This devices are mainly used for governing the speed in the machinery. Two main causes of maintaining the rate of machinery by using variable speed drives are to regulate the process also to conserve energy. Though these drives are produced for process control, energy conservation is becoming its prime objective.
Many industrial processes need different speed to operate different products. We can save energy by controlling the speed of those processes. Since we are able to find the speed from the pre-set ranges, it's called the "adjustable" speed. This can be referred as variable speed because its output could be changed without undergoing any steps. These are purely mechanical variations.
Some advantages of using VSD are, they give smoother operation and acceleration control and enable you to choose different speed for each process, decrease operation for setup purposes, adjust rate of production, control torque, and compensate variables in changing process.
Types of VSD: Speed adjustment techniques: Since the invention of electric motors, mechanical speed changers are actually used for regulating mechanical power created by water wheels and steam engines. In electrical motors, these drives are used for controlling their speed. Now many various sorts of drives cooperate with the other like mechanical drives, hydraulic drive and electrical drive.
Mechanical Drives: There are two types of mechanical drives. They are variable pitch drives and traction pitch drives. Variable pitch drives consist of pulley and belt where the diameter of the pulleys is adjusted. Traction drives are the type where power is transmitted through metal rollers. The speed ratio is adjusted through the movement of rollers and it is diameter in the contact path.
Hydraulic Drives: There are three types of hydraulic drives. One is hydrostatic drive that contains hydraulic motor and a pump. The revolution with the motor is related with a pair of volume of fluid that's resolute the displacement despite its speed. The speed is controlled by setting a valve. In hydrodynamic drives, fluid couples are employed to regulate speed as well as the hydroviscous drive speed is controlled by one or more discs connected on the input shaft.
Electrical Drives: There are three forms of electrical drives. They are DC motor drives, Eddy current drives and AC motor drives.
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