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Synchronous motors are available in self-excited, fractional [3] to industrial sizes. [1] In the fractional power range, most synchronous motors are used to provide precise constant speed. These machines are commonly used in analog electric clocks, timers and related devices.
In an industrial plant, synchronous motors can be used to supply some of the reactive power required by induction motors. This improves the plant power factor and reduces the reactive current required from the grid. A synchronous condenser provides stepless automatic power-factor correction with the ability to produce up to 150% additional vars.
Synchronous motors are occasionally used as traction motors; the TGV may be the best-known example of such use. Huge numbers of three phase synchronous motors are now fitted to electric cars [citation needed]. They have a neodymium or other rare-earth permanent magnet. One use for this type of motor is its use in a power factor correction scheme.
A brushless DC electric motor (BLDC), also known as an electronically commutated motor, is a synchronous motor using a direct current (DC) electric power supply. It uses an electronic controller to switch DC currents to the motor windings producing magnetic fields that effectively rotate in space and which the permanent magnet rotor follows.
A linear induction motor (LIM) is an alternating current (AC), asynchronous linear motor that works by the same general principles as other induction motors but is typically designed to directly produce motion in a straight line. Characteristically, linear induction motors have a finite primary or secondary length, which generates end-effects ...
Synchronous linear motor actuators, used in machine tools, provide high force, high velocity, high precision and high dynamic stiffness, resulting in high smoothness of motion and low settling time. They may reach velocities of 2 m/s and micron-level accuracies, with short cycle times and a smooth surface finish.
In the asynchronous category, we have induction motors, while the synchronous group contains permanent-magnet and current-excited motors. Induction motors have been around since the 19th century.
As dynamic response requirements increase, more specialized motor designs such as coreless motors are used. AC motors' superior power density and acceleration characteristics tends to favor permanent magnet synchronous, BLDC, induction, and SRM drive approaches. [80]