How does work revers on the one phase AC synchronous motor?

[veikolaht]

Could somebody to explain me, please, how works revers system on the one phase AC synchronous motor with two wires only. Model is 50TYZ-E and it is from small ice making machine. Where does this motor get information, that now is time to turn opposite way?

Thanks in advance!

Veiko

 

[Averagesupernova]

Single phase induction motors have a starting winding besides the main winding. How this start winding is connected determines the direction.

 

[jim hardy]

it's a little timer motor? only one i ever reversed was by taking apart and flipping stator.

dont know if yours is reversible that way or if it has to be ordered.
a search on the part number shows it available both directions.

pry tabs and open it up... as supernova says, you'll see a shaded pole or something...

 

[veikolaht]

Thank you for your quick replay!
This motor turns a small plastic bath 90° one way and after ice cubics are ready - 90° opposite way. Small plastic bath - two ends. On the right side is motor, on the left side are two swiches (on the picture) with a distance 90°. To the motor comes two wires only, 230V AC. One wire is connected directly, second is connected through the relay. When I connect 230V AC directly to the motor, then sometimes it turnes CW, sometimes CCW - no rules.
The problem is, that this motor is connected to the plastic bath, which can turn 90° only, but it seems the motor has power enough to break the plastic connection with its axle. Yes, there are two swiches which should stop turning of motor, but I think the problem is not there. It can be, that already in the beginning of the refrigeration process the motor sometimes starts turning wrong way and breaks the plastic bath.
I found not much information from Internet about this. For example inside of this permanent magnet of rotator is a "switch" and if turning of rotator will be to heavy for motor, it starts turning opposite way. But there is a gearbox and I tried to stop it with nippers - no results, it turns anyway to the same direction and I even could not easily stop it.
English is not my mother language, but I hope my story is still understandable.

 

[jim hardy]

wow! that's a good one.

something somewhere has to tell that motor which way to run.

could there be a mechaniical link inside the motor that we're not seeing?

that black piece looks like the rotor
and it looks like pole pieces down in the recess

lift that white plastic termination block and the flat plate, see if there's something to switch the windings or move a magnet... I'm suspecting a tiny magnetic memory switch of some sort that makes it reverse directions every time it's energized..

but that's an unscientific, uneducated guess.

 

[Carl Pugh]

Motor is permanent split capacitor motor.

If the motor is designed for reversing, then when the line is connected to one side of the capacitor, the motor runs clockwise.
If the line is connected to the other side of the capacitor, the motor runs counter clockwise.

 

[veikolaht]

The motor has two wires only, so there is no place for capacitor. :)
The direction of rotation depends from the position of rotor in the beginning of the activation. If I turn the rotor manually ca 45 degrees to the left or to the right from the neutral position, it starts rotation opposite way.
It seems like this motor does not belong to this ice making machine. :)
The rotor itself is one piece. Of course, it is possible to open it, but I am afraid I will not put it together again. There is a plastic core and it is melted together.

 

[jim hardy]

"""The direction of rotation depends from the position of rotor in the beginning of the activation. If I turn the rotor manually ca 45 degrees to the left or to the right from the neutral position, it starts rotation opposite way. ""

ahhh now you're homing in on it.

i believe you'll find a rotor with a permanent magnet poles on it, that's what makes it synchronous, and a reversing pawl .

here's a link with more than anybody wants to know about little clock motors. read text surrounding figure 4...

http://sound.westhost.com/clocks/motors.html

likely a "kerosene overhaul" will fix it.

 

[veikolaht]

Yes, this is very interesting link, but ...
In my case the motor has to rotate both of way. Here is no wrong direction, both of directions are correct, just they have to be on correct time.

 

[jim hardy]

well i don't know what's inside it either.
but it's significant that a single phase motor is happy to run either direction - you just got to get it started.

here's the relevant text from that link

When the power is first applied, the rotor typically just jiggles around for a short time, until a N on the rotor aligns perfectly with a S on the stator. As the poles alternate between N and S magnetic polarity, the rotor follows the field and turns, jumping from one pole to the next to maintain attracting magnetic polarities. It may choose to run in either direction at this time.

By adding a direction-sensitive pawl, the motor is usually set up to ensure the pawl engages with the rotor should the motor spin in the wrong direction. This stops the rotor, but adds sufficient "bounce" to force the motor to run the right way. The lug on the rotor can be seen in Figure 4 - the pawl is attached to the first "wheel", driven by the rotor pinion. A simple viscous (oil) drive pushes the pawl into the rotor should it spin in the wrong direction. Correct rotation keeps the pawl against the right hand red post and out of the way.

i don't know what's inside it but expect you'll find a two pawl arrangement to make it swap direction on every start. that's my best guess.

maybe somebody else has taken one apart ?

over and out.