EP3326190B9 - Magnet armature, contactor having a magnetic armature, and method for switching a contactor - Google Patents

Description

The invention relates to magnetic armatures, e.g. magnetic armatures for electromagnetic contactors, contactors with magnetic armatures and methods for switching a contactor.

In electromagnetically operated contactors, a magnetic armature is generally a moving part that can electrically connect two electrodes by moving a contact stamp. Contactors are used to switch strong electrical currents and/or high electrical voltages, possibly in a protective gas atmosphere. The immediate processes of closing or opening the switch and the arcs that occur in the process represent a great stress when high electrical power is to be switched, particularly for the material of the electrodes and the contact stamp. The risk of these electrical contacts sticking increases with the number of switching operations.

Contactors with a so-called booster circuit to reduce the closing time are known. When switched on, the electromagnet is briefly subjected to an overvoltage, i.e. a few milliseconds, in order to increase the attraction force. The document US6360707 discloses a magnetic armature according to the preamble of claim 1.

There is therefore a desire for switching operations with reduced stress on the electrode material, in particular for switching operations with a reduced risk of the contacts sticking together.

The magnetic armature described here, in particular the magnetic armature according to independent claim 1, enables such switching processes. Other claims specify advantageous embodiments of the armature.

The magnet armature comprises a first spring element with a first spring stiffness k1, a second spring element with a second stiffness k2, a rest position, an end position and a middle position which is located between the rest position and the end position. The first spring element is intended to be elastically deformed during a switching process during the transition from the rest position to the middle position, but not during the transition from the middle position to the end position. The second element is intended to be elastically deformed during the transition from the middle position to the end position, but not during the transition from the rest position to the middle position.

The rest position, the middle position and the end position represent the positions of the magnet armature relative to its surroundings, e.g. within an electromagnetic switch. The middle position does not necessarily have to be the same distance from the rest position as from the end position. The rest position indicates the position in which the magnet armature is when no magnetic force acts on it. The end position indicates the equilibrium position when the magnetic force intended for closing a switch acts on the magnet armature and the electrical contact to be closed is permanently closed.

The first stiffness k1 of the first spring element and the second stiffness k2 of the second spring element can be different. The fact that the magnet armature moves against the restoring force of the first spring element when moving from the rest position to the middle position and against the spring force of the second element when moving from the middle position to the end position can reduce the switching time. In particular, if the spring stiffness k1 of the first spring element is less than the spring stiffness k2 of the second spring element, the magnet armature works against a smaller resistance force when tightening, so that greater acceleration and thus a shortening of the switching time is achieved.

When the magnet armature is in its end position, the restoring force of the second spring element essentially causes rapid opening when the magnetic force on the magnet armature is removed (i.e. when the switch is opened).

This means that a magnetic armature is specified which does not experience a simply linear resistance force when closing and opening. Rather, a magnetic armature is specified whose resistance force acting on it can increase successively due to different spring stiffnesses.

It is possible that the first spring element and the second spring element are arranged in series. With spring elements arranged in series, the resulting spring stiffness of the combination of the two springs is the reciprocal of the sum of the reciprocals of the individual spring stiffnesses. Two spring elements arranged in series therefore behave like a single spring element with the corresponding Replacement stiffness. In order for the magnet armature to perceive different spring stiffnesses when activated during one phase of the movement from the rest position to the middle position and during the second phase during the movement from the middle position to the end position, additional technical precautions are necessary, e.g. mechanical stops and/or applying a spring preload to individual spring elements and/or providing a movable bushing, as described below.

Therefore, the magnet armature additionally comprises a bushing which is arranged between the first spring element and the second spring element. The bushing can touch the one end of the first spring element directed towards the bushing and the one end of the second spring element directed towards the bushing.

