Tripping device for an electrical switching unit and electrical switching unit including such a tripping device

Patent metadata

Field	Value
Publication number	US-10818461-B2
Application number	US-201816211804-A
Country	US
Kind code	B2
Filing date	Dec 6, 2018
Priority date	Dec 21, 2017
Publication date	Oct 27, 2020
Grant date	Oct 27, 2020

Abstract

A thermomagnetic trip assembly includes a thermal trip, a magnetic trip, and first and second actuation levers. The thermal trip includes a bimetal strip that is capable of deforming in order to actuate the first actuation lever. The magnetic trip includes a movable armature, a fixed armature and an electrical conductor. The movable armature is capable of moving in order to actuate the second actuation lever. The electrical conductor and the bimetal strip are electrically connected in series with one another between first and second connection terminals of the trip assembly. The movable armature is connected to the first connection terminal, the fixed armature is connected to the second connection terminal, and the respective contact areas of the fixed armature and of the movable armature are made of electrically conductive materials that exhibit a low degree of mutual weldability.

First claim

The invention claimed is:

1. A thermomagnetic trip assembly for an electrical switching unit said assembly comprising:
a thermal trip,
a magnetic trip, and
a tripping arm intended to be mechanically coupled to a switching mechanism of the electrical switching unit, said tripping arm comprising first and second actuation levers;
the thermal trip comprising a bimetal strip that is capable of deforming when the current passing through it exceeds a first predefined threshold;
the magnetic trip comprises a movable armature, a fixed armature and an electrical conductor;
the movable armature being capable of moving from a first position, wherein the movable armature is distanced from the fixed armature, toward a second position, wherein the movable armature is in contact with the fixed armature at contact areas, when the current which flows through the electrical conductor exceeds a second predetermined threshold, the movement of the movable armature toward the second position actuating the second actuation lever;
the electrical conductor and the bimetal strip being electrically connected in series with one another between first and second connection terminals of the trip assembly;
the movable armature is connected to the first connection terminal, and in that wherein the fixed armature is connected to the second connection terminal,
and wherein the respective contact areas of the fixed armature and of the movable armature are made of electrically conductive materials that exhibit a low degree of mutual weldability.

2. The thermomagnetic trip assembly according to claim 1 , wherein the contact areas are formed by an added element fixed on a body of the corresponding fixed or movable armature.

3. The thermomagnetic trip assembly according to claim 1 , wherein at least one contact area is made of a metal material, chosen from the group comprising copper, steel, aluminium, Dural alloy, an alloy of aluminium having the French designation A-G3 or A-G4, and wherein the materials of the contact areas which are part of the fixed and movable armatures, respectively, are different.

4. The thermomagnetic trip assembly according to claim 1 , wherein at least one contact area is made of graphite.

5. The thermomagnetic trip assembly according to claim 1 , wherein the contact area or areas of the movable armature are directly connected to the first terminal.

6. The thermomagnetic trip assembly according to claim 1 , wherein the contact area or areas of the fixed armature are directly connected to the second terminal.

7. The thermomagnetic trip assembly according to claim 1 , wherein the magnetic trip comprises a return spring, in order to bring the movable armature back toward the first position, said return spring being coated with an insulating material.

8. The thermomagnetic trip assembly according to claim 7 , wherein the insulating material is Teflon.

9. The thermomagnetic trip assembly according to claim 1 , wherein the electrical conductor and the bimetal strip together form a first branch of an electric circuit such that an electric current flows between the connection terminals,
wherein, in the second position, the fixed and movable armatures in contact with one another form a second branch of the electric circuit such that an electric current flows between the connection terminals, said second branch being electrically arranged in parallel with the first branch,
and wherein the first branch has an impedance greater than the impedance of the second branch.

10. An electrical switching unit comprising:
a cut-off block having separable electrical contacts;
a trip assembly capable of triggering the opening of the electrical contacts of the cut-off block when an electrical fault is detected;
wherein the trip assembly is the thermomagnetic trip assembly according to claim 1 .

11. The thermomagnetic trip assembly according to claim 1 , wherein the electrical switching unit is a circuit breaker.

12. The thermomagnetic trip assembly according to claim 1 , wherein the bimetal strip of the thermal trip is capable of deforming when the current passing through it exceeds the first predefined threshold to actuate the first actuation lever.

13. The thermomagnetic trip assembly according to claim 2 , wherein the added element is a covering, a plate, or a contact pad.

14. The thermomagnetic trip assembly according to claim 7 , wherein the return spring is a coil spring.

15. The thermomagnetic trip assembly according to claim 9 , wherein the impedance of the first branch is ten times greater than the impedance of the second branch.

16. The thermomagnetic trip assembly according to claim 9 , wherein the impedance of the first branch is one hundred times greater than the impedance of the second branch.

17. The electrical switching unit according to claim 10 , wherein the electrical switching unit is a circuit breaker.

Assignees

• Schneider Electric Ind Sas

Inventors

• Heraud Sebastien
• Delcarmine Grigori

Classifications

• H01H37/52

  actuated due to deflection of bimetallic element · CPC title

• H01H3/001

  Means for preventing or breaking contact-welding · CPC title

• H01H2071/168

  Provisions for avoiding permanent deformation and thus decalibration of bimetal, e.g. due to overheating or action of a magnet · CPC title

• H01H2201/026

  non precious · CPC title

• H01H71/40 Primary

  Combined electrothermal and electromagnetic mechanisms · CPC title