The starting characteristics of induction type motors

The three-phase induction motor finds a wide field of application in most modern industries owing to its low initial cost, comparative ease of starting and low cost of starting equipment. A further advantage is its low cost of maintenance. It has, however, the disadvantage of poor power factor when running on reduced loads. The synchronous motor, on the other hand, has the characteristic of good power factor, together with the possibility of power factor improvement, but it suffers from the disadvantage that it will not run up from rest. For this reason, various types of synchronous motors and machines, such as synchronous condensers and rotary condensers and rotary converters, which may be run up either by a separate induction motor or by a separate induction winding built into the machine itself, have been evolved.