The magnet armature additionally comprises a cylindrical section. The first spring element, the bushing and the second spring element coaxially surround the cylindrical section - or each a separate cylindrical section with a different radius if necessary. The end of the first spring element pointing towards the bushing is intended to move relative to the cylindrical section during the transition from the rest position to the middle position, but not during the transition from the middle position to the end position. The bushing and the end of the second spring element pointing towards the bushing are intended to move relative to the cylindrical section during the transition from the middle position to the end position, but not during the transition from the rest position to the middle position.

It is possible that a transition from the rest position to the end position corresponds to a displacement by a distance h = h1 + h2, where h can be between 1.5 mm and 2.5 mm long.

The distance h from the rest position to the end position is the full stroke that the magnetic armature travels when activated in order to connect two electrodes of a contactor with a contact stamp.

The stroke h can be, for example, 2 mm.

It is possible that a transition of the armature from its rest position to its middle position corresponds to a displacement by a distance h1 which lies in an interval between 0.4 and 0.6 times the total stroke h = h1 + h2.

In other words, the middle position can be in an interval between 40% and 60% of the full stroke h.

The partial strokes by a distance h1 from the rest position to the middle position and h2 from the middle position to the end position can be equal: h1 = h2 = h/2.

It is possible that the spring stiffness of one of the two spring elements is approximately 3.3-3.6 times the spring stiffness of the other. The second spring element can have the higher spring stiffness: 3.3 ≤ k2/k1 ≤ 3.6.

Specifically, it is possible that the spring stiffness of the first spring element is between 0.5 N/mm and 0.9 N/mm. The stiffness of the second spring element can be between 2.3 N/mm and 2.7 N/mm.

It is possible for the magnet armature to further comprise a contact stamp and/or a magnetizable material in addition to at least one cylindrical section. The contact stamp is arranged at one end of the region of the armature with the one or more cylindrical sections. The optional magnetizable material can be arranged at the opposite end. The contact stamp comprises an electrically conductive material and is intended to connect two electrical contacts in the end position of the magnet armature. The magnetizable material can comprise iron, cobalt and/or nickel or consist of iron, cobalt or nickel. The magnetizable material can allow the magnet armature to interact magnetically with its surroundings (e.g. an adjacent magnet coil in a yoke), in particular to prevent displacement between the three positions, i.e. a

To enable switching by means of the contact stamp.

Furthermore, the cylindrical section has a first section and a second section. The first section has a first diameter and the second section has a second diameter. Between the two sections, the cylindrical section and thus the diameter has a step. The step between the two sections represents a stop for the bushing, which is referred to below as the magnet armature stop.

Furthermore, the bushing touches the magnet armature stop during the transition from the rest position to the middle position (MP), but not during the transition from the middle position to the end position.

This makes it possible for the bushing to decouple the two springs at least in one position, e.g. the rest position, or during the transition from the middle position to the rest position, which improves the switching behavior of a suitably equipped contactor.

A contactor may comprise a magnetic armature as described above with a bushing between the two spring elements, a yoke with an integrated coil and a guide with a first mechanical stop. The magnetic armature and the yoke form an electromagnetic actuator which is intended to move the magnetic armature relative to the yoke and the guide. In positions between the rest position and the middle position, the bushing does not contact the first mechanical stop. In positions between the middle position and the end position, the bushing contacts the first mechanical stop.

The middle position is therefore defined as the position from which the bushing touches the stop during closing. From the rest position to the middle position, the first spring element essentially counteracts a closing force: If the magnet armature moves from its rest position to the middle position, the first spring element is essentially compressed. The second spring element can be subjected to a preload that is greater than the tension on the first spring element in the middle position. This means that the second spring element is Transition from the rest position to the middle position is not compressed.

If the bushing hits the mechanical stop, the tension on the first spring element cannot increase any further because the force is transferred to the guide via the bushing and the mechanical stop. As a result, further movement from the middle position to the end position is made possible by compressing the second spring element.

It is possible that the contactor in the yoke includes one or more coils that can generate a magnetic field and, together with the magnetizable material of the armature, form an electromagnet.

