We need to change rotation on a 4160V, 500hp (50 Amp) motor every few months.
Because of NFPA70e rules, we can no longer do it in the MCC bucket (can't shut off the line side of the switch).
The motor is fed with an armored cable. We can change the motor connection box to about any size we...
Is it possible to determine the power factor of a motor when you only have the amp reading off of the motor? Is there a way to interpolate the approximate power factor from the amps reading only?
We have a motor on an air compressor with a GE Multilin meter. The meter has CTs, but PTs.
The...
I have run across a couple of instances where ground fault relays trip when induction motors are starting.
For example, a 75hp, 480V, 3ph motor (113 FLA) would trip the main breaker on a ground fault condition during startup. The ground fault trip level was set at 160 Amps.
We raised the trip...
When designing electrical circuits for 3-phase NEMA (60hz) motors, I use table 430.150 in the NEC.
I have found these values to be higher than the typical nameplate amperages on the actual motor, thus I factor of safety built into my design.
Is there a corresponding table with motor amps that...
We have an industrial customer that wants to put an indoor unit substation indoors. The specs are:
Square-D unit substation
13,200V primary fused switch
13,200V-->480/277V 2500kVA transformer
3000A main switchboard (42kA interrupting rating)
This equipment will be located on the 2nd floor of...
We are working on selecting a new transformers and main switchboard for an industial facility. We plan on using two 2500 kVA transformers (13,200 to 480 volts) and a main-tie-main main switchboard.
We can locate the transformers either indoors or outdoors.
What are the advantages and...
Is there any reason (safety, technical, or otherwise) that 13.2 kV and 480V conduits cannot be run on the same conduit rack?
If so, what should be the minimum separation between conduits of these two voltages?
Thanks!
Mike
We have a 460V/3ph/60hz 125/62.5 hp 143/99amp dual speed motor that is regularly tripping a main breaker on startup in low speed. The circuit breaker trips about once every 5 low-speed starts. We have recorded amp readings of 1700+ on A phase, 1300 on B phase, and 1100 on C phase.
The startup...
