Running 3 phase 780s on single phase power

You can say that again. A few years ago at work we had a vacuum motor which was plugged into a *normal* UK 3 pin 240v socket. When switching it on we often saw blue or green sparks from the socket and eventually got an electrician in to advise on various health & safety issues. Said vacuum pump is now connected to the mains via a special box (sorry don't know the name) that looks just like the start/stop box you get on tooling machinery (industrial drills, lathes etc.), with the green button for on and red for off. Sorry for going OT. Regards, Andrew B aliensrcooluk at yahoo.co.uk --- On Wed, 21/1/09, Paul Koning <Paul_Koning at dell.com> wrote: From: Paul Koning <Paul_Koning at dell.com> Subject: Re: Running 3 phase 780s on single phase power To: cctalk at classiccmp.org Date: Wednesday, 21 January, 2009, 5:08 PM Motors are the original "high starting current" devices. That's why protection devices for motors are different from conventional circuit breakers. A "locked rotor" motor draws a LOT more current than a spinning one -- some vague memory says it might be 10x or so. And the initial surge as the motor is accelerating looks like the locked rotor case, briefly. How briefly depends on the machinery that the motor is driving; if it's a high load it could take some time before the motor is spun up to speed. paul