How can I convert a DC motor into a generator? What factors need to be considered?

Answer 1

This really depends on what type of DC motor it is.

If it's a simple permanent magnet DC motor, simply disconnecting its power source and running it backwards turns it into a generator. Rotations at the old "output" will cause an emf (a voltage) across the old "input." If you put a load on the old "input" then that EMF will start to drive a current. When that current starts flowing, it will become more difficult to turn the old "output" because more power will be demanded.

However, the motor's impedance may not be appropriate for being a generator. In other words, you may have trouble transmitting much power to your load. A small DC motor (for example, a small fan) that is meant to be a light load on a battery really shouldn't be made a source of power. It has most likely been designed to run with as little current as possible as quickly as possible. However, when you run it as a generator you are asking for it to generate as much current as possible. The components involved simply won't be optimal for this new task.

Note that if it's not a simple permanent magnet DC motor, then disconnecting the power source may also disconnect the source of magnetism within the motor. That will prevent any emf generation within the motor.

Also, if it's a "brushless" motor, running it in reverse will not turn it into a generator because the electronic components that are used to replace the brushes and control its output speed simply cannot be run "in reverse." (this is similar for other DC motors, especially more finely-controlled ones, like DC stepper motors)

Answer 2

Dc Motor Generator

Answer 3

As others have said, you could just hook it up. However, if you're using this for a real windmill (as opposed to a science project) you won't be happy with the results. Most DC motors won't provide enough power for practical use, and the voltage they generate is proportional to the speed at which they rotate, which makes it difficult to regulate the power for your use. A much better choice for this is the alternator from an automobile. An alternator has an exciter coil, which can be driven strongly at low speeds, and weakly at high speeds, so you always get the correct voltage out. Also, an alternator is meant to handle much higher currents than pretty much any DC motor you'll ever find. You can use both the alternator itself and the regulator (which is often built into the alternator) - just wire it up and it will produce 12 volts (in truth, more like 13.5-14.5 volts) at practically any rotation speed and load (within reason!) The regulator controls the exciter current to get the correct voltage out (and also includes diodes on the output coils to turn the AC output back into DC). You can get an alternator very cheaply from a junkyard, or not too expensive off of e-bay (or free from a dark parking lot with a few hand tools - Just Kidding!!!) it's an awful lot easier than trying to re-wind motor coils!!!

Answer 4

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RE:
How can I convert a DC motor into a generator? What factors need to be considered?

Answer 5

Let me correct TED.
A dc motor does NOT have to be spun backwards to generate dc power it can be rotated in either direction.

Answer 6

Depending on what you are doing you may want to use an AC Generator (Alternator) and add a 3-Phase diode bridge to rectify the output to DC.

Answer 7

just spin it. If you can contol the field winding you can contol the output voltage. The output is determined by two things
1. How fast a wire cuts the magnetic flux lines
2. How many flux lines - ie how strong is the magnetic field.

So rpm and field current are the determining factors.

Answer 8

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By applying torque to the shaft, you can make it produce energy; however, if you want to produce stable energy flow in both "high rpm" and "low rpm", then you need a two pole stator with the use of a stator winding.

Answer 9

All electric motors are generators. All generators are electric motors.

The only difference is how you are using it.

Answer 10

Generators are generators, and Motors are motors...
You can't without extensive modification, A motor cannot generate stable current without a voltage regulater circuit, not to mention the heat will burn up the coils