EP2337045B1 - Phase inverter device with contact rings - Google Patents

Description

TECHNICAL AREA

The invention relates to a device for reversing the direction of operation of a three-phase electric motor by reversing the connection between two phases. More generally, the invention relates to a mechanical device for inverting the connection between pairs of conductors.

STATE OF THE ART

To comply with their operating limits, the motors are associated with protection systems that make it possible, for example, to isolate the motor from the network by actuating a cut-off device in the event of detection of a short circuit or overload. . Fuses, circuit breakers, overload relays, or devices that jointly offer several types of protection have been developed to be associated with engine starts.

Moreover, in a three-phase electric motor, the direction of rotation of the motor is determined by the sequence of the phases of the power supply source. However, in some applications, the motor must be able to work in both directions, for example for a valve or a pump, a conveyor or an elevator, or another machine tool. To achieve the desired direction of starting the motor, devices have been designed to reverse the connection between two of the phases, the third remaining unchanged.

A solution is thus the integration of the inversion function in the switching or protection device: two conventional contactors / circuit breakers are associated with the aid of a mechanical lock that locks them one and the other so that the simultaneous activation of both contactors is forbidden: see for example FR 2,756,412 . This solution, however, requires a large number of parts, with doubling of cut-off devices and locking system.

For most uses, the cut-off device which ensures the starting and protection of the motor is kept, simply associated downstream with a phase reversal device (see for example FR 2 586 325 ); it is important then that the inversion device does not prevent the restart after activation of the breaking means and correction of the fault. With reference to the figure 1 , the three-phase supply circuit 1 L1, L2, L3 of the motor 2, which is provided in the illustrated frame with an upstream cut-off device 4, comprises three connection terminals 6 to which three terminals 8 of the motor 2 come to connect. feeding each of the phases T1, T2, T3. In order to allow a reversal of the direction of rotation of the motor 2, a reversing device 10 is connected to the terminals 6, 8 of each line, and comprises contacts 12, 14 with double or single break which, according to their position, make it possible to cross two of the three phases L1, L2 and T1, T2, one of the L3-T3 phases being retained.

To prohibit the inversion of the phases under load, the inverter 10 usually comprises auxiliary contacts 16 controlled by the cutoff device 4 present upstream and whose position allows or not the control 18 of the phase inversion, it is of the movement of the contacts 12, 14.

To ensure the passage of the rated current of the motor starter and withstood shocks and vibrations, the contacts 12, 14 of the reversing device 10 may be provided with silver pellets, and they are conventionally controlled by springs. Moreover, since the high currents, and in particular the short-circuit currents, tend to spread the poles connecting the supply lines L and the transmission lines T, to ensure short-circuit operation, the contacts 12 , 14 are also provided with an electromagnetic device which, under the effect of the passage of the short-circuit current, leads to an increase of the pressure on the phase reversal contacts: see for example FR 2 795 226 . This architecture thus requires a large number of parts and induces, in fact, a high cost.

SUMMARY OF THE INVENTION

Among other advantages, the invention aims to optimize the design of phase inverter devices and in particular to reduce the number of parts to reduce their cost. Despite this simplification in the design, the invention aims to keep the resistance of the inverter to short circuits of 10 kA or 50 kA, and in particular to tolerate short circuit current passages for 2.5 ms.

An inverter device according to the invention thus comprises at least two input terminals and two output terminals which are connected to an inversion assembly; a third input terminal and a third output terminal fixedly connected by a conductor may be present.

The inversion assembly includes multi-contact rings for connection to the input and output terminals. A multi-contact ring used in an inversion assembly for a device according to the invention comprises an annular ring with an inner surface and an outer surface that can be connected to an electrical circuit. The inner surface of the ring is provided with slats or other flexible elements biased towards the center of the ring so as to ensure contact with a rod passing through the ring. Furthermore, the electrical conduction is provided between the lamellae and the outer surface and preferably the ring is conductive.

The inversion assembly further comprises means for alternately electrically connecting the rings two by two; said means are movable in translation and adapted to urge the inner slats of the rings.

