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EP-4439617-B1 - A MAGNETIC ACTUATOR FOR LOW-VOLTAGE ELECTRIC SYSTEMS

EP4439617B1EP 4439617 B1EP4439617 B1EP 4439617B1EP-4439617-B1

Inventors

  • PIASECKI, WOJCIECH
  • TUEYSUEZ, ARDA
  • Kassubek, Frank Jürgen
  • BIALAS, MARCIN

Dates

Publication Date
20260506
Application Date
20230330

Claims (15)

  1. A magnetic actuator (1) for low-voltage electric systems, wherein magnetic actuator comprises a magnetic circuit (10) including: - a fixed magnetic armature (2) and a movable magnetic armature (3), said movable magnetic armature being reversibly movable between a first position (C) and a second position (O) relative to said fixed magnetic armature; - a permanent magnet (4) configured to feed said fixed and movable magnetic armatures (2, 3) with a first magnetic flux (Φ 1 ) having a predefined direction, when said permanent magnet is in a magnetized condition; wherein said magnetic actuator further comprises an excitation coil (5) wound on said magnetic circuit (10) and configured to be fed with an electric current (I C ) having a predetermined direction, when a tripping manoeuvre of said magnetic actuator is required, wherein said magnetic circuit (10) includes: - a first branch (10a) including a first portion (21) of said fixed magnetic armature, a first portion (31) of said movable magnetic armature, said permanent magnet (4) and a first airgap region (G 1 ) between said fixed magnetic armature (2) and said movable magnetic armature (3); - a second branch (10b) including a second portion (22) of said fixed magnetic armature, a second portion (32) of said movable magnetic armature and a second airgap region (G 2 ) between said fixed magnetic armature (2) and said movable magnetic armature (3); - a third branch (10c) including a magnetic shunt region (G 3 ) between said fixed magnetic armature (2) and said movable magnetic armature (3); wherein said magnetic circuit (10) includes a first magnetic loop (L 1 ) formed by said first and third branches (10a, 10c) and a second magnetic loop (L 2 ) formed by said second and third branches (10b, 10c), wherein first and second airgap regions (G 1 , G 2 ) are arranged at different distances relative to said magnetic shunt region (G 3 ) along said first and second magnetic loops or have different shape or areas, wherein said excitation coil (5) is configured to feed said magnetic circuit (10) with a second magnetic flux (Φ 2 ) having an opposite direction compared to said first magnetic flux (Φ 1 ) along said second branch (10b) and having a same direction compared to said first magnetic flux (Φ 1 ) along said third branch (10c), when said excitation coil is fed with an electric current; wherein said movable magnetic armature (3) is subjected to a first magnetic force (F 1 , T 1 ), which is directed in such a way to move said movable magnetic armature (3) away from said first position (C), and to a second magnetic force (F 2 , T 2 ), which is directed in such a way to move said movable magnetic armature (3) towards said first position (C), said first and second magnetic forces (F 1 , T 1 , F 2 , T 2 ) depending on the position (p) of said movable magnetic armature (3) relative to said fixed magnetic armature (2), wherein: - said first magnetic force (F 1 , T 1 ) increases and said second magnetic force (F 2 , T 2 ) decreases, when said movable magnetic armature (3) moves from said first position (C) to said second position (O), - the rate of change of said second magnetic force (F 2 , T 2 ) is higher than the rate of change of said first magnetic force (F 1 , T 1 ) in response to a movement of said movable magnetic armature, when said movable magnetic armature starts moving away from said first position; wherein, when said movable magnetic armature (3) is in said first position (C) and said excitation coil (5) is fed with no electric current, said first magnetic force (F 1 , T 1 ) is lower than said second magnetic force (F 2 , T 2 ), so that said movable magnetic armature is held in said first position (C); wherein, when said movable magnetic armature (3) is in said first position (C) and said excitation coil (5) is fed an electric current (I C ) higher than a threshold current (I TH ), said second magnetic force (F 2 , T 2 ) decreases due to the circulation of said second magnetic flux (Φ 2 ) and becomes lower than said first magnetic force (F 1 , T 1 ), so that said movable magnetic armature is moved away from said first position (C) towards said second position (O), characterised in that , when said movable magnetic armature (3) has slightly moved away from said first position (C), said second magnetic force (F 2 , T 2 ) remains lower than said first magnetic force (F 1 , T 1 ) even if said excitation coil (5) is no more fed with an electric current (I C ), so that said movable magnetic armature continues to be moved away from said first position (C) until reaching said second position (O), wherein, when said movable magnetic armature (3) is in said second position (O), said first magnetic force (F 1 , T 1 ) is higher than said second magnetic force (F 2 , T 2 ), so that said movable magnetic armature is held in said second position (O).
  2. Magnetic actuator, according to claim 1, characterised in that a first magnetic reluctance (R 1 ) of said first branch (10a) decreases and a second magnetic reluctance (R 2 ) of said second branch (10b) increases, when said movable magnetic armature moves from said first position (C) to said second position (O).
  3. Magnetic actuator, according to one of the previous claims, characterised in that a ratio between a second magnetic reluctance (R 2 ) of said second branch (10b) and a third magnetic reluctance (R 3 ) of said third branch (10c) increases, when said movable magnetic armature (3) moves from said first position (C) to said second position (O).
  4. Magnetic actuator, according to one of the previous claims, characterised in that said permanent magnet (4) is coupled to said first portion (21) of fixed magnetic armature, wherein said first airgap region (G 1 ) is formed between said movable magnetic armature (3) and said permanent magnet.
  5. Magnetic actuator, according to one of the previous claims, characterised in that said excitation coil (5) is wound on said second portion (22) of fixed magnetic armature (2).
  6. Magnetic actuator, according to one of the previous claims, characterised in that the third branch (10c) of said magnetic circuit (10) comprises a third portion (23) of said fixed magnetic armature (2) facing said movable magnetic armature (3).
  7. Magnetic actuator, according to one of the previous claims, characterised in that the third branch (10c) of said magnetic circuit (10) comprises a third portion (33) of said movable magnetic armature (3) facing said fixed magnetic armature (2).
  8. Magnetic actuator, according to one of the previous claims, characterised in that said movable magnetic armature (3) is rotationally movable relative to said fixed magnetic armature (2).
  9. Magnetic actuator, according to one of the claims from 1 to 7, characterised in that said movable magnetic armature (3) is roto-translationally movable relative to said fixed magnetic armature (2).
  10. Magnetic actuator, according to one of the claims from 8 to 9, characterised in that said first and second airgap regions (G 1 , G 2 ) are arranged at different distances relative to a rotation axis (A) of said movable magnetic armature (3).
  11. Magnetic actuator, according to claim 10, characterised in that the rotation axis (A) of said movable magnetic armature (3) is located at said magnetic shunt region (G 3 ).
  12. Magnetic actuator, according to one of the claims from 1 to 7, characterised in that said movable magnetic armature (3) is translationally movable relative to said fixed magnetic armature (2).
  13. Magnetic actuator, according to one of the previous claims, characterised in that it comprises a movable plunger (6) configured to be actuated by said movable magnetic armature (3), when said movable magnetic armature moves from said first position (C) to said second position (O).
  14. Magnetic actuator, according to one of the previous claims, characterised in that it comprises a bumper (11) configured to limit a travel of said movable magnetic armature (3), when said movable magnetic armature moves from said first position (C) to said second position (O).
  15. Magnetic actuator, according to claim 14, characterised in that said bumper (11) comprises an element (11a) made of elastic material configured to come in contact with said movable magnetic armature (3) when said movable magnetic armature comes in proximity of said second position (O).

