ovn Over-Voltage during Constant Speed fault in delta drive

ovn Over-Voltage during Constant Speed fault in delta drive troubleshooting

Description

ovn indicates the DC bus voltage is too high while the motor is running at a set speed. Since there is no deceleration occurring, regeneration shouldn't technically happen, making this fault indicative of input power or specific load types.

Causes

1. Input Voltage High: The facility's transformer tap might be set too high, or there is unstable grid power.
2. Overhauling Load: If the load pushes the motor (e.g., a downhill conveyor belt or an elevator going down with a heavy load), the motor runs faster than the drive command, generating energy continuously.
3. Capacitor Issues: The drive's internal DC bus capacitors may be degrading, causing voltage ripple that is interpreted as peak over-voltage.

Solution

Focus on the supply and the load nature:
1. Check Mains Voltage: Monitor the incoming AC voltage over time. If it consistently runs high, adjust the facility transformer.
2. Braking Unit: If the load is "Overhauling" (pushing the motor), you absolutely need a Braking Resistor and potentially a Braking Unit (chopper) for larger drives to dissipate this constant energy generation.
3. Input Reactor: Install an AC input reactor to smooth out voltage fluctuations entering the drive.
4. Bus Measurement: Verify the DC Bus voltage matches the display on the keypad (often accessible via the 'User' menu or 'u' parameters).