Design and Development of Autotransformer Motor Starter for Induced Draft Fan (IDF) of Batangas Sugar Central Inc.

Induction motors as a rotating machine draw a higher current during starting operation than under full load running conditions. With the use of reduced voltage, it limits the adverse effect of the starting current and torque that develops during across the line starting. This is in the case of Batangas Sugar Central Inc. (BSCI) where a wye – delta reduced voltage starting method was utilized in the induced draft fan (IDF) motor. Investigation of the present wye – delta starting method was done to identify the behavior of the voltage, current and torque at different stages of the operation to determine the causes of the operational problem. Performance and characteristics of the current in the present method during the switching transition were found to be defective (5 times the rated value) hence, the reason for analysis. In this study, the characteristics of the various starting method for three phases of induction motors were closely observed and comparison of the stated parameters were made in order to develop a proposed autotransformer motor starter prototype to serve as a basis of starting the IDF motor for the BSCI. Different design requirement based on National Electrical Manufacturers Association (NEMA), Philippine Electrical Code (PEC) and National Electrical Code (NEC) were considered. The voltage, current and torque based on the motor used in the study were computed and the values obtained were compared to the measured value of the parameters using the proposed starting method in order to ensure reliability, accuracy and applicability. The specification of the autotransformer was computed also based on the actual motor of BSCI and the corresponding values for the input parameters such as voltage, current and torque were then computed and analyzed. The results served as the basis for the BSCI in the implementation of the proposed autotransformer starting method. The computed value of the different input parameters was supported with the measured values using the autotransformer motor starter since the values obtained were almost equal. It showed that the computed value for the starting voltage was almost the same as the actual value. The same thing was true with the computed values of current at different stages in the operation of the motor where it was concluded to be almost equivalent to the measured value using the prototype