According to a first embodiment, the inversion assembly comprises a movable shaft between a group of five multi-contact rings separated by a distance substantially equal to each other, said separation distance being greater than or equal to the thickness of a ring taken along its axis and in respect of isolation distances. The shaft is insulating on its ends, and comprises two conductive parts separated by an insulating part, the length of the conductive parts being greater than or equal to the distance separating the lamellae of two rings, and the sum of the lengths of a conductive part and the insulating portion being substantially equal to the distance separating three rings. The tree is otherwise adapted to be able to move easily between the rings while maintaining a contact between its outer surface and the slats of the rings.

According to a second embodiment, the inversion assembly comprises two movable shafts each between a group of three multi-contact rings, separated for each group by a distance substantially equal to one another. The shafts are insulative at their ends, and comprise a conductive portion whose length is substantially identical to the distance between two rings of the group in which the shaft is placed; advantageously, the conductive parts of the two shafts and the distances separating the rings of each group are identical. The shafts are also adapted to be able to move easily between the rings while maintaining contact between their outer surface and the slats of the rings.

Advantageously, the rings of the inversion assemblies are identical to each other, and the conductive portions of the shafts are formed by a coating, for example made of copper or bronze, of an insulating shaft which may be made of polytetrafluoroethylene to minimize friction; preferably, the outer surface of the shaft is substantially planar.

The movement of each shaft between the rings is translational, and the reversing assembly is coupled to actuating means, for example a jack, allowing each shaft to take a first position and a second position separated from the first by a translation equivalent to the separation distance between two rings of the group in which it is placed, and the alternation of the connection between input and output terminals.

Thus, in the first embodiment, the actuating means drives the shaft of a first position in which its first conductive portion connects a first end ring to a second adjacent ring, to a second position in which its first conductive portion connects the second ring adjacent to the central ring of the group; the second conductive part undergoes the same movement between the rings on the other side of the central ring. From an end ring, four rings are alternately connected to the input and output terminals of the inverting device by conductors, preferably flexible; the fifth end ring is in turn coupled to the first end ring by a conductive element. Thus, between the first and second positions of the shaft, there is reversal of the connections between the input and output terminals.

In the second embodiment, the same result is obtained by driving by means of actuating each shaft of a first position in which their conductive part connects a first end ring to the central ring and a second position in which the conductive portion connects the central ring to the second end ring; the first end rings are each connected to an input terminal (respectively output terminal) and the central rings are each connected to an output terminal (respectively input) by advantageously flexible conductors; the second end rings of each group are connected by conductive elements to the first end ring of the other group. Preferably, the trees are parallel; they can move in the same direction, in which case the conductive elements between the two groups are crossed, or in the opposite direction.

Advantageously, the inversion device further comprises means for controlling the actuating means, for example associated with auxiliary contacts that can be coupled to a switchgear. Preferably, sensors are provided in the inverting device so as to optimize the operation of the control means and the actuating means. In particular, a position sensor can determine whether the shaft is in the first or second position; the position sensor may be a direction of rotation sensor if the actuating means drive the shaft in rotation to effect the translation. Load sensors and / or the number of maneuvers can be associated with the reversing device according to the invention.

BRIEF DESCRIPTION OF THE FIGURES

• La figure 1, déjà décrite, illustre un départ-moteur muni d'un inverseur de phase.
• La figure 2 montre schématiquement une bague pouvant être utilisée dans un dispositif selon l'invention.
• Les figures 3A et 3B montrent la première position et la deuxième position d'un ensemble d'inversion pour un dispositif selon un mode de réalisation de l'invention.
• La figure 4 représente un dispositif d'inversion selon un mode de réalisation de l'invention.
• La figure 5 montre un autre ensemble d'inversion pour un dispositif selon l'invention.

Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention, given by way of illustration and in no way limiting, represented in the appended figures.

