High Performance Line Voltage Regulator

A new high performance class of line voltage regulators is introduced for application to computer and other communication type loads. It utilizes thyristors to smoothly buck or boost the input voltage to the proper level to compensate for variations in input voltage or load, and maintains plus or minus 1/2% output voltage regulation. Correction to within 5% of normal voltage is possible within 1 cycle after a step input or load change. The output harmonics introduced by the thyristor control are attenuated to 5% or less by the use of a unique parametric filter which permits stable operation even with severely non-linear loads. Configurations for single and three phase service are described. Effects of load unbalance and overload are discussed. Provisions for attenuation of input over-voltage transient is made with an accessory transient suppression circuit. Initial experience in applying this regulator in uninterruptible power systems is related.