Mitsubishi FR-E700 Fault E.OV2 Regenerative Overvoltage
Getting the E.OV2 error on your Mitsubishi FR-E700 drive? Learn how to troubleshoot regenerative overvoltage during constant speed, adjust Pr. 22, and use braking resistors.
If you are operating a Mitsubishi FR-E700 series inverter and the display suddenly trips with E.OV2, you are dealing with a specific type of overvoltage. While most overvoltage trips happen during braking, the "2" in E.OV2 specifically indicates Regenerative Overvoltage during constant speed operation.
This means that while the motor was supposed to be running at a steady frequency, energy was "pushed" back from the motor into the drive, causing the internal DC bus voltage to rise above safe limits. Here is a human-made guide to help you stabilize your load and clear the fault.
What Triggers the E.OV2 Fault?
In the FR-E700, the DC bus voltage limit is typically around 400V (for 200V class) or 800V (for 400V class). E.OV2 triggers when this limit is exceeded while the drive is not in an acceleration or deceleration ramp. Common causes include:
- Sudden Load Changes: A mechanical surge or a "pushing" load (like a downhill conveyor or a large fan being moved by wind) forces the motor to spin faster than the drive's commanded speed.
- Stall Prevention Settings: If Pr. 22 (Stall prevention operation level) is set too low, the drive may react poorly to load fluctuations.
- Inertia Mismatch: The load is highly variable, causing the motor to oscillate and regenerate power.
Step-by-Step Troubleshooting & Remedies
1. Inspect the Mechanical Load
Since the fault occurs at constant speed, the mechanics are the first place to look.
- Verify Stability: Ensure the load is stable. Check for slipping belts, broken couplings, or intermittent jams that cause the motor to "kick back" energy.
- Overhauling Loads: If your application involves gravity (like a hoist or downhill belt), the motor is acting as a generator. You must use a braking resistor in these cases.
2. Adjust Stall Prevention (Pr. 22)
Parameter 22 defines the current level at which the drive begins to adjust its frequency to prevent a stall. If this value is too small, the drive might trigger overvoltage protections prematurely during a load spike.
- The Fix: Check the setting of Pr. 22. Ensure it is set to the motor's rated current or slightly above (usually 150% by default). If it was lowered manually, try increasing it to see if the E.OV2 fault clears.
3. Enable Regeneration Avoidance (Pr. 882 – Pr. 886)
Mitsubishi drives have a specialized "Regeneration Avoidance" function. This feature allows the drive to automatically increase its output frequency slightly to "eat up" the returning energy when the DC bus voltage starts to rise.
- Action: Set Pr. 882 (Regeneration avoidance operation selection) to "1" or "2" to enable the function.
- Fine-Tuning: Adjust Pr. 883 (Regeneration avoidance operation level) to set the voltage point where the drive starts to react.
4. Install a Braking Resistor or Brake Unit
If your parameters are optimized but the physical energy returning from the motor is simply too much for the capacitors to hold, you need a hardware solution.
- Braking Resistor: Connect a resistor to the P/+ and PR terminals. This allows the drive to "burn off" the excess DC voltage as heat.
- Parameter Check: When adding a resistor, ensure Pr. 30 and Pr. 70 are configured to tell the drive that external braking hardware is present.
Summary Checklist
| Checkpoint | Action |
|---|---|
| Mechanical Load | Ensure no sudden "pushing" or overhauling forces. |
| Parameter 22 | Verify Stall Prevention level is not too low. |
| Regeneration Avoidance | Use Pr. 882 to help the drive manage small surges. |
| Braking Hardware | Add a resistor if the load is high-inertia or downhill. |
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