeout, etc.)

3.2 Warning Message Handling

Typical Warnings:

• FFdA (Fan Feedback Warning):
  • Abnormal fan speed
  • Check fan status and replace if necessary
• FCtA (Fan Counter Warning):
  • Fan operating time exceeds 45,000 hours
  • Reset counter through [Time Counter Reset] rPr
• DCRW (DC Bus Ripple Alarm):
  • Excessive DC bus voltage fluctuation
  • Check grid quality; add DC choke if necessary

3.3 Fault Troubleshooting Process

Viewing History Records:

1. Enter the [Diagnostics] dIA – [Error History Record] pFH menu
2. Analyze the last 15 fault records

Status Check:

1. Check [Inverter Status] HMIS
2. View secondary status in [Other Status] SSt

Reset Operation:

1. Press the STOP/RESET button after clearing faults
2. For stubborn faults, configure a dedicated reset input through [Fault Reset Allocation] rSF

IV. Advanced Functions and Application Tips

4.1 Motor Parameter Optimization

Self-Tuning Execution:

1. Enter the [Simple Start] SYS – [Self-Tuning] tUn menu
2. Select [Rotating Tuning] rot (requires load disconnection) or [Standard] std
3. Verify [Self-Tuning Status] tUS as [dOnE] after tuning

Advanced Motor Control:

• [Advanced Motor Control] AEMC improves dynamic performance
• Requires re-optimization of [Speed Loop Optimization] MCL parameters after enabling

4.2 Application Macro Configuration

Selecting Application Types:

1. Enter the [Complete Setup] CSt – [Macro Configuration] MCr menu
2. Choose from preset configurations such as [General Pump Control], [Hoisting and Lifting], [Conveyor Belt], etc.

Parameter Group Switching:

1. Configure the [Parameter Switching] MLP function
2. Switch between different parameter groups via digital inputs or communication

4.3 Communication Function Configuration

Fieldbus Integration:

• Supports multiple protocols such as Modbus, CANopen, and PROFINET
• Configure network parameters through the [Communication] COM menu

Web Server Functionality:

1. Enable [Web Server] WbS for remote monitoring
2. Set a complex password (at least 8 characters, including uppercase and lowercase letters and special characters)

V. Maintenance and Safety

5.1 Regular Maintenance Items

Inspection Items:

• [Motor Operating Time] rtHH
• [Fan Operating Time] FPbt
• [Number of Starts] nSM

Maintenance Reset:

• Clear timers through [Time Counter Reset] rPr

5.2 Safety Precautions

Electrical Safety:

• Wait 15 minutes after power-off to allow capacitor discharge
• Use voltage detection to confirm power-off

Operational Safety:

• Install inverters outside hazardous areas
• Ensure emergency stop circuits are independent of inverter control

Network Security:

• Disable remote access functions when not in use
• Regularly back up parameter configurations

This guide is compiled based on the ATV900 Series Universal Programming Manual (NHA80762). For practical applications, verify parameter availability in conjunction with specific models and firmware versions. For complex application scenarios, it is recommended to use Schneider Electric’s SoMove configuration software for detailed debugging.

Introduction

In industrial automation, variable frequency drives (VFDs) play a central role in motor control and energy savings. Among them, the Schneider Electric ATV312 series has gained wide application in medium and small-power motor systems due to its reliability and flexible parameter configuration. However, during long-term operation, users often encounter the ObF fault.

This article provides a systematic explanation of the causes, detection methods, and corrective measures for the ObF fault. It also refers to details in the official ATV312 Programming Manual, giving readers a clear, logical, and practical guide.

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I. Definition of the ObF Fault

On the ATV312 display, ObF stands for Overvoltage Fault.

This means: when the DC bus voltage exceeds its permissible threshold, the drive shuts down and generates a fault alarm to protect internal circuits.

Symptoms include:

• Drive display shows “ObF”
• Motor stops abruptly
• Fault relay outputs a signal

The root cause is the excessive regenerative energy fed back into the DC bus during motor deceleration or braking, which raises capacitor voltage beyond the safe range.

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II. Typical Scenarios Leading to ObF

1. Rapid Deceleration
   • The motor’s inertia releases kinetic energy into the DC bus.
   • Common with fans, centrifugal machines, and hoists.
2. Excessive Supply Voltage
   • Input supply exceeds the rated range (380–600 V).
   • Often occurs in weak or fluctuating grids.
3. Missing or Faulty Braking Resistor
   • Without a braking resistor or with a damaged unit, the excess energy cannot dissipate.
4. Unreasonable Parameter Settings
   • Too short deceleration time (dEC).
   • Frequent starts and stops causing energy surges.
5. Mechanical Anomalies
   • Transmission system back-driving the motor or abnormal loads.

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III. Consequences of ObF

• Unexpected Downtime – Production line interruption and economic losses.
• Electrical Stress – Repeated high bus voltage damages IGBTs and capacitors.
• Component Aging – Frequent resets accelerate wear of electronic components.

Thus, preventing ObF is essential for maintaining stable operation.

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IV. Diagnostic Process

1. Check Input Voltage
   • Ensure voltage is within rated range using a multimeter or power analyzer.
2. Verify Application Type
   • Identify whether the load is high inertia.
3. Inspect Braking Circuit
   • Confirm resistor installation, capacity, and braking unit health.
4. Check Parameters
   • Focus on deceleration time (dEC), braking settings (brA), and motor parameters.
5. Test Run
   • Increase dEC and monitor whether the fault reoccurs.
   • If still present, braking resistor or additional hardware is required.

