An innovative method to achieve minimum tripping current conformity for type A RCCBs

Abstract

This paper presents an innovative method to decrease the discreteness of minimum tripping current for type A residual current operated circuit breakers (RCCBs). Different but continuous time intervals' detection method is proposed to identify the residual current's type and judge whether its root mean square (RMS) value has exceeded the rated value in one cycle. That is, after the timer is started, 0-3 ms ²135°leakage current is detected, 3-7 ms ²90°is detected, 7-12 ms ²0°is detected, 3-7 ms and 12-16 ms type AC is detected. What's more, the method is fabricated in a mixed-signal 0.5 µm CMOS process, and test results show that the type A RCCB's tripping current variation is decreased to 2.8 mA, which greatly improves the chip's reliability and anti-interference ability.