Synchronous Motors Design and Application to Meet Special Requirements

Many present day applications of synchronous motors call for modifications of normal motor characteristics, as regards starting torques, thermal capacity of the starting winding, synchronizing ability, maximum synchronous torque, and mechanical design. The salient-pole motor with squirrel-cage amortisseur winding has advantages over other types which have led to the general adoption of this type as standard. Without abandoning this form, the starting and the synchronous characteristics can be adjusted to meet a variety of requirements by changing the proportions of the design and by using special forms of control equipment. Other forms, such as the synchronous induction motor, the phase-wound damper motor, and the supersynchronous motor, are sometimes justified for meeting strict starting current limitations or for accelerating extremely heavy inertia loads. In the mechanical design of machines for definite space requirements, fabricated construction allows changes in construction to be made at small expense, and often permits motors to be built integral with the driven machine.