• The figure 1 , already described, illustrates a motor starter equipped with a phase inverter.
• The figure 2 schematically shows a ring that can be used in a device according to the invention.
• The Figures 3A and 3B show the first position and the second position of an inversion assembly for a device according to an embodiment of the invention.
• The figure 4 represents an inversion device according to one embodiment of the invention.
• The figure 5 shows another inversion assembly for a device according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In an inverter device 100 according to the invention, the contacts between the phase conductors L _i , T _j are formed by means of multi-blade rings, also called multi-contact rings or cylindrical connectors, which allows, without adding additional parts, to ensure a contact pressure during the passage of the current.

In particular, as illustrated in figure 2 , a ring 110 used in the contact system according to the invention is connected by its outer surface 112 to any type of circuit, and is equipped on its internal face 114 with multiple conductive flexible strips 116, or other spring means, defining a diameter Ø ₁₁₆ less than the internal diameter Ø ₁₁₄ of the ring 110. This configuration makes it possible to connect, with possibility of relative movement, a conductive rod 120 located inside the ring 110, and of diameter Ø ₁₂₀ between the diameters Ø ₁₁₄ and ₁₁₆ defined by the inner face 114 and the lamellae 116 of the ring 110, and the circuit connected to the outer surface 112 through the lamellae 116 connected thereto; advantageously, the ring 110 is entirely conductive. Depending on the choice of materials and the guiding of the relative movement of the rod 120 and the ring 110, the number of translational movements between the two elements 110, 120 can be substantial, and can be as high as 1 million maneuvers.

The device 100 according to the invention uses for inversion principle a translational movement of a cylindrical shaft 120 between multi-contact rings 110 _i ; the insulating shaft 120, for example made of polytetrafluoroethylene, comprises, for the preferred application, two conductive parts 122 spaced apart from the ends, for example a copper cover, tin-plated or not, or bronze, separated by an insulating part 124; preferably, to avoid wear, the outer surface of the three segments 122 ₁ , 124, 122 ₂ is substantially flat. Five rings 110 _i of thickness h, preferably identical, are aligned along the shaft 120, separated from each other by a distance d; the length l of the conductive portions 122 ₁ , 122 ₂ is greater than the distance separating the part of the lamellae 116 defining the diameter less than or equal to that of the shaft Ø ₁₂₀ of two adjacent rings, and preferably corresponds substantially to the distance d + 2h separating the first face of a ring 110 _i and the opposite face of the adjacent ring 110 _{i + 1} , the length l 'of the insulating part 124 is such that the first face of each conducting portion is substantially separated from the distance 2d + 2h separating three rings. The rings 110 are alternately connected to input terminals 106 and output 108 of the inverter 100, with one of the terminals 108 _1, connected to two end rings 110 _1, 110 ₅ of the alignment; the two end rings 110 ₁ , 110 ₅ are further connected to each other, for example by a rod or a conductive braid 126.

The inversion assembly 130 illustrated in the figures 3 clarifies the operating principle. In a first position of the shaft 120 illustrated in figure 3A the first conductive part 122 ₁ is located between the first end ring 110 ₁ corresponding to the phase T1 of the motor 2 and the adjacent ring 110 ₂ corresponding to the supply phase L1; the second conductive part 122 ₂ is located between the central ring 110 ₃ corresponding to the phase T2 of the motor 2 and the adjacent ring 110 ₄ corresponding to the supply phase L2. In the second position of axis 120 illustrated in figure 3B , the first conductive part 122 ₁ is located between the ring 110 ₂ corresponding to the supply phase L1 and the central ring 110 ₃ corresponding to the phase T2 of the motor 2; the second conductive part 122 ₂ is located between the second end ring 110 ₅ corresponding to the phase T1 of the motor 2 and the adjacent ring 110 ₄ corresponding to the supply phase L2. Thus, between the first and the second position, there has been a reversal of the connection between the phases.

The translation of the shaft 120 may be carried out by any means 132 adapted, for example motor or electromagnet type; the actuating means 132 may be bistable, or it may be monostable and combined with a rack system. In addition, it is possible to minimize the coefficient of friction ring 110 / shaft 120, which allows to use a low effort actuator. In particular, in a preferred embodiment illustrated in figure 4 the drive is performed by an electric jack 132.

