ABSTRACT
In high horsepower applications, such as turbo-compressors, induced and forced draft fans and boiler feed pumps, very high mechanical efficiencies can be achieved through the use of adjustable speed motor drives, resulting in substantial energy savings. In this drive, two static converter bridges are connected on their Direct Current (DC) side by means of a so-called DC current link having only a link inductor on the DC side. The machine side converter normally operates in the inversion mode. In general, operation from a converter supply involves modes of operation in which the stator current is changing rapidly followed by intervals in which the current is essentially constant. Load commutation of a synchronous machine is accomplished by adjusting the field current such that the emf is sufficiently large (and lagging the current) to ensure transfer of current from phase to phase. The synchronous machine used in this application is typically of salient-pole construction.
