Today the VFD could very well be the most common kind of result or load for a control program. As applications are more complicated the VFD has the ability to control the swiftness of the motor, the direction the motor shaft is turning, the torque the engine provides to a load and any other electric motor 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 extremely versatile device that not merely controls the speed of the electric 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 regulates during ramp-down. The largest financial savings that the VFD provides can be that it can ensure that the motor doesn’t pull excessive current when it starts, therefore the overall demand element for the whole factory could be controlled to keep carefully the utility bill only possible. This feature by itself can provide payback more than the price of the VFD in less than one year after buy. It is important to remember that with a traditional motor starter, they will draw locked-rotor amperage (LRA) when they are starting. When the locked-rotor amperage takes place across many motors in a manufacturing plant, it pushes the electrical demand too high which often results in the plant having to pay a penalty for every one of the electricity consumed during the billing period. Since the penalty may be as much as 15% to 25%, the cost savings on a $30,000/month electric costs can be used to justify the purchase VFDs for virtually every motor in the plant even if the application may not require functioning at variable speed.
This usually limited how big is the motor that could be controlled by a frequency and they 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 sized resistors into circuits with capacitors to make different slopes.
