Induction Motor Modeling for Development of a Secure In-Phase Motor Bus Transfer Scheme

This paper presents techniques to model an induction machine during the transient periods of a motor bus transfer operation and then develops a more secure in-phase motor bus transfer scheme. To increase the robustness of the electrical power supply, two independent power supplies are typically routed to the industrial facilities with large motor loads. The motor loads are split between two buses. If one of the two power supplies becomes unavailable due to a fault on the power line, the supply for the faulted bus is tripped, and the two buses are paralleled to keep the facility fully operational. The machines supplied by the source that experiences the failure start to slow down when the voltage sags, potentially leading to severe transient torques on the motor shafts upon resynchronization, complicating the transfer process. Efficiently and accurately modeling the induction machines allows the creation of transfer schemes that lead to successful in-phase motor bus transfers where the worst-case torque on any of the motor shafts is limited to 6 p.u. This enables the motor to be synchronously connected to an alternative power source in the event of a supply disruption.