As illustrated in figure 4 , the inverting assembly 130 is housed in a housing 134, which is preferably similar in shape and size to those of the protection devices 10 of the line 1 and the same mounting system, in particular for a DIN rail. The inversion assembly 130, associated with its actuating means 132, is mounted integral with the housing 134, the shaft 120 being put in place within guiding means 136 allowing a translational movement with less play not soliciting 110 rings unnecessarily. The housing 134 comprises, in a conventional manner, three input terminals 106 and three output terminals 108; an input terminal 106 ₃ and an output terminal 108 ₃ are interconnected by a fixed conductor 138, for example a braid or a copper strip. The other terminals 106 _1, 106 ₂ , 108 ₁ , 108 ₂ are connected to the rings 110 _i of the inverting assembly 130, advantageously by flexible braids 140 so as not to subject the rings 110 to the clamping forces on the terminals 106 , 108 during electrical assembly.

The design of the contact according to the invention, per cylinder 120 and multiple lamellae 116, makes it possible to dispense with any spring, or other, intended to prevent the reopening of the contacts 12, 14 during repulsion due to short-circuit current flow. ; in particular, the cost of the coil or other magnetic circuit disappears. Furthermore, the actuating means 132 of the inverter 100 may be reduced in size: it is thus possible to integrate the reversing assembly 130 according to the invention into a housing 134 of width L = 45 mm for applications up to 7000 A, or at least 10 kA short circuit.

The inverter 100 according to the invention advantageously comprises an electronic control system 142 for placing the inverting assembly 130 in the first or second position in a controlled manner. The simplicity of the movement involving the phase change allows optimal management of the inversion time, so that the power of the actuating means 132 and their consumption can be rationalized.

In order to avoid charging operations, the upstream lines L may be equipped with load sensors 154. It is also possible to provide the inverter 100 with sensors making it possible to obtain additional information at the level of the shaft 120. cheaper. For example, a sensor 156 can sum the number of inversions, which makes it possible to know the wear of the inversion assembly 130 to ensure preventive maintenance and to limit downtime. The relative position of the shaft 120 can be controlled by position sensors 160; this relative position makes it possible to verify that the command 142 is not erroneous and / or redundant with the last maneuver of the inversion assembly 130, and in particular to serve to fulfill the auxiliary contact function. These various means, taken together or individually, allow an optimization of the control system 142 and in particular, by appropriate programming to prohibit or allow the charge reversal depending on the case.

Furthermore, in case of excessive space requirement, caused for example by an increase in the necessary insulation distances and / or a greater width h of the rings 110, it is possible to modify the inversion assembly 130 according to the invention. for a "two-story" design illustrated in figure 5 . Six rings 110 ', 110 "are set up, in two groups, on two shafts 120', 120" each comprising a conductive portion 122 ', 122 ", advantageously, the shafts 120', 120" are parallel, and the parts conductive 122 ', 122 "are of the same length Two adjacent rings 110' of a first (respectively second) group are connected to the first (respectively second) input and output terminals 106 ₁ , 108 ₁ (respectively 106 ₂ , 108 ₂ ) and the end rings of each group are connected together The two shafts 120 ', 120 "can be moved in the same direction or in the opposite direction depending on the actuating means 132. In particular, in the frame shown, the connecting conductors 126 'between rings 110', 110 "of each group are crossed, in first position, the first (respectively second) phases are interconnected, and in a second position in which the two shafts 120, 120 "move in the same direction of the same distance, the phases are crossed.

The device 100 according to the invention thus makes it possible to perform a reversal function of two phases by a limited number of parts, reducing the cost of mounting the device. Moreover, the design allows the use of certain parts several times, which further reduces the costs of implementation: for example, five identical rings for two-phase inversion.

