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Synchronous motors use electromagnets as the stator of the motor which create a magnetic field that rotates in time with the oscillations of the current. The rotor with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field.
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.
A superconducting rotor does not have the inherent damping of a conventional rotor. Its speed may hunt or oscillate around its synchronous speed. Motor bearings need to be able to withstand cold or need to be insulated from the cold rotor. As a synchronous motor, electronic control is essential for practical operation.
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.
The AC electric motor used in a VFD system is usually a three-phase induction motor. Some types of single-phase motors or synchronous motors can be advantageous in some situations, but generally three-phase induction motors are preferred as the most economical. Motors that are designed for fixed-speed operation are often used.
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.
The switched reluctance motor (SRM) is a type of reluctance motor. Unlike brushed DC motors , power is delivered to windings in the stator (case) rather than the rotor . This simplifies mechanical design because power does not have to be delivered to the moving rotor, which eliminates the need for a commutator .
It is used to dampen the transient oscillations and facilitate the start-up operation. [ 2 ] Since the design of a damper winding is similar to that of a asynchronous motor , the winding technically enables the direct-on-line start and can even be used for the motor operation in the asynchronous mode.