Double disc alternators with hybrid excitation

The authors investigate a version of a double disc alternator which uses both a stationary coil on the armature side of the airgap and permanent magnets on the rotor side for excitation. The machine is brushless without the use of rotating diodes, but nevertheless can be voltage regulated. Experimental comparisons are drawn between two machine configurations, one using hybrid and the second using coil excitation. It is shown that both leakage factor and efficiency are improved by the hybrid construction. Excellent agreement is obtained between experimental and theoretical results using finite-element analysis