Pony Motor

[LesL]

Hi Guys,

I wish to upgrade from a 150kW 4 pole motor to a 330kW 4 pole motor. The application is a wood chipper in a sawmill.

The supply to the MCC this motor will be supplied from is not large enough to support any thing greater than a 250 kW motor.

I am thinking of using a pony to run up the large motor and when at sync DOL the motor.

I am also considering using a second 150kW coupled directly to the existing 150

Has any one any experience in this type of hook up

Thanks
Les L

 

[cbarn24050]

Hi, 1 of the more amusing propositions iv'e seen for a while

 

[jwerthman]

I have seen both approaches used successfully. The tandem 50% capacity motors has some appeal particularly if there are times when only half the power is required. It can also provide some redundancy at reduced capacity, which may or may not be worthwhile in a sawmill application. With either approach, just make sure that you have sufficient torque to accelerate everything that is on the shaft.

 

[GGOSS]

Hello LesL,

Both options are potentially valid and worthy of further consideration. However before one can comment with a YES/NO type response some additional information regarding the supply is needed.

When you say the suppy is capable of 250kW, can you please explain whether that determination has been made on the basis of continuous capactity or on starting capacity ie maximum starting/overload current?

Regards,
GGOSS

 

[edison123]

LesL,

I agree with jwerthman especially with starting torque. However, you may have to enhance your supply system to support the present load of 330 KW.


cbarn24050,

ignorant and insulting as usual.

 

[imok2]

If your main concern is mainly with starting load, then maybe you should consider a new soft start starter

 

[ScottyUK]

LesL,

We use the pony motor arrangement successfully to bring a 2000HP 3.3kV motor up to running speed prior to energising. This minimises the surge on the 3.3kV network compared with a DoL start.

cbarn24050, what is it you find amusing? Or do you laugh at everything that is beyond you?

 

[jbartos]

Suggestion: It depends on the motor shaft load requirements that are not very clear from the original posting. Definitely, the MCC can supply 250kW to 330kW motor only.
What about buying a diesel generator under an assumption that the MCC feeder is not possible upgrade to 330kW +.

 

[rhatcher]

jwerthman has some good points with respect to the benefits of tandem 150kw motors and Imok2 is correct that a soft starter on a single 330kw motor is a simple and direct approach.

A pony motor is not most practical approach on a motor of the size you are talking about. A soft starter or reduced voltage starter for the 330kw would probably be less expensive than installing a separate pony motor with an additional starter, wiring, and installation costs. However, as mentioned by scottyuk, a pony motor would work and does make sense on larger motors and at higher voltages. Which brings me to my last point, cbarn24050's comments are inappropriate and unprofessional. I hope he doesn't discourage your creative thinking or discourage others from asking legitimate questions on this forum.

 

[tmahan]

Actually for the case where the motors are coupled only a 150kW softstarter may be required.

If the application permits it is possible to use a softstarter to start the first motor. Once the motor is "at speed", a contactor can be used to switch the second motor onto the line.

This still does nothing for you if the MCC is limited to 250kW. Power requirements and limitaions are really independent of starting method selected.

 

[jbartos]

Suggestion: The 250kW MCC and 150kW motor leave 100kW spare, which is not enough for the “would be added” 150kW motor. 50kW is missing. However, if the 150kW motors happen to be loaded on their shafts 75kW only, then there will be 100kW spare within the MCC left.
Therefore, the LesL original posting needs to be elaborated on in this respect.