US 11,698,417 B2
Earth fault detection apparatus
Yasuyuki Mochizuki, Makinohara (JP); Norio Sudo, Makinohara (JP); and Ryosuke Arigaya, Makinohara (JP)
Assigned to YAZAKI CORPORATION, Tokyo (JP)
Filed by Yazaki Corporation, Tokyo (JP)
Filed on May 24, 2022, as Appl. No. 17/752,178.
Claims priority of application No. 2021-091491 (JP), filed on May 31, 2021.
Prior Publication US 2022/0381850 A1, Dec. 1, 2022
Int. Cl. G01R 31/52 (2020.01); G01R 31/12 (2020.01); G01R 27/26 (2006.01)
CPC G01R 31/52 (2020.01) [G01R 27/2605 (2013.01); G01R 31/12 (2013.01)] 9 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; and
a control unit configured to calculate a reference value based on each charging voltage of the capacitor in each of the first to third measurement paths, and configured to calculate the insulation resistance with reference to a predetermined conversion map, wherein
the conversion map includes a conversion map corresponding to a capacitance of the capacitor, and
the control unit is configured to estimate the capacitance of the capacitor, and refers to the conversion map corresponding to the capacitance of the capacitor that has been estimated.