SYNRM

The SynRM combines the stator from conventional induction motors with an innovative rotor design, creating a highly efficiency, speed-adjustable motor, capable of achieving an IE5 efficiency rating, allowing up to 20% energy savings compared to an equivalent induction machine. Its performance is comparable to permanent magnet motors, without the environmental and financial cost of rare earth metals. The controller for the SynRM is essential for its operation, ensuring the correct energisation of the windings to produce the required motion.

The stator of the synchronous reluctance motor is similar to that of the traditional induction motor; however, its rotor is made only of laminated silicon steel sheets, with no windings. The silicon steel sheets are designed with hollow air gaps as magnetic field barriers. The direction of these barriers is called the quadrature (q) axis, while the direction of the path with the continuous silicon steel sheet is called the direct (d) axis.

The stator of the SynRM contains windings which are energised from a three-phase supply which results in a rotating magnetic field. The diagram shows the flow of flux from three pairs of windings, the others are omitted for clarity. When the voltage of the first phase is a maximum, the rotor aligns itself so the reluctance is at a minimum (A), the reluctance paths for the other phases are much greater. As the second phase voltage reaches a maximum, the first phase voltage has reduced and the rotor re-aligns with the second phase, as this now presents the path of least reluctance. This is then repeated with the third phase and so on. As the field rotates, the rotor follows it synchronously.

A SynRM is a synchronous speed-regulating motor in which the rotor operates synchronously with an applied sinusoidal magnetic field. It needs to be powered by a dedicated KSYC series controller to control the speed and torque.

The load applied to the motor is never completely constant and, usually, the motor does not need to run at its full speed or power. By adjusting the speed and torque to match the operation of the motor to the load, between 25% to 30% of the electric energy can be saved. For example, valves are often used to control the flow rate of water in water pumps. This is equivalent to slowing a car by applying the brakes without releasing the accelerator, which is a waste of energy. By adjusting the speed of the motor in real time, the controller removes the need for valves, gears or brakes to control the speed of the equipment driven by the motor, and there will be no waste of electrical energy which would result from mechanical speed regulation.