Today the VFD is perhaps the most common type of result or load for a control system. As applications are more complex the VFD has the ability to control the acceleration of the Variable Speed Drive Motor electric motor, the direction the motor shaft can be turning, the torque the engine provides to lots and any other motor parameter which can be sensed. These VFDs are also available in smaller sized sizes that are cost-efficient and take up much 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 motor, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs also provide ways of braking, power improve during ramp-up, and a variety of settings during ramp-down. The largest savings that the VFD 
provides can be that it can ensure that the electric motor doesn’t pull excessive current when it starts, so the overall demand factor for the whole factory can be controlled to keep the domestic bill as low as possible. This feature only can provide payback more than 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) if they are starting. When the locked-rotor amperage takes place across many motors in a manufacturing plant, it pushes the electric demand too high which often results in the plant having to pay a penalty for all of the electricity consumed through the billing period. Since the penalty may be as much as 15% to 25%, the savings on a $30,000/month electric expenses can be used to justify the buy VFDs for virtually every electric motor in the plant even if the application form may not require working at variable speed.
This usually limited the size of the motor that could be managed by a frequency and they were not commonly used. The initial VFDs used 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 resistors into circuits with capacitors to create different slopes.
Automatic frequency control contain an primary electrical circuit converting the alternating electric current into a immediate current, then converting it back into an alternating electric current with the required frequency. Internal energy loss in the automated frequency control is rated ~3.5%
Variable-frequency drives are widely used on pumps and machine tool drives, compressors and in ventilations systems for large buildings. Variable-frequency motors on supporters save energy by enabling the volume of air flow moved to complement the system demand.
Reasons for employing automated frequency control can both be linked to the functionality of the application form and for saving energy. For example, automatic frequency control is used in pump applications where the flow is certainly matched either to volume or pressure. The pump adjusts its revolutions to a given setpoint with a regulating loop. Adjusting the circulation or pressure to the real demand reduces power usage.
VFD for AC motors have already been the innovation which has brought the usage of AC motors back into prominence. The AC-induction engine can have its acceleration transformed by changing the frequency of the voltage used to power it. This implies that if the voltage applied to an AC electric motor is 50 Hz (used in countries like China), the motor works at its rated quickness. If the frequency is improved above 50 Hz, the engine will run faster than its rated velocity, and if the frequency of the supply voltage is usually less than 50 Hz, the motor will operate slower than its rated speed. Based on the variable frequency drive working basic principle, it’s the electronic controller specifically designed to modify the frequency of voltage supplied to the induction electric motor.