An induction generator (same thing as an induction motor) functions by being connected to the AC power line, just as it would be as a motor. Using a common squirrel cage motor as a generator is feasible, but not in the free-standing mode you imagine. The reason nobody has posted a circuit to turn your shaded pole AC motor into a generator is because it can't be used as you had hoped. The simplest option is a car alternator? Designed to give a regulated 15V out over quite a range of speed, though you will have to gear the input up to a decent output current, I'd guess a couple of thousand revs at least. The only type I can think of like that which you may find in scrap is a washing machine motor?Īs these are mains voltage, you should be able to get some useable power out at relatively low speeds. Ideally you want one with a 'shunt' field, where the field coils are designed to run off a separate supply.
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Many smaller motors (like electric drills etc) use series field coils, so they need lots of current to energise them. To use a motor as a generator, it needs some form of magnetic poles, whether these are wound field coils (so electromagnets) or actual permanent magnets. The rotor is an array of copper bars without any form of magnetic element, the magnetic field is _induced_ by transformer effect while they are powered from the AC supply (hence induction motor). Turn the motor at 3000 rpm and it will generate AC at 50HZ.Ī lot of AC motors are of 'squirrel cage' design. The only way to make your motor function as a generator would be to take it to pieces, remove the "shading rings" (the copper loops), and replace the rotor with a powerful permanent magnet. To charge a battery, you will need to put a diode in series with the motor so that the current cannot flow backwards and run the motor! When turned fast - via a gearbox - it should generate some useful current. I have found that "Maxon" motors are very good. You should feel some resistance to turning compared to when the terminals are open. To test if the motor is any good, try shorting its terminals and try turning it by hand. It needs to have an operating voltage a bit higher than the voltage you want to generate. If you want to charge a low-voltage battery your best bet would be to find a good quality, brushed, permanent magnet DC motor. Although it is feasible to use an AC induction motor as a generator your motor is probably not the best type to use.