Help with 240V lathe motor. What is this mystery box?

Hello all,

I'm not sure if this is right place to ask this as there is no VFD or phase converter involved but I expect there are many knowledgeable people here who might be able to help.

I have a 240V single phase motor that came with a Schaublin lathe that I am restoring. The motor looks like it has seen better days but I had it running when I received it last year. In the mean time it has been sat in the garage and then gone through a house move.



This is the state of the wiring at the moment! I have limited electrical knowledge but I have ascertained that the cylinder is the starting capacitor, and as the motor starts I can assume that this is ok.

My question is the function of the other sealed unit?




When I plugged in the motor again after it's ordeals it started running very hot and started smoking after about a minute of running, so I switched it off pretty quickly.

I suspect it might just be that the windings are shot but wanted to find out the function of this black box before I go any further.

Here is the motor plate for reference:



Sorry for the rotation issues in the photos, they are the correct orientation on my computer

Any advice would be greatly appreciated.

Matt

Without having a clear shot at the wiring my first guess would be some sort of current relay for control of the start winding instead of the usual centrifugal switch. It is common to see such an arrangement on small, cheaply made appliance motors. It's less common with standardized-frame industrial motors but they do exist. Usually in places where a very compact, high power-density motor is required.

If you have a clamp-on ammeter, measure the current on the start and run windings during operation. Make sure the run windings are within the motor's nameplate FLA. Make sure the start winding is cutting out properly once the motor has started. That will give you a direction to work from.

Secondly I might suggest tracing out the wiring and drawing up a basic diagram so we can see how things are connected without having to trace out a rat's nest remotely via JPEG.

yup if you don't hear a click when it starts or stops from the motor then more then likely there's no centrifugal switch and that's a electronic switch doing the same thing bringing the start cap in to play . at one of the shops i play at they have two jet tanks for cleaning parts that have 5hp 240 volt single ph. motors with start and run caps they had style of electronic switch on them that went bad and the replacement cost was about 275 each so all i did being the motor is with in 2 feet of the start timer was to remove the electronic switch install a momentary manual push switch so now when you start it you first push in one before turning the other and after it starts stop pushing the start cap switch and yes one could use a delay timer with a relay and yes one could get electrocuted if there was a short by having both hands on the machine at the same time but hey life is about taking a chance

Since all the wires are different colors you can make a drawing. That will give a clue.

sounds like sparky has got it right.

have you contacted Schaublin? it really shouldn't be hard to find a wiring diagram for this.

it does sound like the starting winding isn't cutting out. once you get the diagram, confirm the relay is operating, but don't let it run long enough to smoke!

P.S. there is a Schaublin section on here, that's the place for this post