US 11,714,119 B2
Earth fault detection apparatus
Yasuyuki Mochizuki, Makinohara (JP); Norio Sudo, Makinohara (JP); Haruhiko Yoshida, Makinohara (JP); and Ryosuke Arigaya, Makinohara (JP)
Assigned to YAZAKI CORPORATION, Tokyo (JP)
Filed by Yazaki Corporation, Tokyo (JP)
Filed on May 23, 2022, as Appl. No. 17/750,834.
Claims priority of application No. 2021-091490 (JP), filed on May 31, 2021.
Prior Publication US 2022/0381812 A1, Dec. 1, 2022
Int. Cl. G01R 31/12 (2020.01); G01R 31/52 (2020.01); G01R 27/26 (2006.01); G01R 27/02 (2006.01)
CPC G01R 31/1227 (2013.01) [G01R 27/025 (2013.01); G01R 27/2605 (2013.01); G01R 31/12 (2013.01); G01R 31/52 (2020.01)] 2 Claims
OG exemplary drawing
 
1. An earth fault detection apparatus to be connected with a non-grounded battery and for calculating an insulation resistance of a system including the battery, the earth fault detection apparatus comprising:
a capacitor configured to be operated as a flying capacitor;
a switch group configured to switch between a first measurement path, a second measurement path, and a third measurement path, the first measurement path including the battery and the capacitor, the second measurement path including the battery, a negative-side insulation resistance that is an insulation resistance between a negative-side line of the battery and ground, and the capacitor, the third measurement path including the battery, a positive-side insulation resistance that is an insulation resistance between a positive-side line of the battery and the ground, and the capacitor;
a reference resistance and a test switch connected in series between the positive-side line or the negative-side line of the battery and the ground; and
a control unit configured to calculate a first reference value based on each charging voltage in a case where the test switch is opened and the capacitor is charged for a first time in each of the first to third measurement paths, and configured to calculate the insulation resistance with reference to a conversion map that has been created to correspond to an electrostatic capacitance between the ground and each of the positive-side line and the negative-side line of the battery, wherein
the control unit calculates a second reference value based on each charging voltage in a case where the test switch is closed and the capacitor is charged for a second time in each of the first to third measurement paths, the second time being shorter than the first time, and configured to estimate the electrostatic capacitance with reference to a predetermined test conversion map.