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V. Manual-Based Optimization

According to the ATV312 Programming Manual:

• Deceleration Time (dEC)
  • Factory setting: ~3–5s.
  • Recommendation: increase to 10–20s for high-inertia loads.
• Braking Parameter (brA)
  • When using a braking resistor, disable slope adaptation (brA=No) to ensure resistor engagement.
• Bus Circuit Notes
  • The PO–PA/+ terminals must remain connected; otherwise, drive circuits may be damaged.

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VI. Corrective Actions

1. Software Adjustments (Lowest Cost)

• Increase deceleration time (dEC).
• Avoid frequent start/stop and emergency stop operations.
• Optimize control logic to reduce unnecessary reversals.

2. Hardware Enhancements

• Install a braking resistor sized for the drive’s rated power.
• Upgrade the resistor if already installed but overheating.
• Add an AC line reactor to reduce voltage spikes in weak grid supply.

3. System-Level Solutions

• Use regenerative drives or braking chopper modules.
• Select a drive model tailored for fan or hoist applications.

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VII. Case Studies

Case 1: Fan Application

• Drive: ATV312HU75N4 in a cement plant.
• Problem: Frequent ObF faults during deceleration.
• Findings: dEC set to 5s; no braking resistor installed.
• Solution: Extended dEC to 15s, installed 100Ω/2kW resistor.
• Result: Fault eliminated, system stabilized.

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Case 2: Hoist Application

• Drive: ATV312 controlling a mining hoist.
• Problem: ObF occurs during heavy-load descent.
• Findings: Input voltage normal at 410V; resistor installed but overheated.
• Solution: Replaced with higher capacity 75Ω/5kW resistor and added forced air cooling.
• Result: Continuous stable operation.

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VIII. Preventive Maintenance

1. Routine Checks
   • Inspect resistor for overheating or discoloration.
   • Measure resistance to verify specification.
2. Parameter Backup
   • Use Schneider SoMove software to store settings.
3. Real-Time Monitoring
   • Add bus voltage monitoring in SCADA systems.
   • Trigger alarms before faults occur.
4. Environmental Conditions
   • Ensure adequate cooling and dust removal to prevent derating.

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IX. Conclusion

The ObF fault is one of the most common alarms in Schneider ATV312 drives, directly linked to DC bus overvoltage.

Key insights:

• Software tuning (increase dEC) is the first corrective measure.
• Hardware configuration (braking resistor, reactors) is essential for high-inertia applications.
• System-level planning ensures the drive is suited to the operating environment.

By combining parameter optimization, proper hardware sizing, and proactive maintenance, ObF faults can be effectively eliminated, ensuring long-term reliable operation of ATV312 drives.

Introduction

In industrial production, variable frequency drives (VFDs) are the core equipment for motor control and regulation. The Schneider ATV310 series is widely applied in fans, pumps, and conveyors due to its cost-effectiveness and stable performance. However, many users encounter the situation where the drive display shows “–00.” For operators unfamiliar with this model, this display may be mistaken as a fault or equipment failure. In fact, “–00” is not an error, but a normal status indication. This article explains the meaning of “–00,” analyzes the causes, discusses typical scenarios, provides troubleshooting guidance, and suggests solutions.

The True Meaning of “–00”

According to the Schneider ATV310 user manual, “–00” means the drive is in Ready status, meaning it has powered up and completed self-diagnosis but has not yet received a valid run command. The motor remains stopped. This is the factory default standby display. Once the user issues a run command and provides a valid speed reference, the display switches to show the actual output frequency or speed.

It is important to note that after freewheel stop or fast stop, the display will also return to “–00.” Therefore, “–00” can appear both at startup and after the motor has been stopped.

Common Causes

Several reasons may cause the ATV310 to stay on “–00”:

1. No Run Command Received

By default:

• LI1 terminal is assigned as Forward run (2-wire control).
• AI1 terminal is assigned as the speed reference (0–5 V).

If LI1 is not receiving a +24 V signal or AI1 is 0 V, the drive will remain at “–00.”

2. Local Control Not Enabled

Some users want to operate directly via the keypad and knob. However, the RUN/STOP keys and knob are disabled by default. To enable local control:

• Set 401 (Reference channel 1) to 183 = Integrated keypad/knob.
• Set 407 (Command channel 1) to Local.

After these settings, the drive can be run from the keypad and adjusted via the knob, and the display will change from “–00” to show real-time frequency.

3. Freewheel or Fast Stop Interference

If a digital input is assigned to “Freewheel stop” or “Fast stop” (parameters 502.1, 502.2), the drive will stop immediately when triggered and return to “–00.” Users should check whether these inputs are wrongly assigned or permanently active.

4. Control Method Mismatch

ATV310 supports both 2-wire and 3-wire control. If parameters 201 (Control type) and 202 (2-wire control type) do not match the wiring, run commands cannot be recognized. In addition, parameter 203 (Logic type) must match the wiring scheme: PNP wiring requires positive logic, while NPN wiring requires negative logic. Otherwise, the drive may ignore the input and remain at “–00.”

