my 2 speed motor is toast, I think...

[solarguy]

I just bought an early 80's series I bridgeport from a local guy. The price was good, he said everything worked.

Everything but the motor.

I'm looking for a reality check, that the motor really is bad, and it's not something obvious.

The motor is the 2 speed high/low, 2hp, 3-phase.

I have residential single phase 220V. I have a brand spanking new rotary phase converter, proudly made in the USA by American Rotary. It is designated a 3 hp rpc. This is the size they recommended for a 2 hp Bridgie. It starts, runs and acts normally. It is sitting about 8 feet from the (new) breaker panel, being fed by a short piece of 12-3 romex on a brand new 220V breaker.

The bridgeport will almost start in low speed, but the rpc shuts down. The rpc has a little board to sense when things have run horribly amok and shuts down to prevent damage to the phase converter. On high speed, it grunts a little, the spindle rotates very slowly, and the rpc shuts down almost immediately.

There is no mechanical binding, the brake is not on, when it does spin up the mill seems quiet enough and normal.

The motor is convertible to either 220V or 440V, and based on the wiring diagram, is currently wired for 220V.

The switch on the mill that selects high or low range had two crimp on terminals that easily pulled off the wire, replacing these with good solid crimps changed nothing. Everything else inside the switch looks virtually new. Contacts not pitted, snap action very crisp and definite. Nothing burned.

The master 3 phase disconnect switch on the back of the mill, everything is bright and tight inside.


For the motor, it doesn't matter which phase I hook the manufactured leg to, right?

I don't want to tear the motor off and take it somewhere, just to discover that I had the phases hooked up wrong or some other hiccup.

Thanks in advance,

troy

[gus]

sounds like the motor is not getting the 3rd phase. Make sure you have a straight path for all three phases from the converter to the motor.

check the output of the converter. 3rd leg will be unstable but measurable

mebee see if you can borrow some 3 phase item to test it with

[Al_The_Man]

If the seller claimed the motor was bad and it is hooked up right, there is a good chance the motor is actually bad, either one phase open internally or burnt winding.
You could also check for grounds with a megger.
Make sure any overloads or fuses are not tripped or blown.
Run it in to a local motor winding shop for a quick test if you do not have true 3 phase available to check it.
Al.