US 12,265,113 B2
Monitoring device for emergency standby operation
Roland Jungreithmair, Wels-Thalheim (AT); Stefan Wieser, Wels-Thalheim (AT); Martin Wolf, Wels-Thalheim (AT); and Bernhard Doppelbauer, Wels-Thalheim (AT)
Assigned to Fronius International GmbH, Pettenbach (AT)
Appl. No. 18/038,877
Filed by Fronius International GmbH, Pettenbach (AT)
PCT Filed Nov. 25, 2021, PCT No. PCT/EP2021/082950
§ 371(c)(1), (2) Date May 25, 2023,
PCT Pub. No. WO2022/112393, PCT Pub. Date Jun. 2, 2022.
Claims priority of application No. 20210023 (EP), filed on Nov. 26, 2020.
Prior Publication US 2023/0408569 A1, Dec. 21, 2023
Int. Cl. G01R 31/14 (2006.01); G01R 31/12 (2020.01)
CPC G01R 31/1227 (2013.01) 16 Claims
OG exemplary drawing
 
1. A method for determining an AC insulation resistance between the AC connections of an inverter and a ground potential, comprising:
applying a DC voltage between DC connections of the inverter; and
applying an AC voltage between the AC connections of the inverter,
wherein the DC connections are connected to a DC power source,
wherein, in an emergency standby operation, the AC connections are connected to an AC energy sink in order to transmit energy from the DC energy source to the AC energy sink, and an insulation test is performed,
wherein an AC fault current flowing between an AC connection and the ground potential is determined from an insulation voltage present between one of intermediate circuit connections and the ground potential or an intermediate circuit midpoint and the ground potential, and from an insulation impedance between the intermediate circuit connection and the ground potential or the intermediate circuit midpoint and the ground potential,
wherein a phase shift between an AC phase angle of the AC voltage and a fault current phase angle of the AC fault current is calculated, and
wherein the AC insulation resistance is calculated from the phase shift.