How Dryer Motors Work

Photo of a typical clothes dryer motor

Most dryers in the United States are plugged into a 220 Volt A/C receptacle. However the motor on most dryers in the US, only uses 110 Volts A/C of that.

So why do most dryers require 220 volts? Well it is because dryers need 220 volts to supply enough voltage and current flow to the heater to produce enough heat to dry clothes.

By the way, most dryer motors outside the United States operate on 220 / 250 volts A/C.

A complete explanation of motor fundamentals is beyond the scope of this forum. However, we will briefly describe how dryer motors work. Like any other motor a dryer motor converts electromagnetic energy to mechanical energy to turn the dryer blower and the dryer drum. Dryer motors that run on 110 Volts A/C have two sets of windings. These windings have a different electrical resistance. Usually the start winding has a higher resistance than the run winding. The resistance in the winding delays the current flow in the motor windings. This delay allows the windings to create essentially four separate electromagnetic fields that help the motor to start. As soon as the motor starts to rotate the start windings need to be disengaged from the circuit. If not the motor will burn up because of the competing electromagnetic fields. This is a key function of the centrifugal switch on the motor. In addition to switching the heater on and off when the motor comes up to speed or shuts down, the centrifugal switch disengages a set of contacts that supply power to the start windings.

The best way for non-technical people to check a dryer motor is to inspect it. When a dryer motor fails it usually burns up the windings inside the motor. Looking inside the motor you can see if the windings are burned. There is an odor associated with burned windings. Dryer motor bearings also seize up due to dirt, friction and heat.

If your dryer motor is humming when you press the start switch you can be about 85% sure the motor needs to be replaced. That’s because for a dryer motor to hum when the start button is pushed the electrical circuit to the motor must be complete and most likely the motor windings, motor bearings or centrifugal switch contacts are damaged. It is possible that the centrifugal switch is dirty holding the start windings open so make sure the switch is clear and clean before you condemn a dryer motor as defective. Exactly how to access a dryer motor will depend on the brand and model dryer. However generally speaking motors are secured to the dryer mounting cradle with a spring loaded clamp. To remove a dryer motor from the motor mount use a nut driver on the edge of the clamp and press down. The clamp acts as a very tight spring keeping the motor secure to the dryer motor mount. Simply reverse the process to install the new motor. Make sure the motor is positioned on the cradle so that it will clear the dryer drum.