# DC Generator As Motor



## Harold in CR (Sep 8, 2008)

I bought this Brushed Generator over 30 years ago. 

I have a 30V DC Brushed Generator, from Aircraft, I believe. It's 100 Amp output. I know Starter-Generators can be used as motors. Can this Generator be used as a motor, and, what kind of power can I expect out of it ??

Seems that 30 X 100 = 3000, so, that would be 3KW, or about 4 HP ?? If it is powered up with 72 Volts, would that KW be the same, or, will it change much ?? Would I need to advance the brushes a little. to help dampen the arcing on the commutator ?

Reason I ask is, I nearly bought a Motorcycle today, with a blown engine. Would this motor be sufficient to run a Motorcycle on the road, without being slow enough to get run over ??? Motorcycle was a single Cyl., at 150CC. Probably about equal to a Ninja 250 or so. ??

Thanks for any ideas or info.


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## major (Apr 4, 2008)

Hi Haro,



Harold in CR said:


> I bought this Brushed Generator over 30 years ago.
> 
> I have a 30V DC Brushed Generator, from Aircraft, I believe. It's 100 Amp output. I know Starter-Generators can be used as motors. Can this Generator be used as a motor,


Sure, generators will run as motors, if properly excited.



> and, what kind of power can I expect out of it ??


Pretty much the same power as motor or generator.



> Seems that 30 X 100 = 3000, so, that would be 3KW, or about 4 HP ?? If it is powered up with 72 Volts, would that KW be the same, or, will it change much ??


Possibly the same continuous rated power for motor or generator operation because the machine losses would about the same and that determines the machine heating and therefore the rated power. Like when these guys run motors at above nameplate voltage, the RPM vs load increases. The same would apply to the generator. Higher voltage, higher RPM, and higher power for a given load (torque or amps). And like motors, generators will have higher peak power than the nameplate continuous rating.



> Would I need to advance the brushes a little. to help dampen the arcing on the commutator?


This depends on the particular design of the generator. Some of the old generator/starters for aircraft had interpoles, so no brush advance.

Hey, you got it, just start playing around with it. Get it running at 12V and go up from there. What's the worst that could happen? Waste some time? But you'll learn something, hopefully 

major


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## Harold in CR (Sep 8, 2008)

Thank You Major.

Only reason I ask these questions is, the Gen is 1300 miles away. A $350.00 Plane ticket, or, $250.00 to ship a small crate down here, before I start letting out the Magic Smoke. 

A WAG, what type controller would I need ?? Are these compound wound or sepex wound ?? I can't for the life of me remember how many connection studs are on the Gen. Starter-Generators require a special controller, although, I did read an article, where a guy was using an Alltrax controller and a rheostat for the field windings. Just was a very old article from the 70's, and no way to try to contact the guy. 

Really appreciate the input. Thank you again. Harold


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## major (Apr 4, 2008)

Harold in CR said:


> Only reason I ask these questions is, the Gen is 1300 miles away. A $350.00 Plane ticket, or, $250.00 to ship a small crate down here, before I start letting out the Magic Smoke.


Hey Harold,

In that case, you might reconsider. 30 years old machine 1300 miles away for $300. Can you do better finding a used fork motor, like from eBay or locally?



> A WAG, what type controller would I need ?? Are these compound wound or sepex wound ??


That's the other problem. Don't really know how that generator is wound, shunt or compound, so don't know if there even is an available controller which would work 

I thought you had the generator in hand. I'd think twice before spending that much to ship it when the same money could go towards a system more likely to work out for a first time conversion.

But if you're emotionally attached to the machine and want to work with her, WTH 

major


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## Harold in CR (Sep 8, 2008)

No attachment at all. You should take a week and come down for a visit. It's nearly impossible to find what I want, and, when they see the blue eyes, they double the prices. I'm slowly learning how to get back at them, though. 

I go to Fl. at least once a year, so, the cost would be absorbed as "family visit time". Then, I can carry back 100 pounds of goods for $30.00 as baggage. Generator is probably 30#. 

My Son is coming down in May, and, might bring a friend. That make more baggage room for my junk. I will see if he can dig through the warehouse bay and find the Gen and tell me the connection studs location and amount. 

I also have 3 Alternators here to play with, as motors. Controllers are $140.00, though. ?????


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