This paper focuses on studying the synchronous reluctance motors as an alternative to low-power commutator motors. Analysis is done for the improved design of synchronous reluctance motor with a segmental external rotor. Relevant equations and a suitable method are proposed for calculating characteristics of the synchronous reluctance motors operating in a specific mode with electronic commutation as switched reluctance motors. It is concluded that synchronous reluctance motors in this mode can provide a wide range of characteristics and are quite competitive with commutator motors used in low-power devices.
The paper focuses on studying the external-rotor synchronous reluctance motor. The analysis is performed to estimate the influence of the number of stator slots and non-magnetic areas in the rotor (i.e., flux barriers) on the electromagnetic torque and torque ripple of the studied motor. It is concluded that the increase in the number of stator slots Z = 6 to Z = 18 causes an approximately twofold decrease in the ripple factor, but torque increases by 5 %. Electromagnetic torque will be increased approximately by 24 %, if non-magnetic flux barriers are created in the rotor of the studied synchronous reluctance motor.
The paper presents new designs for synchronous reluctance motors that have external rotor (segment-shaped rotor, rotor with additional non-magnetic space to the quadrature axis of the rotor, and rotor with several flux barriers). Impact of the external rotor configuration on the electromagnetic torque and torque ripple is analysed. Electromagnetic torque ripple factor is calculated for each studied motor using the results of magnetic field numerical calculations.
The authors consider the features and operation specifics of the synchronous permanent magnet motors and the synchronous reluctance motors with electronic commutation in servomotor operation modes. Calculation results show that mechanical and control characteristics of studied motors are close to a linear shape. The studied motor control is proposed to implement similar to phase control of induction servomotor; it means that angle θ (angle between vectors of the supply voltage and non-load electromotive force) or angle ε (angle between rotor direct axis and armature magnetomotive force axis) is changed. The analysis results show that synchronous electronically commutated motors could be used as servomotors.
The paper presents the comparison of two synchronous reluctance motors with the inner rotor and the outer one. The aim of the research is to determine the influence of motor type on electromagnetic torque and ripple factor. The results indicate that a maximum value of electromagnetic torque and the amplitude of the first harmonic of electromagnetic torque increase for the motor with the inner rotor, and the value of ripple factor increases as well. If both motor types with equal rated power, rotation frequency and current density are compared, the results show a possibility to reduce the volume of motor with the inner rotor by 15 %.
The paper presents the research on evaluation of accuracy of magnetic field calculations of synchronous reluctance motor in comparison with the results obtained in experiments. Magnetic field calculations are performed with the finite element method to determine values of the magnetic flux and electromagnetic torque according to the current value in motor stator and load angle between the rotor direct-axis and axis of stator magnetomotive force (MMF). Experimental values of magnetic flux and electromagnetic torque are obtained on motor with locked rotor while equivalent direct current is applied to the stator windings. The research shows that the results obtained from the magnetic field calculations coincide well with the experimental data.