Advantages of Large Solid-Pole Brushless Synchronous Motors for Centrifugal Compressor Drives

There is an increasing requirement for self-starting electric motors to drive large centrifugal compressors. The solid-pole brushless synchronous motor meets these requirements with capabilities beyond the practical limitations of the laminated-pole motor. The solid-pole construction and the slip energy to be absorbed during starting are considered together with the loss and temperature distribution within the poleshoes. The uses of vendor data for equivalent circuits, reactances, and time constants are considered in relation to starting, and differences between solid-and laminated-pole motors are highlighted. An improved brushless excitation circuit is described.