system voltage drop
system voltage drop
(OP)
A senior electrical designer is trying to convince me that on a 480 system voltage drop isn't really a consideration. Here's the situation. We have a feed to an 800A MCC with about 434 TCHP / 514 KVA of motor load. He insists that since the voltage drop over the feeder is on 1-2% that the voltage at the MCC bus is only around 470V. I am trying to explain that the total system voltage drop (%) isn't equal to the sum of each branch circuits voltage drop %. I calculated 9.5% voltage drop at the bus, 434V! The overall substation bus was, 440V. The total design load is 1380 kva on a 1MVA trans. This is a continuous production line, with probably an 80% DF and 10% diversity. Am I the naive one here? What would be a simple explanation / brief example to calculate the overall system voltage with just a few motors?
Thanks j.d.
Thanks j.d.






RE: system voltage drop
The Eaton Cutler-Hammer Consulting Engineering guide has some simple tables that will allow you to get a good handle on approximate voltage drop through a feeder, based on expected load current. You also have to factor in the voltage drop across the transformer.
The power factor of the load has a significant effect on voltage drop.
RE: system voltage drop
RE: system voltage drop