SPIM TERMINALS

[derick007]

The attachment shows a 50W single phase induction motor taken from a tumble dryer. There are 3 connections from the motor, 2 of which go straight to a cylindrical 8 uF capacitor, the other I am not sure about.
The resistance between the 2 connections going to the capacitor is 80 ohms, the resistance between each of these connections and the third connection is 40 ohms.
I initially thought the mains supply to the motor would be just across the capacitor and the third connection was just something like a thermistor, which I did not have to concern myself with, but now after doing some research I understand that single phase motors require a starting mechanism such as a capacitor and start winding in series with the main winding.
I would like to be sure of what I am doing before I start experimenting with attaching a mains supply. Any help with the identification of the 3 motor connections would be most helpful.
The information on the motor name plate is very vague. I think the manufacturer is OLONG ? The type seems to be YYG50-4-004. I did find some data on the net but nothing on the terminals.

 

[Les Jones]

Measure the resistance between the wire that does not go to the capacitor and each of the wires that goes to the capacitor. The lower of the two resistance values will be the main winding. the other will be the start winding. This will be in series with the centrifugal switch which disconnects the start winding when the motor is up to speed. Woy will connect the mains to the wire that does not go to the calacitor and that one that gave the lower resistance reading to this wire.

Les.

 

[derick007]

This one is a bit of a mystery.
I measured the resistance as you suggested and both are about 40 ohms.
I have tried wiring the mains across the capacitor, with the third terminal (black/orang wire) left open cct. The motor just shook telling me that there was no starting mechanism. I then wired mains between one terminal of the capacitor and the third connection (black/orange wire), leaving the other capacitor terminal open cct. The motor started to spin. I then wired the mains to the other capacitor terminal (the one which had been left open cct.) and the same third connection (b/o wire) and the motor started to spin.
Therefore as long as I have the mains wired between the third terminal and one capacitor terminal the motor will start to spin.
My question now is why are there three wires ? I can only imagine it must be to allow the capacitor to be switched out of circuit when the motor is up and running. If this is the case then it should be noted that both windings will still have the mains wired across them. Maybe this is just the design of the motor i.e. to have 2 windings in circuit while the motor is running upto speed and in operation, while only have the capacitor in circuit to get the motor upto speed and then switch it out while running. I have never come across such a design ?

 

[Les Jones]

This is a type of motor that does not have a centrifugal switch. The capacitor provides phase shift to the winding that is not directly to the mains. Connecting one leg of the mains to one side of the capacitor causes the motor to rotate on one direction. If it is transferred to the other side of the capacitor the motor will rotate in the opposiet direction.

Les.

 

[derick007]

Ahhhhh.... the penny has dropped.

Three wires are required to allow rotation in either direction.

Thanks Les