speed of the motor

Is it possible to change the speed of the motor without using variable frequency drives (VFD)? If yes,how? Thanks

 

[electricpete]

if it's a wound induction rotor motor you can introduce resistance into the rotor circuit.

Separate topic. Quite a remarkable products at:

http://www.magnadrive.com/

The product that they call and "adjustable speed drive" takes the place of the coupling and allows variable (externally-controllable) slip between the motor and the load (pump, fan etc). Take a look at their video.

 

With small motors and for some drives as ventilators is possible.
It is normal in a motor of 220Vac that must apply 150Vac or less depends it the motor and the resistant pair.
The reduction is with a autotransformer.
Excuse my English