A system for automatic power factor control is proposed which modulates reactive power compensation. This proposed shunt systen comprised a fixed size capacitor and a system of coupled fixed ratio and variable ratio transformers. The modulating control can not cause electric transients, which are an undesirable characteristic of the old art of capacitor switching. In those systems in which the distorted sine wave is strongly present, the watt loss control adopted by this system assumes greater importance than the power factor control. The fact that there is a possibility of having to do with a distorted sine wave brings the probability of getting into resonance in one of the harmonics, the 5th, 7th, 9th, or I I th. The amplitude of the harmonic might become so significant that it may exceed the allowable limits of the equipment. That requires insertion of a harmonic suppressing reactor into the power circuit. The practical solution seems now to be a detection system for d 1 2 /dVAR before the corresponding current reaches a harmful level, and subsequent disabling of the progress of the shunt device by stopping the variable transformer in the combination: variable transformer, fixed transformer, fixed capacitor. During normal operation the suppressing reactor is bypassed by a shunt circuit which includes a contactor. When suppression is required, the shunt contactor is opened after disabling the variable transformer which inserts the suppressing reactor into the main circuit. From this moment on, the progress of the variable transformer is reinstated and current reaches the desired optimum value. Experimental verification of this is required, and is an important component of the research program.The potential commercial application as described by the awardee: Research will lead to minimized reactive power losses and increased useful power in systems having distorted waveform; substantial reduction of capital and operating costs for large power users (10,000kva and up), because of high capacitor voltage; and transient free, high p.f. power for high sensitivity loads (e.g., computers).
