| 摘要 |
A self-power circuit (30,40) for a protecting relay includes: a rectifying circuit section (30) rectifying an AC current from an electric power system; a power source circuit section (40) includes: a comparator (41) comparing whether an output voltage from the rectifying circuit section exceeds a reference voltage and a semiconductor switch (42) configured to be switched by an output from the comparator, and supply the output voltage from the rectifying circuit section, as a constant voltage to a microcomputer unit (50) of the protecting relay; an inductor (L1) configured to, when a DC current supplied from the rectifying circuit section is rapidly increased, gradually increase the DC current to flow to thus have an increased voltage thereacross; and a bidirectional diode (D3) connected between the power source circuit section and a ground and turned on to form a bypass path of a current when a DC voltage supplied from the power source circuit section is rapidly increased. Fig. 2 |
