control circuit><

halo, nice to meet u .
it's my first times to post thread..
i have some question about the control><
what is the different between YY/Y and star/Y control??
thx a lot~~:)

Good Day Darren! I do not understand what you are asking. The symbol YY/Y is used by compressor manufacturers to indicate that the motor windings are connected for a Part Wind electrical starter. The second symbol Star/Y I do not understand either. Give us some more information and the worldwide resources of www.refrigeration engineer .com will be ready to help you!

A YY wound motor has two totaly separate motor windings constructed on to one stator that means there are six coils where 3 are for each complete motor stator, it is another method used for reducing start up current of a 3 phase motor insted of using the star / Y method where the motor is started up in star then after a short period it changes to delta.

i know that these motion..YY/Y is used 2 contactor to do motion.Time delay is 1secs and star/Y is used 3 contactors(M.D.Y) to motion.Time delay is 6~7secs.
i could want to know that YY/Y advantages and disadvantages.
YY/Y control is better than star/Y?
In my suggestion, i don't like to used YY/Y. It is because the motor easy to fault by simple error.

Yes, PWS (YY/Y) is better in terms of lower LRA than star/delta. But the symbol of star/delta is Y/D, not star/Y

You need 2 contactors for Y/YY and 3 for star/delta.

If you don't unload with a star/delta then there's a change that compressor will bock on Y start-up.

Lower start peaks as said with Y/YY.

one more duestion,most of copeland compressor are used the Y/YY control to start??
Y/YY start current is about (running current X 6)= =+
Y/D start current is about (runnning current X3)<--i'm not sure.

the difference is one use's part windings start and the other use star/delta.. meaning the wiring configuration of the motor is change via the contactor. Now ....sum refrigeration compressors use part winding start, meaning only 2 windings are intiated at the start to provide more torque! ( remembering that all 3phase motors consist of 3 windings) now after the comp has began to turn and has obviously lowered the amount of torque required to turn it the second contactor wired to the third winding in the motor will now cut in.. via a contactor, thus dropping out the primary contactor used to start the motor due to the fact that once turning the motor only requiers one winding to continue turning! therefore lowering current draw...

Setrad7791, your explanation of the part winding is not correct, how can you rotate an electrical motor while energizing only 2 windings?

You're missing the complete rotating magnetic field, necessary to start up the motor.
You have a serious gap in the rotating magnetic field and the motor will 'stall' and never start up.

The motor will cut out on its overload protection.

Then this low load start system the way you explained it will also work when one of the 3 wires is broken? :confused: So starting up with 2 wires and then after some seconds the 3rd missing wire??
:confused:

The working principle of a part-winding motor is completely different. I think you should re-read once thoroughly how this works.:o

Darren AND Setrad , read once this bulletin http://www.bitzer.de/_doc/k/kt-400-2.pdf;) :o

Darren, it all has to do with the small gap in the switch over with a star-delta motor

Windings, wires and poles are three different things.
Windings are (in the sense of PWS) a complete motor, which size in a PWS is just 50%. A PWS is made up of two windings, engaged 1s apart.
Wires are always three for three phase, or two for single phase motors.
Poles are the number of electromagnetic inductance per revolution. 2 poles have less torque than 4 poles. Increasing the number of poles increases the torque and reduces the rotational speed. As noise is a direct byproduct of speed, fans are normally 6 or 8 poles, while motors of compressors and pumps are 2 poles.
4 poles pump motors are becoming more and more common, though.