HOW TO SELEC A MOTOR WITH VFD TO START A GENERATOR?

Hello,

I have a Generator of 1000KVA, PF 0.8, 1800rpm, 2300V, 251A, I need to select a motor in order to start the generator.

Background:

The motor will be start with a VFD
The main use of the generator is to test motors without load, to verifiy vibrations. So, we will a various types of motor most MV.

Does the application of the generator can help me reduced the power needed for the motor?

Thanks for your support!


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Why not just use a 1MVA VFD to drive your motors under test ?

+1

There is a facility in the adjacent town of Sparks that tests very large electric motors for fan blade pushing / moving natural gas in buried 6 foot diameter steel tubing across this country...

They get a full load tank truck of liquid N2 every other day from the bay area by interstate 80 when testing new motors using nitrogen as a simulated natural gas...

Power is brought by high tension 3 phase 60 Hz power lines from Valmy a coal generating power plant in middle Nevada..

I guess you lost some dots along the way....

100KVA, PF 0.8, 1800rpm, 230V, 25.1A looks more realistic for a home or light industrial user.

But if you want to use a motor to run a generator that in return powers another motor: Then you only get a lot of losses and waste about 50% of the power.
Far better to drive the motor directly with a suitable controller or motor drive.
If it is an ongoing thing with a lot of tests you can consider a capacitor bank to even out the inductive load on the grid.
Too much inductive load is not good and you might be charged more than with a proper compensation.

iceng18 days ago

After you start this very large 1_million VA generator what do you use to keep it running ?

Is the 1MVA generator a 3 phase 60 cycle machine ?

Is the start motor an IC engine (Internal Combustion) fuel motor ?

I think he wants to power a small town or his own particle generator.

Wow! That's a big generator. I mean, like, 800 KW. That's enough electric power to run a small town... well, maybe a neighborhood. I think the usual rule of thumb is about 1KW per house.

Anyway, it must be a big machine. I am kind of guessing it is in the same class as some kinds of giant construction machines. For example there are giant dump trucks (Wikipedia calls them haul trucks) that have engines with megawatt scale mechanical output power. E.g. the Caterpillar 797B,
https://en.wikipedia.org/wiki/Caterpillar_797B

has engine capable of like 2500 KW, mechanical.

It is surprising to me that your giant machine did not come with a mechanism for to get it started; e.g. a starter motor, or possibly even a smaller engine, whose only job is to start the big engine.

I am also surprised this machine did not come with a manual.


For something that big, I would definitely want a manual, or whatever documentation is available.

Also I am not sure what you are asking in the second question,

"Does the application of the generator can help me reduced the power needed for the motor?"

I mean, I can give you a hand-waving type explanation of the physics involved in starting an engine. Basically the work the starter has to do is some work to overcome friction, and also some work that goes into the kinetic energy of the engine's moving parts. Of course both of those scale with the size of the engine. So a bigger engine requires a bigger starter.

Also it may be the case for diesel engines, that diesel engines require more energy to start, because, I think, for diesel engines there is a thermal component too; i.e. the starter has to put energy into increasing the engine's temperature. Although, honestly, I am not sure about this. I really do not have much experience with diesel engines

Also, I guess Wikipedia, can maybe give you general information about engine starting,

https://en.wikipedia.org/wiki/Starter_(engine)

Unfortunately, I do not have any knowledge really specific to starting your machine... besides my suggestion that you find a copy of the manual, or whatever documentation is available for your machine.