Here's a larger file. Resistance measured with a Fluke 87V with alligator clamps on the wires. Nothing to distinguish between windings.

The windings are similar because it is a reversible split capacitor motor.

 

These are the connections made through the reversing switch and the power supply input.

Forward
PCB1 connected to L2 (N)
PCB2 connected to L1 (L)
PCB3 connected to L1 (L)

Reverse
PCB1 connected to L1 (L)
PCB2 connected to L2 (N)
PCB3 connected to L1 (L)

You can see that PCB3 is connected to L1 (L) in both forward and reverse.
PCB1 and PCB2 Are connected to L1 and L2 in forward and reverse but with opposite polarity.
The labels in brackets are those used in the diagram of the control box.

I can't give you any other wiring suggestions as you are not prepared to try my suggested schematic.

Les.

 

The windings are similar because it is a reversible split capacitor motor.

Not usually, the PSC motor is usually 1/2hp max, and does not have two capacitors, just a permanent run type.

 

@elissquires First try direct like this,

 

I have never seen a split capacitor motor that large but it would explain the two windings being the same.
From the diagram in post #44 connect PCB3 to the junction of the two windings. Connect PCB1 to the other end of one winding and PCB2 to the other end of the other winding. The wiring of the reversing switch would have to be different to the diagram in post #1. If it is wired as in that diagram there will be a very low resistance reading between PCB3 and PCB1 with the switch in one direction and between PCB3 and with the switch in the other direction. If it is connected the required way for the diagram in post #44 in one direction it should read open circuit and the other direction you should read the resistance of the primary of the 24 volt transformer.

Les.

 

I have never seen a split capacitor motor that large but it would explain the two windings being the same.

Me neither, never come across a split phase motor with equal windings using a run AND start cap.
And one over 1/2hp. ?

 

Another question. That drawing of the machine wiring shows a reversing arrangement. Does the lathe actually contain a reversable control arrangement? Also, there is a type number for the motor on that same drawing, have you tried a search for that model number? And if the motor has a manufacturers name, have you searched for that? Or do an on-line search for the lathe manufacturer.
One more thing is that the drawing lists two voltages, perhaps the two windings might be intended for series operation? Is that worth considering?
Another suggestion is to actually measure the running current. There is a small chance that it is the overload device that has gone soft.
I am just hoping to cover some options that may not have been tried. Something here is missing.

 

Thanks Les/Max, I'm going to give that a shot and see what happens.

Hi Bill, yes, the lathe has a built-in reversible switch as per post #13. Post #1 (DSC_0033) is the motor plate which identifies it as a YL90L-4. I've searched extensively online for information. The best I found was the link in post #26 to describe this type of motor. I wondered if the overload switch was malfunctioning as well, so put a clamp on ammeter on PC-B1 when starting the motor. It got to about 12.5A before the 8.5A overload switch tripped.

Just a note, long before this saga started, I had to replace the 220V to 24V transformer. When they put the lathe on it's back, some oil had gotten into the original transformer and snap crackle popped when power was applied. Also burnt out one of the fuses on the 2 lines going to the 220V side of the transformer. Ordered and installed a new (Canadian made) transformer with appropriate specs and the output is 24V as advertised. The 24V control circuit has worked ever since.

I'd like to thank everyone for their input as I fumble my way through this. I don't have a background in electronics or electrical engineering so it's a struggle to understand some of the concepts.

Today's a beautiful day and the ground is frozen, so I'm headed out to cut down some spruce trees and winch them into the barn. Will get back to the lathe on a rainy or snowy day!

 

OK, so a reversing switch and some connections to contactors in a box someplace. Or were the contactors also in the part that was damaged? Unfortunately that drawing does not supply wire numbers and so it does not really help much. But it does tell us, IF IT IS CORRECT, that reversing the polarity of one set of connections is what is required, AND that there are two sets of connections to the motor.
The fact that the motor starts and reverses tells us that things are sort of correct. So now there is a question about the capacitors: Is the correct capacitor being disconnected by the starter switch? Was that connection damaged and possibly changed? Is the box with the contactors still present? Are there any numbers on those wires?
Given that the logical things have been explored, I think that it is time to chase the less likely ones. And the calibration of the 8.5 amp overload device is one thing to check.

