An electric machine is a device that produces electricity or does work using electricity. It usually has a motor that drives a set of gears and belts. An electric machine may not have any moving parts at all. One example of an electric machine is the electrical generator, which produces electricity using a source of mechanical energy, such as an engine running on a fossil fuel, a turbine, an electric motor, steam, wind, or water.
Electrical generators may be either alternating current (AC) or direct current (DC) generators. Power utilities produce AC voltages in several thousands of volts that are then distributed and stepped down using a transformer. Cars and other means of transportation use DC generators to generate about 13.8 volts direct current (VDC) to power up built-in equipment, such as ignition systems, stereos, two-way radios, and laptops.
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An electric machine may use either an AC or DC motor. AC motors are very popular where AC power is available. In homes, they are used in fans, air conditioners, washing machines, dishwashers, and other appliances. DC motors are popular in smaller equipment and where only DC power is available. In cars, DC motors are used in power windows, wipers, engine starters, and blower fans.
Electric motors are used in all industries, and range from simple machines that shape materials to machines that create miniaturized high-density circuit boards. Either humans or computers act as the controller. Computers are able to repeat processes under tight tolerances, whereas humans are normally unable to work in such conditions.
Special machines are capable of storing energy as kinetic energy (KE) in satellites. Using a magnetic bearing, a KE storage device is able to bear a 331 lb (150 kg) rotating flywheel at about 3,600 revolutions per minute. The flywheel spins while suspended in a vacuum. When the satellite in orbit is in view of the sun, solar photovoltaic panels generate the needed electricity for the satellite and to maintain the spin of the flywheel. During dark times, the battery system takes over. At prolonged darkness, the battery voltage drops below cut off, which is where the flywheel is engaged to generate electricity.
New electric machines are also foreseen in the nanotechnology field. Very small machines are thought to be one day capable of closed surgical processes, for example. The impact is that patients may undergo major surgery from outside the body, and it would be like nothing is happening.