ovA Over-Voltage during Acceleration fault in delta drive

ovA Over-Voltage during Acceleration fault in delta drive troubleshooting

Description

ovA indicates that the DC bus voltage inside the VFD has exceeded its maximum limit (e.g., 410V for 220V class, 820V for 440V class) while the drive was accelerating. This is a less common fault than over-current during acceleration but points to specific power supply issues.

Causes

1. Input Voltage Surge: The mains power supply might have spiked. If using a capacitor bank for power factor correction on the main grid, switching it on can cause voltage swells.
2. Restarting a Spinning Motor: If the VFD attempts to accelerate a motor that is already spinning (windmilling fan), the back EMF generated by the motor can sum with the drive voltage, causing a DC bus spike.
3. Peripheral Hardware: Incorrectly wired braking units or faulty internal capacitors.

Solution

To fix ovA:
1. Check Input Power: Measure the input voltage (R-S-T). Ensure it is within the drive's rated tolerance (usually +/- 10%). Install an AC Line Reactor (Input Choke) to absorb grid spikes.
2. Enable Speed Search: If the application involves high inertia fans that spin freely, enable the "Speed Search" or "Catch on Fly" parameter. This allows the drive to detect the motor speed before engaging, preventing voltage collisions.
3. DC Bus Check: Measure the DC bus voltage terminals (+ and -) with a multimeter to verify the internal sensing is accurate.