INVT GD20, GD10, GD200A VFD Error Codes Breakdown and Diagnostics
When fault codes appear on the display of INVT GD20, GD10, or GD200A inverters, the drive blocks operation to protect the internal silicon power modules. Most shutdowns caused by overcurrent (OUT), overvoltage (OV), undervoltage (UV), or overload (OL) faults originate from incorrect acceleration or deceleration settings, motor defects, or mains power instability. Our engineers recommend checking the acceleration and deceleration time constants first, and measuring the actual line voltage directly at the drive power terminals.
Every single fault code points to a specific physical condition. Because modern vector-controlled drives, such as the GD20 and GD200A series, run advanced control algorithms, a poorly executed motor parameter autotuning sequence will lead to current trip events as the drive transitions to run frequencies. The smaller GD10 series, on the other hand, operates purely on scalar V/f control, meaning that during high-inertia operations, it trips more frequently due to mechanical shaft overload.
The table below provides a detailed troubleshooting grid containing the main fault codes of INVT frequency converters, their root causes, and practical repair actions:
| Error Code | Fault Name | Root Physical Cause | Corrective Action |
|---|---|---|---|
| OUT1 | Overcurrent during acceleration | Acceleration rate is too steep, or there is a short circuit in the motor windings or output cabling. | Increase the acceleration time in parameter P00.11. Run a motor autotuning sequence via P02.07. Test the motor insulation with a megohmmeter. Reduce manual torque boost in P01.01. |
| OUT2 | Overcurrent during deceleration | Deceleration rate is too steep for the inertia of the connected load. | Increase the deceleration time in parameter P00.12. Check the dynamic braking resistor connections and parameter P08.37 settings. |
| OUT3 | Overcurrent during constant speed | Sudden load spike or severe mechanical jam on the motor shaft. | Check the mechanical assemblies for mechanical binding. Make sure the shaft turns freely. Decrease load. |
| OV1 | Overvoltage during acceleration | Bursty or unstable input line voltage, or regenerative feedback during ramp-up. | Check the stability of the incoming AC line voltage at terminals R, S, T. |
| OV2 | Overvoltage during deceleration | Regenerative energy returned from the motor due to sudden deceleration of a high-inertia load. | Increase the deceleration time in parameter P00.12. Install a dynamic braking resistor (for GD20/GD200A, connect directly to (+) and PB; for GD10, use an external braking unit). Tune parameters P08.37 and P08.38. |
| OV3 | Overvoltage during constant speed | Rapid line voltage surges or regenerative forces pulling the motor shaft faster than synchronous speed. | Install an AC input reactor to smooth line surges. Verify that the overvoltage protection levels in P08.38 are correct. |
| UV | Undervoltage on DC bus | Critical drop in the AC input line voltage, loss of an incoming phase, or a failing internal pre-charge relay. | Measure the incoming AC line voltage under full load. Check the contact health of the input contactor and circuit breaker. |
| OL1 | Motor overload | Motor runs above its rated current limit for an extended period, overheating the windings. | Reduce the mechanical load on the machinery. Verify that the motor rated current in P02.05 matches the physical motor nameplate rating. |
| OL2 | VFD overload | Output current exceeds the VFD overload threshold rating. | Select a VFD with a higher power rating. Decrease the carrier frequency in parameter P00.14 to reduce switching losses in the IGBT modules. |
IGBT and Rectifier Stage Diode Testing with a Digital Multimeter
Before unmounting or sending a faulty frequency inverter to a repair center, we recommend conducting a manual test of the input rectifier stage and output IGBT power modules. You only need a standard digital multimeter set to diode test mode. Always perform these measurements on completely de-energized hardware.
Follow this exact testing sequence for the INVT power modules:
- Disconnect all AC power connections from terminals R, S, T and remove the motor cabling from terminals U, V, W. Wait at least 15 minutes to allow the DC bus capacitors to discharge fully. Use a voltmeter in DC mode to measure across terminals (+) and (-) — verify that the residual voltage is below 36 V before proceeding.
- Switch the multimeter to diode testing mode (the display will show the forward voltage drop in millivolts).
- Input Rectifier Test: place the red multimeter probe on the negative DC bus terminal (-) and touch the black probe to the R, S, T terminals sequentially. The meter should display a forward drop of 300 to 700 mV (the forward drop of the rectifier diodes). Next, move the black probe to the positive DC terminal (+) and touch the red probe to terminals R, S, T sequentially — the meter should read 300 to 700 mV. Reversing the probes must show an open circuit (O.L on screen). Any short or zero drop means a diode is blown.
- IGBT Output Stage Test: place the red probe on the negative terminal (-) and touch the black probe to terminals U, V, W sequentially. You should read a forward drop of 300 to 700 mV (the forward drop of the freewheeling diodes inside the IGBT package). Next, place the black probe on the positive terminal (+) and touch the red probe to terminals U, V, W sequentially — you must read 300 to 700 mV. Reversing the probes should result in an open circuit (O.L). A zero drop or continuous beep indicates a blown power transistor on that phase.
CAUTION: NEVER confuse the low-voltage control board logic ground (GND terminal) with the high-voltage power bus negative terminal (-) or (N).
