Abstract: An electrical control means useful in systems wherein a motor, such as a blower motor for an air handling unit, must be run at different speed levels and wherein low voltage power must simultaneously be supplied to another part of the system such as a condenser unit. The invention combines auto-transformer and transformer technologies into a single motor control unit. Wiring to the auto-transformer portion of the unit is arranged in such manner that it may be readily field changed to accommodate the various line voltage and frequency levels encountered worldwide. Thus, a signle standardized unit allows accurate motor speed control and simultaneous low voltage power supply without motor overheating or instability under various line voltage and frequency conditions encountered throughout the world.

Abstract: A variable frequency drive for a motor-generator/alternator set which is used to supply electrical power to computer or data processing equipment. Power failures in commercially supplied power results in aberrations and erroneous computations in computers and data processing equipment. An induction motor is used to drive a generator/alternator. The induction motor is driven below the synchronous speed of the generator/alternator and a variable speed drive increases the velocity supplied to the generator/alternator, preferably to a point above its synchronous speed. Therefore, when there is a commercial power failure, the generator/alternator remains within a desired frequency range for a longer period of time than a comparable generator/alternator driven at synchronous speed.