Yes, but you also significantly lower the load.
I've run a number of fans at low speed by reducing the voltage and they don't even get warm.

Hi,

Some years back i ran a mid sized fan with a variac for several months at a time. With the variac there was no noise and never had a problem with the fan except maybe it needed oiling now and then.

 

Hi KAN3KI5, I've received ths exact project and have been assigned the same part as you (controlling the speed of the motor) for my design module. Can you please explain how you went about controlling the speed, I feel highly confused.

Hi Guys, how will I go about ensuring that the speed of the motor is dependent on external analogue signal that's received from another guy? The signals have to correspond to low, medium and high voltage.

 

Hi guys, if I want the speed of the motor to be controlled by an external analog signal (Can either be LOW - 80v, MEDIUM - 150v, HIGH - 220v), how can I receive the signal and make the motor drive at that specific speed? I am currently using Fairchild's AN - 3006 as a reference.
Note: Microcontrollers cannot be used