Size of generator for a large electric motor

[Peter G. ShawParticipant @peterg-shaw75338]

Hi folks,

This is a real oddity!

My grandson, who works with his dad as an agricultural contractor has dreamed up an idea for powering a specialised agricultural piece of equipment from a rather large electric motor powered in turn from a diesel generator. I think this piece of kit is currently powered by a tractor so if it could be powered separately, then the tractor could be released for use elsewhere.

Anyway, he has seen a motor on Ebay so these are the details from the advert:

200kW, 400V, 3 phase, 50Hz, 342A 1488 rpm.

The question is, what size of diesel generator would be required to power the motor?

I've already suggested that the genny will need to be somewhat larger to allow for the startup current – at least that's my very limited understanding of motors tells me. Other than that, I've no idea.

Regards,

Peter G. Shaw

[Peter G. ShawParticipant @peterg-shaw75338]

[David Standing 1Participant @davidstanding1]

I'm suspecting you didn't really mean 200 kw

[Tim StevensParticipant @timstevens64731]

200 KW is about 268 Horsepower.

Assume losses of 50% (well it will be used on a farm …) so we need a bit over 500 HP from the Diesel motor. There's a man in Oregon with something vaguely suitable, perhaps:

NEW OEM Complete Audi Q7 CCGA V12 6.0L TDI Diesel Engine Long Block 500HP 08-04

So if your lad has 18,000 dollars to spare …

Regards, Tim

[JasonBModerator @jasonb]

Well if 200KW was right then something like a 300KVA generator would be needed

Edited By JasonB on 18/09/2017 18:31:54

[oldveloParticipant @oldvelo]

Hi

Perhaps I Have read this wrong.

What is the Tractor Horse Power? Then a diesel of similar power to drive the machine directly would be the way to go.

Eric

[Michael GilliganParticipant @michaelgilligan61133]

Posted by David Standing 1 on 18/09/2017 18:13:38:

I'm suspecting you didn't really mean 200 kw

.

Why ?

Peter also mentioned 342A at 400V

MichaelG.

[Matt de HoestParticipant @mattdehoest99598]

Try this calculator (http://www.dieselserviceandsupply.com/Power_Calculator.aspx). My understanding is that kW draw ought to be 0.6-0.8 of kVA produced by the generator but happy to be corrected.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Peter G. Shaw on 18/09/2017 18:03:38:

… Anyway, he has seen a motor on Ebay so these are the details from the advert:

200kW, 400V, 3 phase, 50Hz, 342A 1488 rpm.

The question is, what size of diesel generator would be required to power the motor?

.

That will need to be one big generator set !!

Something roughly the size of a shipping container, methinks

MichaelG.

[Les Jones 1Participant @lesjones1]

I am guessing that this is the advert for the motor. I agree with JasonB that you would require a generator greater than 200 Kw to alow for the starting current even when using a star delta starter. Why not just buy a large diesel engine to power it directly and save the power conversion losses.

Les.

[Martin CargillParticipant @martincargill50290]

Why not power it directly from a diesel engine? No need for a motor or a generator…..

[Neil WyattModerator @neilwyatt]

Guy Martin has a Merlin that needs a job to do

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Here we go …

**LINK**

https://www.generac.com/industrial/products/diesel-generators/configured/300kw-diesel-generator

MichaelG.

[Phil WhitleyParticipant @philwhitley94135]

Why not just power it directly with the diesel engine? Friend of mine at a local farm needed more current , and powergrid came up with some ridiculous cost for upgrade, so he bought an ex hospital V8 diesel stand by generator, but this now runs an entire seed cleaning and processing plant. I cannot imagine a single machine that needs 268HP, what the devil is it?

[Nick_GParticipant @nick_g]

.

I remember years ago working on a farmers out buildings that were powered by a generator.

I cannot remember the size of the generator but I do remember it being powered by a big Rolls Royce Eagle engine.

Nick

[JasonBModerator @jasonb]

Posted by Phil Whitley on 18/09/2017 18:51:03:

I cannot imagine a single machine that needs 268HP, what the devil is it?

