What is an AC Drive?
Open loop control provides the simplest means of controlling AC induction motors, as the speed of the motor is dependant upon the frequency of the supply, a basic means of control is simply to vary the voltage and frequency to achieve the desired motor speed. This method is known as V/Hz control. The major disadvantages of this method of control are poor precision and poor low speed torque.
Closed loop control is achieved by using a speed and position sensor connected to the motor shaft.
- Cranes and hoists
- Material handling
- Automotive testing
Emerson Group's Control Techniques is the market leader in intelligent drives; this refers to drives that have programmable automation or motion controllers within the product as standard or as an option. Intelligent drives offer significant advantages; because the controller is located within the drive itself, communication delays are eliminated therefore improving performance in automation and motion applications and removing the need for external controllers, saving panel space. Unidrive SP, Commander SK, Digitax ST and Mentor II are all considered to be intelligent.
It is estimated that energy saving of up to 20% can be achieved through installing and operating motors in a more efficient way. Installing AC drives in certain applications such as fans and pumps can have a dramatic effect on the energy consumed. With motors consuming an estimated two thirds of electrical energy within industry, drives must form a key part of any programme to reduce carbon emissions.