Today the VFD could very well be the most common type of result or load for a control program. As applications are more complicated the VFD has the ability to control the velocity of the engine, the direction the electric motor shaft is certainly turning, the torque the motor provides to lots and any other engine parameter which 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 motor, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs also provide ways of braking, power enhance 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 extreme 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 buy. 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 outcomes in the plant having to pay a penalty for every one of the electricity consumed through the billing period. Since the penalty may become as much as 15% to 25%, the cost savings on a $30,000/month electric expenses can be used to justify the purchase VFDs for virtually every electric motor in the plant also 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 plus they weren’t commonly used. The initial VFDs used linear amplifiers to regulate 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 sized resistors into circuits with capacitors to produce different slopes.
While others have created about the topic of Variable Speed Gear Motor, my hope is that this short article brings an unique viewpoint.