PERFORMANCE OF A HYBRID SYNCHRONOUS RELUCTANCE MACHINE CAPABLE OF ULTRA – HIGH OUTPUT POWER

The performance of a hybrid synchronous reluctance machine capable of ultra-high Xd/Xq ratio and output power has been studied. A d-q model (voltage and flux linkage) of the hybrid synchronous reluctance machine has been idealized and developed. Also, the impedance and current loci from the steady state analysis of the synchronous reluctance machine was obtained. The effect of capacitor loading in the auxiliary windings was investigated. The power factor and torque developed in the hybrid synchronous reluctance machine was compared with conventional synchronous reluctance machine. This hybridized synchronous reluctance machine improved the major constraints of conventional synchronous reluctance machine: – low output power and poor power factor due to low ratio of direct to quadrature axis reactance (Xd/Xq). To achieve this, two elemental synchronous reluctance machines were conceived. Both were integrally wound with two identical windings in the stator. The rotor of one of the synchronous reluctance machine component is round while the other has salient pole. Both machine halves were mechanically coupled together. One set of the windings of both machines were connected in series and fed from the ac mains while the other set was also connected in series (but transposed between the two sections of the machine) and then connected to a balanced three-phase variable capacitance load. The Voltage and flux linkage equations were written in abc reference frame for the hybrid machine and then transformed to dqo variable. The steady state and dynamic equivalent circuits of the hybrid machine were developed using classical means. The impedance and current loci for the developed model were generated using Matlab m-files for various values of load angles and capacitance as parameters. The power factor and torque developed in the hybrid machine were compared with those of the conventional synchronous reluctance machine. It is shown that the capacitance loading of the auxiliary windings makes the overall Xd/Xq ratio of the hybrid machine to be a variable that can theoretically attain values between zero and infinity. This translates to ultra-high power output and unity power factor. Also, it is shown that the hybrid synchronous reluctance machine has a power factor control, a feat which is not feasible in conventional synchronous reluctance machines.

A synchronous machine is an alternating current rotating machine whose speed under steady state condition is proportional to the frequency of the current in its armature. The magnetic field created by the armature currents rotates at the same speed as that created by the field current on the rotor, which is rotating at the synchronous speed, and a steady torque results. Almost all the electric power used throughout the world is generated by synchronous machine driven either by hydro, steam turbine or combustion engine. Just as the induction machine is the workhorse when it comes to converting energy from electrical to mechanical, the synchronous machine is the principal means of converting energy from mechanical to electrical. Thus, the fundamental difference between a synchronous machine and an induction machine is that the rotor currents of the induction machine are induced while those of the synchronous machine are not. The rotor of synchronous machine is equipped with a field winding and one or two damper windings. The rotor windings have different characteristics [1].

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