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#196468 - 10/06/10 12:56 PM Generators & Mtrs
Yoopersup Offline

Registered: 03/04/03
Posts: 826
Loc: Michigan
150 KW 480 three phase generator.
Whats largest size mtr. it can start with cross the line starter?
Largest size mtr. with soft start.??
Largest size motor with VFD.
I;m looking for a place I can refer to for this info.
Thanks yoopersup

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#196473 - 10/06/10 03:00 PM Re: Generators & Mtrs [Re: Yoopersup]
mxslick Offline

Registered: 10/24/04
Posts: 785
Loc: Atomic City, ID USA
Not enough info provided..the real answer will depend on many variables, such as the motor's design and efficiency, and most importantly what kind of mechanical load the motor is driving.

You will need to look at it on a case-by-case basis to be sure your generator can handle the largest motor load.

And the sequence of load pick-up will make a difference.
Stupid should be painful.

#196474 - 10/06/10 03:19 PM Re: Generators & Mtrs [Re: mxslick]
Tesla Offline

Registered: 06/16/04
Posts: 1280
Loc: Sacramento, CA
Normally, the factory would supply those stats.

Is the unit asynchronous, synchronous, or synthetic wave form?

What constitutes an unacceptable voltage sag?

What is the duty rating for the alternator?

What is the duty rating for the motor?

Does it start loaded or unloaded?

What are the specs on the VFD?

These are engineering issues best resolved by the factory.

#196476 - 10/06/10 05:16 PM Re: Generators & Mtrs [Re: Tesla]
Yoopersup Offline

Registered: 03/04/03
Posts: 826
Loc: Michigan
Is there a site or Computer program all info can be put in answer come out.
I know Generator suppliers well also supply the info. Just looking for a simple way to actess
same info.

#196477 - 10/06/10 05:36 PM Re: Generators & Mtrs [Re: Yoopersup]
Yoopersup Offline

Registered: 03/04/03
Posts: 826
Loc: Michigan
The formula is: Motor HP x KVA per HP x (1000 / (Volts x 1.73)) = LRA. Example: A 20 HP Code G motor connected to 460 Volts requires what LRA? Refer to Chart A and select 6.29 KVA/HP, from Chart A, for Code G. The formula becomes: 20 x 6.29 x (1000 / (460 x 1.73)) = 125.8 x 1.26 = 158.5 = 159 LRA. The generator must produce 159 Amps at 460 Volts, to safely start this motor. Use formula: 1.73 x Volts x Amps x .8 / 1000 for generator KW size.
Found it! heres part of it harts for mtrs. also on it.


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