VARIABLE SPEED DRIVE

Variable Speed Drive is an energy saving device for AC motor speed controls, also named variable frequency drives and adjustable speed drives by manufacturers... Most variable speed drive manufacturers require a reference to the neutral point of the winding, particularly for larger equipment. This connection serves as their primary "check" for unbalance in phase-phase and phase-ground circuits. As a side benefit, it keeps the VSD from accidentally damaging the machine winding insulation by over-voltaging the terminals by keeping the VSD and motor neutral at the same value... When an application requires more current at a reduced speed, that means more heat and less cooling at the lower speeds. Most VSDs have limits to protect the VSD and consequently the motor. Too low a setting and there will be lot of trips. Too high a setting and there may be damage in high ambient temperatures.