Dynamic Performance of a Hybrid Synchronous Machine with Ultra-High XD/XQ Ratio

Abstract

This paper presents a hybrid synchronous machine with ultra-high X_D/X_Q ratio. A conventional synchronous machine has two components of output power; the excitation and the reluctance component. The reluctance power which depends on the saliency ratio (X_D/X_Q  ) is negligible when compared with the excitation component. A hybrid machine with variable X_D/X_Q  ratio has the capability of raising the reluctance component of the power to infinity theoretically. The stator frame of the hybrid machine is stacked with two identical cylindrical cores (A, B) that are magnetically isolated. A hybridised rotor; salient cum cylindrical is used. There are two windings on the stator core stacks identifiable as the main and control windings respectively which are electrically isolated but magnetically coupled. The main windings are connected in series across the two stacks (A and B) and the terminals connected to the utility supply for motor operation while for generator, the terminals feed the load busbar. The control windings are transposed in passing from one stack to the other and terminated across a balanced adjustable capacitor bank. It is shown that the quadrature axis reactance (X_Q) of the hybrid machine can be adjusted from zero to infinity (0<=X_Q<=inf.)  theoretically by varying the balanced adjustable capacitor bank. The reluctance component of the output power of the machine which depends on the reactance ratio (X_D/X_Q ) is also seen to theoretically increase to infinity. The reluctance power is shown to be twice the excitation power when the capacitor of 800uf is connected to the control winding. Depending on the value of the capacitive reactance, the reluctance power can be made even ten times the excitation power.