Application in Switched Reluctance Motor Control
Switched reluctance motor structure and features:
Switched Reluctance Motor (SRM). It is mainly composed of a stator and a rotor. Both the stator and the rotor are salient pole structures. The number of teeth of the stator and the rotor is different. The number of teeth of the rotor is generally two less than that of the stator. The stator teeth are sleeved with concentrated coils, and the stator teeth coils with opposite spatial positions are Phases are connected in series to form a phase winding. The rotor is made up of laminations of iron core with no windings on it. The working mechanism of a switched reluctance motor is based on the principle that the flux always closes along the path with the largest permeance. When the center line of the rotor teeth does not coincide and the magnetic conductance is not maximum, the magnetic field will generate a magnetic pull force, forming a reluctance torque, and turning the rotor to the position where the magnetic flux is the largest. When current is sequentially applied to the stator phase windings, the motor rotor will rotate step by step in the opposite direction of the energization phase sequence. If the order of energization of the phases of the stator is changed, the motor will operate in reverse. However, the change in the direction of the phase current flow does not affect the steering of the rotor. Switched reluctance motors have the following characteristics:
(1) There is no winding on the rotor of the switched reluctance motor. The end of the stator coil is short, easy to manufacture, and the heat generation is small. The motor utilization factor is 1.4 times that of the asynchronous motor, and the manufacturing cost of the motor is greatly reduced.
(2) The moment of inertia is small and has a high torque/inertia ratio, which is especially suitable for high speed operation.
(3) The current in each phase winding can be a single-direction current (pulse), and the number of power switching components is small, which can avoid the bridge arm through.
However, as far as the current level of development is concerned, SR motors still have some shortcomings:
(1) Since it is a reluctance motor, its energy conversion density is lower than that of an electromagnetic motor;
(2) The torque ripple is large, usually 15%. When the power switching element is turned off, a high voltage spike is generated at the motor stator winding end and the switching device.
(3) The need for position detection sensors increases the complexity and cost of the system.
