- The electric motor was created in 1821 by Michael Faraday, although his device is not a true motor in the modern sense. That honor goes to Ányos Jedlik's self-rotor, made in 1827. Both of these devices utilized direct current as their source of power. It wasn't until 1888 that Nikola Tesla invented the alternating current motor. His AC motor not only generated electricity efficiently, but it also was a highly more efficient means of transmittin electricity with relatively low loss.
- The introduction of Tesla's AC motor sparked a war of the currents between Tesla and his AC current and Edison and his DC current. One of the biggest advantages of AC over DC is the low transmission losses that come from the ease with which AC is converted to and from higher voltages. Today, high voltage lines transmit power at upwards of three-quarters of a million volts. Eventually, Tesla and AC won out, and AC is the default current used today.
- The most common type of AC motor is the squirrel cage motor. This kind of motor is present in just about every fan, dishwasher, washing machine and any appliance that features a rotating component. The squirrel cage motor operates through the induction of magnetic fields between the outer and inner coils. If the inner coils are rotating at a speed not equivalent to what the design dictates, a magnetic field is produced to speed up or slow down the inner rotating coils. When there is a load on the motor, more current is consumed in generating this field.
- In order to maintain the rotation of the inner rotor, the magnetic field in the outer coils must rotate around the coils. In a three-phase motor, where the alternating current is provided through three phase wires, each wire will sequentially possess the high current and thus produce a rotating magnetic current. However, this requires a three-phase source, and home wall sockets only provide single-phase power. Single-phase motors make use of other means in order to affect a rotation of the magnetic field as needed for motor operation.
- Another type of AC motor is the wound rotor motor, which provides the means for a variable speed of revolution through the use of an external resistor. You can find this type of motor in a kitchen blender, where the different buttons select different resistances, which in turn select different motor speeds and torques. Other special AC motors include those made for highly efficient operations, those with built-in feedback protection, those destined for use as alternators for the production of electricity, and many others.
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