Today the VFD could very well be the most common kind of result or load for a control program. As applications become more complicated the VFD has the ability to control the velocity of the motor, the direction the engine shaft is definitely turning, the torque the electric motor provides to a load and any other motor parameter that can be sensed. These VFDs are also obtainable in smaller sizes that are cost-efficient and take up less space.
The arrival of advanced microprocessors has allowed the VFD works as an exceptionally versatile device that not only controls the speed of the electric motor, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs provide methods of braking, power increase during ramp-up, and a number of controls during ramp-down. The largest cost savings that the VFD provides is that it can ensure that the engine doesn’t pull extreme current when it begins, therefore the overall demand aspect for the whole factory can be controlled to keep carefully the domestic bill only possible. This feature alone can provide payback in excess of the cost of the VFD in less than one year after purchase. It is important to remember that with a traditional motor starter, they will 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 outcomes in the plant spending a penalty for all the electricity consumed during the billing period. Since the penalty may become just as much as 15% to 25%, the cost savings on a $30,000/month electric bill can be used to justify the purchase VFDs for virtually every motor in the plant also if the application form may not require working at variable speed.
This usually limited how big is the motor that may be controlled by a frequency plus they were not commonly used. The initial VFDs used linear amplifiers to control 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.
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