Most office network fans use asynchronous motors with a squirrel-cage rotor. Such a motor can only convert electrical energy into mechanical energy, but not vice versa. When its shaft rotates forcibly, electron movement cannot occur in its windings, since there is no magnetic field on the rotor.
But it is still quite possible to use such an engine as a generator, after simple modifications.
Converting an asynchronous motor into an alternating current generator
We disassemble the engine into parts. Usually it is held by 4 long screws in the corners, after unscrewing which the motor is divided into two covers and a stator winding.
The stator will not be modified; we will leave it as is. We move on to the rotor and remove the cast short-circuited winding from the shaft.
Instead, we will remake the rotor with permanent magnets. To do this, we will drill out a ring from thick PCB using a metal ring bit.
Let's press this ring onto the shaft, and then, using superglue, glue permanent neodymium magnets with alternating polarity onto it.
To check, connect to the output of one of the windings Light-emitting diode.
As soon as you turn the motor shaft a little, Light-emitting diode it immediately flares up.
If you put an impeller from a fan on the motor shaft and drive it with air movement from another fan, then Light-emitting diode it will simply burn very brightly, if it does not burn out quickly of course, since the voltage is quite high.
Measuring voltage
If you use a three-phase rectifier with a pulse step-down converter to increase efficiency, then the energy of such a generator will easily be enough to charge a cell phone.
Now this can be used in wind turbines, hydraulic turbines or for other purposes. Due to its small dimensions, such a generator can even be installed on a bicycle.