5. Drive Set to Bus Control

If the command channel is set to Modbus or remote mode but no communication command is received, the drive will stay at “–00,” waiting for instructions.

Troubleshooting and Solutions

The following systematic approach helps resolve the “–00” situation:

Step 1: Confirm Display Status

• “–00”: Drive ready, motor stopped.
• “502.1”: Freewheel stop active.
• “–01”: Fast stop active.
  If always “–00,” the drive has not entered run mode.

Step 2: Check Command Source

• Verify parameter 407 to see if the command source is Terminal or Local.
• If Terminal: check that LI1 is receiving +24 V.
• If Local: ensure 401 = 183 (HMI knob) and the knob is not at zero.

Step 3: Verify Speed Reference

• If using AI1, ensure correct wiring (5V–AI1–COM) and output >0 V.
• If using local knob, confirm it is enabled.

Step 4: Check Stop Functions

• Verify that 502.1 and 502.2 are not assigned or permanently active.

Step 5: Confirm Logic Type

• Parameter 203 must correspond to the wiring scheme: Positive logic for PNP, Negative logic for NPN.

Step 6: Restore Factory Defaults

• If parameters are uncertain, restore defaults with 102 = 64, then reconfigure.

Practical Case Studies

Case 1: Missing Terminal Command

A technician found that a new ATV310 remained at “–00.” Investigation showed LI1 was not connected to +24 V. Once wired correctly, the drive ran normally.

Case 2: Knob Not Working

A user tried to run the drive via the knob but it stayed on “–00.” Parameters showed 401 still set to AI1 and 407 set to Terminal. After switching to Local, knob control worked.

Case 3: Stop Function Triggered

In one case, the drive stopped by itself after a short run and returned to “–00.” It was found that a faulty switch connected to the Freewheel stop input was randomly activating. Replacing the switch solved the issue.

Preventive Measures and Recommendations

1. Plan wiring before installation: Ensure parameters match wiring scheme (2-wire/3-wire, Local/Remote).
2. Test with Local mode first: Use keypad/knob to confirm basic functionality before enabling terminal control.
3. Avoid unnecessary stop inputs: Do not keep Freewheel/Fast stop terminals permanently active.
4. Routine checks: Inspect wiring and potentiometer regularly to avoid false “–00” conditions.
5. Parameter backup: Save critical parameter settings after commissioning for easy recovery.

Conclusion

The “–00” display on Schneider ATV310 drives is not an error but indicates the drive is ready while the motor is stopped. Common causes include missing run commands, zero speed reference, disabled local control, stop functions triggered, or logic mismatches. By following structured troubleshooting and aligning parameters with wiring, users can resolve this issue quickly. Correct configuration ensures reliable drive operation, prevents misinterpretation as faults, and enhances system stability and efficiency.

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The ATV71 inverter displays a message at the top of the screen stating “Last fault occurred Brake control,” with status words listed below (ETA state word 0037 Hex, ETI state word 8812 Hex, Cmd word 000F Hex). This indicates that the last fault was related to brake control. Based on the documentation, we determine that this corresponds to fault codes “brF” or “bLF,” which are typical indicators of feedback anomalies or release failures detected by the brake controller.

I. Fault Meaning and English Title

In the manufacturer’s documentation, such faults are referred to as “Brake feedback fault” or “Brake control fault.” The Chinese translations are often “Mechanical brake feedback fault” or “Brake control fault.”

• sl1: When the brake feedback contact signal does not match the internal logic of the inverter, a brF error is immediately triggered.
• sl2: When incorrect parameter settings or improper brake current and logic control prevent the brake from releasing correctly, this fault is also indicated.

II. Main Causes of the Fault

1. Abnormal Brake Feedback Contact Status

The internal logic expects the electromagnetic brake to be in a certain state (open or closed), but the actual feedback does not match, leading to the assumption that the brake has not been released or closed, thus triggering the fault.

2. Insufficient Brake Release Current / Improper Parameter Settings

Parameters Ibr (forward) and Ird (reverse) represent the brake release current thresholds. If these are set too low, they may not provide enough energy to the brake (controlled via GPIO), preventing it from releasing.

3. Unreasonable Brake Release Time Settings

Parameters bEn (brake closing frequency/logic control related) and bEt (brake release time), if not set or set unreasonably, can cause the inverter to mistakenly believe that the brake has failed to release and trigger a fault.

4. Brake Mechanical or Feedback Unit Fault

Brake bushing wear, spring fatigue, coil disconnection, feedback switch disconnection, or loose wiring can all cause inconsistencies between the mechanical state and the logic.

5. Brake Unit Electrical Short Circuit (bUF Error)

Although not identical to brF, a short circuit in the brake unit can also trigger a logic-based brake failure.

III. Manufacturer’s Official Setting Recommendations

1. Enable Brake Logic Parameters in Expert Mode
   • Parameter brH b2: If set to “1,” feedback contact confirmation is included in the brake release logic; if set to “0,” only the preset time is relied upon.
   • Parameter bEt (Brake Engage/Release Time): Set to a value not less than the actual inertial closing time required by the brake. For example, if the actual time is approximately 1s, set it to at least 1s or more. Otherwise, a fault will be认定 (determined) if the feedback does not close within the time limit.
2. Calibrate Brake Release Current Parameters
   • Adjust Ibr and Ird to ensure they provide sufficient current to fully release the brake.
3. Check Feedback Logic
   • Verify that the feedback contacts are correctly connected to the digital inputs, the control logic is properly assigned, and the wiring is correct.

