Method and apparatus for pulse width modulation control of an AC induction motor

An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a flyback DC-DC converter circuit for recharging the battery

Comprehensive Plan & State of the City Lorena,TX

One course developed designs for the construction of a new complex at the existing City Hall site at the intersection of Center and Borden Streets. Another course developed designs for a new complex at the site of the old middle school on Borden Street. Comprehensive Plan- Three courses were devoted to the development of the comprehensive plan. Special features include development of long-range development goals and a downtown revitalization plan. State of the City Report- One course determined the existing community conditions to adequately project needs and services for the comprehensive plan.Texas Target Communitie