What are Electric Motors?

The 'AC' in AC motors stands for alternating current and indicates that these machines use an alternating current to provide power. An alternating current means that the electrons traveling along the conductor switch direction regularly, so that they flow first forwards and then backwards. AC electricity was first invented by Nikolas Teklas in the 1880s. AC electric motors can retain energy more efficiently than DC machines and they are also better able to transfer different amounts of power.

AC electric motors consist of two main parts: the external stator and the internal rotor. The stator is responsible for producing a rotating magnetic field which in turn produces the torque received by the rotor. There are two different categories of AC machines, the induction and the synchronous. Induction electric motors use an induced current to produce the magnetic field and will always runt at a slightly slower or faster speed than the supply frequency. Conversely, synchronous machines do not rely on an induced current and are able to run at exactly the same speed as the supply frequency.

Most AC machines use squirrel cage rotors, named for their resemblance to the exercise toy for rodents. These rotors have two ring shaped windings at either end with bars running along the length of the rotor. The squirrel cage rotors used in AC electric motors generally act as transformers, acting to bring the rotor into synchronisation with the stator's field. As the mechanical load on the machine increases, the rotor also increases the power used.

AC electric motors are used for a variety of applications, from washing machines and dishwashers to heavy industry.