Reversing Motor

Hi Keith,
The NVR switch in the picture is not suitable for the way I suggested wring it. This is because both ends of the coil are directly connected to the output. In this NVR switch on ebay there is a picture showing that one end of the coil winding is brought out to a separate terminal. (Marked A1) Any NVR which with one end of the coil brought out to it's own terminal can be used. It looks like there is no direct connection between K and AZ. The way your meter behaved is what I would expect when it is effectively connected to a capacitor. (In this case the run capacitor..I think the only way to confirm that the centrifugal switch is not the changeover type that Noel suspects is to partly dismantle the motor.

Les.

Thanks for the advice on the NVR

What would I be looking for if I could see behind the board?

I would like to do what I can, not just for my benefit but this will probably help lots of others too 

Edited By Keith Jenkins 1 on 09/02/2021 21:19:30

You would be looking to see if there are any wires or links on the back of the board. For example terminal K only has a white wire from the run capacitor so unless there is something is connected to K on the underside of the board the run capacitor is not serving any purpose. IF Noel's suspicion that the centrifugal switch has changeover contacts is correct and the NO contact is connected to terminal K then the run capacitor would be connected in series with the run winding when the motor was up to speed. (Which is how it should be in circuit when the motor is up to speed.) I have only ever seen centrifugal switches which connect the start capacitor in parallel with the run capacitor until the motor is up to speed. Most motor are easy to take apart. There is normally 4 threaded rods holding the end plates together. There may also be bearing retainer plates that are held in place with two screws close to the bearing housings. The bearing will probably remain on the shaft when an end plate is removed. Take care to note the position of any springy washers that might be in the bearing housing.

Les.

Thanks Les,

I wasn't intending to take the end off the motor but because there has been so many responses and it seems there may be some anomalies that need clearing up, I will have a look in the next day or two

Many thanks

Les, It is NOT a suspision ! I have seen a motor of this type once before. There is NO need to take the motor apart as I have posted the photos of what you will see. If you understand the redrawn circuit diagram from Tubal Cains book then all should be clear, it also tallys with the wiring diagram on the OPs motor cover plate.

That you and others have never seen a motor of this type does not mean it does not exist, and Tubal Cains listing is as a SPECIAL !

I would like to thank you and others for hours of endless fun. Best wishes Noel

Ps I have work with electronic and electrical gear for over 50 years.

Hi Noel,
I can see that the motor in your pictures has a changeover centrifugal switch but I don't understand how you KNOW that Keith's motor has this type of centrifugal switch. To reduce the number of conductors required between the motor and reversing switch I propose to swap over the blue and purple wires rather than the blue and yellow wires. (This is assuming yellow is connected to Z.) This is because the points A and AZ are already available at the reversing switch. If it is a changeover centrifugal switch I think the purple wire is the common of the changeover switch and the NO contact is connected to terminal K. BEFORE suggesting this I want to be SURE that there is no hidden connection between the main winding and auxiliary winding / capacitors / centrifugal switch.

Les.

Les, As it has been confirmed by Keith the motor reverses direction by swapping blue/yellow wires as advised by the manufacturer wouldn't it be simpler to remove the blue and yellow conductors from A and Z and extend them to the fwd/rev switch (DPDTcentreOFF), then add another pair from the switch back to the motor terminals A and Z, you may need to add a cpc if the changeover switch is not double insulated.

With careful planning there is just about enough space in the connection box for 2xblue in-line crimp connectors.

Keith, none of your pictures show an earth (cpc) conductor terminated at the screw provided within the terminal connection space, best ensure it is earthed as it must have been during your test running.

Emgee

Hi, The earth from the 3 core cable loops back out of the gland and is secured to one of the frame through bolts but I had noticed the screw in the connection space.

Keith

A big thank you to everyone for taking the time to help!

All the best, Keith

Keith

Glad you got it all sorted.

Emgee

Hi All,

A quick update.

I ended up using my original NVR switch that does not have the extra leg and just ran Blue and Yellow out of the motor to the forward/reverse switch and back to motor again. Everything is earthed and seems to work fine.

Start and stop with the NVR and change direction with the forward/reverse switch.

According to some this is not the correct way to do things but it does seem safe and used the lathe all day today.

Many thanks everyone

Keith

No problem with that as long as you only operate the FWD/REV switch when the motor is OFF and spindle stationery and never change direction without stopping the motor first.

It would offer more protection to the motor if you had a DOL starter with overload fitted but as you say will work without it.

Emgee