Iduction motors, Dual speed, Dual voltage, Y/Delta

[kalabdel]

Greeting to all,


I seem to never get a handle on motors and their operation and I was reading this WEG pdf which puzzled me.


So we have dual voltage motors that have their winding wired in series or parallel.


Y start and Delta run, motor starting method for certain applications.


Dual speed (Dahlander) Motors, and that's where things went sideways for me. The wiring illustrations (see image "Page 30") dual speed motors wired for three different applications, Constant Torque, Constant Horsepower and Variable Torque.


Assume we have the same voltage for all (that's my assumption).

• Constant Torque low speed:
  • Pole pairs are wired in series and the three phases are wired in delta configuration.
  • Constant Torque high speed:
  • Pole pairs are wire in parallel and the phases are wired in Y configuration.
  • Question #1: Will the windings in this configuration "see" more voltage? (see middle drawing in image "Page 19")
  • Question #2: Doesn't fewer poles (wired in parallel) produce less torques?
• Constant Power:
  • The wiring diagrams are place opposite to the one above it.
  • The Wye configuration with parallel pole pairs should be the high speed and the Delta should be the slow speed.
  • Questions #1: What I missing concerning the speed?
  • Question #2: How did it become constant power?
• Variable torque:
  • I think I understand this one, they Wye configuration with winding wired in series will drop the current and the torque goes down with it and with Delta configuration we will have less poles(paralleled) and more current meaning more torque, am I on the right track?

Last question: What is the symbol "SH1" in the image "symbol"? It is noted as Control Button and there are two contacts, one is NO and the other is NC. If it is a button and they're the contacts are linked then when the button is pushed nothing would happen; so there must be something I'm missing.


Thanks

 

[soultrader]

"I seem to never get a handle on motors and their operation"


And you choose to start with a Dahlander circuit?



I've only come acrross this circuit once, on the inlet screw pumps at a sewage works.



SH1 is a clumsy representation of the Start & Stop buttons and also the Running Lamp.



It's a bad schematic - SH1 is shown 3 times:


SH1 n/c , terminals 21-22 = STOP Button


SH1 n/o, terminals 13-14 = START Button


SH1 Lamp, terminals X1-X2 = RUNNING Lamp

 

[widelto]

@Kalabdel:
My best source about AC motors is Cowern papers:
https://www.baldor.com/Shared/manuals/pr2525.pdf
Edward Cowern used to work for Baldor Motors now a division of ABB.

 

[kalabdel]

Thanks gentlemen.

@soultrader, constant torque and constant power was mentioned in passing in a conversation I had with a motor repair technician and I got curious as to how they worked. That led me to that WEG pdf and Dahlander.
The switch didn't make sense to me, the way the two contacts are linked, and thought there maybe some specialized buttons for this application. Thanks for clearing this up.

@widelto, I had a quick browse and it looks good. I will dig deeper into it tonight.

Cheers
Kal