Instructables

Can a vacuum cleaner motor generate electricity?

I have a vacuum cleaner motor that runs off straight AC from the wall. I think it's like 120 V AC right?.. anyways it's got a huge amount of toque and i'd like to attach it to a stationary bicycle and pedal it to generate electricity. I know all the instructables for this my only quam is the type of motor. I'm not buying one. This is what I have and furthermore I don't even know if it's like universal i guess they call them..I do know that it is a brushed engine (as in it's not brushless) by the way if you haven't caught it yet my electrical jargin is very weak. Thanks for any help you can give me.-Ask me if you need more info.

frollard5 years ago
I may be wrong, but I think it's more hassle than its worth.

a motor works by inducing a current in a wire in a magnetic field, which in turn generates motion. In your AC motor, the magnetic field is also generated by the electricity input. No input = no magnetic field - thus there is no stationary magnetic field to work with. Therefore; I dont think it's nearly as simple as a standard DC motor generator.
ImageMaker2 years ago
If your vacuum cleaner motor is a brushed type, it's almost certainly a "universal" motor; this kind *can* be converted to a DC generator, but the voltage and current regulation are poor. I explained how you could do this in a reply below, but be aware that the output voltage will increase with the current draw as well as with the rotation speed -- it works, but it doesn't work very well.

A permanent magnet DC motor makes a better bicycle driven generator; the current won't affect the voltage, only your pedaling speed. Even better is an alternator, like the ones in cars, along with its rectifying and voltage regulating system, but those typically require more mechanical power to operate than a person on a bicycle can produced for very long.
bill35045 years ago
no an ac motor will not generate electricity it has to be a dc motor
Actually, if you can apply an external magnetic field to the motor's field core, you can generate DC from a "universal" motors -- those with the field and armature wired in series, most of which will also run on either AC or DC. This includes most small power tools like circular saws, angle grinders, corded drills, and so forth (I fix these for a living, BTW, and had some electrical engineering courses in college).

The simplest way to do this is to expose the field (say, cut two holes in opposite sides of the housing, centered on the two field windings) and apply two strong permanent magnets to the core, arranged so their fields add (put the N pole on one side of the core, and the S pole on the other). This will provide a starting excitation; once current begins to flow, it will augment the field from the permanent magnets, and as long as you have a load to power, you'll continue to receive current (the faster you turn the generator, the more voltage and current you can draw). The output will be DC, BTW -- polarity depends on the orientation of the "exciter" magnets relative to the rotation direction of the motor.

You *could* even remove the exciter magnets once you've started to draw a load, but if the load is switched off (say, you turn off the lamp), you'll need the exciters to start generating power again unless the field core retains enough residual magnetism to do the job (it might, after prolonged use in DC operation).
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So my generator out back has a DC generator which is changed to AC?
Most likely it has an alternator -- a generator that produces AC directly. There's a speed control to give the correct frequency (50 or 60 cycles per second, depending where you are) and a system to regulate the output voltage. There used to be conversion kits that would let you tap AC voltage off one phase of a car alternator and convert it to 120 V to run power tools or appliances -- without preventing the alternator from running the car's accessories and charging the battery!
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