Trying to find info about adding capacitors to 25hp 240v 3 phase ac motor single speed that runs a cat pump at my car wash? There seems to be commercial units but they hook up to main line and as I have two
25hp motors that start together at times this doesn't seem reasonable.How would I size the capacitors? I do pay a demand charge.Thank you PAUL
If you have demand metering, then inhibiting the motors from starting simultaneously might yield greater savings. Use a couple of time-delay relays such that if motor A(B) starts, then motor B(A) is inhibited for
5-10sec. That way you don't get a surge that registers as a high demand.In addition, check to see if there any other loads that you can "shed" while running the motors.
Several projects I have had cut power bills by stopping steam generators when pumps were running.
Starting of motors doesn't have much effect on demand which is based on a longer period of time to allow, fairly, for starting transients. What the capacitors do is provide compensation for lagging power factor of the motors and this will affect demand. Capacitors of about 5KVA/phase for a 25HP motor would be an initial guess (going to full pf compensation might entail a higher incremental cost that what would be saved.
Maybe give this a try lad
Kirk Johnson "Extreme Stretching Specialist"
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.