Patent ID: 9515474
Filing Date: 2016-12-06
CPC Classification: H02H

Claim Text:
1. A power off device comprising: a first detector for detecting an electric arc and turning on a first switching element, based on a voltage induced in a high frequency choke coil by a high frequency pulse current caused by the electric arc at a power line, and outputting a first electric current during turning-on of the first switching element, wherein the first electric current has a form of a pulse with an amplitude and a width, which correspond to those of the high frequency pulse current; a second detector for detecting a high current arc and outputting a second electric current during turning-on of a second switching element made based on variation of a magnetic field generated at a coil installed at the power line due to the high current arc generated at the power line, wherein the second electric current has a form of a pulse with a level and a generation time, which correspond to those of a voltage induced by the high current arc; a delay unit for accumulatively charging the first electric current or the second electric current in a delay capacitor at a predetermined time constant, and outputting an arc detection signal when a voltage across the delay capacitor reaches a predetermined level; a power off unit for electrically disconnecting a load from the power line when an operating voltage is applied; and a first switch for connecting the operating voltage to the power off unit in response to the arc detection signal, wherein the first detector comprises an inductor installed at the power line, to establish a loop together with the high frequency choke coil; the loop comprises a second capacitor connected in series between the inductor and a first terminal of the high frequency choke coil, a first diode, and a first capacitor, the first diode and the first capacitor being connected in series between the inductor and a second terminal of the high frequency choke coil; a fourth diode is connected between the second terminal of the high frequency choke coil and another power line; and the high frequency choke coil is connected in common, at the first terminal of the high frequency choke coil, to a control terminal of the first switching element and the second capacitor via a high frequency rectifier diode, and is connected, at the second terminal of the high frequency choke coil, to an input terminal of the first switching element, an anode of the second diode, and an anode of the fourth diode.