Today the VFD could very well be the most common type of result or load for a control program. As applications become more complex the VFD has the capacity to control the quickness of the engine, the direction the electric motor shaft is turning, the torque the motor provides to lots and any other engine parameter which can be sensed. These VFDs are also obtainable in smaller sized sizes that are cost-effective and take up less space.
The arrival of advanced microprocessors has allowed the VFD works as an extremely versatile device that not only controls the speed of the electric motor, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs also provide ways of braking, power boost during ramp-up, and a number of controls during ramp-down. The largest financial savings that the VFD provides can be that it can ensure that the electric motor doesn’t pull excessive current when it begins, so the overall demand factor for the entire factory can be controlled to keep carefully the domestic bill as low as possible. This feature alone can provide payback in excess of the cost of the VFD in under one year after purchase. It is important to remember that with a normal motor starter, they’ll draw locked-rotor amperage (LRA) when they are beginning. When the locked-rotor amperage occurs across many motors in a manufacturing facility, it pushes the electric demand too high which frequently outcomes in the plant having to pay a penalty for all the electricity consumed through the billing period. Because the penalty may be just as much as 15% to 25%, the financial savings on a $30,000/month electric bill can be utilized to Variable Speed Gear Motor justify the buy VFDs for practically every motor in the plant also if the application may not require working at variable speed.
This usually limited the size of the motor that may be managed by a frequency plus they were not commonly used. The initial VFDs utilized linear amplifiers to regulate all aspects of the VFD. Jumpers and dip switches were utilized provide ramp-up (acceleration) and ramp-down (deceleration) features by switching larger or smaller sized resistors into circuits with capacitors to create different slopes.
Automatic frequency control contain an primary electric circuit converting the alternating electric current into a direct current, after that converting it back to an alternating current with the mandatory frequency. Internal energy reduction in the automatic frequency control is rated ~3.5%
Variable-frequency drives are widely used on pumps and machine device drives, compressors and in ventilations systems for large buildings. Variable-frequency motors on supporters save energy by allowing the volume of air flow moved to match the system demand.
Reasons for employing automatic frequency control can both be related to the efficiency of the application and for saving energy. For example, automatic frequency control can be used in pump applications where in fact the flow is matched either to volume or pressure. The pump adjusts its revolutions to confirmed setpoint via a regulating loop. Adjusting the stream or pressure to the actual demand reduces power consumption.
VFD for AC motors have already been the innovation which has brought the use of AC motors back into prominence. The AC-induction engine can have its velocity transformed by changing the frequency of the voltage used to power it. This means that if the voltage put on an AC motor is 50 Hz (used in countries like China), the motor functions at its rated acceleration. If the frequency can be improved above 50 Hz, the electric motor will run quicker than its rated acceleration, and if the frequency of the supply voltage is usually significantly less than 50 
Hz, the motor will run slower than its rated speed. Based on the adjustable frequency drive working basic principle, it is the electronic controller specifically designed to modify the frequency of voltage supplied to the induction electric motor.