Redesign of DC Motors for Applications with Thyristor Power Supplies

The accelerated trend toward the use of solid-state controlled power conversion equipment, as a replacement for the conventional Ward-Leonard motor generator set in direct current adjustable speed industrial drive systems, has focused attention on a number of undesirable side effects which detract from their outstanding advantages. These effects are due to the high ripple content in the rectified voltage output of the conversion units, which ´ causes increased heat generation in the dc drive motor and adversely affects its ability to commutate armature currents without sparking at the brushes. These effects are described and analyzed for several basic configurations of converter power circuits. The use of a laminated steel frame motor construction instead of the conventional solid steel frame ring to miniimize these effects is discussed.