FR2557353A1 - MAGNETOTHERMIC TRIGGER IN SHAPE MEMORY MATERIAL, ASSOCIATED WITH CIRCUIT BREAKER MECHANISM - Google Patents

Abstract

1. Thermal-magnetic trip device with a mechanism (40) of an electric circuit breaker comprising : - a stationary core (18) associated with a movable core (20) sliding by means of an air-gap (22), - a tubular control coil (12) surrounding coaxially said stationary and movable cores (18, 20), the air-gap (22) being crossed by a magnetic flux due to the passage of the current in the coil (12), - a spring (36) resetting the movable core (20) in spreaded position when the current intensity for excitation of the coil (12) is lower than the electromagnetic trip threshold, - a thermomechanical sensor (44) of shape memory effect alloy, sensitive for the temperature rise of the control coil (12), - and unlocking means cooperating with the movable core (20) and the thermomechanical sensor (44) to ensure the automatic tripping of the mechanism (40), characterized by the fact that the thermomechanical sensor (44) of shape memory effect alloy comprises a helical spring (46) arranged in a closed space (42) insides the insulating duct (14) supporting the coil (12), and that the ampere-turn number of the coil (12) is constant for all sizes of a range.

Description

EQUIJIVE CIRCUIT BREAKER OF A MAGNETOTHERMIC TRIGGER IN

MATERIAL WITH SHAPE MEMORY.

  The invention relates to a magnetothermal trip unit associated with a mechanism of an electric circuit breaker comprising: a fixed core associated with a sliding mobile core via an air gap, a tubular control coil coaxially surrounding said cores fixed and movable, the gap being traversed by a magnetic flux due to the passage of the current in the coil, - a return spring of the movable core in the remote position when the intensity of the excitation current of the coil is below the threshold of electromagnetic tripping, - a thermomechanical sensor in shape memory alloy, responsive to the heating of the control coil, - and unlocking means cooperating with the core

  mobile device and the thermomechanical sensor to ensure

  automatic triggering of the mechanism.

  A known magnetothermal trip of the kind mentioned is described in the European patent application N 37490. This type of trip is devoid of bimetallic and the means of

  unlocking the lock associated with the mechanism are action-

  born by the mobile core in case of short circuit, and by the thermomechanical sensor in shape memory alloy in case of overload. The triggering of the mechanism requires

  two separate mechanical connections respectively cooperating

  with the sensor and the mobile core. The implementation of such a trigger is complicated, and it is also essential to adapt the thermomechanical sensor to each

circuit breaker rating.

  The object of the invention is to remedy these drawbacks and

  to allow the realization of a magnetothermal trigger

  reliable and simplified structure using the same thermomechanical sensor for all calibres of a range

circuit breakers.

  According to the invention, the thermomechanical sensor of shape memory alloy comprises a helical spring, housed in

  an enclosed space inside the insulating sheath of

  wearing the reel. The number of ampere-turns of the coil is constant for all the calibres of a range. The insulating sleeve of the control coil is formed by a tubular sleeve closed at one of its ends by

  a bottom and at the opposite end by the fixed core. The res-

  shape memory and the mobile core are arranged coaxially in the enclosed space between the fixed core and the

  bottom of the scabbard and are likely to cause a

  unique unlocking night axially crossing the

fixed core.

  The unlocking pusher is associated with a return spring which serves at the same time as a return spring to the movable core and as a biasing member to the shape memory spring. According to a first embodiment, the shape memory spring surrounds the mobile core while resting on the bottom of the sheath, and cooperating at its opposite end with a magnetic pallet capable of displacing the

  pushing towards the active position trigger by al-

  length of the spring as a result of exceeding the

  critical temperature in the enclosed space while the movable core remains stationary in a remote position. The magnetic pallet has a bridge shape whose one face is equipped with a guide pin mounted to slide axially in a hole of the movable core, and the other face cooperates with the

unlocking pusher.

