Electriman
Senior Member
- Location
- TX
Is there any chart or table that determine the VA rating of electric motors or should I use NEC tables and multiply the current by voltage?
I think you’re looking for KW. 760 watts per Hp was schoolbook IIRC.Is there any chart or table that determine the VA rating of electric motors or should I use NEC tables and multiply the current by voltage?
Single phase or three phase?Is there any chart or table that determine the VA rating of electric motors or should I use NEC tables and multiply the current by voltage?
That will give output power. Maybe the OP wants to get input kVA.I think you’re looking for KW. 760 watts per Hp was schoolbook IIRC.
746. I have been corrected.
BothSingle phase or three phase?
I think you’re looking for KW. 760 watts per Hp was schoolbook IIRC.
746. I have been corrected.
That is right.That will give output power. Maybe the OP wants to get input kVA.
OK.Both
That's why I mentioned nameplate data. That doesn't mean it will necessarily run at that at all times. Loading may be cyclic for some applications.It will change with load and applied voltage.
But simply multiplying volts times amps gives you VA. For 3 phase use amps * volts (line-line) * 1.732.
-Jon
OK.
For single phase you can take the product of nameplate Volts and Amps for input VA.
For three phase you need sqrt(3) times the Volts and Amps.
Service factor is not something we come across on this side of the pond. Continuously maximum rated (CMR) is normally what we use. Sometimes, an intermittent short term rating is given for particular applications.I’m guessing the motor amperage should be multiplied by the service factor first to get the maximum possible amperage it could possibly see in normal use.... thoughts on this?
I would use the NEC tables for current (with the appropriate exceptions), then calculate kVA based on the normal formula for single or 3 phase.
It’s not a good idea to use Service Factor continuously. It CAN be done and is often done by machinery OEMs in order to avoid having to buy a larger motor, but just because you can, doesn’t mean you should. The end user is who has to live with the long term consequences because the motors will likely outlast the OEM’s warranty.