The contactor can further comprise a cavity in which the contact stamp on the magnet armature and two electrodes spaced apart from one another are arranged. The cavity can be filled with a gas, e.g. a noble gas. The distance between the electrodes and the contact stamp is preferably smaller than the total stroke h of the magnet armature.

The magnet armature can also have another spring element that can compensate for manufacturing tolerances in the distance between the electrodes and the contact stamp and generates the actual contact force. This is particularly important when the material of the electrodes or the contact stamp is worn away by repeated switching operations at high electrical power.

The electromagnet of such a contactor can be operated with an operating voltage of 12 V, 24 V, 48 V or any other available voltage.

The contactor can have a cavity, e.g. a cavity filled with an inert gas in which the contacts to be switched are located. Contactors with a gas-filled cavity are usually also referred to as GFC (Gas Filled Contactor). Since such contactors are particularly suitable for switching high voltages, they are also known as HVC (HVC = High Voltage Contactor).

The increased service life due to the nonlinear counterforce can be further increased by the gas filling in the cavity.

It is possible that the contactor has a guide with a third stop. The third stop can represent a limitation for the movement of the magnet armature. The magnet armature can touch the third stop in its rest position.

The third stop can in particular absorb the force of the first spring in the rest position. The position of the third stop therefore determines the position of the magnet armature relative to the guide in the rest position, a defined rest position.

In order to achieve a defined value for h1 independent of the ratio of the spring rates and to decouple the spring forces, the cylindrical section should have the mechanical magnet armature stop, which can be achieved as described above by two different diameters on the cylindrical section and the corresponding step. This allows the second, e.g. stiffer, spring element to be dimensioned independently of the first, e.g. softer, spring element and to be connected via the bushing and the mechanical Magnetic armature stop with defined preload must be installed.

The ratio of the spring rates is not limited. The numerical values depend on the size, among other things, and are only intended as examples.

A series connection of the two spring elements is possible but not mandatory. The mechanical stops, in particular the first stop and the magnet armature stop, can decouple the springs.

• Aktivieren des Elektromagneten in einer Ruheposition,
• Beschleunigen des Kontaktstempels gegen die Rückstellkraft des ersten Federelements bis zu einer mittleren Position,
• Bewegen des Kontaktstempels gegen die Rückstellkraft des zweiten Federelements bis zu einer Endposition.

A method for switching an electromagnetic contactor having an electromagnet, a contact plunger and a first spring element comprises the steps:

• Activating the electromagnet in a rest position,
• Accelerating the contact stamp against the restoring force of the first spring element to a middle position,
• Moving the contact stamp against the restoring force of the second spring element to an end position.

A method for switching an electromagnetic contactor comprising an electromagnet, a contact plunger, a first spring element and a second spring element is defined according to claim 11.

In the following, the functional principle and exemplary embodiments are shown and explained in more detail using schematic figures, whereby the Figures 1-3 show a cross-section of a simplified magnet armature to illustrate the respective positions.

Fig. 1:

die Ruheposition,

Fig. 2:

die mittlere Position,

Fig. 3:

die Endposition,

Fig. 4:

einen Querschnitt durch eine Ausführungsform eines Magnetankers mit Federelement für einen Toleranzausgleich und mit Kontaktstempel,

Fig. 5:

einen Querschnitt durch ein Schütz mit einem Magnetanker und mit einem Kontaktstempel, einer ersten Elektrode und einer zweiten Elektrode in einem Gas gefüllten Hohlraum, entsprechend den Beispielen der Figuren 5 und/oder 6.

Fig. 6:

einen Querschnitt durch eine Ausführungsform eines Magnetankers MA mit einem dritten A3 und einem Magnetanker-Anschlag A4,

Fig. 7:

einen Querschnitt durch die Ausführungsform der Fig. 6 in der mittleren Position,

Fig. 8:

einen Querschnitt durch die Ausführungsform der Fig. 6 in der Endposition,

Show it:

Fig.1:

the resting position,

Fig. 2:

the middle position,

Fig. 3:

the final position,

Fig.4:

a cross-section through an embodiment of a magnet armature with spring element for tolerance compensation and with contact stamp,

Fig.5:

a cross-section through a contactor with a magnet armature and with a contact stamp, a first electrode and a second electrode in a gas-filled cavity, according to the examples of Figures 5 and/or 6.