Connecting multimeter probes, oscilloscope grounds, or test sensors to the low-voltage GND terminal while attempting to measure high-voltage power lines will immediately vaporize the control board circuitry, destroy the IGBT gate drivers, and lead to total VFD failure that is not covered under warranty.
Dynamic Braking Resistor Selection and Parameter Configuration
For applications where VFDs operate high-inertia mechanisms (such as massive ventilation fans, overhead cranes, or centrifuges) or require rapid deceleration, dynamic braking is necessary. During deceleration, the motor behaves as a generator, feeding energy back into the VFD, which raises the DC bus voltage and triggers an OV2 fault. This excess energy must be dissipated through a dynamic braking resistor.
Be aware of the physical hardware differences between the INVT series:
- The INVT GD20 and GD200A series VFDs include a built-in dynamic braking chopper. The braking resistor is wired directly to the power terminals (+) and PB.
- The budget INVT GD10 series lacks an internal braking chopper! Wiring a resistor directly to the power terminals of a GD10 VFD will cause it to burn out or damage the DC bus. To use dynamic braking with a GD10 drive, you must buy an external braking unit, wire it to terminals (+) and (-) / N, and then connect the braking resistor to this external chopper unit.
To configure and activate dynamic braking, use the parameters listed below:
- P08.37 (Dynamic braking duty ratio). This sets the chopper active duty cycle percentage. The factory default is 10%. If an OV2 fault continues to trip during deceleration because the resistor cannot dissipate heat fast enough, this value can be increased (up to 50% or 100% depending on the resistor cooling conditions).
- P08.38 (Dynamic braking start voltage). This determines the DC bus voltage threshold that opens the braking chopper. For 380 V drives, the default start voltage is approximately 700 V; for 220 V VFDs, the threshold is about 380 V.
We have compiled a precise selection guide matching motor capacities to braking resistor values, based on official INVT guidelines and real-world commissioning experience from our technical engineers:
| Motor Rating (kW) | Input Power Class | Recommended Resistance (Ohms) | Minimum Resistor Power (W) |
|---|---|---|---|
| 0.75 kW | 1-phase 220 V | 150 Ohms | 80 W |
| 1.5 kW | 1-phase 220 V | 100 Ohms | 150 W |
| 2.2 kW | 1-phase 220 V | 70 Ohms | 250 W |
| 0.75 kW | 3-phase 380 V | 300 Ohms | 150 W |
| 1.5 kW | 3-phase 380 V | 220 Ohms | 250 W |
| 2.2 kW | 3-phase 380 V | 200 Ohms | 300 W |
| 4.0 kW | 3-phase 380 V | 130 Ohms | 400 W |
| 5.5 kW | 3-phase 380 V | 90 Ohms | 500 W |
You can purchase matching resistors directly in the braking resistors section on our website.
Frequently Asked Questions
Why does the INVT GD20 VFD trigger an OUT1 fault upon motor startup?
The OUT1 fault indicates overcurrent during acceleration. This is typically caused by an excessively short acceleration time set in parameter P00.11, incorrect motor data configured in parameter group P02, or a short circuit in the motor windings or output cable. To resolve this, increase the acceleration time, perform motor autotuning via P02.07, or check the motor insulation with a megohmmeter.
Can a braking resistor be wired directly to the power terminals of the INVT GD10 drive?
No, direct wiring of a braking resistor to the (+) and (-) terminals of the GD10 series is strictly prohibited because this VFD does not contain an internal braking chopper. Attempting direct connection will result in continuous current flow, burning the resistor or damaging the VFD DC bus. To use dynamic braking with GD10, you must install an external dynamic braking unit.
What value should be configured for parameter P08.37 for optimal dynamic braking?
Parameter P08.37 sets the dynamic braking duty ratio (chopper duty cycle). The factory default value is 10%, which is suitable for light loads. For high-inertia systems where the VFD shuts down with an OV2 fault during deceleration, you can gradually increase this ratio to 50% or 100%, provided the resistor has sufficient heat dissipation and ventilation.
How do I test the VFD IGBT power transistors using a digital multimeter?
Set the multimeter to diode test mode. Place the red probe on the negative DC bus terminal (-) and touch the black probe to the U, V, W output terminals sequentially — the meter should read a forward drop of 300–700 mV. Next, place the black probe on the positive terminal (+) and touch the red probe to U, V, W — it should read 300–700 mV. Reverse tests must show open circuit (O.L).
What does the UV fault code represent on the display of INVT GD200A inverters?
The UV fault stands for undervoltage on the DC bus. This fault occurs due to a sudden drop in the input mains voltage, a loss of one of the incoming phases, or burnt contacts on the input contactor or circuit breaker. To troubleshoot, measure the incoming AC voltage under load and verify the integrity of all wiring and switching components in the line.
Conclusions and Technical Assistance
Resolving faults on INVT frequency converters begins with the correct adjustment of acceleration, deceleration, and motor autotuning parameters. If OUT or OV faults occur even under no-load conditions, perform diode tests on the input rectifiers and output IGBT modules following our instructions. We carry original manufacturer accessories and components at our Kyiv warehouse. If you need to replace your drive, feel free to choose a new controller from our frequency converters catalog, or select proven industrial drives from our INVT VFDs section, which lists all GD20, GD10, and GD200A models with official warranties.
