The voltage regulator is a mechanism that permits the change in turns ratio or output voltage of a distribution transformer for providing a constant magnitude voltage to the load. The arc occurs under oil in each tap changing operation because one of the moving contactors needs to move from one tap to another. The arcing results in an ablation of contact material every time a tap change is made, which reduces the lifetime of the transformer. Due to the increasing requirement of more frequent tap changing operations, the power electronics assisted method becomes an attractive solution to eliminate the arcing during tap changing. This thesis first reviews the development of arcless technology applied to the voltage regulator. Then, a hybrid switch based arcless voltage regulator is presented to eliminate the arc in tap changing events by using two anti-parallel thyristors and two electro-mechanical contactors. Simulation results validate the feasibility of the proposed arcless voltage regulator. A 12 kVA arcless voltage regulator prototype is developed to validate the arcless procedure. This proposed method requires minimum changes to the existing step-type voltage regulator and increases the number of operations and the lifetime of the conventional voltage regulator.