Fig.6:

a cross section through an embodiment of a magnet armature MA with a third A3 and a magnet armature stop A4,

Fig.7:

a cross-section through the design of the Fig.6 in the middle position,

Fig.8:

a cross-section through the design of the Fig.6 in the final position,

Figure 1 shows the cross-section of a magnetic armature MA in its rest position RP. The magnetic armature MA has a first spring element F1 and a second spring element F2. The two spring elements F1, F2 determine the restoring forces during the transition from its rest position to its end position. In particular, the first spring element F1 determines the restoring force during the transition from the rest position to the middle position. The restoring force during the transition from the middle position to the end position is determined by the spring stiffness of the second spring element F2. h1 is the length of the path covered during the transition from the rest position to the middle position. h = h1 + h2 is the length of the path covered during the transition from the rest position to the end position.

Figure 1 shows, in addition to the magnet armature MA, a guide FÜ which limits the movement of the armature during the transition between the positions to a displacement along an axis. The guide FÜ can thus represent a guide rail with a first stop A1. A bushing B is arranged between the first spring element F1 and the second spring element F2. The magnet armature MA has a cylindrical section ZA. The first spring element F1, the second spring element F2 and the bushing B are arranged coaxially around the cylindrical section ZA. The contact stamp KS is arranged at one end of the cylindrical section ZA. A magnetizable material M is arranged at the other end of the cylindrical section ZA. If the magnet armature MA, shown lying down, moves relative to the guide FÜ in the direction of left, the spring element with the lower spring stiffness, here the first spring element F1, is essentially compressed. If the second spring element F2 has a significantly higher spring stiffness or if the second spring element F2 is under a preload that is greater than the tension of the first spring element F1 in the middle position, the second spring element F2 is not compressed or is only compressed insignificantly during the transition from the rest position RP to the middle position MP. During the transition from the rest position RP to the middle position MP, the bushing B moves by the distance h1 until the bushing B hits the first stop A1. During this phase of the movement, the restoring force acting on the magnet armature MA is essentially or exclusively determined by the spring stiffness of the first spring element F1.

Figure 2 shows the magnet armature in its middle position MP. The bushing B touches the first stop A1. If the magnet armature is moved further to the left relative to the guide FÜ, the bushing B rests on the first stop A1 so that the first spring element F1 cannot be compressed any further. With further movement, the second spring element F2 is inevitably compressed.

Accordingly, Figure 3 the magnet armature in its end position EP. The second spring element F2 is compressed until the magnet armature has reached its end position, which can be predetermined, for example, by a second mechanical stop A2.

The magnet armature is now in a position in which an electrical switch belonging to the magnet armature is closed by touching the contact stamp of two electrodes.

When closing, a short closing time can be achieved because the electromagnet only has to work against the weak restoring force of the first spring element F1, particularly in the critical initial phase, and can therefore accelerate quickly. The electrical switch can be opened quickly because the second, stronger restoring force of the second spring element F2 takes effect immediately when the electromagnet is deactivated.

Overall, a magnetic armature is specified which enables both rapid closing and rapid opening and which, in particular, reduces the burning time of a resulting arc and the risk of the contacts sticking.

Figure 4 shows an embodiment of the magnet armature MA, in which a movable bushing B is also arranged between a first spring element with a first spring stiffness k1 and a second spring element with a second spring stiffness k2. The rear end of the magnet armature MA has a conical elevation arranged coaxially around a cylindrical section of the contact stamp in the direction of the contact stamp KS. The associated guide has a correspondingly shaped conical recess that points towards the end of the armature. When the switch is closed, a self-centering guide is thus obtained. Between the contact stamp KS and the remaining section of the armature MA, a further spring element FTA is arranged, which has height tolerances can compensate and generates the actual contact force. A section made of an insulating material IM is arranged between the further spring element FTA and the remaining section of the armature in order to galvanically isolate the electrical contacts to be switched via the contact stamp KS and the magnet armature.

