Quote Originally Posted by rpoldervaart
Wow. Glad I posted a popular topic. I wasn't aware of the Power Factor. And it sounds like I need to do some more research on calculating motor costs.

I've found several articles on the web to read, but alas, my work is calling me... In addition to the PF number, there also seems to be a .00173 number that is also being thrown in. This was used to calculate kVA. Siting from http://www.cop.com/SEUhtmDOCS/SEU17.htm, the formulas are:
kVA = 0.00173 * V * amps

This is for a 3 phase motor. Standard motors are kVA = 0.001 * V * amps

kw = kVA * PF * .01 (PF being % between 1-100)
running for one hour would be kwh and then multiply by number of hours times cost per kwh.

Now, looking at the calculations above and the linked site, they are using the stated amps on the nameplate, where I am using the measured amps on my amp meter. It looks like the only place they're using the measured amps is to help calculate the PF.

So what is the 0.00173 number? If I throw in the .00173 number and a 90% power factor, I'm actually increasing my kwh because the .00173 increases more than the .9 decreases it.

Robert
See comment above.

Also, to make it simple, kwh = Volts * Amps / 1000 * (PF%/100)