Power and Dielectric Testing of a PCB-mounted Electronic Voltage Regulator

In this work, an electronic voltage regulator (EVR) with a voltage rating of 800V and a current rating of 30A has been tested experimentally. The EVR has been developed to control the output voltage in a regulated transformer, fulfilling the function of a conventional tap changer. Before building the device, to perform a validity test, the electronic voltage regulator has been simulated in PSCAD to check the steady state and transient values of voltage and current during different loading and fault conditions. The simulation results showed that the EVR can inject the required voltage and keep the load voltage in an acceptable range. The result of transient voltage and current helps the designer to select the components that suit performance characteristics of the circuit. Considering this, a TRIAC, being a pair of anti-parallel connected thyristors, with a rating of 1120V and 30A has been chosen as a principal switching component. To minimize the space of the device, the thyristors were placed at a distance of 3 cm from each other, and they were soldered professionally on the PCB board. Next, experimental testing has started. At lower voltages up to 400V, the results matched perfectly, and the device did not show any problems. After increasing the voltage from 400V to 500V, a flashover happened to the TRIAC, and subsequently all TRIACs in the circuit became shorted. The first issue to analyze should be the temperature of the TRIACs. However, the cooling system was also on, to ensure that the TRIACs are properly cooled during the test, and the temperature of the TRIACs showed that they are significantly lower than the maximum temperature that they can operate at. Therefore, the hypothesis of the thermal fault due to excessive temperature has been rejected. The next reason could be the insulation failure of the power electronic device, or breakdown of the space between them. To verify this hypothesis, more research has been performed, along with studying technical notes of the manufacturer and contacting them to ask more specific questions. It turned out the TRIAC requires more space from each other, although the distance selected in the circuit was two times more than the recommended value in the datasheet. The situation will be worse if the rating of the device is higher. Therefore, the power electronic devices must be far away from each other probably by a factor of 4-5 of the recommended distance in the datasheet. The paper will show results of the simulations and experiments.