How do I overvolt a DC motor?

[Electric Mongoose]

I have a bunch of small motors lying around, and I wanted to see how much voltage they can take until they burn themselves out. I've heard of using train transformers, but the only ones I've seen go up to about 14 volts. I connected eight 9-volt batteries together (72 volts) and all of my motors still held together. I like how much voltage I can get out of the 9-volt batteries, but I don't want to be using them all up. If anyone can give me a suggestion on what I can use, it would be greatly appreciated.


Thanks,


EM


P.S. I live in the US and our outlets are 120V.

 

[FRITZHID]

Get a variac (autotransformer) 0-132v AC that can be fullwave rectified to DC

 

[mattheww50]

I would be careful overvolting DC motors. They can do much more than simply overheat. Push them hard enough, and the Rotor assembly disintegrates into Shrapnel. When I was a Univeristy Student we had a before and after photo on the wall in the motors lab. It was a 750 hp shunt wound DC motor. The shunt winding had been inadvertently opened. That caused the motor to run away, and the rotor assembly did indeed disintegrate. The area looked like Bulldozer had driven through the building.

 

[FRITZHID]

I don't believe he's talking about multi-HP motors, let alone 100s of hp.
Most smaller motors will fail before flying apart. Bearings seize, coils fry, brushes burn, etc.

 

[bwDraco]

Pretty sure he's talking about low-power motors. The first thing that fails with these kinds of motors when subjected to overvoltage is the insulation of the stator windings. The wire overheats under excessive voltage and the insulation melts, resulting in shorts between loops of the wire. This permanently reduces the power output of the motor, and further insulation melting can eventually result in total failure of the motor. This is what is typically happening when you see a motor generating smoke.

—DragonLord

 

[thinkFlashlights01]

I have a bunch of small motors lying around, and I wanted to see how much voltage they can take until they burn themselves out. I've heard of using train transformers, but the only ones I've seen go up to about 14 volts. I connected eight 9-volt batteries together (72 volts) and all of my motors still held together. I like how much voltage I can get out of the 9-volt batteries, but I don't want to be using them all up. If anyone can give me a suggestion on what I can use, it would be greatly appreciated.


Thanks,


EM


P.S. I live in the US and our outlets are 120V.

Just apply a lm317 (Or whatever it is) to the motor and you have your variable voltage control.