Switching device having a measuring apparatus

Patent metadata

Field	Value
Publication number	US-9726728-B2
Application number	US-201314646737-A
Country	US
Kind code	B2
Filing date	Nov 27, 2013
Priority date	Nov 27, 2012
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

A switching device has a current transformer for measuring in a potential-free manner a current to be switched by the switching device, a current sense amplifier, to which the unrectified measurement current of the current transfer is fed on the input side, and a controller, to which the output current of the current sense amplifier is fed on the input side and which is configured so as to digitalize the fed output current and to perform one or more performance-related measurements and to output the measurement results.

First claim

The invention claimed is:

1. A switching device, comprising:
a current transformer, configured to measure, in a potential-free manner, a current to be switched by the switching device;
a current measurement amplifier, configured to receive, as an input, an unrectified measuring current supplied by the current transformer; and
a controller, configured to:
receive, as an input, an amplified measuring current supplied by the current measurement amplifier,
digitize the amplified measuring current supplied by the current measurement amplifier,
carry out one or more power-based measurements using information included in the digitized amplified measuring current, the information included in the digitized amplified measuring current including amplitude information and phase information of the current to be switched, and
output one or more measurement results,

wherein the current measurement amplifier includes a differential amplifier having an input to which a voltage is supplied that drops at a resistor through which the unrectified measuring current supplied by the current transformer flows, and
wherein the voltage that drops at the resistor through which the unrectified measuring current supplied by the current transformer flows can be amplified while maintaining original phase information of the current to be switched.

2. The device of claim 1 , designed to switch a plurality of currents of different phases, the device including, for each phase, a separate current transformer including a downstream current measurement amplifier,
wherein the controller is further configured to digitize currents supplied by all current measurement amplifiers,
wherein the controller is further configured to carry out one or more power-based measurements using information included in the digitized currents, and
wherein the controller is configured to output the measurement results.

3. The device of claim 1 , wherein the controller is further configured to calculate a residual current using information included in a digitized amplified measuring current.

4. The device of claim 1 , wherein the controller is further configured to execute one or more protective functions of the switching device based on the information included in the digitized amplified measuring current.

5. The device of claim 1 , configured to be a three-pole circuit breaker.

6. The device of claim 1 , wherein the controller is further configured to carry out a calibration to reduce measurement tolerances occurring as a result of at least one current transformer.

7. The device of claim 1 , wherein the controller is further configured to carry out a calibration to reduce measurement tolerances occurring as a result of at least one current measurement amplifier.

8. The device of claim 1 , wherein the controller is further configured to carry out a calibration to reduce measurement tolerances occurring as a result of at least one current transformer and at least one current measurement amplifier.

Assignees

• Eaton Electrical Ip Gmbh & Co

Inventors

• Arenz Bernd
• Schwarz Wolfgang
• Suchalla Marc

Classifications

• H03F2203/45116

  Feedback coupled to the input of the differential amplifier · CPC title

• H02H3/083 Primary

  for three-phase systems · CPC title

• H03F3/45076

  characterised by the way of implementation of the active amplifying circuit in the differential amplifier · CPC title

• G01R21/00

  Arrangements for measuring electric power or power factor (G01R7/12 takes precedence) · CPC title

• G01R31/333 Primary

  Testing of the switching capacity of high-voltage circuit-breakers {; Testing of breaking capacity or related variables, e.g. post arc current or transient recovery voltage} · CPC title