Help wiring an electric motor

[SimonH2]

That makes more sense than the diagram in the OPs post.

The white wires are almost certainly a centrifugal switch which opens when the motor is up to speed. If we look at the connections when it's open (ie the motor is already up to speed) ...
Power is applied directly across winding U - so we can assume this is the main winding. Then windings V and Z are in series across the mains - the difference between running directions is simply reversing the direction of the windings relative to the U winding. The capacitors Crun and Cst provide a phase shift so that the V & Z windings add a rotating field element to that provided by the U winding.
The V winding is shorted out during start, so more current will flow through Cst and the Z winding - giving a stronger rotating field element during starting.

This isn't what I'd expect to see if it were a standard 3 phase motor wired for single phase operation, so I assume that the windings are not all the same - but I suspect not many of us have the gear to measure them accurately.

 

[Mindaugas]

That makes more sense than the diagram in the OPs post.

The white wires are almost certainly a centrifugal switch which opens when the motor is up to speed. If we look at the connections when it's open (ie the motor is already up to speed) ...
Power is applied directly across winding U - so we can assume this is the main winding. Then windings V and Z are in series across the mains - the difference between running directions is simply reversing the direction of the windings relative to the U winding. The capacitors Crun and Cst provide a phase shift so that the V & Z windings add a rotating field element to that provided by the U winding.
The V winding is shorted out during start, so more current will flow through Cst and the Z winding - giving a stronger rotating field element during starting.

This isn't what I'd expect to see if it were a standard 3 phase motor wired for single phase operation, so I assume that the windings are not all the same - but I suspect not many of us have the gear to measure them accurately.

So I have white wires connect between V1 and V2? After that my motor starts noisy and draws 30A. I dont know where is the problem, because I connected with a given circuit diagram to rotate CW. What can happen if I start motor with the same circuit, but without white wires between V1 and V2?

 

[SimonH2]

It's possible that the switch is faulty - in which case the motor would stay in it's start configuration when running.
Leave the white wires disconnected and it should still start - but with a lot less torque so might not be able to get many types of loads running. For something like a fan it should be OK, it'll just start much more slowly - but with something like a compressor it won't start at all. With no load, it should startup almost normally, and you should find the white wires go open circuit when it's up to speed. It shouldn't need saying, but you need to take extreme care when taking measurements with the power on and the motor running
If the switch is faulty, then you'll need to open up the motor (if it can be opened) and replace it (if you can get a replacement). Once upon a time it was easy to get the parts and to get at them, these days things tend not to be designed to be maintainable

 

[SUNRAY]

That makes more sense than the diagram in the OPs post.

The white wires are almost certainly a centrifugal switch which opens when the motor is up to speed. If we look at the connections when it's open (ie the motor is already up to speed) ...
Power is applied directly across winding U - so we can assume this is the main winding. Then windings V and Z are in series across the mains - the difference between running directions is simply reversing the direction of the windings relative to the U winding. The capacitors Crun and Cst provide a phase shift so that the V & Z windings add a rotating field element to that provided by the U winding.
The V winding is shorted out during start, so more current will flow through Cst and the Z winding - giving a stronger rotating field element during starting.

This isn't what I'd expect to see if it were a standard 3 phase motor wired for single phase operation, so I assume that the windings are not all the same - but I suspect not many of us have the gear to measure them accurately.

I can't access my previous attachment from here but tbe measured resistances of one such motor are shown.
These are not 'standard' 3ph motors with U, V, Z markings

 

[Mindaugas]

It's possible that the switch is faulty - in which case the motor would stay in it's start configuration when running.
Leave the white wires disconnected and it should still start - but with a lot less torque so might not be able to get many types of loads running. For something like a fan it should be OK, it'll just start much more slowly - but with something like a compressor it won't start at all. With no load, it should startup almost normally, and you should find the white wires go open circuit when it's up to speed. It shouldn't need saying, but you need to take extreme care when taking measurements with the power on and the motor running
If the switch is faulty, then you'll need to open up the motor (if it can be opened) and replace it (if you can get a replacement). Once upon a time it was easy to get the parts and to get at them, these days things tend not to be designed to be maintainable

I have tried to start motor without white wires between V1 and V2 and it worked. Motor current was 4-5A. This means, that motor at startup does not uses starting capacitor, but only run capacitor? When i connected tester on these white wires, after motor start they stayed short circuited. Propably centrifugal switch is faulty. Is it possible to replace centrifugal switch with a motor starter contactor NC auxiliary contact or do I need time relay? It will be enough delay time for startup capacitor? Thanks for reply.

P.S. How to check if there is not centrifugal switch, but for example PTC thermistor or similar thermal contact, which opens when winding temperature reaches specific value?

 

[SimonH2]

I have tried to start motor without white wires between V1 and V2 and it worked. Motor current was 4-5A. This means, that motor at startup does not uses starting capacitor, but only run capacitor?

Actually, both caps are in use all the time - the naming is rather misleading. The difference is that for starting, winding V is shorted out which will significantly increase the current in winding Z - thus increasing the strength of the rotating field component it creates, and hence increasing starting torque (and drawing significantly more current).

When i connected tester on these white wires, after motor start they stayed short circuited. Propably centrifugal switch is faulty. Is it possible to replace centrifugal switch with a motor starter contactor NC auxiliary contact or do I need time relay?

I would be very wary of not using a centrifugal switch. In theory you could use a time relay, but it would be tricky to get right. Too short a delay and you risk startup problems - depending on the load, potentially not getting running and either tripping something or just burning the motor out. Too long a delay and you'll be putting excessive current through the motor windings for too long - again at the risk of burning out a winding.

It will be enough delay time for startup capacitor?

I don't think you realise what the caps do. It's not a case of "it charging up while the motor starts", this is AC where the voltage reverses 100 times a second - so each capacitor charges and discharges 100 times a second.
Cst is in series with the windings, and I suspect doesn't do much while running. During startup (winding V shorted) it'll provide a significant phase shift for the current in winding Z. In running config, I suspect it does little but pass current.
Crun is in parallel with winding Z, and while running it'll alter the currents in both V and Z windings so as to create a rotating field.
In principle, the motor could run with just winding U once up to speed - but it would be a bit rougher without the extra field components created by windings V and Z (plus Crun).

P.S. How to check if there is not centrifugal switch, but for example PTC thermistor or similar thermal contact, which opens when winding temperature reaches specific value?

The only sure way to to open it up and see - or see the manufacturer's information if they have provided it. Any reasonable manufacturer would have data sheets with torque curves and stuff like that, together with information on correct overcurrent protection etc.

 

[Mindaugas]

I got answer from manufacturer. These white wires are thermal contact. Also this motor has centrifugal switch, but it is internal and I do not need any additional connection between V1 and V2. So I am going to leave these white wires not connected, or connect in series with STOP button in contactor circuit.

 

[SUNRAY]

or do I need time relay?

That appears to be the way it was done in my second attachment