Patent ID: 8203319
Filing Date: 2012-06-19
Classification: H01H

Abstract:
1. An on-load tap changer for a transformer winding, comprising: a first micro-electromechanical system (MEMS) switch module directly coupled in series with a first tap on the transformer winding and a neutral terminal; a second MEMS switch module directly coupled in series with a second tap on the transformer winding and the neutral terminal; and a controller operably coupled to the first MEMS switch module and the second MEMS switch module, the controller is configured to generate a first and second signal to be received by the first and second MEMS switch modules respectively to induce the first MEMS switch module to transition to a closed position and induce the second MEMS switch module to transition to an open position to obtain a first predetermined turns ratio on the transformer winding at a first time, the controller further configured to generate a third signal to the second MEMS switch module to induce the second MEMS switch module to transition to a closed position at a second time after the first time, the controller further configured to generate a fourth signal to be received by the first MEMS switch module at a third time after the second time, the first MEMS switch module configured to transition from the closed position to an open position at a detected zero crossing of an alternating current in response to the fourth signal to obtain a second predetermined turns ratio on the transformer winding; control circuitry coupled to the first MEMS switch module and the second MEMS switch module, the control circuitry configured to prevent the creation of high circulating current between transformer windings when the first MEMS switch module and the second MEMS switch module are each in the closed position, and wherein at least one of the first MEMS switch module or the second MEMS switch module includes a current sensor for detecting the zero crossing of the alternating current.