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Generators & Motors General Discussion Antique Generators, Light Plants and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Motors General Discussion

Turn motor into generator


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  #1  
Old 07-05-2007, 06:31 PM
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vern0n vern0n is offline
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Default Turn motor into generator

I have an old 110 volt 1hp motor, the kind with brushes. Has anybody turned one into a generator? How would you rewire it? What volt range would it be? Just looking to display something and wondered if I could use this old motor. Thanks!
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Old 07-05-2007, 08:49 PM
armandh armandh is offline
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Default Re: Turn motor into generator

yes a typical AC/DC "Brush Type" motor can be run as a DC generator.
Chances are the brush position is not ideal for gereration.
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Old 07-05-2007, 09:27 PM
Douglas Douglas is offline
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Default Re: Turn motor into generator

That sounds like it could be a repulsion motor.

How old is old?

And is this an AC motor?
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Old 07-05-2007, 10:12 PM
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Default Re: Turn motor into generator

It is an A/C motor, looks like it was made in the 30's-40's. I don't know what a repulsion motor is. You can move one of the brushes to change the speed. It's a big heavey thing.
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Old 07-05-2007, 10:41 PM
Franz Franz is offline
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Default Re: Turn motor into generator

Dust it off gently & cherish it.

You have a Repulsion/Induction motor there, and they are becoming rare.
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Old 07-07-2007, 12:40 AM
Raymond Raymond is offline
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Default Re: Turn motor into generator

Search my many posts on induction generators. No rewiring or connection is necessary. just connect it across the line and spin it at the rated slip above synchronous speed. IE if its rated at 1750, rpm, you would spin it at 1850 rpm for full output which will be the power input minus the losses. A 1 hp motor would generate about 5oo watts with a 1 HP driver.
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Old 07-07-2007, 06:47 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Turn motor into generator

A motor hooked to line voltage and overdriven will generate current, but won't it quit if the line voltage fails?
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Old 07-07-2007, 07:12 PM
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Talking Re: Turn motor into generator

Quote:
Originally Posted by J.B. Castagnos View Post
A motor hooked to line voltage and overdriven will generate current, but won't it quit if the line voltage fails?
Yes it will quit, generating power if the Grid fails, which is why Induction
Generators are easy to setup and use as coGeneration Systems. Never
have to worry about "Islanding".

Bruce in alaska
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Old 07-07-2007, 08:35 PM
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Default Re: Turn motor into generator

This info isn't for a repulsion start motor. However I would think a repulsion start motor would make a better generator if one had the proper knowledge to make the conversion. Take a look at the link below.

http://www.redrok.com/cimtext.pdf
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Old 07-07-2007, 09:41 PM
Jim Rankin Jim Rankin is offline
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Default Re: Turn motor into generator

repulsion start/induction run motors behave as a common split phase motor once they are spinning above about 3/4 rated speed. this is when the centrifugal mechanism lifts the brushes and shorts the armature effectively converting the rotor to a squirrel cage design.

so it should act as an induction generator and might also be useful as a "starter" for the engine that will drive it due to the good starting torque. It may generate enough power (roughly regulated voltage most likely) to run some lightbulb etc when self/statically excited, but will likely quit generating when a significant load is placed on it unless it is operated in parallel with a stiff source of reactive current like the power grid.

I would use the rated amperage of the motor as a guide to loading it safely. Remember, when connected as an induction generator, in parallel with the mains electricity, the output of the "motor" is regulated by the speed of the driver. Since the grid can ultimately absorb any amount of power it may generate, amperage is minimal at synchronous speed and increases above (generating) or below (motoring) synchronous rpm.

A DC generator or alternator would probably be a more easily controlled demonstration unit with a battery on board to smooth the output.
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Old 07-12-2007, 12:29 AM
Keith Kessler Keith Kessler is offline
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Default Re: Turn motor into generator - syncronos motor?

Hi,

Not trying to hijack the thread but I have a related question. I've got a rather large (100 hp) syncronos (sp) motor. It sure looks like ac generator inside. It has what looks like an exciter on one end of the shaft that feeds into the main windings. Anyone have any experience with stuff like this?

Thanks,

Keith
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Old 07-12-2007, 08:02 AM
armandh armandh is offline
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Default Re: Turn motor into generator

you say that the brushes can be moved to vary the speed.

is there a knob to do this or are tools required?

if a knob it may be a DNR type motor. where there is a rotating [brush/slip ring fed] stator and an external field fed DC from movable brushes on a commutator with windings co-wound with the stator

http://www.faurndau.de/en/produkte_dreh_typ_lauf.html
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Old 07-12-2007, 09:44 PM
Jim Rankin Jim Rankin is offline
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Default Re: Turn motor into generator

Keith,
look at the posting under Buda/Century generator on this board. I put up some links to the threads with pictures of the Century alternator that milesdw and I have. I believe it would be a similar arrangement to what you have.

the problem with synchronous motors is they don't get themselves up to speed under a load very well. there's several techniques to get around this little problem.

one is to disconnect/clutch in the load after the motor is up to speed. this is pretty costly in gearboxes and clutches.

The armature can have a squirrel cage winding to allow it to accelerate as an induction motor (with slip) before the field wound on the armature is energized and it locks into synchrony with the stator field. I believe this is the reason for the squirrel cage winding on the Century generator/synchronous motor.

another driver can be used to accelerate both the motor and load until the field is energized and the motor locks into synchrony.

there are also non synchronous, wound rotor induction motors where a series of resisters is placed across the slip rings to accelerate the motor in a stepwise lessening of slip until the final "run" slip is at a minumum, but still not synchronous.

the advantage of synchronous motor as a driver is efficiency due to no slip. Another benefit in an industrial setting is to run it overexcited to correct the overall power factor of a factory so the utility doesn't charge a penalty for poor power factor. this is more and more being done with capacitor banks and controllers to switch them in as needed to keep power factor in the desired range.

You should be able to look up information about most large motors online if you need to have more information.
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