dual voltage motor issue

[BRT]

Every one of my 2 capacitor 240v single phase motors are reversing, and one capacitor starts the motor in one direction, and one starts the motor in the other direction. I am busy swapping them for 3 phase motors, and I am not the all knowing motor guru, but the only cap start cap run motor I have does not have the capacitors mounted to the motor, they are in the motor controller, and the caps are very different.

Again, I am well versed in 3 phase squirrel cage motors, but all of my 2 cap motors that have the caps mounted on the motor are reversing.

For simple reversing in a 1 phase motor the same capacitor does both directions. For reverse you change the relationship between the start winding and the run winding. Commonly 2 different capacitors means it is capacitor start, higher torque, and capacitor run, better efficiency. If the 2 capacitors are the same the most common reason is they are wired in parallel to double the start capacitance. However there are single phase motors that can be reversed while still turning forward and having never dealt with one I don't know how they work.

 

[Wookie]

For simple reversing in a 1 phase motor the same capacitor does both directions. For reverse you change the relationship between the start winding and the run winding. Commonly 2 different capacitors means it is capacitor start, higher torque, and capacitor run, better efficiency. If the 2 capacitors are the same the most common reason is they are wired in parallel to double the start capacitance. However there are single phase motors that can be reversed while still turning forward and having never dealt with one I don't know how they work.

Mine are all on Anchor Windlasses. Well, except for the one in the Air Conditioner. That has the start and run caps in the motor controller.

 

[2airishuman]

Mine are all on Anchor Windlasses.

Single phase, hoist duty motors sometimes have an extra start cap and (IIRC) an extra start winding to simplify the wiring of the reversing contactor.

Without the extra cap you need a three-pole double-throw switch, usually a drum switch, to reverse directions. I wired one once on a silo unloader hoist.

 

[2airishuman]

So I picked up another shop compressor to run my booster. I has a 3hp 120/240V motor on it. Unfortunately the wiring sticker is worn away so I can't tell if it's jumpered for 120v or jumpered for 240v. The 4 terminals are not labelled at all. How can I tell these apart with a multimeter?

(it has 2 capacitors on top if it matters)

First of all, you should be aware that the motor doesn't have thermal protection, so be careful not to burn up the windings as that is an expensive mistake.

As pointed out upthread, the motor leads are nearly always marked with the terminal numbers along their entire length.

You cannot reliably determine which terminal is which with a multimeter. What you can do is separate them into winding pairs because those will have continuity when checked with a meter. 1-2 is one pair and 3-4 is the other pair. But a multimeter will not tell you the difference between 1 and 2 or between 3 and 4.

A confident electrician would guess and have a 50% chance of being correct, since it doesn't matter if both pairs are backwards and doesn't matter which pair is which. If incorrect the motor either won't start at all or won't reach full speed, and will burn up in a matter of seconds. A very brief test with no load on the shaft usually won't hurt anything and is diagnostic.

There are other, more sophisticated methods that involve running the motor at 120v on one winding and looking at the voltage and phase relationships between the powered winding and the unpowered winding.

 

[BRT]

Mine are all on Anchor Windlasses. Well, except for the one in the Air Conditioner. That has the start and run caps in the motor controller.

An anchor windlass would have to be instant reversing. I don't remember ever working on an instant reversing single phase motor.

 

[Wookie]

An anchor windlass would have to be instant reversing. I don't remember ever working on an instant reversing single phase motor.

And I’d never seen one before this one. I’ll post the wiring diagram later.

 

[rjack321]

First of all, you should be aware that the motor doesn't have thermal protection, so be careful not to burn up the windings as that is an expensive mistake.

As pointed out upthread, the motor leads are nearly always marked with the terminal numbers along their entire length.

You cannot reliably determine which terminal is which with a multimeter. What you can do is separate them into winding pairs because those will have continuity when checked with a meter. 1-2 is one pair and 3-4 is the other pair. But a multimeter will not tell you the difference between 1 and 2 or between 3 and 4.

A confident electrician would guess and have a 50% chance of being correct, since it doesn't matter if both pairs are backwards and doesn't matter which pair is which. If incorrect the motor either won't start at all or won't reach full speed, and will burn up in a matter of seconds. A very brief test with no load on the shaft usually won't hurt anything and is diagnostic.

There are other, more sophisticated methods that involve running the motor at 120v on one winding and looking at the voltage and phase relationships between the powered winding and the unpowered winding.

I found this picture online and pretty sure this is the same sticker as on my motor.

I found an additional terminal on my motor that I didn't realize I had in the process. So I have a jumper on the top terminal. And a jumper on what I am guessing is terminal 4 and an empty terminal hidden partially behind the case at the very bottom (#5)

So now I am thinking this is a 120V motor. Is it worth checking as a 120V version by applying power to L1 and having a neutral on L2 for a second to see if it spins under no load?

The junky existing wiring to the pressure switch is thick (#8 I think) like it was sized for 17amps (120v) not 8.5 amps (240V). And there is no return or ground in the bundle just a red and a black (which is less helpful).

 

[2airishuman]

The picture shows a total of six connection points. Gray wire, white wire, four terminals. You would have a thermal reset button, usually red, if that diagram matches your motor.

Motors connected at the wrong voltage will still appear to work but will overheat or stall when a full load is applied

You'll have to decide yourself

 

[broncobowsher]

Can you post a picture of the actual parts you are working with?

 

[rjack321]

As far as I can tell there is no terminal #1
#2 has the grey jumper
4/5 are joined and jumpered white
#6 has nothing

Pretty sure its 120V based on the diagram above