Generator as Motor

[Harold in CR]

Didn't know where to post this, so, it's here.

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.

 

[amberwolf]

AFAIK, the constant power you can get out of using the gen as motor is about the same as what it could provide as a gen. So as long as that 100A isn't a peak, but is continuous, then you could run that thru it ok, at 30V.

You can probably even run it at 60-100VDC, too, though brush and comm wear will be accelerated, for higher peak power at the same current levels, but you'd not want to be drawing the full 100A for very long at the higher voltages, unless you are actively cooling the motor better than it was at it's original ratings.

Brush advance might help, if it's capable of it (depending on how it's made, even if it doesn't have that built in you might be able to remachine the mounting points of the brush-end motor cover plate if the holder is mounted to that, so it can rotate and be locked down in a new position). But advancing the timing for it's higher speed will increase the problems at lower RPMs, so you have to makea tradeoff between the two depending on how much you expect to operate along each range, and which part is more important to your application.

As for how much power it'll take to run any particular vehicle, best option is to first look thru http://evalbum.com for vehicles like the one you're considering, and see what power it takes them at what speeds, so you can see what it'll probably take you for the same speeds. (as an example, it could potentially take half-again the power at 60MPH to go 70MPH, depending on the vehicle's aero and such).

If you're running the motor at higher voltages to get higher speeds, also make sure you're not exceeding it's max RPMs. Brushed motors don't tend to take well to that, moreso for the larger diameter ones than smaller. Dunno what size yours is.

 

[Harold in CR]

Thanks AW. Aircraft Generators are high RPM units. The larger one I have is rated at 3000-8000 RPM's. This one should be, at least, 3000-5000 I would think. Can't remember what is on the Name Plate.

Do you think my numbers are close to what I can get out of it ?? The Generators are used as welders, so, that 100A is continuous. 60MPH would be good as cruising speed.

I'm trying to have a Motor Guru get back to me, on his opinion, but, he might be busy getting the Lightning EV Moto Racer prepped.

I DO Know a guy that has a 400A Starter-Generator, that's about the same physical size as this one, and, he put it in a Carmen Ghia, at 72V. He got around 60MPH with it, so, I'm thinking mine should be good for 60 on a Moto ???

Thanks again, Harold

 

[amberwolf]

I'd guess it'll probably work fine, but I don't know for sure. Without just trying it, the best bet is to look around on evalbum for similar size/weight vehicles and see what power usages they had at speeds you want to run. Then at least you'll know about what you'll have to have out of it to do what you want, and then you can experiment with what it can actually do.

If the bigger (larger diameter?) motor is capable of a certain RPM, then the smaller (lesser diameter?) motor should be able to spin even faster, depending on it's design--if they're both made the same way, same quality, then smaller=faster, usually.

 

[Harold in CR]

Only reason I posted this, is, the Generator is 1300 miles away, in Fl. I wanted some idea of what this might be capable of, before I had it shipped down here.

Thanks for your input, AW. I just wish one of the Motor guys, or, an Engineer might have some ideas ??

 

[amberwolf]

You might check over on DIY Electric Car forums, there are a couple of motor experts there, such as Major and Jim Husted, that often answer such questions. It's been asked there before so there should be a thread already for aircraft generators as motors, but I don't remember what it was called.

Other than that thread, then best thread to try in other than a new one specifically about this specific one is the Using a Forklift Motor and Choosing a Good One (as I recall other motors than forklift motors being asked about in that thread).

 

[Harold in CR]

I did post on the DIY Car forum. Major has been MIA until recently. I will shoot him a PM.

This is NOT a starter-generator. It is just a generator. I have searched a lot of site to see how this might function. Seems that generators are so "old School" most people don't know anything about these.

I'm mostly concerned about brush location on the commutator.

In the old days, Ford Starter motors were used for long-line fishing line winders. Generators were motored to see if they had open or shorted circuits. Then, one would hold the field points open on the regulator to "Flash" the field, and start the Generator charging again. This was usually needed after turning the Commutator and installing new brushes.

Never tried long term motoring of a Generator, though.

 

[Harold in CR]

Major got back with me about the Generator.

Has been several views on this thread, so, I'm sharing what I was told.

Generators, brushed, are about the same as motors, IF excited properly. Name plate info is conservative, same as DC Forklift motors. Overvolting the generator would allow for more RPM's-power. This generator might be 5000 RPM's or so, as is.

Now, just need to find a way to control it.

Need to find a Snowmobile or Moto CVT tranny. Make an Automatic shifting Motorcycle. :wink: :wink:

 

[John in CR]

I heard about this guy with a 3kw continuous/10kw peak 36V brushed motor and Comet 10hp CVT with extra belt all mounted up on a motorcycle swingarm with rear wheel all ready to go. The guy even has a 400A 36-48V Curtis controller, and best of all it's all in Costa Rica already and for sale at bargain prices, because he knows that brushless is the future.