ABB sine wave filter

If the ABB filter produces 10% voltage drop at the motor, it means that the filter reactor is around 16% impedance (10%Voltage Drop/60% reactive current=16% reactance) which is to me excessive. This will create a slugish speed control, going up and down around the operating speed. This unstable reaction on a fan is annoying but on a pump is unsustainable as it could damage the pump over time. I suggest that you go back to the ABB designer to redesign a suitable drive filter that will bring back the filter output voltage to the motor rated value, using an auto-transformer part of the filter design.

Beside the technical aspect, the cost of sine wave filters is very high even compared to the motor, while the physical size requires to have enough space in the electrical room. There is also the fact that capacitors are the most sensitive components regarding temperature, making a drive system less reliable.

Under reduced voltage, the torque will decrease as the motor flux is reduced by the reduction of voltage. The rated current of the motor is still the same so the torque capability remains a function of the % of voltage reduction only (not a square relation). Consequently, the power will also be reduced by the factor reduction of voltage.