A short discussion on the Regenerative Over-voltage Trip during Deceleration or Stop – Drive Error (E.Ov3) for VFD Inverter (FREQROL) drives
This type of error occurs when a VFD is requried to decelerate a load (or stop), within a time period which is too low, for a load too high (increasing the load inertia), taking into account the energy being regenerated from the motor, back into the VFD.
This error is intended to protect the inverter from absorbing this exessive energy load – and is therefore essential.
Lets look at the possible solutions:
First off, it must be pointed out that; CONTINUOUS REGEN TRIPS WILL REDUCE THE LIFETIME EXPECTANCY OF YOUR EQUIPMENT (INCL- MOTOR AND VFD).
That said, and clearly pointed out, the following possible solution options to look at;
Solution Option 1: Increase the deceleration time to a reasonable time period value. This time value is obviously a function, proportional to the load momentum being controlled by the drive, via the motor.
In other words, the larger the load, the more the momentum, thus the more the regen energy to be absorbed over time period (t).
Thus, if time period (t) is increased, more time is provided to absorb the excessive regen energy.
Traditionally, this variable is usually given by Pr.8 – Deceleration Time
Solution Option 2: Installation of a Braking Unit (FR-BU2) in conjunction with a Braking resistor(s) (FR-BR) to the drive.
This combination will allow the drive to dissipate the regen energy into the form of thermal heat (via the resistors).
it is important to point out that the size selection of the resistor value is proportional to the amount of braking energy (%) to be absorbed.
This addition is ideal for sharp braking applications (low braking time period (t), being Pr.8
Solution Option 3: Installation of a motor brake system (controlled via the VFD or a PLC) – usually in the form of mechanical brake clamping.
The intention of this braking option is to absorb the momentum energy, while it is still in a mechanical (kinetic) energy form, before it could be translated into electrical regen energy.
This too is ideal for applications where sharp braking (small Pr.8) value is required, along with a large load connected to the motor (large momentum).