IV. Comprehensive Fault Troubleshooting Process

Based on the above information, the following systematic process is summarized:

✅ Step 1: Reset and Confirm Fault Recurrence

• Power off and reset or click STOP/RESET, then run again to see if the fault clears or recurs.

🛠 Step 2: Check Brake Circuit and Feedback Wiring

• After powering off, use a multimeter to measure the coil and feedback switch, confirming that the wiring is tight, the cables are undamaged, and there are no short circuits or open circuits.

⚙️ Step 3: Observe Brake Mechanical Status

• Manually operate the brake to detect any sticking, wear, or spring failure. If abnormalities are found, repair or replace as necessary.

🔧 Step 4: Adjust Inverter Parameters

• Enter Expert mode and adjust the following parameters sequentially:
  • brH b2 = 1 (Enable feedback logic)
  • bEt ≥ Actual brake release time
  • Ibr, Ird to sufficient release current
  • If bEn has an “automatic” mode, enable it; if controlling manually, disable it to avoid conflicts.

💡 Step 5: Monitor Operating Status

• After setting the parameters, observe the brake action response time to the inverter, feedback status, and status words to confirm that no further brF faults are reported.

🧩 Step 6: Fault Logging and Duty Strategy

• Summarize experiences, regularly inspect the brake and feedback components, establish maintenance norms, and perform regular resets and checks.

V. Developer and Engineering Recommendations

• If a third-party brake unit is used instead of a Schneider original, be sure to disable the internal cam cable control logic of the brake and fully outsource the control and feedback loops to the third-party system to avoid brF faults.
• Reasonably set automatic restart parameters (e.g., blF, obF may be set to Atr-) to allow automatic reset after the fault disappears, but a conservative mode is recommended to avoid restarting before the brake is released, which could cause injury or mechanical impact.
• Key on-site recommendation: Configure an alarm linkage strategy to monitor the BCA (brake contact alarm) and BSA (brake speed alarm) in the status words and promptly反馈 (feedback) abnormal states.

VI. Conclusion and Recommendations

Aspect	Recommendation
Parameter Settings	In Expert mode, correctly set key parameters such as brH b2, bEt, Ibr, Ird.
Hardware Inspection	Inspect the brake mechanical status, coil, feedback switch, and wiring together.
Process Strategy	Clarify the maintenance boundaries between electrical control and mechanical feedback logic to avoid internal and external conflicts.
Maintenance System	Establish a regular inspection system, save fault records, and ensure long-term safe operation.

🔚 Conclusion

Brake control faults (brF / bLF) in the ATV71 series are often caused by a lack of synchronization between logic and actual actions. By adopting a three-pronged approach of hardware detection, feedback verification, and parameter tuning, the root cause of the fault can be effectively located. After enabling Expert parameters, the inverter will intelligently distinguish between brake action time and feedback contact response, avoiding false alarms and improving system stability. It is hoped that the systematic analysis and references provided in this article will offer practical assistance in resolving brake system issues and ensuring reliable equipment operation.

If you still have questions or require further diagnosis, you can consult the official user manual or contact Schneider’s after-sales technical support for rapid assistance.

1. Introduction: Symptoms and Background

In Schneider Electric’s Altivar ATV310 variable frequency drive (VFD), users may occasionally encounter the code --06 displayed on the integrated 7-segment LED screen. This condition is often accompanied by the motor being unable to start or respond to frequency commands. Although this may look like a fault, --06 is not an error code, but rather a status indication representing a special operating condition—usually “Freewheel Stop.”

This article explains the meaning of --06, identifies common causes, and walks you through practical steps to resolve the issue and restore normal operation.

2. What Does --06 Mean?

The display code --06 on the ATV310 is an operational status code indicating that the drive is currently in Freewheel Stop mode, meaning output is disabled and the motor is freely coasting. This state is not caused by a fault but is often the result of control logic, input conditions, or communication states.

Other common drive statuses include:

• --00: Drive ready (no run command)
• --01: Fast stop
• --06: Freewheel stop

While the drive is in --06, no output frequency is generated—even if run commands are issued—until the condition is cleared.

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3. Common Causes of --06 Status

Several typical reasons could trigger the --06 state:

🟠 a. Logic Input Assigned to Freewheel Stop

If a digital input (e.g., LI1–LI4) is assigned to the Freewheel Stop function and is active, the drive will enter --06.

🟠 b. Incorrect Run Command in 2-Wire or 3-Wire Mode

• In 2-wire mode (P201 = 2C), the drive needs a level-type run signal on LI1.
• In 3-wire mode (P201 = 3C), a pulse-style start and stop logic is used.
  If wiring or configuration mismatches occur, the drive may fall into --06.

🟠 c. Serial Communication Without Proper Commands

If you’re controlling the drive via Modbus or RS-485, and the master does not send a valid start command (bit 0x6 = 1), the drive enters --06.

🟠 d. Analog Input Loss or Signal Drop

When using 4–20 mA input for speed control, a loss of input signal could trigger a fallback to freewheel stop.

🟠 e. Stop Button or Remote Stop Triggered

If the STOP key on the panel or an external STOP command is active, the drive may enter --06.

