A controlled current AC-AC converter for circuit breaker testing

This paper presents an application of single-phase ac-ac converter with ac output current controls according to requirements of circuit-breaker (CB) testing standard (IEC 60898). Traditionally, the current sources for CB tests are simply designed to use the motor driven tap changing of auto-transformer for ac output current regulation. However, this kind of current source cannot provide the step change of high ac output current from the beginning of testing time due to slow dynamics of mechanical control. Thus, the proposed controlled current ac-ac converter is designed to solve this problem to meet the CB testing standard. All starting requirements such as ramp and step changes of ac output current are digitally implemented in the proposed ac-ac converter. Both simulation and experimental results successfully verified the current control operations of proposed ac-ac converter for CB testing application. In addition, the power factor correction (PFC) are also included in the proposed ac-ac converter and presented in this paper.