On Sat, 13 Mar 2004 12:51:32 -0600, "Bob Swinney" wrote:
Gary sez: " These are the kinds of home made converters typically discussed
here.
They are safe to start and walk away, reasonably confident that you
can come back and not find the shop has burned down due to a momentary
power failure."

Good point - let's hope all the RCMer's home made converters are the safe
type!! But a question remains: That is, suppose someone had a rotary phase
converter with pony-start or rope-start and no fail safe (power failure)
protection. Also, suppose that the converter was connected through a
properly sized set of breakers. *Emphasize properly sized*
The converter is running unattended and the power fails. When the power
returns, couldn't the circuit breakers be depended upon to trip under the (5
or 6 times normal running current) inrush? I'm beginning to see some light
here --
"Duh! the breakers are already sized to accommodate the inrush current and
they might hold long enough start some crispies in the motor!!!

Because the motor won't actually try to spin up when fed only 1 ph, the starting
surge isn't all that much over normal running current, impedance limited. So the
breaker probably won't trip. But the converter motor will just sit there humming,
no cooling air flow, and will rapidly overheat. The chance of electrical fire is high.
That's why dropout protection is a must.

Gary