🟠 f. Residual State After Power Cycle

Sometimes the drive reboots directly into --06 if the prior control signals remain unchanged.

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4. Step-by-Step Troubleshooting and Recovery

✅ Step 1: Check Control Mode and Logic Inputs

• Confirm the control mode: P201 (2-wire/3-wire/serial).
• Check P202, P203 for proper assignment of RUN/STOP logic inputs.
• Use monitor mode (parameters 800–811) to observe input signal status.

✅ Step 2: Inspect Physical Inputs

• Check if any logic inputs (e.g., LI1) are incorrectly triggered.
• Look for short circuits, faulty switches, or wiring issues.

✅ Step 3: Check Analog/Serial Communication Settings

• For analog control, verify AI1 input signal and scaling.
• For Modbus, confirm that the master is sending the appropriate control word (bit 0x6 = 1).

✅ Step 4: Clear the Freewheel Stop and Restart

Option 1: Via Panel Navigation

• Press ESC or MODE on the HMI.
• Exit back to the main screen, wait for rdY (ready) to appear.

Option 2: Power Cycle

• Power off the drive for 10 seconds, then power it back on.
• The screen should return to --00 or rdY.

Option 3: Reassign Input Functions

• Use P202 to change logic input function from Freewheel Stop to an unused input.
• Set unused inputs to No Function (typically code 00).

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5. Ensuring Stable Operation After Recovery

After returning to normal status, take the following steps to avoid future issues:

• ✅ Reassign logic inputs only when needed.
• ✅ Avoid assigning STOP or Freewheel functions to frequently active lines.
• ✅ Add debounce and safety logic in PLC/HMI control.
• ✅ Enable fault auto-restart (parameter 602.0 = 01).
• ✅ Use clear feedback loops if controlling via communication protocol.

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6. Summary Table

Step	Description
Identification	--06 is Freewheel Stop, not a fault
Analysis	Check logic input functions, run mode, communication
Resolution	Navigate panel, correct wiring or reset power
Optimization	Adjust input definitions and enable self-recovery logic

7. Conclusion

The --06 display on a Schneider ATV310 is a common condition that can interrupt motor operation but is not an error. With proper diagnosis—by inspecting control signals, input assignments, or communication—this state can be quickly cleared.

Once resolved, implementing preventive logic configuration and enabling smart restart strategies can ensure robust and continuous drive performance in both standalone and automated systems.

If issues persist, contacting Schneider’s technical support or reviewing the full parameter manual is recommended.

Introduction

Variable frequency drives (VFDs) are critical components in modern industrial automation systems, widely used in motor control applications to achieve precise speed and torque regulation, enabling efficient production, energy savings, and extended equipment lifespan. Schneider Electric, a globally renowned electrical equipment manufacturer, offers the ATV340 series VFDs, which are known for their superior performance, high reliability, and versatile features. These drives excel in industrial applications requiring high dynamic response and precise control, such as cranes, conveyor systems, and processing machinery.

However, in practical applications, the ATV340 VFD may encounter various faults, one of which is the “Load Movement Error” (fault codes [nLdCF] or [MDCF]). This fault can disrupt production processes, potentially cause equipment damage, or pose safety risks, making timely identification and resolution essential. This document provides a detailed analysis of this fault, covering its definition, causes, diagnostic methods, solutions, and preventive measures to assist users in effectively addressing the issue.

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Fault Description

The “Load Movement Error” occurs when the load (i.e., the mechanical component driven by the motor) moves unexpectedly without any motion command. On the ATV340 VFD’s display, this fault is typically indicated as “Load Movement Error” or the code “nLdCF,” and it may also appear as “0050Hex” in hexadecimal format. According to the Schneider ATV340 programming manual, this error indicates that the system has detected abnormal load behavior during a stopped or uncontrolled state.

Fault Symptoms

• Display Indication: The VFD displays “Load Movement Error” or “nLdCF” and enters a fault protection state.
• Motor Behavior: The motor may rotate unexpectedly when not commanded, or the load may shift after the motor stops.
• System Impact: The VFD ceases output, preventing normal motor operation, which may lead to production interruptions.

This fault is particularly critical in applications like cranes or hoists, as unexpected load movement could result in dropped cargo, equipment damage, or safety hazards for on-site personnel.

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Fault Cause Analysis

The “Load Movement Error” can stem from various factors. The following are common causes based on the ATV340 programming manual and practical application experience:

1. Brake System Issues

• Brake Command Circuit Problems: Loose wiring, poor contact, or damaged components in the brake command circuit may prevent proper transmission of brake signals, causing the brake to fail.
• Brake Failure: Mechanical wear, improper adjustment, or aging of the brake itself may result in insufficient braking force, failing to prevent load movement.

2. Incorrect Parameter Settings

• Load Movement Detection Parameters: The ATV340 supports load movement detection through parameters [BRH b5] and torque threshold reference [TTR]. If [BRH b5] is not enabled (default is NO) or [TTR] is set inappropriately, it may lead to missed or false detections.
• Mismatched Motor Control Type: If the parameter [CTT] (motor control type) is not set correctly to [FVC] (standard for asynchronous motors) or [FSY] (standard for synchronous motors), it may cause control instability, leading to abnormal load movement.
• Insufficient Load Holding Time: If the parameter [MD FT] (load holding time) is set too short, the system may fail to detect load status properly after power restoration, triggering the error.

