Help needed for wiring a three phase motor

Thread Starter

mywaytos

Joined Jan 22, 2019
7
Recently got a Baldor Motor: EFM4316T 75HP, 1780RPM, 3PH, 60HZ, 365T, A36068M, TEFC.

The wiring diagram coming with the motor suggests the motor could be started using Y collection and run the motor using DELTA collection.
https://www.baldor.com/api/products/EFM4316T/drawings/416820-002

Now I am wondering if I can start the motor using the following way (a way between Y and DELTA) to get higher starting torque?
https://drive.google.com/open?id=1q1Tcxm2zBo-20GNIgddh6Zy4GnyDoD1S

Any suggestion would be appreciated.
 

MaxHeadRoom

Joined Jul 18, 2013
19,980
Starting Star-Delta offers a Lower starting torque until motor has obtained speed in order to avoid the high inrush current.
But your intention is to attain high starting torque?
You may run into problems by trying to increase the normal starting current depending on the load at start.
What is it driving? Is there insufficient torque now?
Max.
 

Thread Starter

mywaytos

Joined Jan 22, 2019
7
Thanks Max.
The motor is used to drive a metal granulator. Sometimes the AC contactor burned out when starting the machine with some metal pieces remaining in the chopping chamber. I was thinking these metal pieces may apply too much resistant torque to the motor, so I am trying to see if increasing the starting torque of the motor could help.
I saw this new starting wiring diagram in a book, but found no information about this wiring diagram elsewhere.
 

MaxHeadRoom

Joined Jul 18, 2013
19,980
There is also a danger that if the starting current continuous because of jammed M/C there could be damage to the motor.
If the proper O/L's were fitted between contactor and motor, there should be no damage to the contactor.
For one, I would think that whoever starts the granulator, they should be responsible in ensuring that the machine is clear, if the chamber is visible.
I would think you are attacking the problem from the wrong end.
Max.
 

drc_567

Joined Dec 29, 2008
773
... Another approach ... is to arrange for a drive pulley, run directly on the motor shaft, and a driven pulley, placed on the load shaft. The drive shaft pulley will be somewhat smaller in diameter than the pulley diameter at the load shaft, resulting in greater torque at the load. The only compromise is that the load shaft speed will be reduced in proportion to the diameter ratio of the two pulleys. ... If the load pulley is twice the diameter of the drive pulley, the load pulley will have twice the 1:1 ratio torque and will necessarily run at half the rotational speed.
.... I had a 120 VAC air compressor that employed the pulley concept to create the large start-up torque needed by the air compressor piston. The machine worked just fine as long as the ambient temperature was warm enough, despite the 70 Amp AC start-up current. However, as cold weather moved in, the piston cylinder walls contracted and caused excessive starting frictional forces, resulting in repetitive trips to reset the AC circuit breaker.
 

Thread Starter

mywaytos

Joined Jan 22, 2019
7
There is also a danger that if the starting current continuous because of jammed M/C there could be damage to the motor.
If the proper O/L's were fitted between contactor and motor, there should be no damage to the contactor.
For one, I would think that whoever starts the granulator, they should be responsible in ensuring that the machine is clear, if the chamber is visible.
I would think you are attacking the problem from the wrong end.
Max.
Yes, Max. Currently we should check if the chopping chamber is clean before each restart to avoid damage to the AC contactor. I am just looking to see if there is a foolpoof solution to this problem.

There is also a danger that if the starting current continuous because of jammed M/C there could be damage to the motor.
If the proper O/L's were fitted between contactor and motor, there should be no damage to the contactor.
For one, I would think that whoever starts the granulator, they should be responsible in ensuring that the machine is clear, if the chamber is visible.
I would think you are attacking the problem from the wrong end.
Max.
 

Thread Starter

mywaytos

Joined Jan 22, 2019
7
... Another approach ... is to arrange for a drive pulley, run directly on the motor shaft, and a driven pulley, placed on the load shaft. The drive shaft pulley will be somewhat smaller in diameter than the pulley diameter at the load shaft, resulting in greater torque at the load. The only compromise is that the load shaft speed will be reduced in proportion to the diameter ratio of the two pulleys. ... If the load pulley is twice the diameter of the drive pulley, the load pulley will have twice the 1:1 ratio torque and will necessarily run at half the rotational speed.
.... I had a 120 VAC air compressor that employed the pulley concept to create the large start-up torque needed by the air compressor piston. The machine worked just fine as long as the ambient temperature was warm enough, despite the 70 Amp AC start-up current. However, as cold weather moved in, the piston cylinder walls contracted and caused excessive starting frictional forces, resulting in repetitive trips to reset the AC circuit breaker.
Thanks drc_567. Now we do have a pulley v-belt transmission for this granulator. Change the size of the pulley will contribute. However, the speed of the granulator shaft should be limited to be a range, so the size of pulleys could not be randomly adjusted. That's why I turned to the electrical side to solve this problem.
 

MisterBill2

Joined Jan 23, 2018
5,173
You could also use a centrifugal clutch so that the motor could get up to speed before engaging the shredder. Requiring an inspection of the shredding chamber is OK but eventually somebody will not check. One other option would be to reverse directions for every start to allow jams to clear themselves.
 
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