Hi!
Just seeking help in regards to sizing cables to 415v 3ph motor's (DOL) on an industrial site on the basis of voltage drop. I beleive one technique is to use the locked rotor current and the power factor of the motor at the instant of start (locked rotor pf ?) in the voltage drop calculation (info available from motor vendor's I presume). Obviously if just the LRC was used, the cables would be huge, so I'm guessing that the reduced pf at start is what brings the cable size down? These cable sizes seem to be a couple of sizes up from what they may have been if the volt drop calc was done using just the full load amps. What are the main factor's/reason's to consider when sizing these cables: motor terminal volts to enable the motor to start under load; preventing excessive voltage drop on the MCC bus?? Also thanks to those who replied to my "under voltage relay setting" enquiry. I am still checking into that problem.
Just seeking help in regards to sizing cables to 415v 3ph motor's (DOL) on an industrial site on the basis of voltage drop. I beleive one technique is to use the locked rotor current and the power factor of the motor at the instant of start (locked rotor pf ?) in the voltage drop calculation (info available from motor vendor's I presume). Obviously if just the LRC was used, the cables would be huge, so I'm guessing that the reduced pf at start is what brings the cable size down? These cable sizes seem to be a couple of sizes up from what they may have been if the volt drop calc was done using just the full load amps. What are the main factor's/reason's to consider when sizing these cables: motor terminal volts to enable the motor to start under load; preventing excessive voltage drop on the MCC bus?? Also thanks to those who replied to my "under voltage relay setting" enquiry. I am still checking into that problem.
