Two-Speed Constant Torque Winding

[zlatkodo]

The ratio: low speed HP / hi speed HP is usually 1:2, for the majority of two-speed Dahlander motors with constant torque winding. However, there are many such motors where the ratio is 1: 1.5. Are the internal connection diagrams and wiring the same in both cases or they are different? Does anyone have an example?
Zlatkodo

 

[electricpete]

Pole Amplitude Modulation is a technique used to obtain speed ratio's other than two. It is of course different than Dahlander, so connections will not be the same.

http://books.google.com/books?id=4-...onepage&q="Pole Amplitude Modulation"&f=false

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(2B)+(2B)' ?

 

[zlatkodo]

Hi, Electricpete,
I know what is the PAM winding, but my question is not about the PAM windings than about the two speed, constant torque , Dahlander windings with speed ratio 1:2 .
Zlatkodo

 

[Motorwinder]

The Dahlanders seem to be constant torque 2Y/1Y connections. They would be the same connections for a 1:2 or a 1:1.5 hp ratio. The only reason they derate the 1:2 is to maintain a decent flux.

 

[electricpete]

Sorry, I misunderstood your question.

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(2B)+(2B)' ?

 

[zlatkodo]

Hi, Motorwinder,
Probably, you thought:
"The Dahlanders seem to be constant torque 2Y/D connections."
Zlatkodo

 

[starkopete]

Figures 03 & 04 on the link below show both the D/YY and Y/YY Dahlanders connection. It appears that the connection depends on application.

http://www.tiba.si/en/clanki/priklopi-trifaznih-asinhronskih-motorjev.html

Thanks

 

[zlatkodo]

Hi, Starkopete,
You talk about the difference between constant torque and variable torque, but my question relates only to constant torque, ie question is: is the internal connection diagram the same for both cases:
- the two-speed Dahlander constant torque, D/YY winding with HP ratio 1: 2,
- the two-speed Dahlander constant torque, D/YY winding with HP ratio 1: 1,5
Zlatkodo

 

[starkopete]

Hi Zlatkodo,
Now I'm really going to confuse things. From a WEG motor catalog in reference to Dahlander two speed motors:

"Constant torque:
Torque is constant on both speeds and rated power ratio is 0.63:1 In this case, motor has a D/YY connection.
Example: 0.63/1HP motor – IV/II pole - D/YY.
This connection is suitable for applications where the load torque curve remains constant with the speed variation."

The .63:1 power ratio can be re-written as 1:1.58, if it is truly a "constant torque" connection you'd expect a 1:2 power ratio. Any one have any ideas.

Thanks

 

[starkopete]

Hi,
I checked with one of EASA's Engineers and he gave me the following reply:

"NEMA uses an artificially simple 2:1 or constant torque, and 4:1 for variable torque, where the IEC motors use the actual torque / KW ratio instead."

Based on that reply the answer to your OP would be yes, the internal connection diagrams and wiring are the same.

Thanks

 

[LionelHutz]

Maybe this is over simplifying but if both motors are D/YY connected then both would connect the same.

I would also agree that the statement that the typically quoted 2:1 or 1:1 HP ratio is a simplification and many motors do not actually have a 2:1 or 1:1 HP ratio.