Implementation of AC-AC Voltage Controller for Reduce Transient Current at Three Phase Induction Motor

Induction motor is one type of electric motor that is most often applied in the industrial world, especially the three phase induction motor. Induction motors have several advantages compared to other types of motors, such as construction that is very simple, price and low maintenance. But the problem is that when the motor is activated directly, the motor will draw a current of five to seven times the nominal current.[2] The high start current can cause voltage drop and disrupt the system from the installation. To resolved these high current, a soft starting device will be designed, namely by regulating the motor slip by regulating the input voltage in the motor gradually so that the problem of starting three phase induction motor can be resolved. This system consists of a three phase induction motor which is supplied from a three phase source through three TRIACs in each phase which functions to regulate the voltage entering the motor gradually. In this system it also detects the current entering the motor in each phase so that it can determine the exact ignition angle of each TRIAC used. The sensor also detects the starting current which starts to drop when the motor speed will reach nominal so that when it detects it, the ignition angle on TRIAC will be adjusted until the voltage reaches nominal. So the control system will reduce the start current in the three phase induction motor by setting the right ignition angle for each TRIAC used.