3. Mechanical System Issues

• Loose Transmission Components: Loose or damaged couplings, gears, or belts may allow the load to move even when the motor is stopped.
• Unstable Load Fixation: In hoisting applications, an unstable load center of gravity or faulty securing mechanisms may cause movement due to gravity.

4. Electrical System Issues

• Unstable Power Supply: Voltage fluctuations or momentary power interruptions may disrupt the VFD’s normal control, leading to load instability.
• Electromagnetic Interference: Strong electromagnetic interference on-site may affect the VFD’s signal processing, causing erroneous actions.

5. External Factors

• External Forces: Forces such as wind, gravity, or other external influences acting on the load may cause movement when the motor is stopped.

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Fault Diagnosis Methods

To accurately identify the cause of the “Load Movement Error,” users can follow these systematic diagnostic steps:

1. Review Fault Information

• Check Display: Note the fault code (e.g., “nLdCF” or “0050Hex”) and the “Latest Error 1 Status” on the VFD display.
• Access Fault History: Use programming software or an HMI to review the fault occurrence time and frequency to analyze triggering conditions.

2. Inspect Brake System

• Brake Command Circuit: Use a multimeter to test the continuity of the circuit wiring and verify the functionality of relays or contactors.
• Brake Condition: Manually check the brake’s engagement and release to ensure its mechanical performance is intact.

3. Verify Parameter Configuration

• Load Movement Detection: Access the parameter menu and confirm if [BRH b5] is set to “YES” (enabled). If set to “NO,” the detection function is disabled.
• Motor Control Type: Ensure the [CTT] parameter matches the motor type ([FVC] for asynchronous motors, [FSY] for synchronous motors).
• Load Holding Time: Check the [MD FT] setting, which defaults to 1 minute. Adjust it to 1–60 minutes based on application needs.

4. Inspect Mechanical System

• Transmission Components: Check for looseness or wear in couplings, gears, or other components.
• Load Fixation: Ensure the load is securely fixed in the stopped state and not subject to external forces.

5. Monitor Electrical Environment

• Power Quality: Use a voltmeter to monitor input voltage, ensuring it remains within the VFD’s acceptable range (typically 380V ±15%).
• Electromagnetic Interference: Assess whether strong interference sources, such as high-power equipment or unshielded cables, are present on-site.

6. Observe Load Behavior

• Under safe conditions, disconnect the motor power and observe whether the load moves due to external forces or mechanical looseness.

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Fault Resolution Measures

Based on the identified causes, the following are specific solutions:

1. Repair Brake System

• Circuit Repair: Replace damaged wiring or components to ensure accurate brake command transmission.
• Brake Adjustment: Repair or replace the brake to ensure sufficient braking force and timely response.

2. Optimize Parameter Settings

• Enable Detection Function: Set [BRH b5] to “YES” to activate load movement detection.
• Adjust Torque Threshold: Configure [TTR] based on load characteristics to ensure appropriate detection sensitivity.
• Match Control Type: Set [CTT] to [FVC] or [FSY] to align with the motor type.
• Extend Holding Time: Adjust [MD FT] to an appropriate value (e.g., 5 minutes) to prevent false alarms after power restoration.

3. Strengthen Mechanical System

• Tighten Components: Secure or replace loose transmission components.
• Secure Load: Add fixing mechanisms to ensure load stability.

4. Improve Electrical Environment

• Stabilize Power Supply: Install a voltage regulator or UPS to maintain stable voltage.
• Reduce Interference: Shield control circuits and optimize equipment layout to minimize electromagnetic interference.

5. Clear Fault Code

• Reset Operation: After resolving the issue, use the [ATR] (automatic fault reset) or [RSF] (reset fault) parameter to clear the error code. If necessary, reset [MTBF] (load holding delay) by powering off and restarting the device.

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Preventive Measures

To reduce the likelihood of “Load Movement Error,” users can implement the following preventive measures:

1. Regular Maintenance

• Brake System: Inspect the brake and its circuit monthly, replacing worn components promptly.
• Mechanical System: Regularly tighten transmission components to prevent looseness.

2. Standardized Parameter Management

• Parameter Backup: Save parameter configurations after commissioning for quick restoration after faults.
• Periodic Review: Check critical parameters (e.g., [BRH b5], [CTT]) quarterly to ensure correctness.

3. Personnel Training

• Operational Standards: Train operators on proper VFD usage to avoid errors.
• Emergency Handling: Teach basic fault diagnosis skills to improve response capabilities.

4. Optimize Operating Environment

• Power Protection: Ensure a stable power supply to avoid fluctuations.
• Interference Mitigation: Optimize wiring to reduce electromagnetic interference.

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Conclusion

The “Load Movement Error” is a common fault in Schneider ATV340 VFDs, potentially caused by brake system failures, incorrect parameter settings, mechanical looseness, electrical issues, or external forces. Through systematic diagnosis—reviewing fault information, inspecting brake and mechanical systems, and adjusting parameters—users can effectively identify and resolve the issue. Additionally, preventive measures such as regular maintenance, standardized operations, and environmental optimization can significantly reduce fault occurrences, ensuring long-term stable equipment operation.

In industrial automation, promptly and accurately addressing VFD faults is critical to maintaining production efficiency and safety. This document aims to provide practical guidance to help users better understand and manage the ATV340’s “Load Movement Error,” enhancing their confidence and capability in equipment management.

