Today the VFD could very well be the most common kind of output or load for a control system. As applications become more complex the VFD has the ability to control the velocity of the electric motor, the direction the motor shaft can be turning, the torque the electric motor provides to lots and any other electric motor parameter which can be sensed. These VFDs are also available in smaller sized sizes that are price-effective 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 engine, but protects against overcurrent during ramp-up and ramp-down conditions. Newer VFDs also provide ways of braking, power increase during ramp-up, and a number of handles during ramp-down. The biggest savings that the VFD provides is definitely that it can ensure that the motor doesn’t pull extreme current when it starts, so the overall demand factor for the whole factory can be managed to keep the utility bill as low as possible. This feature by itself can provide payback more than the cost of the VFD in under one year after purchase. It is essential 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 takes place across many motors in a manufacturing facility, it pushes the electrical demand as well high which often outcomes in the plant paying a penalty for every one of the electricity consumed through the billing period. Because the penalty may end up being just as much as 15% to 25%, the financial savings on a $30,000/month electric bill can be used to justify the buy VFDs for virtually every engine in the plant even if the application might not require functioning at variable speed.
This usually limited the size of the motor that could be managed by a frequency plus they were not commonly used. The earliest VFDs utilized linear amplifiers to regulate 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 make different slopes.
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