Figure 5 shows a cross-section through a possible embodiment of a contactor SCH in its rest position RP. In addition to the magnet armature with its magnetizable material M, the contactor SCH has a yoke J in which electrical windings of a coil SP are arranged. Figure 5 also shows a cavity HR in which the ends of a first electrode and a second electrode are opposite the contact stamp KS. If the magnet tanker is first moved against the resistance of the first spring element and then against the stronger resistance of the second spring element, the contact stamp KS is pressed against the ends of the two electrodes EL1, EL2, whereby the two electrodes EL1, EL2 are connected to one another. The cavity HR contains a gas, e.g. a noble gas, in order to extinguish an arc as quickly as possible, especially when the contact is opened, in order to protect the material of the electrodes and the contact stamp KS.

Figure 6 shows an embodiment of the magnet armature MA with a magnet armature stop A4 and an embodiment of the contactor SCH with a third stop A3, each in the rest position RP. The position of the armature MA and guide FÜ in the rest position RP is determined by the third stop A3.

Figure 7 shows an embodiment of the magnet armature MA with a magnet armature stop A4 and the contactor SCH with a third stop A3 in the middle position MP. This position represents a moment in the movement sequence in which the second spring element F2 becomes active.

Figure 8 shows an embodiment of the magnet armature MA with a magnet armature stop A4 and the contactor SCH with a third A3 stop in the end position EP. The position of the armature MA and guide FÜ in the end position EP is determined by the second stop A2.

From the Figures 6, 7 and 8 the following becomes clear: in order to achieve a defined value for h1 independent of the ratio of the spring rates and to decouple the spring forces, the cylindrical section ZA has the mechanical magnet armature stop A4 in the form of a step in the diameter. As a result, the second spring element F2 and the first spring element F1 are decoupled during a phase during activation until the contactor SCH reaches the middle position. In particular, the mechanical stops one A1 and four A4 decouple the springs F1, F2.

Despite its complex magnetic armature design, a contactor with improved electrical performance is specified that can maintain common geometric dimensions and can therefore be easily integrated into existing external circuit environments.

Neither the magnet armature nor the contactor nor the method for switching the contactor are limited to the embodiments shown. Magnet armature with additional stops, devices for pre-tensioning in particular the second spring element and other measures for reducing the load the electrodes of a contactor represent objects according to the invention.

List of reference symbols

A1:

first mechanical stop

A2:

second mechanical stop

A3:

third mechanical stop

A4:

mechanical magnetic armature stop

B:

Rifle

EL1:

first electrode

EL2:

second electrode

EP:

End position

Q1:

first spring element

Q2:

second spring element

FTAs:

Spring element for tolerance compensation

FÜ:

guide

H:

Distance of the length of the transition from the rest position to the end position

h1:

Distance of transition from rest position to middle position

h2:

Length of the transition from the middle position to the end position

MR:

cavity

IN THE:

insulating material

J:

yoke

KS:

Contact stamp

M:

magnetizable material

MA:

Magnet armature

MP:

middle position

RP:

Resting position

SCH:

Schütz

ZA:

cylindrical section

ZA1:

first section

ZA2:

second section

Claims (11)

1. Magnet armature (MA), comprising

   - a first spring element (F1) with a first stiffness k1,

   - a second spring element (F2) with a second stiffness k2,

   - a bush (B) between the first spring element (F1) and the second spring element (F2),

   - a cylindrical section (ZA), wherein the cylindrical section (ZA) has a first subsection (ZA1) with a first diameter, a second subsection (ZA2) with a second diameter and a step between the two subsections (ZA1, ZA2),

   - the step between the two subsections (ZA1, ZA2) constitutes a magnet armature stop (A4), and

