Performance of Lorenz-type medium-frequency inductor alternators on load

Earlier papers have discussed the air-gap flux-density distribution in inductor alternators and have verified the theory by measurement. It is the aim of this paper to show that, with a knowledge of flux-density distribution, it is possible to predict the load performance of these machines from the open-circuit curve¿an easily calculable starting point. First, the measured open-circuit voltages are compared with those calculated from previous knowledge of the flux-density wave, which in turn has earlier been compared with that calculated from air-gap geometry. By taking the correct components of armature reaction, it is shown that the voltage at any load point can be obtained by combining these with the open-circuit flux distribution, to obtain a resultant flux distribution, and hence voltage. This involves the intersection of generalised curves, expressing the vector-diagram geometry, with the special curve for the particular machine, expressing the open-circuit-voltage/field-current relation. Examples of this method are given both for the experimental machine and for a much larger commercial alternator, and are shown to predict the load curves under widely varying conditions.