Well you can get a John Deere with 600HP so there must be a need for them down on farm

[Nick_GParticipant @nick_g]

Posted by Phil Whitley on 18/09/2017 18:51:03:

I cannot imagine a single machine that needs 268HP, what the devil is it?

.

Farmers often branch off and dip their toes into other areas.

I know one that went into renting aggregate machines. ……. Rock crushers, screen and conveyor machines and the like.

Nick

[Peter G. ShawParticipant @peterg-shaw75338]

A little bit more info:

It's a grain crusher which does indeed require, I think he said, 200 kW. But since the OP, he's also said that the rpm required is about 500 so he's now thinking, in broad terms, that if it was geared down from 1500 (nominal), then that would possibly reduce the motor & genny requirements by about a third.

FWIW, between them they do have a lot of heavy duty equipment. I've seen some of it – huge tractors with 16 or more gears. In each direction at that! A device which is literally dragged through the ground to overcome the cumulative effects of the ground being crushed; hedge cutters, post knockers, etc.so I'm not that surprised at the power requirements.

Anyway, he's having another think.

I think what I'll do is point him at this thread, then he can digest the info herein at his leisure.

Many thanks,

Peter G. Shaw

[MuzzerParticipant @muzzer]

Most of the tractors we tend to see around the farms are actually surprisingly low powered but they are designed to run flat out all day. You'd need one of the big beasts to run that kind of gear I'm guessing.

This is John Deere's UK range. (Some) farmers are funny buggers and stick to one brand. My cousin and his late father always go / went for the green and yellow ones on their cereal farms.

Murray

[David Standing 1Participant @davidstanding1]

Posted by Peter G. Shaw on 18/09/2017 19:28:16:

FWIW, between them they do have a lot of heavy duty equipment. I've seen some of it

A device which is literally dragged through the ground to overcome the cumulative effects of the ground being crushed

Peter

A subsoiler. Not a big deal, every farm has one

[David Standing 1Participant @davidstanding1]

Posted by Peter G. Shaw on 18/09/2017 19:28:16:

I think what I'll do is point him at this thread, then he can digest the info herein at his leisure.

Many thanks,

Peter G. Shaw

Peter

Shouldn't take him long, there's plenty of vague here, as the original requirement still isn't clear!

That's not a criticism of you, but the reality is that all we know is that it is a 'grain crusher', and don't know what it is or its actual power requirements.

[Jeff DaymanParticipant @jeffdayman43397]

Whatever way you slice it, to build a high HP machine such as is being discussed is likely not going to be cheap. Unless they are in a very remote area or have an enormous qty of crop to process, I'd recommend getting quotes from local milling firms for the grain crushing. Chances are they will have plant for it already and usually rates for custom milling (at least in North America) are far lower than machine build or buy rates with depreciation and amortization of costs. Compared to cost of equipment build/ownership milling services are very inexpensive.

Now your grandson would certainly learn a lot building such a machine, you can't put a price on that . (but Dad might think twice if it's him buying 500 HP diesels, generators, 3" shaft couplings, fuel systems, motors, cables, switchgear…….)

Just my $0.02 worth, your mileage may vary.

[David Standing 1Participant @davidstanding1]

Jeff

Ah, but is it grain crushing, or milling? Two totally different things………

As I said above, the requirement is far from clear, so this just becomes a thread of endless guessing

[JasonBModerator @jasonb]

Posted by David Standing 1 on 18/09/2017 19:54:21:

 

As I said above, the requirement is far from clear, so this just becomes a thread of endless guessing

Does it matter what the use is. Original question was what size generator is required for a 200Kw motor. That would require a 300KVA genny to give a bit to play with.

Edited By JasonB on 18/09/2017 20:05:05

[Tim StevensParticipant @timstevens64731]

The speed of the device is low, but the power required is still going to be 200Kw, surely, whatever the speed. You can alter the torque by changing the gearing, but the power required stays the same.

Cheers, Tim

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