Hi, today i would make a circuit of starting of a single-phase motor, but i don't know how choose right capacitor, this motor is: 230V 50-60Hz 30W...
So which capacitor i have to choose? ty

 

C=4800*i(A)/U(V) For example 2,2kW 220V motor has i=2200/220=10A, then C=4800*10/220=~~40 microfarads. When (if) coils are capturing this current serially (two oif them), then factor is 2800 instead of 4800.

The practical method is to set motor with stable nominal load (mechanical load), switch the probe capacitor and measure voltage on capacitative branch to the one and to the other network wires. Ideally both voltages must be equal. If capacitor eats up too much voltage, the microfarads must be increased and vice versa.

For starting needs capacitor must be 2-fold of normal work (that means the normal C must add just the same value parallely. If the very hard start conditions are expected, then maximum 3-fold, what is double capacitance is added to wirk capacitor for few seconds.

 

First is this a PSC (permanent start cap motor) or a dedicated start/run winding motor? if the former, the winding's are equal, if dedicated then the winding's are both different, in either motor, the respective currents are different, the phase shifted winding is only there to give a ~90° phase shift.
If only 30w then I would expect it to be a PSC variety. And the capacitor relitevely small, a few uf's.
Max.

 

First is this a PSC (permanent start cap motor) or a dedicated start/run winding motor? if the former, the winding's are equal, if dedicated then the winding's are both different, in either motor, the respective currents are different, the phase shifted winding is only there to give a ~90° phase shift.
If only 30w then I would expect it to be a PSC variety. And the capacitor relitevely small, a few uf's.
Max.

it's similar to this
https://media.rs-online.com/t_large/F4548332-01.jpg

 

That one appears to be a shaded pole motor, if so no cap used, is it possible this is the same as yours?.
If yours is a PSC then the cap would not be very large at all.
Max.

 

[QUOTE = "MaxHeadRoom, post: 1294667, membro: 212212"] Quello sembra essere un motore a poli ombreggiati, in tal caso non è stato usato nessun cappuccio, è possibile che questo sia uguale al tuo ?.
Se il tuo è un PSC, allora il cap non sarebbe molto grande.
Max. [/ QUOTE]

But, if cap is so low, have i need to conenct a capacitor to motor?

 

C=4800*i(A)/U(V) For example 2,2kW 220V motor has i=2200/220=10A, then C=4800*10/220=~~40 microfarads. When (if) coils are capturing this current serially (two oif them), then factor is 2800 instead of 4800.

The practical method is to set motor with stable nominal load (mechanical load), switch the probe capacitor and measure voltage on capacitative branch to the one and to the other network wires. Ideally both voltages must be equal. If capacitor eats up too much voltage, the microfarads must be increased and vice versa.

For starting needs capacitor must be 2-fold of normal work (that means the normal C must add just the same value parallely. If the very hard start conditions are expected, then maximum 3-fold, what is double capacitance is added to wirk capacitor for few seconds.

But 4800 is standar? sorry but i have little expirience...

 

First you have to find out if you have 3 connections, PSC motor etc , if so, measure the resistance of each winding and see if identical.
Max.

 

First you have to find out if you have 3 connections, PSC motor etc , if so, measure the resistance of each winding and see if identical.
Max.

just to understand, if I have a three-phase motor, I have to understand before that engine is, then see the resistance between the windings and then calculate the capacitor? instead if it is a single phase is it the same or not?

 

A three phase motor does not need a capacitor. You seem to be giving contradictory information on the motor. Post pictures of the ACTUAL MOTOR with one showing the rating plate. Also the data sheet on the motor if possible. I agree with Max that the picture in the link in post #4 looks like a shaded pole motor which does not need a capacitor. Without clear information we can't answer your question.

Les.

 

A three phase motor does not need a capacitor. You seem to be giving contradictory information on the motor. Post pictures of the ACTUAL MOTOR with one showing the rating plate. Also the data sheet on the motor if possible. I agree with Max thet the picture in the link in post #4 looks like a shaded pole motor which does not need a capacitor. Without clear information we can't answer your question.

Les.

these are all property technic of motor single-phase: OSM-20 30W CL.H 220-240V 50-60Hz OH SUNG A1004185...
And this motor have to rotate only a fun.
But my question is which is formula to find uf of capacitor...
I do not know if I have explained myself well...

 

As per post #8, show resistance of winding's you should have at least three conductors from the motor.
Max.

 

More specific table of formulas.
http://vzhik.info/uploads/posts/2012-05/1336406098_table1.jpg

 

30W may start with the 0,5 mkF and then variate it from 0,25 to 1,0. IF this really is a capacitor type motor. Because it may be motor with resistive winding startup, like most of home type fridges has to do. Then work coil is those with small resistance and start coil is those with very large resistance. Yet for capacitor type of motors both coils are identic, thus the placement of capacitor makes only reversal of turn direction.

 

More specific table of formulas.
http://vzhik.info/uploads/posts/2012-05/1336406098_table1.jpg

That chart appears to be for a motor with both start and run winding's/caps?
Max.

 

For three phase motors what is aimed to switch in one phase feed. But somehow formulas are very the same as to one-phase two winding capacitative type of motors, for work capacitor. The start capacitor is then totally 2...3 of work capacitor.