Current transformer, protection device and electrical circuit breaker including such a transformer

Patent metadata

Field	Value
Publication number	US-2020176166-A1
Application number	US-201916684928-A
Country	US
Kind code	A1
Filing date	Nov 15, 2019
Priority date	Nov 29, 2018
Publication date	Jun 4, 2020
Grant date	—

Abstract

The current transformer includes a magnetic circuit made of magnetic material that is intended to be placed around a primary conductor, and a secondary winding that is wound onto a portion of the magnetic circuit in order to deliver a secondary current to processing circuits. In this current transformer the magnetic circuit includes at least one device for varying the magnetization of a portion of the magnetic circuit according to the temperature in order to limit or to decrease the magnetic flux in the magnetic circuit when the temperature of the magnetic circuit increases. The protection device and the electrical circuit breaker include such a transformer.

First claim

1 . A current transformer comprising:
a magnetic circuit made of magnetic material that is intended to be placed around a primary conductor; and a secondary winding that is wound onto a portion of said magnetic circuit in order to deliver a secondary current to a processing circuit, wherein the magnetic circuit comprises at least one device for varying the magnetization of a portion of said magnetic circuit according to the temperature in order to limit or to decrease the magnetic flux in the magnetic circuit when the temperature of the magnetic circuit increases.

2 . The current transformer according to claim 1 , wherein the device for varying magnetization limits the circulation of the magnetic flux to a value that is less than 50% of the value at 20° C. when the temperature is higher than 150° C.

3 . The current transformer according to claim 1 , wherein the device for varying magnetization creates an additional complete or partial gap in the magnetic circuit in order to limit the circulation of the magnetic flux when the temperature exceeds a predetermined threshold.

4 . The current transformer according to claim 3 , wherein said predetermined threshold is between 120° C. and 180° C.

5 . The current transformer according to claim 1 , wherein the device for varying magnetization comprises a mechanical device housed in a recess of the magnetic circuit in order to produce a gap or to increase a gap by opening the magnetic circuit when the temperature reaches said predetermined threshold.

6 . The current transformer according to claim 5 , wherein the mechanical device comprises bi-metal strips which are mounted head-to-tail and are housed in a recess in order to effect a separation of the magnetic circuit, generating a gap.

7 . The current transformer according to claim 6 , wherein the mechanical device comprises from 6 to 12 strips of bi-metal.

8 . The current transformer according to claim 6 , wherein said gap is greater than 0.5 mm when the temperature is higher than 120° C. or the magnetic circuit experiences a temperature increase of 120 K.

9 . The current transformer according to claim 1 , wherein the device for varying magnetization comprises a static device housed in a section of said magnetic circuit, said static device being made up of a magnetic material having a Curie point or a Curie temperature that is lower than that of the magnetic material of the magnetic circuit.

10 . The current transformer according to claim 9 , wherein the material of the static device has a Curie temperature between 80° C. and 200° C.

11 . The current transformer according to claim 9 , wherein the material of the static device is predominantly made up of iron-nickel or of ferrite.

12 . The current transformer according to claim 9 , wherein the material of the static device comprises cutouts for avoiding current losses through eddy currents.

13 . An electronic protection device comprising an electronic processing unit connected to at least one current transformer and delivering an electronic signal in response to protection functions, said device further comprises a current transformer according to claim 1 having a secondary winding connected to said processing unit in order to deliver a secondary measurement or electrical power supply current.

14 . An electrical circuit breaker comprising at least one main electrical contact for interrupting a current in an electrical circuit, a mechanism for controlling the opening of said electrical contact and a protection device delivering a control signal to said control mechanism, wherein at least one current transformer according to claim 1 connected to a processing unit of said protection device.

Assignees

• Schneider Electric Ind Sas

Inventors

• Mas Patrick
• Shi Xiaodong

Classifications

• H01F27/008 Primary

  with temperature compensation · CPC title

• H01H71/7463

  Adjusting only the electromagnetic mechanism · CPC title

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• H01F27/24 Primary

  Magnetic cores · CPC title

• H01F38/28 Primary

  Current transformers · CPC title