An interesting single phase motor

This interesting motor came with a small lathe I picked up for parts. It is 115-230 volt, single phase, reversible and has capacitor start. What makes it interesting is that it will instantly reverse directions on the fly, without the need to stop or slow down first. And if that isn’t enough, it has an electrical, non-mechanical, brake built in and the brake energizes when the power is disconnected.
I have been doing this stuff for decades and I have never seen another single phase motor like it. As a point of interest, the motor does not have brushes and a relay has been used in lieu of a centrifugal start switch. This type of motor is such a game changer it makes me wonder why it has not become the standard for single phase tool motors.
I installed this motor on my drill press with a foot switch and the brake, along with the instant reverse, has made drilling and tapping so fast and convenient that it is damn near fun.
Have fun with it, Mike

Pretty neat, I have seen one other that would do that, it was on a small lathe, maybe a Southbend. Might have been made by G.E.
James

Is this one of those fancy pants motors that was common on high end sewing machines?

that is just a simple capacitor start motor (capacitor motor) using a potential relay instead of a centrifugal switch to switch the starting cap and winding out after you fire it up. The one you have is an older model with the totally open relay instead of the little black plastic cube.

It is basically the same design as the motors in the sealed compressors in A/C units. The newer compressors use 2 capacitors to increase their efficiency. (capacitor start / capacitor run) whereas the older ones used just one capacitor (capacitor start / induction run) this design with one capacitor is what we all just refer to as a "capacitor motor".

Frank

Except that this motor will reverse while running. The starting winding must be engaged when he hits reverse. Presumably the connection to the potential relay is switched in a way to reduce the voltage on it or reversed so voltages cancel, or whatever. It has large contacts that show considerable arcing, so it has been switching a load. They are larger than I would expect on a centrifugal switch for that size motor.

Bill

I would like to get my hands on one of these. Does anyone have a source?

I wonder if it might have been designed for use in heavy-duty garage door openers? Regardless, it would be nice to find out where to buy them.

W.W.Grainger (and others) used to sell them. IIRC, they are called "instant reversing" motors.


Frank

No magic to it, the elimination of the centrifugal switch is all it takes to do that. Plenty of people do that with after-market potential relays rather than repair old centrifugal switches that are no longer made. Without having to wait for the speed to drop to allow reconnecting the start winding, you can instantly reverse it.

But almost nothing is harder on a motor than plug reversing! That's why you don't see it done more often, because it's not necessary to take that risk most of the time. You DEFINITELY don't want to do this on a cheap POS motor or it will come to pieces.