Magnetically driven trip mechanism for an overload relay

• US 9,711,307 B2
• Filed: 10/29/2014
• Issued: 07/18/2017
• Est. Priority Date: 10/29/2014
• Status: Active Grant

• Current Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Original Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Inventors: Weiden, Conrad S.
• Primary Examiner(s): Gandhi, Jayprakash N
• Assistant Examiner(s): SUL, STEPHEN SANGJIN
• Application Number:
  US14/526,863
• Publication Number:
  US 20160126039A1
• Time in Patent Office: 993 Days
• Field of Search: 337 99, 337134, 337 13, 337 42, 337105, 337343, 337344, 337365, 337366, 337367, 337390, 337 12, 337 53, 337 54, 337 90, 337 98, 337136, 337318, 337281, 337400, 337411
• CPC Class Codes: H01H 2051/2218 having at least one movable permanent magnet
• CPC Class Codes: H01H 36/0073 actuated by relative movement between two magnets
• CPC Class Codes: H01H 37/52 actuated due to deflection of bimetallic element
• CPC Class Codes: H01H 61/02 wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively
• CPC Class Codes: H01H 71/16 with bimetal element combined with detection of imbalance of two or more currents H01H83/223
• CPC Class Codes: H01H 71/164 Heating elements
• CPC Class Codes: H01H 71/32 having permanently magnetised part
• CPC Class Codes: H01H 71/323 with rotatable armature

Abstract

In an overload relay, a tripping actuator 12 has a first magnet 18 and a moveable contact carrier 20 has a second magnet 28 mounted opposed to the first magnet. A moveable contact 22 on the moveable contact carrier is urged by repulsion between the magnets, to make a normally closed connection with a stationary contact 24, when the tripping actuator is in an ON position 15 and the contact carrier in a first stable position 26′. The magnets pass through an over-center tripping position (T) when the tripping actuator is moved to an OFF position 23 in response to an overcurrent condition sensed by a bimetallic thermal overload sensor 16. The magnets repel each other after passing through the over-center tripping position, to thereby urge the moveable contact into a second stable position 26, away from the stationary contact, to break the normally closed connection with the stationary contact.

Claims

1. A magnetically driven trip mechanism for an overload relay, comprising:

a tripping actuator having a first permanent magnet;

a moveable contact carrier having a second permanent magnet mounted in an opposed orientation to the first permanent magnet;

a moveable electrical contact on or actuated by the moveable contact carrier, the moveable electrical contact configured to be urged, by repulsion between the first and second permanent magnets, to make a normally closed electrical connection with a stationary electrical contact, when the tripping actuator is in an ON position and the moveable contact carrier in a first stable position;

the first permanent magnet passing the second permanent magnet in a first direction through an over-center tripping position when the tripping actuator is moved to an OFF position in response to an overcurrent condition being sensed by an overcurrent sensing mechanism, the first permanent magnet propelling the second permanent magnet by mutual repulsion to move through the over-center tripping position; and

the first and second permanent magnets being configured to repel each other after the first permanent magnet passes through the over-center tripping position, to thereby urge the moveable contact carrier and its moveable contact toward a second stable position, the moveable contact thereby moving in a second direction opposite to the first direction, to break the normally closed electrical connection with the stationary electrical contact, the first permanent magnet propelling the second permanent magnet by mutual repulsion to move through the over-center tripping position.

2. The magnetically driven trip mechanism for an overload relay of claim 1, further comprising:

the first permanent magnet passing the second permanent magnet in the second direction opposite to the first direction, through the over-center tripping position, when the tripping actuator is moved to an ON position after the overcurrent condition subsides; and

the first and second permanent magnets being configured to repel each other after the first permanent magnet passes through the over-center tripping position in the second direction, to thereby urge the moveable contact carrier and its moveable contact toward the first stable position, the moveable contact thereby moving toward the stationary contact, to make the normally closed electrical connections with the stationary electrical contact.

