Part-winding motor starting ATL?

[KKADM]

Can a 3-phase, 460v, 6 lead motor wound for a part winding start be started across the line by tying together leads 1&7, 2&8, 3&9?? Even if possible, is this a good practice??

 

[jraef]

Yes it's possible.

Is it a good practice? Only you can decide that. Someone went out of their way to specify a part winding start; it takes a special motor and starter. Second guessing that decision may leave you open to whatever problem they were trying to solve.

 

[KKADM]

I think the reasoning behind using a part winding start motor in this particular application is that it was what was available on short notice for the particular frame size needed. I haven't been able to find much information on part winding start motors other than the basic terminal connections and starting torque and current (when using part winding start and not ATL). Can anyone provide any additional info??? THANKS

 

[ankervik]

Not long ago we had problems identifying the internal connections of 6 lead part winding start compressor motor (prior to rewind). We don't run into these much in Europe but I found some dusty old notes describing what you may be looking for.
Quote: "Part Winding: This method used only a portion (usually one-half, but sometimes two-thirds) of the motor winding, increasing the impedance seen by the power system. It is to be used only for voltage recovery, and must not be left on the start connection for more than 2 to 3 seconds. The motor is not expected to accelerate on the start connection, and may not even turn.
Starting Characteristics: Starting current is 60-75% of full load, depending on the specific winding connection. Starting torque is low typically 50% (may not even turn the shaft). Winding heating is very high on start connection.
Applications: Where power system has automatic voltage recovery and normal inrush would cause unacceptable voltage dip. Should not stay on start connection more than 2 to 3 seconds."
Our motor turned out to be series wye on start (half of the winding in) & parallel wye on run (whole winding). It was tagged the same as you mention for run connection.

 

[petronila]

Hello KKADM,

Yes you can do that, but take account the DOL Curent will be greater than PW Start.From the U.S Electrical Motors technicall Information : "This method used only a portion (usually one-half, but sometimes two-thirds) of the motor winding, increasing the impedance seen by the power system. It is to be used only for voltage recovery, and must not be left on the start connection for more than 2 to 3 seconds. The motor is not expected to accelerate on the start connection, and may not even turn.

Part Winding Start
Starting Characteristics:
1. Starting current is 60-75% of normal, depending on the specific winding connection.
2. Starting torque is very low (may not even turn the shaft).
3. Winding heating is very high on start connection.
Applications:
Where power system has automatic voltage recovery and normal inrush would cause unacceptable voltage dip. Should not stay on start connection more than 2 to 3 seconds"

Regards

Petronila

 

[ankervik]

So that's where our dusty old shop notes originated? Anyone know if this book is still in print?

 

[jraef]

anervik,
It's available on-line, print at your own expense

http://www.usmotors.com/Products/ac_hsc.pdf