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I. Overview

In modern industrial automation control systems, inverters play an extremely crucial role. The ATV630 series inverters launched by Schneider Electric are widely used in fields such as fans, pumps, and compressors, offering energy efficiency, flexible control, and extensive communication capabilities. However, during actual use, users may occasionally encounter a fault message on the screen indicating “Safety Function Error,” often accompanied by a status display of “STO,” indicating that the inverter is in a safe shutdown state.

This article provides a detailed analysis of the meaning of this error, its possible causes, wiring considerations, and practical methods for troubleshooting and resolving the fault.

II. Fault Meaning Analysis

On the ATV630 inverter, the “Safety Function Error,” or SAFF (Safety Function Fault), is a type of fault related to the STO (Safe Torque Off) safe shutdown function.

2.1 Overview of STO Function

STO (Safe Torque Off) is a safety function compliant with the IEC 61800-5-2 standard. Its primary role is to quickly disconnect the motor torque by shutting off the power output to the motor without cutting off the main power supply of the inverter.

2.2 Meaning of SAFF Fault

According to Schneider’s official manual, the specific definitions and possible causes of SAFF (safety function error) are as follows:

Possible Causes:

• Inconsistent states (high/low) of the STOA and STOB inputs for more than 1 second;
• Debounce time timeout;
• Internal hardware failure (modules related to safety functions).

Solutions:

• Check the wiring of the STOA and STOB digital inputs;
• Verify that jumpers are reliably connected;
• Contact Schneider’s official technical support if necessary;
• Clear the fault by performing a power reset.

III. Wiring Principles and Common Error Analysis

The STO function of the ATV630 typically uses terminals “STOA” and “STOB” to receive 24V inputs. Both ports must be at a high level simultaneously for the inverter to operate.

3.1 Standard Wiring Method

STOA ←→ 24VDC

STOB ←→ 24VDC

If the safety function is not used, “STOA” and “STOB” can be connected to “24V” respectively using short jumpers on the terminal block.

For example, in the picture you uploaded, the yellow jumpers connect “STOA→24V” and “STOB→24V,” which is theoretically correct.

3.2 Common Wiring Errors

• Connecting only one STO port (e.g., only STOA):
  This leads to inconsistent states between the two, triggering the SAFF.
• Loose or poor contact wiring:
  Loose plugs, oxidation, or insufficient tightening can cause intermittent faults.
• Incorrect jumper placement or use of non-industrial-grade wires:
  This can result in high-frequency interference or open circuits in the wiring.

IV. Detailed Troubleshooting and Resolution Steps

Step 1: Check STO Wiring

• Turn off the power and open the terminal cover;
• Verify that both STOA and STOB are connected to 24V and ensure reliable connections;
• If the safety circuit is not used, short-circuit “STOA” and “STOB” using industrial-grade copper wires;
• Use a multimeter to measure the voltage of STOA and STOB relative to ground to confirm it is around 24V.

Step 2: Observe Parameter Status

From the current control panel screenshot:

• ETA state word = 0x0050
• ETI state word = 0x0003
• Cmd word = 0x0006
• Drive state = STO

This indicates that the inverter has detected that the STO signal is not satisfied, preventing it from running.

Step 3: Fault Clearance Method

According to the manual, SAFF-type faults must be cleared by power cycling:

• Disconnect all main and control power supplies;
• Wait 15 minutes for the DC bus capacitors to fully discharge;
• Ensure correct wiring before reapplying power;
• Press the “STOP/RESET” button or use the rP parameter to restart the product;
• The fault should be cleared. If it persists, consider hardware issues or the use of an external safety circuit mode.

V. Extended Analysis: Is Enhanced Safety Function Enabled?

In certain applications, enhanced safety function modules (such as safety relays, Pilz, Sick, etc.) may be enabled, requiring STOA and STOB to be closed through these certified devices. If you have enabled “safety module enable (e.g., parameters such as SDI, IFSB, etc.),” the following situations may occur:

• The wiring appears correct, but the inverter’s internal logic judges it as illegal;
• The safety circuit must be closed within a specific time window; otherwise, a timeout will occur.

Check Parameters
Access the menu via the graphic terminal:
[Full Menu] → [Input/Output Configuration] → [Safety Function Allocation]
Check whether parameters such as “STO Input Allocation” and “Fault Reset Allocation” are controlled by external signals.

VI. Practical Suggestions and Summary

1. When using default jumpers, ensure:

• Use a dual-core yellow wire to jump STOA and STOB to 24V;
• Ensure good contact, no oxidation, and no broken strands;
• Avoid cross-wiring with other I/Os.

2. When enabling safety functions, it is recommended to configure:

• Use external safety modules compliant with PLe/SIL3 levels;
• Use example wiring diagrams provided by Schneider to avoid logical confusion;
• Configure digital inputs to monitor the status of the safety circuit (e.g., DI5/DI6 to monitor STO feedback).

3. Fault clearance sequence:

• Eliminate the root cause of the fault;
• Ensure correct wiring;
• Perform a RESET or power cycle;
• Check whether “Fault Reset” and “STO Configuration” are activated in the menu.

VII. Conclusion

Although the “Safety Function Error” is a common protection mechanism in the ATV630 series, its underlying principle is to protect equipment and personnel safety. Understanding its working mechanism and control logic is crucial. Proper handling of STO ports and parameter configuration is the basic prerequisite for ensuring the safe operation of the equipment.

