Capacitor selection.

Jerry --

Rule of thumb for 230 volts is 20 microfarads of 370 volt oil filled capacitors per horsepower of driven motor. The 3 phase idler motor should be the next higher standard motor size above the driven motor. Don't use electrolytic caps. They'll overheat and explode.

I've had a setup like this on my 2hp 3phase Jet turret mill for 20 years and it works fine. The idler motor is a 3hp TEFC (keeps chips out) sitting next to the mill and wired to its own motor starting switch up on the mill's electrical junction box. The 40 microfarads worth of capacitors are mounted inside an small old steel fishing tackle box hanging on the side of the mill. I run it from an old water heater 30 amp 230 volt single phase circuit. Turn the idler on and it growls and complains until the driven mill motor is switched on then it quiets right down.

Ed Weldon