   - the magnet armature can move between an idle position (RP), an end position (EP) and a central position (MP) between the idle position (RP) and the end position (EP), wherein the idle position is that position in which the magnet armature is located when there is no magnetic force acting on it, characterized in that

   - the magnet armature stop (A4) constitutes a stop for the bush (B),

   - the bush (B) touches the magnet armature stop (A4) during the movement from the idle position (RP) to the central position (MP), and

   - the bush (B) does not touch the magnet armature stop (A4) during the movement from the central position (MP) to the end position (EP),

   - the second spring element is biased or the stiffness of the second spring element is considerably higher than that of the first spring element, so that:

   - the first spring element (F1) is elastically deformed during the movement from the idle position (RP) to the central position (MP), but not during the movement from the central position (MP) to the end position (EP), and

   - the second spring element (F2) is elastically deformed during the movement from the central position (MP) to the end position (EP), but is not deformed or is deformed only to an insignificant extent during the movement from the idle position (RP) to the central position (MP).
2. Magnet armature according to the preceding claim, wherein the first spring element (F1) and the second spring element (F2) are arranged in series.
3. Magnet armature according to any one of the preceding claims, wherein

   - a movement from the idle position (RP) to the end position (EP) corresponds to a displacement by a distance h = h1 + h2 which is between 1.5 and 2.5 mm long, and

   - the movement from the idle position (RP) to the central position (MP) constitutes a displacement by h1, and

   - the movement from the central position (MP) to the end position (EP) constitutes a displacement by h2.
4. Magnet armature according to any one of the preceding claims, wherein a movement from the idle position (RP) to the central position (MP) corresponds to a displacement by a distance h1 which lies in an interval of between 0.4 times and 0.6 times the distance h = h1 + h2 of the displacement from the idle position (RP) to the end position (EP).
5. Magnet armature according to any one of the preceding claims, wherein 3.3 ≤ k2/k1 ≤ 3.6.
6. Magnet armature according to any one of the preceding claims, wherein 0.5 N/mm ≤ k1 ≤ 0.9 N/mm and 2.3 N/mm ≤ k2 ≤ 2.7 N/mm.
7. Magnet armature according to any one of the preceding claims, further comprising

   - a contact stamp (KS) and a magnetizable material (M), wherein

   - the contact stamp (KS) comprises an electrically conductive material and, in its end position (EP), is intended to interconnect two electrical contacts (EL1, EL2), and

   - the magnetizable material (M) comprises iron, cobalt and/or nickel.
8. Magnet armature according to any one of the preceding claims, wherein

   - the bush (B) decouples the two springs (F1, F2) at least in one position (RP, MP, EP).
9. Contactor (SCH), comprising

   - a magnet armature (MA) according to any one of the preceding claims having a bush (B) between the two spring elements (F1, F2),

   - a yoke (J) and

   - a guide (FU) with a mechanical stop (A1), wherein

   - the magnet armature (MA) and the yoke (J) form an electromagnetic actuator which is intended to move the magnet armature (MA) relative to the yoke (J) and to the guide (FU),

   - the bush (B) does not touch the mechanical stop (A1) in positions between the idle position (RP) and the central position (MP),

   - the bush (B) touches the mechanical stop (A1) in positions between the central position (MP) and the end position (EP).
10. Contactor according to the preceding claim, wherein

    - the guide (FU) has a third stop (A3),

    - the third stop (A3) constitutes a limit for the movement of the magnet armature (MA), and

    - the magnet armature (MA), in its idle position (RP), touches the third stop (A3).
11. Method for switching an electromagnetic contactor (SCH) according to claim 9 or 10 having a solenoid, a contact stamp (KS), a first spring element (F1) and a second spring element (F2), comprising the steps of:

    - activating the solenoid in an idle position (RP),

    - accelerating the contact stamp (KS) against the restoring force of the first spring element (F1) up to a central position (MP),

    - moving the contact stamp (KS) against the restoring force of the second spring element (F2) up to an end position (FP).

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