carl r edwards
Member
- Location
- Virginia Beach, Virginia
I am a pump station contractor, and when starting up a station with two 20 hp, dry-pit submersible, 240 volt, 3-phase sewage pumps, whose Pump Control Panel had 2-phase soft starters for both pump motors, one of them exhibited a nasty-sounding starting noise. The leads were swapped, and the noise stayed with that motor. It was suggested that the starting noise might be an unintended consequense of the 2-phase soft starter, so we ultimately installed a 3-phase soft starter for that motor, which cured the problem. Swapping leads again, the other motor is OK with either the 2- or 3-phase soft starter, but the problem motor makes the noise on the 2-phase, but not on the 3-phase soft starter. It seems to be common knowledge (or common sense) that the 3-phase soft starter is superior and applies its torque more evenly, but I can't seem to find any documentation to the effect that a tendency for motor starting noise is a drawback of 2-phase soft starters. Can anyone steer me to some technical support, or shed any light on this?