3. The magnetically driven trip mechanism for an overload relay of claim 1, further comprising:

an adjustable mounting on the tripping actuator, the adjustable mounting supporting the first magnet, the repulsion between the first and second magnets being adjustable by changing the orientation of the first magnet in the adjustable mounting, thereby changing a location of the tripping position.

4. The magnetically driven trip mechanism for an overload relay of claim 1, wherein the overcurrent sensing mechanism is a bimetallic thermal overload sensor.

5. The magnetically driven trip mechanism for an overload relay of claim 1, wherein the overcurrent sensing mechanism is a bimetallic thermal overload sensor that employs a bimetal strip associated with a current carrying heater coil connected in series with a power source and a motor, the bimetal strip being configured to deflect from heat produced by the heater coil when an overcurrent condition occurs, thereby moving the tripping actuator in the first direction, through the over-center tripping position.

6. The magnetically driven trip mechanism for an overload relay of claim 5, wherein when the overcurrent condition subsides and the heater coil cools, the bimetal strip is configured to reverse its deflection, thereby moving the tripping actuator in the second direction, back through the over-center tripping position.

7. The magnetically driven trip mechanism for an overload relay of claim 1, wherein the tripping actuator has a pivoted end mounted on a pivot on a base, the tripping actuator having the first permanent magnet mounted on an end opposite to the pivoted end, with north-south poles of the first permanent magnet oriented in a substantially radial direction with respect to the pivot, the first permanent magnet moving in the first direction when the overcurrent sensing mechanism causes the tripping actuator to move in the first direction in response to the overcurrent condition being sensed by the overcurrent sensing mechanism;

and

wherein the moveable contact carrier is slideably mounted on the base, the moveable contact carrier having the second permanent magnet mounted thereon with north-south poles of the second permanent magnet being oriented in a substantially opposite direction with respect to the direction of orientation of the north-south poles of the first permanent magnet, the moveable contact carrier and its moveable electrical contact sliding in the second direction away from the stationary electrical contact, when the tripping actuator is moved to the OFF position in response to the overcurrent condition being sensed by an overcurrent sensing mechanism.

8. The magnetically driven trip mechanism for an overload relay of claim 1, wherein the overcurrent sensing mechanism is connected in series with a power source and a motor, the overcurrent sensing mechanism being configured to sense a prolonged motor overcurrent.

9. The magnetically driven trip mechanism for an overload relay of claim 1, wherein, in response to the overcurrent condition being sensed to subside by the overcurrent sensing mechanism, the tripping actuator moves in the second direction back through the over-center tripping position, thereby urging the contact carrier toward the first stable position and moving the moveable electrical contact in the first direction toward the stationary electrical contact, to thereby automatically reset the normally closed electrical connection with the stationary electrical contact.

10. The magnetically driven trip mechanism for an overload relay of claim 1, further comprising:

the moveable contact carrier further including a second moveable electrical contact on or actuated by the moveable contact carrier, the second moveable electrical contact configured to be urged, by the repulsion between the first and second permanent magnets, to remain disconnected in a normally open electrical connection with a second stationary electrical contact, when the tripping actuator is in the ON position and the moveable contact carrier in the first stable position;

the second moveable electrical contact configured to make a connection with the second stationary electrical contact in the normally open electrical connection, when the first permanent magnet passes the second permanent magnet in the first direction through the over-center tripping position, when the tripping actuator is moved to the OFF position and the moveable contact carrier is in the second stable position in response to the overcurrent condition being sensed by the overcurrent sensing mechanism.

11. The magnetically driven trip mechanism for an overload relay of claim 10, further comprising:

the second moveable electrical contact configured to break the connection with the second stationary electrical contact in the normally open electrical connection, when the first permanent magnet passes the second permanent magnet in the second direction through the over-center tripping position, when the tripping actuator is moved to the ON position and the moveable contact carrier is in the first stable position in response to the overcurrent condition being sensed to subside, by the overcurrent sensing mechanism.