MV Motor Optimization: Copyright Material IEEE, Paper No. PCIC-2018-29

摘要

This paper presents two alternatives to make choosing the appropriate cost-effective AC machine for a given application easier. One option increases the short circuit capacity (SCC) at the motor bus; the other uses a synchronous machine (SM) in lieu of an induction machine (IM). Both methods have the potential to yield higher efficiency designs with better transient ride-through capability. There are well-defined relationships between applied voltage, applied current, and output torque. In short, higher voltages and/or currents allow a rotating machine to develop more torque. For obvious reasons, this relationship becomes extremely important for the transient performance associated with direct-on-line (DOL) starting. Adding more SCC minimizes the voltage drop, yielding more efficient and less costly designs. Over the life of a typical machine (e.g. 5000 HP IM), even a relatively small efficiency improvement realizes significant savings - enough to purchase the medium voltage (MV) distribution equipment. At 10 000 HP, the efficiency gains achieved through use of a SM instead of an IM are even greater, yielding more savings. As an added benefit, the increase in SCC leads to a more stable system, allowing the motor to ride through low voltage fault conditions that might otherwise have caused a trip. This in turn means more consistent throughput and a more profitable facility.