Hi,have a 25hp piston air compressor wired to run on 230v 3 phase. I do not have the availability of 480v 3 phase. When the unit kicks on there is noticible drain on the whole shop lights, machines etc. Is there a way to add capacitors to help on start up??
I have a large enough transformer to boost to 480v but my understanding is that energy is constantly used even when nothing on the out put is running. Am I wrong? This compressor if wired 480v would draw half the amps and probably solve the problem. My power company does not want to run 480v out to me. thanks, Jon.
3 phase motors do not use capacitors, and adding a capacitor anywhere will only make the problem worse. Nor will a step-up transformer work, because it still needs at least as much current on the 240v side. Either the transformer on your power pole is too small to run this motor, or else you have some extra resistance in the leads from the power pole to the motor.
Stepping the voltage up in the shop will not reduce the current draw from the 240 VAC line. The energy use with a transformer will be just a bit higher (due to losses in the transformer) and the only current it draws with no load is magnetizing current.
You may be able to reduce the starting current with use of a capacitor bank similar to a KVAR unit. It may also save you money with your energy bill with using one. Capacitors are cheap and the bank can be assembled easily using oil caps.
But the other 2 responses are correct, increasing the voltage will not help you with the problem. The motor will pull the same amount of wattage no matter what. You would make the compressor less efficient with the transformer because the transformer isn't 100% efficient and it would waste energy as heat.