subject: All About Ac Drive [print this page] AC drives are commonly named as variable speed drives, inverters and frequency converters. These are just like a boon for electronics and electrical industry. It is widely used in many equipments and devices used further to serve many applications. It is the most commonly motor technology used in different electronic machines.
The main advantage about AC drives is that they require very little maintenance and are durable. It can also be considered as a combination of variable frequency inverter and motor. The main power component of the AC drive is used to provide the desired level of current and voltage in a form a motor can easily use. If we connect an AC motor directly to the mains supply, of motor will accelerate very quickly then rotate a fixed speed which is solely depend upon the motor design and electric supply frequency.
This speed is adjustable means an operator working on the machine can adjust the speed of AC motor manually. The AC drive and DC Drive both are available in different sizes and designs as per the needs and requirements. However, for different applications, unbraked deceleration, hard acceleration, and the inability to change the speed and torque symbolize a serious problem.
AC Drives offers a solution by altering the frequency and voltage of the AC supply to the motor attached. Control needed is received by either measuring the speed, known as closed loop control or estimating the motor speed, known as open loop control. Both of these techniques have their own advantages and disadvantages.
Open loop control offers the simple means of controlling AC induction motors, as the speed of the motor is dependent 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. The result of these methods is a large performance and accuracy improvement, however, at low speed performance may still be a problem.
RFC or Rotor Flux Control is another new method of controlling for open loop drives which provides greater dynamic performance and improved stability. While closed loop control is received by using a position and speed sensor attached to the motor shaft. The result of the closed loop is accurate, stable, and torque control. These are used in excluding, material handling, cranes and hoists, and lifts etc. So, make the best use of AC Drives to make your work easy.