Description

The present invention concerns the field of low-voltage electric systems. More particularly, the present invention relates to a magnetic actuator for low-voltage electric systems. As it is known, a magnetic actuator is a device typically designed to provide a mechanical actuation force to an external mechanism (e.g., the switching mechanism of an electric or electronic protection device) in response to receiving an input electrical signal (normally a current signal). An example of magnetic actuator is described in EP 0 829 896 A2, DE 33 11 446 A1, DE 16 39 196 A1 and EP 0 911 850 A1. The magnetic actuator disclosed in EP 0 829 896 A2 includes an actuation coil magnetically coupled to a magnetic circuit including a fixed magnetic yoke, a movable magnetic armature, and a permanent magnet. The magnetic yoke includes a pair of yoke plates arranged in parallel and spaced apart one from another in such a way that an airgap of about 50-100 µm is formed between them. At one end of the magnetic yoke, the above-mentioned magnetic plates diverge one from another in such a way to form a space for accommodating the permanent magnet. The magnetic armature is rotatable about an axis perpendicular to the spaced yoke plates, and it is arranged, so as to bridge laterally these latter. The magnetic armature is mechanically coupled to a pre-loaded spring exerting a mechanical torque directed to rotate the armature away from the polar surfaces. In normal conditions, the magnetic armature is maintained coupled to the yoke plates due to the magnetic force deriving from the magnetic flux generated by the permanent magnet. When a trip of the magnetic actuator is required, for example due to a fault current detected in an electric line, a current is fed into the actuation coil. The coil current generates a temporary magnetic flux in opposition to the magnetic flux generated by the permanent magnet. This allows decreasing the magnetic torque holding the magnetic armature coupled to the magnetic yoke. The movable armature can thus rotate away from the yoke plates due to the mechanical force exerted by the pre-loaded spring. In doing so, the armature pushes a plunger, which can thus actuate an external mechanism operatively associated to the magnetic actuator. The magnetic actuators of the type described above generally show relevant advantages in terms of operation efficiency. However, they still have some critical aspects. As a matter of fact, these devices have a relatively complex structure with a high number of parts, most of them must be assembled with tight mechanical tolerances. These devices thus generally result rather difficult and expensive to manufacture at industrial level. Additionally, in these devices, the behaviour of the magnetic circuit is rather dependant on environmental temperature, which obliges to carefully design the magnetic components to consider the effects of possible temperature drifts. The main aim of the present invention is to provide a magnetic actuator for low-voltage electric systems, which allows solving or mitigating the above-mentioned technical problems. More particularly, it is an object of the present invention to provide a magnetic actuator having a simplified structure with a relatively low number of parts. Another object of the present invention is to provide a magnetic actuator relatively easy to manufacture at industrial level, at competitive costs compared to the available corresponding devices of the state of the art. In order to fulfill these aim and objects, the present invention provides a magnetic actuator for low-voltage electric systems, according to the following claim 1 and the related dependent claims. In a general definition, the magnetic actuator, according to the invention comprises a magnetic circuit including a fixed magnetic armature and a movable magnetic armature. The movable magnetic armature is reversibly movable between a first position and a second position relative to said fixed magnetic armature. According to some embodiments of the invention, said movable magnetic armature is rotationally movable between said first and second positions relative to said fixed magnetic armature. According to other embodiments of the invention, said movable magnetic armature is roto-translationally movable between said first and second positions relative to said fixed magnetic armature. According to yet further embodiments of the invention, said movable magnetic armature is translationally movable between said first and second positions relative to said fixed magnetic armature. The magnetic actuator comprises also a permanent magnet configured to feed said fixed and movable magnetic armatures with a first magnetic flux having a predefined direction, when said permanent magnet is in a magnetized condition. The magnetic actuator further comprises an excitation coil magnetically coupled to said magnetic circuit and configured to be fed with an electric current, when a tripping manoeuvr