Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  1. mhuckaby

    4160V Motor Quick Connection

    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...
  2. mhuckaby

    Determing Power Factor From Amp Reading Only

    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...
  3. mhuckaby

    Motor Starting Ground Fault

    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...
  4. mhuckaby

    IEC 50 hertz motor amps

    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...
  5. mhuckaby

    Indoor Unit Substation Grounding

    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...
  6. mhuckaby

    Dry Type versus Oil Filled Transformer

    Thanks for your help! Michael
  7. mhuckaby

    Dry Type versus Oil Filled Transformer

    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...
  8. mhuckaby

    13.2kV & 480V Conduit Separation

    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
  9. mhuckaby

    Unbalanced motor starting currents

    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...

Part and Inventory Search

Back
Top