Today the VFD could very well be the most common type of output or load for a control system. As applications become more complex the VFD has the ability to control the acceleration of the motor, the direction the electric motor shaft can be turning, the torque the engine provides to a load and any other engine parameter that can 
be sensed. These VFDs are also available in smaller sizes that are cost-effective and take up less space.
The arrival of advanced microprocessors has allowed the VFD works as an exceptionally versatile device that not merely controls the speed of the motor, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs provide methods of braking, power enhance during ramp-up, and a variety of settings during ramp-down. The largest savings that the VFD provides is usually that it can ensure that the electric motor doesn’t pull extreme current when it begins, therefore the overall demand aspect for the entire factory can be controlled to keep the domestic bill as low as possible. This feature alone can provide payback more than the cost of the VFD in under one year after purchase. It is important to keep in mind that with a normal motor starter, they will draw locked-rotor amperage (LRA) if they are beginning. When the locked-rotor amperage happens 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 every one of the electricity consumed through the billing period. Since the penalty may be just as much as 15% to 25%, the savings on a $30,000/month electric expenses can be utilized to justify the purchase VFDs for practically every motor in the plant actually 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 and they were not commonly used. The earliest 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 resistors into circuits with capacitors to create different slopes.
We have actually summarised the bottom lines regarding Variable Speed Gear Motor on our website.