  According to a second embodiment, the shape memory spring is arranged inside the hollow core in the form of a hollow sleeve. The driving head of the pusher being

  directly in contact with the shape memory spring.

  Adjustment means are provided for adjusting the air gap and the counter force of the pusher return spring.

unlocking.

  Other advantages and features will emerge more clearly from the following description of various embodiments of the invention given as non-exhaustive examples.

  restrictive and represented in the attached drawings, in the

  which: - Figure 1 is an axial sectional view of a release according to the invention, shown in the rest position; FIG. 2 is an identical view of FIG.

variant embodiment.

  In FIG. 1, a magnetothermal trip device 10 of a miniature circuit-breaker comprises a control coil 12

  mounted on an insulating sleeve 14 in the form of a tubular sleeve

  closed at one of its ends by a bottom 16. Inside the sleeve 14 is a magnetic core

  fixed 18 separate from a plunger 20 sliding by a

  trefer 22 axial. The magnetic core plunger 20 is solid

  darisée an actuating rod or extractor 24 which

  poured an orifice 26 formed in the bottom 16 of the sheath 14.

  The active end of the extractor 24 is capable of action-

  a contact arm 28 pivotally mounted on an axis 30.

  The plunger core 20 cooperates on its opposite side with an unlocking pusher 32 or firing pin which extends axially along a central opening 34 of the fixed core 18 being biased in abutment with the plunger core 20 by a return spring 36. The active end of the pusher 32 cooperates with a latch 38 or a trip bar,

  intended to cause the automatic activation of the

  40 when a detected overcurrent occurs

  trigger 10. The structure of the mechanism 40 is de-

  described in detail in European Patent Application 27404.

  The coil 12 of the trigger 10 is traversed by the current

  total or by a fraction of the current flowing in the pole.

  The closed space 42 arranged inside the sleeve 14 between

  the fixed core 18 and the bottom 16 is the seat of a warm-up

  predetermined image representing the image of the intensity of the

  excitation current of the coil 12.

  A thermomechanical sensor 44 composed of a metal alloy

  moire form is housed in the space 42 closed sheath

  14, and is shaped as a helical spring 46 disposed co-

  axially with play around the plunger core 20. The

  spell 46 with shape memory is interposed between the bottom 16 -

  and one of the bearing faces of a magnetic pallet 48 in

  bridge shape whose opposite face cooperates with the

  evening 32 unlocking. The pallet 48 is provided with a guide pin 50 capable of sliding axially in a blind hole 52 of the plunger core 20 as opposed to

the extractor 24.

  The critical transformation temperature of the shape memory alloy depends on the material choiSi and the biasing biasing force of the return spring 36. It is advantageously between 90 degrees C and 100 degrees C,

  and constitutes the thermal trip temperature.

  In the initial state of rest, the coil spring 46

  remain at contiguous turns when the temperature in the

  pace 42 is less than the transformation temperature of the alloy (FIG 1). In the active state, the spring 46 is deformed by axial elongation of a few millimeters in

  the direction of arrow F1 if the temperature is exceeded

  thermal trip pattern. The deformation of the

  Fate 46 is carried out against the return spring 36 and causes the pusher 32 to unlock the latch 38 in the same direction. The alloy has a simple memory effect with unidirectional deformation in the direction of arrow F1. When the temperature in the space 42 closed

  descends below the transformation temperature of the alloy

  age, the return spring 36 of the pusher 32 cooperates with the pallet 48 to recompress the memory spring 46 of

  shape towards its initial position with contiguous turns.

2557353. '

  The return to the state of rest of the spring 46 is automatic in the case of a reversible memory effect alloy.

bidirectional deformation.

