Today the VFD is perhaps the most common type of result or load for a Variable Speed Gear Motor control system. As applications become more complicated the VFD has the capacity to control the velocity of the electric motor, the direction the electric motor shaft is turning, the torque the electric motor provides to a load and any other electric motor parameter which can be sensed. These VFDs are also available in smaller sizes that are cost-efficient and take up less space.
The arrival of advanced microprocessors has allowed the VFD works as an extremely versatile device that not merely 
controls the speed of the motor, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs also provide methods of braking, power improve during ramp-up, and a variety of controls during ramp-down. The biggest cost savings that the VFD provides is definitely that it can ensure that the electric motor doesn’t pull excessive current when it begins, therefore the overall demand element for the entire factory could be controlled to keep the utility bill only possible. This feature by itself can provide payback in excess of the cost of the VFD in less than one year after purchase. It is important to keep in mind that with a normal motor starter, they’ll draw locked-rotor amperage (LRA) if they are starting. When the locked-rotor amperage happens across many motors in a manufacturing plant, it pushes the electrical demand too high which frequently results in the plant spending a penalty for all the electricity consumed through the billing period. Because the penalty may be just as much as 15% to 25%, the savings on a $30,000/month electric costs can be utilized to justify the purchase VFDs for virtually every engine in the plant even if the application form may not require functioning at variable speed.
This usually limited how big is the motor that may be managed by a frequency plus they weren’t commonly used. The earliest VFDs used linear amplifiers to regulate all aspects of the VFD. Jumpers and dip switches were used 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 consist of an primary electric circuit converting the alternating current into a immediate current, then converting it back to an alternating current with the required frequency. Internal energy reduction in the automated frequency control is ranked ~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 fans save energy by allowing the volume of surroundings moved to match the system demand.
Reasons for employing automatic frequency control can both be linked to the efficiency of the application and for saving energy. For example, automatic frequency control can be used in pump applications where the flow is matched either to quantity 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 been the innovation that has brought the use of AC motors back into prominence. The AC-induction motor can have its quickness transformed by changing the frequency of the voltage used to power it. This implies that if the voltage put on an AC engine is 50 Hz (found in countries like China), the motor works at its rated swiftness. If the frequency is increased above 50 Hz, the motor will run faster than its rated speed, and if the frequency of the supply voltage is usually less than 50 Hz, the electric motor will run slower than its ranked speed. Based on the adjustable frequency drive working basic principle, it’s the electronic controller specifically designed to modify the frequency of voltage provided to the induction electric motor.