Method for preventing a dangerous, higher-frequency earth fault current for an electrical drive system

US10734800B2 · kind B2 · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Hubert Schierling · Erlangen, DE
• Benno Weis · Hemhofen, DE

Key dates

• Filing date: Aug 17, 2017
• Grant date: Aug 4, 2020
• Expiry date: Aug 17, 2037

Classification

• Technology area (CPC H): Electricity
• CPC primary: H02H7/12
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A dangerous, higher-frequency (>1 kHz) earth fault current in an electrical drive system operated in an electrical grid and having a power converter and an electrical drive machine can be prevented by producing a common-mode voltage with a defined common-mode voltage component in the power converter at a selected low frequency (<1 kHz); in the event of an earth fault in the electrical drive system, flowing at the selected low frequency a common-mode current component of a common-mode current through a predominantly ohmic conductor-to-earth impedance on the basis of the defined common-mode voltage component; measuring a total common-mode current in one of several current circuits of the electrical drive system; determining from the total current the common-mode current component; and when the common-mode current component reaches a reference value, disconnecting the electrical drive system from the electrical grid.