GE MicroVersaTrip Plus Trip Unit Sizing?
GE MicroVersaTrip Plus Trip Unit Sizing?
(OP)
Installing an air compressor with a 400Amp motor, will be powering from a GE AKR-9D-30H 800A frame breaker. The breaker currently has a 800Amp MicroVersaTrip Plus Trip unit (A208LSG) in it. My question is can I just replace the 800A (TR8B800)chip with a 400Amp chip (TR4B400)or do I also need a 400Amp Trip unit (A204LSG). Thanks






RE: GE MicroVersaTrip Plus Trip Unit Sizing?
RE: GE MicroVersaTrip Plus Trip Unit Sizing?
RE: GE MicroVersaTrip Plus Trip Unit Sizing?
The correct rating plug would be TR8B400.
Dissecting the part number helps to understand this. The 8 represents the rating of the circuit breaker current transformers, in this case 800 amps. The 400 represents the continuous current rating of the circuit breaker.
Another option, as pointed out by DPC, is to reduce the long time pickup setting to 0.5x. The pickup setting is a multiplier that is applied to the continuous current rating. In this case, 800 x 0.5 = 400 amps.
For setting the instantaneous pickup, keep in mind that this is also a multiplier of the continuous current rating. Thus, for a 2400 amp instantaneous trip (6x of motor current) the setting would be 3x. This is because 800 x 3 = 2400.
RE: GE MicroVersaTrip Plus Trip Unit Sizing?
The typical scheme would be to use the breaker as the short circuit protection only, then have a TOL or MPR on the motor controller.
"Will work for (the memory of) salami"
RE: GE MicroVersaTrip Plus Trip Unit Sizing?
RE: GE MicroVersaTrip Plus Trip Unit Sizing?
That being said, I agree with Jraef that a combination starter with instantaneous protection and overloads will provide better protection that is easier to coordinate than a LSG breaker. However, I have seen LSG breakers often used as motor starters but this is primarily in power generation stations.