  The operation of the thermomagnetic trip unit 10 according to FIG. 1 is as follows:

SHORT CIRCUIT TRIGGER

  A circulation in the coil 12 of a current of strong

  intensity, in particular of a short-circuit, provokes a

  instantaneously by magnetic attraction of the plunger core assembly 20 and pallet 48 against the polar faces of the fixed core 18. The pusher 32 unlocks the latch 38

  and the extractor 24 pulls simultaneously on the arm of con-

  tact 28 pivoting. The final opening of the contacts is then confirmed after triggering the mechanism 40.

  electromagnetic tripping threshold depends on the inten-

  of the excitation current in the coil 12 and is

  tion of the air gap 22 and the stiffness of the compression spring 36 of the compression type. The shape memory spring 46 does not have time to react because of the thermal inertia

  of the space 42, and it remains in the state of rest.

  TRIGGERING FOLLOWING OVERLOAD

  In the presence of an overload current whose intensity is between the rated current of the circuit-breaker and the

  electromagnetic tripping threshold, the magnetic field

  The gap in the air gap 22 is insufficient to attract the movable core 20 and the extractor 24 which remain stationary in the spaced apart position (FIG. The progressive heating of the space 42 makes it possible to reach the critical temperature of deformation of the spring 46 with shape memory. This results in a time delayed thermal tripping by axial elongation of the spring 46 in the direction of the arrow F1, which causes the pallet 48 and the pusher 32 to the unlocked position of the latch 38. The contacts open

2557 3 * 53 5

  after triggering the mechanism 40, and the coil 12 is

  more traveled by the current. Spring 46 returns to

  following the state of rest as soon as the temperature inside

  in space 42 falls below the temperature of

thermal shutdown.

SETTING THE TRIGGER

  The return spring 36 of the pusher 32 cooperates simultaneously with

  With the plunger core 20 and the shape memory spring 46, the tripping adjustment is effected by varying the preload of the return spring 36 by means of a screw 54 or adjustable ring in a threaded hole 56 of the core.

  fixed 18. The rotation of the screw 54 keeps the air gap 22

  stant, and acts exclusively on the prestressing of the

  recall spell 30 which simultaneously modifies the threshold of

  electromagnetic latching and the characteristic of

thermal shutdown.

  In FIG. 2, the same reference numbers denote parts identical or similar to those of FIG. 1. The

  spring 36 of the pusher 32 rests on a collar

  let 56 of the fixed core 18, the latter being formed by a self-tapping screw screwing into the sheath 14. The plunger core 20 comprises a hollow sleeve inside which

  is housed the spring 46 shape memory. The head of

  dragging the pusher 32 takes direct support on the

  spring 46 with shape memory. The functioning of this

  Trigger is similar to that described with reference to the

  Fig. 1 except the trigger setting which is different.

  This adjustment is effected by screwing or unscrewing the fixed core 18 into the sleeve 14 causing a combined variation in the length of the air gap 22 and the biasing force of the return spring 36. In case of unscrewing of the core 18,

  the gap 22 increases at the same time as the effort of the

  reminder spell 36 decreases. Reciprocally, in case of

  of the core 18, the air gap 22 decreases and the stress

  spring spring 36 increases. The combined variation of 2557353-l

  these two parameters make it possible to keep the trigger threshold

  substantially constant electromagnetic Adjustment of the fixed core 18 substantially modifies the thermal tripping characteristic of the shape memory spring 46 by varying the biasing of the compression spring.

pel 36.

  The arrangement of the shape memory spring 46 within the closed space 42 may be different from that shown in FIGS. 1 and 2. The same shape memory spring 46 can be used for all the calibres of a range provided that a predetermined coil 12 is used, dimensioned at constant ampere-turns (ni = k, n being the number of turns

  of the coil, i the nominal current, and k a constant).

  The adoption of the appropriate coil 12 allows to keep a constant heating in the closed space 42 whatever

  the chosen caliber. A complete range can thus be

  read by keeping all the parts of the trigger 10 to

the exception of the coil 12.

  An adjusting member made of a conductive material

  predetermined thermal capacity, is inserted between the coil 12

  and the shape memory spring 46 for adjusting the con-

  thermal time stant in space 42.

