Demonstrative Video
Synchronous Condenser
The power factor of a synchronous motor can be controlled over a wide range by adjusting its excitation.
At no-load, when the motor is over-excited it may draw the current from mains which leads the voltage by large angle nearly 90°.
Hence, the motor acts like a static capacitor and is known as a synchronous condenser.
Thus, an over excited synchronous motor operating at no-load is called a synchronous condenser or synchronous capacitor.
When an over excited motor is operated on the same electrical system to which some industrial load (induction motors, induction furnaces, arc furnaces, etc.) is operating at lagging power factor, the leading reactive power supplied by the synchronous motor compensates for the lagging reactive power of industrial load and improves the overall power factor of the system.
In large industrial plants, which have a low lagging PF load, it is often found economical to install an over excited SM (synchronous condenser), even though the motor is not required to drive a load.
Consider an industrial load \(P_L\) operating at a power factor \(\cos\phi_1\).
When an over excited motor drawing power \(P_m\) is connected in parallel with the existing load, some of the lagging \(Q\) of the industrial load in compensated by the leading \(Q\) of the motor (\(P_{rm}\)) which improves the over-all power factor to \(\cos\phi_2\).