Today the VFD could very well be the most common kind of result or load for a control program. As applications are more complex the VFD has the capacity to control the velocity of the motor, the direction the motor shaft is definitely turning, the torque the electric motor provides to lots and any other motor parameter that can be sensed. These VFDs are also available 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 engine, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs also provide methods of braking, power increase during ramp-up, and a number of regulates during ramp-down. The biggest savings that the VFD provides can be that it can ensure that the electric motor doesn’t pull extreme current when it starts, therefore the overall demand factor for the whole factory can be controlled to keep carefully the utility bill as low as possible. This feature alone can provide payback more than the price of the VFD in under one year after purchase. It is important to keep in mind that with a normal motor starter, they’ll draw locked-rotor amperage (LRA) when they are starting. When the locked-rotor amperage happens across many motors in a manufacturing facility, it pushes the electric demand too high which often results in the plant paying a penalty for all the electricity consumed through the billing period. Since the penalty may end up being as much as 15% to 25%, the financial savings on a $30,000/month electric costs can be used to justify the buy VFDs for practically every engine in the plant actually if the application may not require working at variable speed.
This usually limited the size of the motor that may be controlled by a frequency plus they Variable Speed Gear Motor weren’t commonly used. The earliest VFDs utilized linear amplifiers to control all areas 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 generate different slopes.
Automatic frequency control consist of an primary electric circuit converting the alternating electric current into a direct current, then converting it back into an alternating electric current with the mandatory frequency. Internal energy reduction in the automated frequency control is rated ~3.5%
Variable-frequency drives are trusted on pumps and machine tool drives, compressors and in ventilations systems for large buildings. Variable-frequency motors on enthusiasts save energy by enabling the volume of air moved to complement the system demand.
Reasons for employing automated frequency control can both be linked to the features of the application form and for saving energy. For example, automatic frequency control can be used in pump applications where the flow is usually matched either to quantity 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 consumption.
VFD for AC motors have already been the innovation which has brought the use of AC motors back into prominence. The AC-induction electric motor can have 
its velocity transformed by changing the frequency of the voltage used to power it. This means that if the voltage applied to an AC engine is 50 Hz (found in countries like China), the motor works at its rated speed. If the frequency is increased above 50 Hz, the electric motor will run quicker than its rated velocity, and if the frequency of the supply voltage is usually significantly less than 50 Hz, the motor will run slower than its ranked speed. According to the adjustable frequency drive working basic principle, it is the electronic controller particularly designed to alter the frequency of voltage provided to the induction electric motor.