Why Do VFD's
In many motor applications, the load on a motor is continually changing. Using a hoist as an example, the motor is powered to lift a load to a certain height. Once this is achieved, that motor must allow the hoist to return to it’s starting position by lowering the load. When this happens, gravitational force helps push the hoist back down, and instead of consuming power to lift the hoist, gravitational energy drives the motor and generates power. This power flows back to the VFD, causing an overvoltage situation. To remedy this, something must be done with the excess power. This is where braking technologies come in.