Although the invention has been described with reference to a device for reversing two phases when starting a three-phase motor, it is not limited thereto: other elements may be concerned by the invention; for example, the design of the device according to the invention is adapted for an inversion of the single-phase current, by eliminating the third phase. In particular, the device according to the invention is suitable for electric braking against the current and / or by reversing the direction of operation of three-phase asynchronous motors. The device according to the invention can also be adapted, for example by aligning seven or eight rings and by connecting them in a suitable way, for the passages of the configuration "star" to the configuration "triangle" of startup of the three-phase motors.

Claims (10)

1. Phase inverter device (100) comprising:

   - a first and a second input terminals (106_i);

   - a first and a second output terminals (108_i);
   characterized in that it comprises

   - an inversion assembly comprising conductive rings (110) each comprising flexible contact plates (116) on its inner surface (114) and means for linking the conductive rings (110) together in pairs, said means (120) being able to move in translation within the rings (110) to alternate the connections between the rings (110);

   - conductors (140) each linking terminals (106, 108) to a ring (110);

   - actuation means (132) for bringing about the translation of the means (120) linking the conductive rings (110);

   - said actuation means (132) making it possible to alternate between the connection of the first and second terminals (106_i, 108_i) and the connection of the first terminals (106_i) with the second terminals (108_i).
2. Phase inverter device (100) according to Claim 1, in which the inversion assembly comprises:

   - a shaft (120) comprising two conductive parts (122) of substantially identical length (I) separated by an insulating part (124);

   - five conductive rings (110) placed around the shaft (120) and adapted in order that the shaft (120) can move in translation with the plates (116) in contact with the outer surface of the shaft (120);

   - a conductive element (126) connecting the two end rings (110₁, 110₅); and in which:

   - the conductors (140) link two adjacent rings (110_i, 110_i+1) alternately to an input terminal (106) and an output terminal (108);

   - the actuation means (132) enabling the shaft (120) to assume a first position in which the first conductive part (122₁) of the shaft (120) links a first end ring (110₁) and the second adjacent ring (110₂), and a second position in which the first conductive part (122₁) links said second adjacent ring (110₂) and the central ring (110₃).
3. Phase inverter device (100) according to Claim 1, in which the inversion assembly comprises:

   - a first and a second insulating shafts (120', 120") each comprising a conductive part (122', 122");

   - a first and a second groups of three conductive rings (110', 110"), the rings of the first, respectively second, group (110') being placed around the first, respectively second, shaft (120') such that the shaft (120') can move in translation with the plates (116) in contact with the outer surface of the shaft (120'), the rings of the first, respectively second, group (110') being also separated from one another by a distance (d) substantially equal to the length (I) of the conductive part (122', 122") of the first, respectively second, shaft (120', 120");

   - two conductive elements (126') connecting the end rings of each group together;

   and in which:

   - the conductors link the first terminals (106₁, 108₁) to two adjacent rings (110'_i, 110'_i+1) of the first group and the second terminals (106₂, 108₂) to two adjacent rings of the second group (110"_i, 110"_i+1);

   - the actuation means (132) enable the shafts (120', 120") to assume a first position in which the conductive part (122') of each shaft (120') links an end ring and the central ring, and a second position in which the conductive part links the other end ring and the central ring.
4. Device according to Claim 3, in which the two shafts (120', 120") are parallel and their conductive parts (122', 122") are of the same length (I).
5. Device according to one of Claims 1 to 4, in which the rings (110) are mutually identical.
6. Device according to one of Claims 1 to 5, in which the shaft (120) is insulating and comprises two coating rings forming the conductive parts (122).
7. Device according to one of Claims 1 to 6, in which the conductors (140) linking the terminals (106, 108) to the rings (110) are at least partially flexible.
8. Device according to one of Claims 1 to 7, also comprising a third input terminal (106₃) and a third output terminal (106₄) linked together by a conductor (138).
9. Device according to one of Claims 1 to 8, also comprising means (142) for controlling the actuation means (132).
10. Device according to one of Claims 1 to 9, also comprising sensors (156)(160) making it possible to determine the position of the shaft (120).

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