The Synchronous Condenser

Author: E.E. Kimberly

Some synchronous motors are built without shaft extensions but with great capacity for over-excitation. Such machines are intended only to produce leading vars and are called synchronous condensers. They are usually built in large sizes only (1200 kv-a or more) because, when the whole cost of the machine must be charged against its var-producing ability, it does not compare favorably economically with static condensers in smaller sizes. It is commonly used in electric power transmission systems to aid in controlling the voltage at points in the system far distant from the generating station. The over-excited synchronous motor that can drive machinery is preferred in industrial plants. A vector diagram of a synchronous condenser is shown in Fig. 19-8.

Fig. 19-8. Vector Diagram of a Synchronous Condenser