Study on Voltage Drop, Transformer Capacity and Impedance during Induction Motor Starting

Induction motors have the disadvantage of generating a voltage drop due to a high current during startup. This voltage drop may have a bad effect on other loads, so the voltage drop must be reduced within a certain range. The improvement of the starting method is also important to reduce the voltage drop, but the contents of the transformer's capacity and percent impedance are also very important. Transformers have different percent impedance depending on their capacity and voltage. The percent impedance is also related to the voltage drop. The higher the capacity of the transformer, the higher the percent impedance, and the lower the capacity, the lower the percent impedance. In this study, in order to limit the voltage drop to within the allowable range when starting the induction motor directly, the transformer capacity was calculated by considering the percent impedance together. ©The Korean Institute of Electrical Engineers