 

But it does tell us, IF IT IS CORRECT, that reversing the polarity of one set of connections is what is required,

It appears that a standard 3ph reversing contactor is being used C/W the O/L.
If you trace the switching action you will see that the run winding and the start winding/capacitor set are simply being reversed WRT each other.
With a motor with two identical windings, a simple SPDT SW with centre off could be used.
Just that the contactor allows some degree of automatic control and extra protection.

 

It appears that a standard 3ph reversing contactor is being used C/W the O/L.
If you trace the switching action you will see that the run winding and the start winding/capacitor set are simply being reversed WRT each other.
With a motor with two identical windings, a simple SPDT SW with centre off could be used.
Just that the contactor allows some degree of automatic control and extra protection.

My thinking was that the wires might be labeled and that could be a clue as to the correct connections. Yes, a single witch could be used, possibly. But I would not do that with a 2 HP motor.

 

I just looked at a textbook on motors and came across one thing that has not yet been mentioned. The text showed that the higher value capacitor is the START capacitor, and the lower value would be the run capacitor. If those two somehow became exchanged that would cause the motor to draw more current, and so that might be the cause of the overload tripping. So there could be another source of the problem. Easy and cheap to verify.

 

I just looked at a textbook on motors and came across one thing that has not yet been mentioned. The text showed that the higher value capacitor is the START capacitor, and the lower value would be the run capacitor. If those two somehow became exchanged that would cause the motor to draw more current, and so that might be the cause of the overload tripping. So there could be another source of the problem. Easy and cheap to verify.

If the motor was ran with the Run capacitor in circuit constantly, typically that capacitor would not last very long, they are intended for no more than 10sec to 20 sec, 30 max in a motor start circuit.
They are dry electrolyte electrolytic types.

 

If the motor was ran with the Run capacitor in circuit constantly, typically that capacitor would not last very long, they are intended for no more than 10sec to 20 sec, 30 max in a motor start circuit.
They are dry electrolyte electrolytic types.

Look at the posted circuit Max, the starter switch only disconnects one of the caps. And my textbook shows exactly that circuit, with the larger value start capacitor being switched out when the motor approaches run speed. My furnace runs for hours with the run capacitor in the circuit. And without a start capacitor.
Or did you do an error in what you meant?

 

Look at the posted circuit Max, the starter switch only disconnects one of the caps. And my textbook shows exactly that circuit, with the larger value start capacitor being switched out when the motor approaches run speed. My furnace runs for hours with the run capacitor in the circuit. And without a start capacitor.
Or did you do an error in what you meant?

It is normal to disconnect the large value cap, the small one is left in as the OP circuit shows.
Having worked and also rewound all types of motors since my training starting in the 50's, I am aware of how the caps are switched and according to the diagram in post #44.
The run cap is a higher value bi-polar dry electrolyte capacitor and therefore can only be subjected to high AC current for a very brief time.
The run cap in your furnace fan is to retain the phase shift action of split phase winding current.
Fans under a certain HP size do not require the secondary high value switched start cap.

 

Les/Max, I've attached your wiring diagram with connections to PC wires. I'll give this a shot.

Bill, the starting capacitor is definitely isolated by the centrifugal switch, not the running capacitor. That said, I'm still not convinced that the switch is operating as it should. Maybe the motor is not reaching sufficient speed to disconnect due to my inferior hookup...

I'll take a photo of the forward/reverse switch. It's buried under the gearbox, so I won't be able to get a great one, but I'll do my best.

 

Before connecting up as the diagram in post #56 you need to either physically verify how the reversing switch is connected or do the resistance tests I suggested in post #45. To do these test you will have to manually operate contactors KM1 and KM2 as the tests have to be done without any power to the lathe.

Les.

 

Will do. Thanks.

 

I have edited post #57 as the resistance tests need to be done without the mains supply being connected. This means that you would have no 24 volts to actuate KM1 and KM2 via the normal controls.

 

Using the diag in #44/#56 I had suggested connecting direct first as shown, and bypass the contactor altogether for now to make it easier