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Motor inside a variable-speed food mixer.
This hair dryer motor and fan can be tested easily using a multimeter.
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Small and large appliances have a motor, a heating element, or both. Motors are important components to hundreds of devices we use in daily life. This guide will show you how motors work and how to fix them when they don't.
A motor turns electrical energy into motion. Actually, it uses electricity's magnetism to attract, then repel components to rotate a shaft. You can attach fan blades, knife blades, wheels, or a dozen other components to the shaft to make useful devices. To name a few: blender, cassette deck, CD player, coffee grinder, computer fan, computer printer head, cordless vacuum, DVD player, electric can opener—you get the idea. These and hundreds of other functional gadgets rely on electric motors to give them motion.
Smaller appliances typically use what's called a universal motor. It's simple, efficient, and relatively inexpensive. It's called "universal" because it can run on either alternating current (AC) or direct current (DC) power. The part that stands still is called the stator and the rotating part is the rotor. It's as simple as that.
Some small appliances use a variation called the shaded-pole motor. It works about the same as the universal motor, but is less expensive to manufacture so it typically goes into lower-cost low-load small appliances.
Larger appliances, as you can imagine, require more power. Many use a split-phase induction motor to develop more rotating power, called torque, than smaller motors can muster. Split-phase induction motors, too, have stators and rotors.
Smaller things, such as battery-operated appliances and tools, get their power from DC batteries so they are made to run on direct current. They don't have much motion or torque, but they get the job done in a small space.
What's the difference? Usually it's cost. Most manufacturers use the least expensive motor they can that does the job. Fortunately, checking whether a motor runs or doesn't is about the same for any type of motor. Unless you're adventuresome, you probably won't dismantle a motor and replace components. If it works, you'll use it; if not, you'll replace or recycle it.
To test an appliance motor:
- Make sure that the power cord wires are disconnected from the motor. If it is easy to do, remove the motor from the appliance, though motors can be tested in place.
- To test continuity (the flow of electricity) through the motor, set the multimeter on the RX1 scale to measure resistance (in ohms). The multimeter's internal battery will send a small electrical current through the motor's wires.
- Attach one of the multimeter's probes to the motor's common lead, usually white.
- Attach the other probe in turn to each of the other wires on the motor. The probe will be checking to see if it can measure the multimeter's input signal at the output. A low or moderate reading (in ohms) means the component is okay. A zero or infinite reading means the motor's windings or another component has a short.
- If it tests faulty, replace the motor with one of the same type, power rating, and size.
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