  The invention is of course in no way limited to the modes

  more specifically described and

  appended drawings, but it

  milking any variant remaining within the scope of the equivalents

  electrotechnical lences, in particular that in which the

  mobile core 20 of the trigger 10 would be devoid of extrac-

  24, or the one in which an auxiliary cylinder head

  magnetic material would be arranged around the coil 12.

REVEHDICATIOHS

  1. Magnetothermic actuator associated with a mechanism (40) of an electric circuit breaker comprising: - a fixed core (18) associated with a movable core (20) sliding through an air gap (22),

  a coaxial surrounding tubular control coil (12)

  said fixed and mobile cores (18, 20), the gap (22)

  having a magnetic flux passing through the neck

in the coil (12),

  a spring (36) for returning the movable core (20) in position

  deviation when the intensity of the excitation current of the coil (12) is less than the electromagnetic tripping threshold, - a thermomechanical sensor (44) of a memory alloy

  form, responsive to the heating of the compression coil (12)

  and unlocking means cooperating with the movable core (20) and the thermomechanical sensor (44) to ensure the automatic triggering of the mechanism (40), characterized in that the thermomechanical sensor (44) made of a memory alloy shape comprises a helical spring (46) housed in a space (42) enclosed within the insulating sleeve (14) for supporting the coil (12), and that the number of amp ends of the coil (12) is constant

for all calibres of a range.

  2. Magnetothermic tripping device according to claim 1, characterized in that the insulating sheath (14) is

  formed by a closed tubular sleeve at one of its ends.

  mismounted by a bottom (16), and at the opposite end by the fixed core (18), and that the enclosed space (42) is arranged between

the fixed core (18) and the bottom (16).

  Magnetothermic trip device according to Claim 2, characterized in that the shape memory spring (46) and the movable core (20) are arranged coaxially in the said space (42) and cooperate with a pusher (32).

  unlocking axially passing through the fixed core (18).

  4. Magnetothermic tripping device according to claim 3, characterized in that the spring (36) for biasing the movable core (20) biases the pusher (32) towards the position

  the shutter release button and at the same time

  polarization spring (46) with shape memory whose critical transformation temperature depends on

  the counterforce of the return spring (36).

  Magnetothermic tripping device according to Claim 4, characterized in that the shape memory spring (46) surrounds the movable core (20) while being supported on

  the bottom (16) of the sleeve (14), and cooperating with its end.

  opposite with a magnetic pallet (48)

  move the pusher (32) to the active position of de-

  latching by axial elongation of the spring (46) following the exceeding of the critical temperature in the space (42) while the movable core (20) remains stationary in position

discounted.

  Magnetothermic trip device according to Claim 5,

  characterized by the fact that the magnetic pallet (48) pre-

  a bridge shape, one of whose faces is equipped with a guide pin (50) axially slidably mounted in a hole (52) of the movable core, and the other face cooperates with

  with the unlocking pusher (32).

  Magnetothermic tripping device according to Claim 4, characterized in that the shape memory spring (46) is arranged inside the hollow sleeve-shaped movable core (20) and the pusher drive head

  (32) is directly in contact with the spring (46).

  8. Thermal magnetic trip device according to claim 5 or 6, characterized in that the spring (36) of the return of the unlocking pusher (32) is supported on a screw (54) or ring whose axial position is adjustable in a hole ' JJ3

  Threaded core (18) for adjusting the setting

  stress of the return spring (36).

  9. Thermal magnetic trip device according to claim 7, characterized in that the spring (36) for returning the pusher (32) is supported on a collar (56) of the fixed core (18) adjustable, the latter comprising an external thread.

  screwing into the sheath (14) for adjusting the

  trefer (22) axial and spring counterforce

(36).

  10. Magnetothermic actuator according to one of the claims

  2 to 9, the movable core (20) being secured to a rod (24) for actuating the movable contact arm (28), characterized in that the bottom (16) of the sleeve (14) has an orifice ( 26) for passage of the core assembly (20) and shank (24), and a setting member made of a predetermined thermal conductivity material, is inserted between the coil (12) and the memory spring (46). of shape to adjust the thermal time constant in

the space (42).