Monitoring device for emergency standby operation
AssigneeFronius International GmbH
InventorsRoland JUNGREITHMAIR, Stefan WIESER, Martin WOLF, Bernhard DOPPELBAUER
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Abstract
To determine an AC insulation resistance between the AC connections of an inverter and a ground potential, the AC connections are connected to an AC energy sink in an emergency standby operation in order to transmit energy from a DC energy source to an AC energy sink and an insulation test is performed in emergency standby operation. An AC fault current flowing between an AC connection and the ground potential is determined, and the AC insulation resistance is calculated from the AC fault current.
Claims10
A method for determining an AC insulation resistance between the AC connections of an inverter and a ground potential, wherein a DC voltage is applied between DC connections of the inverter, and an AC voltage is applied between AC connections of the inverter, wherein the DC connections are connected to a DC power source, and wherein, in 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, wherein, in emergency standby operation, 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, preferably the AC voltage component of the insulation voltage, present between one of the 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.
A monitoring device for determining an AC insulation resistance between AC connections of an inverter and a ground potential, wherein DC connections of the inverter can be connected to a DC power source, and, in an emergency standby operation, AC connections of the inverter can be connected to an AC energy sink, wherein the monitoring device comprises a fault current detection unit which is configured to determine an AC fault current flowing between an AC connection and a ground potential, from an insulation voltage, preferably the AC voltage component of the insulation voltage, present between one of the 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, and wherein the monitoring device comprises a calculation unit which is configured to calculate a phase shift between an AC phase angle of the AC voltage and a fault current phase angle of the AC fault current, and to calculate the AC insulation resistance from the phase shift.
Dependencies are inferred from the claim text.