Perancangan Alat Praktikum Klasifikasi DC Chopper Pada Laboratorium Konversi Energi Elektrik

Abstract

DC chopper is an instrument of power electronic rapidly growth at the present, that it has many functions in industrial field such as rotation speed adjustment of direct current (DC) motor, traction motor control in electric automobile, mobile trolley, ship, etc. DC chopper is a device to convert a fixed-voltage dc source into a variable voltage dc source that conversion result can be varied by adjusting high speed switch between source and load. Classification of dc chopper experiments have been done such as classification of class A dc chopper, class B dc chopper and class C dc chopper. This experiment is done by using various type of switches such as BJT, MOSFET and IGBT. Triggering signal of pulse-width modulation for MOSFET, IGBT and BJT are produced and controlled by Microcontroller ATMega 8535. In the class A dc chopper has been proven that voltage and current values can be positive (first quadrant). In the class B dc chopper, the voltage value is positive and the current value is negative (second quadrant). Then in the class C dc chopper, the voltage value is positive and the current value can be positive or negative (first and second quadrant). Wave form signals of MOSFET are almost like a square. They are caused by time switching “on” and “off” almost same. When MOSFET is given the variation of duty cycle which increase the value of voltage in every interval more stable and approximately to values of calculated output voltage. The time switching “on” of IGBT is longer than the time switching “off” which causes voltage value always higher than the value calculated output voltage. Time switching “on” the BJT is shorter than the time “off”. From the characteristics of each waveform, it can be concluded that MOSFET is the good switching because the time switching “on” and the time switching “off” are almost same.