Insistent demand for energy-saving industrial and home appliances has recently escalated because of energy and environmental matter and the necessity to comply with new energy consumption regulations. These regulations force the development of energy-efficient motors for appliances such as washing machines, air conditioner compressor systems and fans. Electric motors are estimated to consume over 70% of all electricity in industrial applications. Studies accomplished by the Electric Power Research Institute say that over 60% of industrial motors are operating under of their rated load capacity.

Figure 1- Motor Overview

Alternating current AC induction motors (ACIM) are popular in industry and consumer electronics for a number of reasons, see Figure 1. Their construction is extremely optimized, since they have been produced for years. They are very simple and manufacturing costs are favorable. They have no brushes and require minimum maintenance. The robustness of the motor is another strong advantage. Traditionally, these motors have been run with invariable speed control, and are started and stopped frequently in order to achieve the desired result. About 50% of the electricity used during such a process is wasted. Many new methods of reducing electricity are being considered, including new electric motor efficiency technologies. System costs and power consumption can be drastically reduced utilizing digital control of an analog motor circuit. Presented solution of a 3-phase AC Induction motor vector drive based on Freescale's DSC MC56F8013 / 23 microprocessor takes advantage of a cost-efficient solution for consumer and industrial motor drives.

Three-Phase AC Induction Motor

The ACIM is a rotating electric machine designed to operate from a 3-phase source of alternating voltage. Slots in the inner periphery of the stator accommodate 3-phase winding a,b,c. The turns in each winding are distributed so that a current in a stator winding produces an approximately sinusoidally-distributed flux density around the periphery of the air gap. When three currents that are sinusoidally varying in time, but displaced in phase by 120° from each other, flow through the three symmetrically-placed windings, a radially-directed air gap flux density is produced that is also sinusoidally distributed around the gap and rotates at an angular velocity equal to the angular frequency of the stator currents.

The most common type of induction motor has a squirrel cage rotor in which aluminum conductors or bars are cast into slots in the outer periphery of the rotor. These conductors or bars are shorted together at both ends of the rotor by cast aluminum end rings, which also can be shaped to act as fans.