Comparison of Three Types of Induction Motor Control

The use of motors are getting more and more popular in today´s world. From traditional application of pumps and HVAC system to now cars, and even in digital cameras and handphones. Among these motors induction motors are used prevalently because of its cost, ruggedness and low maintenance. Induction motors are said to consume more than 60% of energy in the United States, and 60% in China. It is for this reason the control of energy usage in these motors is very important. Most of these motors are connected directly to the power grid, which provides voltages at a fixed magnitude and frequency and thus the motors are uncontrollable and required to work all the time once it´s started, providing power at all time. Extra power for the applications generated by the motors are then dissipated by using various schemes, producing noise and heat as a result. With the advent of the energy crisis and pollution problems, it´s imperative to save the energy previously wasted by these motors, and one way to do this is through the use of variable speed drives to control the speed of the motors so that less energy will be consumed when no work needs to be done.