Induction motors frequency variations

Here we analyse the effect of variation in the incoming supply parameters (voltage and frequency) on the characteristics and performance of an induction motor (such as its flux density, speed, torque, h.p., etc). We also assess the effect of variation of one parameter on the other, and then choose the most appropriate solid-state scheme to achieve a required performance. We generally discuss the following schemes ... 

Induction generator This is a standard squirrel cage motor with additional treatment to weather the site conditions. The normal specifications are generally the same as for a standard motor. The permissible voltage and frequency variations are, however, wider as noted below ... 

In most applications, output voltage of the inverter must be controlled. This may be to regulate the load voltage with variations in the load current or with variations in the DC (or AC if DC is derived from an AC supply) input voltage. In AC induction motor control apphcations, output voltage to frequency (V//) must be kept constant. There are several ways to control the output voltage of an inverter. Some of them... 

Speed control by way of adjusting power frequency is becoming more and more important for economical throughput or presstme capacity variation of modern process machinery. Several key parameters that must be considered when applying induction motors to adjustable frequency controllers include the load torque requirements, current requirements of the motor and the controller ciurent rating, the effect of the controller wave-shape on the motor temperature rise, and the required speed range for the application. 

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