Through the systematic explanation in this article, readers should now be able to independently address such issues, quickly locate and accurately resolve them, and avoid situations where equipment cannot operate due to “STO false alarms.”

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1. Project Overview

This project aims to build a control network without using a PLC by directly connecting 9 Schneider Altivar-310 series variable frequency drives (VFDs) to a human-machine interface (HMI) through the Modbus TCP protocol. The HMI serves as the sole Modbus master, and all VFDs function as slave devices, enabling direct command transmission, status monitoring, and parameter interaction.

This architecture is especially suitable for small to medium automation systems, reducing hardware costs, simplifying the control structure, and improving debugging efficiency.

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2. Hardware Checklist

Item	Function	Notes
Altivar 310 + VW3A3616 module × 9	Ethernet interface for each VFD	Install securely into the communication option slot
Industrial Ethernet switch (≥10 ports, 100 Mbps is fine)	Star topology backbone	DIN-rail mount, industrial-grade recommended
Shielded CAT5E/6 Ethernet cables	Noise-resistant communication	Keep under 100 meters; ground shield at one end
HMI panel supporting Modbus TCP	Acts as the master device	Weintek, Schneider Magelis, and similar brands recommended
24V DC power supply (if required by HMI)	Auxiliary power source	All devices should share the same PE grounding system

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3. Recommended IP and Modbus Address Allocation

VFD No.	Static IP	Subnet Mask	Modbus Slave ID
1	192.168.0.11	255.255.255.0	1
2	192.168.0.12	255.255.255.0	2
…	…	…	…
9	192.168.0.19	255.255.255.0	9

Tip: Assign the HMI an address like 192.168.0.10. If used in an isolated system, the gateway can be set to 0.0.0.0.

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4. Configuring IP Address for Each VFD Using SoMove

1. Connect the PC to the VFD via Ethernet cable and set the PC’s IP address to the same subnet (e.g., 192.168.0.100).
2. Launch the SoMove software, select Modbus TCP as the communication type, and enter the target VFD’s IP address (default or temporary), with Modbus slave address set to 1.
3. In the Communication → Ethernet menu:
   • Set IP Mode to Manual
   • Enter a unique static IP for each VFD (e.g., 192.168.0.15)
   • Set subnet mask to 255.255.255.0
   • Set gateway to 0.0.0.0 or as required by your network
   • Set protocol to Modbus TCP (value = 0)
   • Set Modbus slave address from 1 to 9
4. Save the parameters and reboot the VFD to apply the new IP.
5. Repeat this process for all 9 drives, assigning unique IPs and Modbus IDs.

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5. HMI Modbus Register Mapping Example

Function	Register Address (Offset)	Data Type	Scaling
Command word (Run/Stop, Direction)	0	16-bit	Bit-level
Frequency setpoint (Hz)	1	16-bit	0.1 Hz per bit
Output frequency feedback	102	16-bit	0.1 Hz per bit
Drive status word	128	16-bit	Bit-level
Fault code	129	16-bit	Integer

Note: The ATV310’s Modbus register map starts at 40001. Some HMI brands use “offset 0”, so register 1 corresponds to 40001.

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6. Network Topology and Installation Practices

1. Star Topology: Connect all 9 VFDs and the HMI to a central switch.
2. EMC Wiring Practices:
   • Separate power and Ethernet cable routing to minimize interference
   • Bond all VFDs and the switch ground terminals to the control cabinet’s PE bar
3. Labeling and Documentation:
   • Clearly label each Ethernet cable with corresponding VFD number and IP
   • Place a printed network topology diagram inside the control cabinet

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7. Commissioning Procedure

1. Ping Test: Use a PC to ping each VFD’s IP address to verify communication.
2. HMI Communication Test:
   • Create a template screen for one VFD
   • Copy it for other VFDs, changing only the IP and Modbus ID
   • Test frequency control, start/stop, and feedback display for each unit
3. Stress Test: Run rapid start/stop cycles and observe response consistency and screen refresh speed (<200 ms is ideal).
4. Project Backup: Save each VFD’s .stm file from SoMove and the full HMI project into a version-controlled system.

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8. Performance & Limitations

Aspect	Details
Max refresh speed	Reading 10 registers per drive takes ~20–40 ms; 9 drives ≈ 200–400 ms total
Real-time behavior	Suitable for monitoring and basic control; not ideal for high-speed interlocks (<20 ms)
Redundancy	A single switch failure disconnects all; consider dual-ring switches for critical uptime
Security	Use VLANs or restrict switch ports to specific MACs to prevent unauthorized connections

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9. Maintenance and Optimization Tips

• Always backup SoMove configuration files after parameter changes
• Stick Modbus slave ID labels onto each VFD’s front panel
• Lock HMI screens with password protection to prevent accidental changes
• Annually inspect Ethernet switch ports; replace the unit if CRC errors or dust buildup is found

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10. Conclusion

By installing VW3A3616 modules and configuring individual IP addresses and Modbus IDs for each ATV310, a clean star-topology network can be built for direct HMI communication. This setup simplifies wiring, eliminates the need for a PLC, and significantly reduces costs. It is particularly suitable for small to medium-sized automation projects that require easy maintenance and flexible deployment.