SE518664C2 - Transfer switch, use of such a transfer switch, facility comprising a plurality of transfer switches, switchgear and method for transmitting a feed of a load - Google Patents

Abstract

In a transfer switch for alternating current two electric switching devices of hybrid type are adapted to establish and break, respectively, a current path between a load and an alternating current supply each for transferring the supply of the load with electric power from one alternating current supply (5) to the other (6). The switching devices have components (15-18) blocking in at least one direction for establishing a temporary current path therethrough when breaking the current path through the switching device and enabling an arc-free completion of the breaking. A control unit (20) is adapted to control a movable part (4) to carry out one single mechanical movement for opening one of the switching devices and closing the other for changing the alternating current supply to the load.

Description

unavn 10 15 20 25 30 35 518 664 2. u »Q u These are usually loads that are sensitive to power outages, and in which power outages could cause large costs or other serious inconveniences, such as personal injury.

An example of a technology area where an interruption in the supply of electrical power to an industrial process would have devastating consequences in terms of cost is high-temperature processes in the installation industry. It is within the scope of the invention, however, that such a transfer switch is used to switch between two different feeds depending on completely different parameters, such as, for example, the price of electrical power delivered from different places relative to each other during different time periods.

“Load” is here to give a broad meaning and this also includes, for example, an alternating voltage network which in this way can be supplied with a supply of electrical power from different directions through a transfer switch.

The element is usually a semiconductor element but it could be of any conceivable kind with said capability, such as for example a variable electrical resistor according to WO 98/149694.

The invention is of course not limited to any particular area of the operating current by such an electrical coupler in the closed state of such a transfer switch, nor to any particular voltage levels present in said current path, but it may nevertheless be mentioned that it is particularly useful for intermediate voltage , ie corresponding to 1-52 kV system voltage, whereby the operating current in question can typically be 1 kA, but both lower and higher voltages and currents than these are conceivable.

It is pointed out that the "leading state" above is to give a broad meaning, and it is not necessary that an element on the way into or in the leading state really leads, but this is also meant to cover that it can be brought to that moment lead if desired, which could be the case for a flammable semiconductor element, such as a thyristor, while a passive semiconductor element in the form of a diode will instead always conduct in the light. the state as defined here.

It is further pointed out that "first connector" and "second connector" include all types of physical appearances of a connector in which a physical separation of two parts during the formation of a gap therebetween occurs upon opening of the connector, and this can be done, for example, by a movable contact connecting two remotely arranged contacts is moved so that they are no longer in communication with each other or that a movable contact is in contact with a fixed contact and is moved away from it. Two movable contacts are also conceivable. “Gap” should also be given a broad meaning. It also includes that an insulator is inserted between the contacts and this can be a solid body that abuts against both contacts. Thus, a contact surface could also be followed by an insulating surface in the same body (which may comprise a movable or bare contact) and in the same plane and the "gap" is then formed by displacing two bodies which in a contact position form a contact relative each other so that such an insulating surface forms the abutment surface of one or both bodies.

The electrical switches arranged at the initially defined transfer switch are usually called hybrid switches, and characteristic of them is that they are capable of producing an arc-free break of the current path through the coupler, as this takes place when the semiconductor element is in the blocking state and no current flows through the coupler. . In couplers with connectors which break current thereby, and thus an arc is generated, either the gas pressure inside the switch used must be high to provide sufficient insulation and breaking capacity or for the same reason a vacuum is provided inside the switch. In the first case a lot of energy is needed to blow out the arc, while in the second case a relatively high contact pressure between the contacts is required for a good contact, which consumes a non-negligible amount of energy. In previously known transfer switches of an initially defined type, said first connector is formed by a vacuum switch with the above-mentioned disadvantage as a result, while the second contactor is formed by a disconnector. In addition, the element is in some cases connected in normal operation, which leads to a great need for cooling thereof. This, together with the requirement for a relatively complicated control electronics, means that such previously known transfer switches become very bulky and expensive.

SUMMARY OF THE INVENTION The object of the present invention is to provide a transfer switch of initially defined type, which can be designed in a much simpler way, with significantly lower space requirements and thus at a lower cost than the previously known such transfer switches discussed above.

This object is achieved according to the invention by providing such a transfer switch, which comprises at least one movable part and by designing the unit to control this part to perform a single mechanical movement to open the two connectors of the first coupler and close the two connectors of the first coupler. the second coupler.

By controlling a single moving part to perform a single mechanical movement when opening the two connectors of one coupler and closing the two connectors of the other coupler, this can be done in a perfectly synchronized manner, without requiring any complicated control device to coordinate these openings and closures with each other. Another advantage is that a single drive device can be used to effect the entire transfer of the feed to the load from one AC power supply to the other by driving the moving part to perform a movement. By opening or closing each electrical coupler of the transfer switch according to the invention through a single mechanical movement, an improved possibility is achieved to make the operation faster, when only one accelerator: 10 15 20 25 30 35 518 664 5. . u. n. ration of a moving part is necessary. This is reinforced by the fact that the couplers of the transfer switch according to the invention can in this way ensure arc-free interruption of the current through the first contact device without arranging a vacuum switch, so that instead the corresponding amount of energy can be used to make the interruption faster. In this way, different types of electrical equipment connected to the said current path can be better protected in the event of faults and material wear of the contacts included in the couplers is reduced. All this means that the transfer switch according to the invention can be made considerably more compact than previously known such transfer switches and they can also be provided at a lower cost.

According to a preferred embodiment of the invention, the transfer switch comprises at least two contacts arranged successively along the path of the movable part for said mechanical movement, the movable part is arranged to form a galvanic connection between said two contacts in the closed state of each coupler, that respective couplers is arranged to be connected via one of the contacts and the movable part in a current path leading through the coupler, that in the respective coupler element the two contacts connect to each other, and the control unit is arranged to control the opening of the current path through the respective coupler. by controlling the movable part to move along such a path and in such a direction that first the galvanic connection between one of said two contacts and the movable part is broken to open the first connector and then the galvanic connection between the second of said two contacts and the movable part is broken to open it other connector. This performs a very simple and inexpensive way of designing the transfer switch according to the invention, since each coupler has to contain only two fixed contacts, a movable contact part common to the other coupler and a single element to ensure arc-free breaking of the current path to one the AC power supply and establishing the current path to the second AC power supply. According to another preferred embodiment of the invention, at least one of said couplers comprises at least three along the path of the movable part for said mechanical movement after each other arranged contacts, the element of this coupler connects a first and a second adjacent of these three contacts with each other, the movable part is arranged to form a galvanic connection between said three contacts in the closed state of said at least one coupler, and the control unit is arranged to break the current through this coupler controls the moving part to move along such a path and in such a direction that first the galvanic connection between the first contact most distant from the third of the contacts and the two other contacts is broken to open the first contact and then the the galvanic connection between the second and third contacts is broken to open the second connector. This embodiment also requires only one semiconductor element per coupler, which makes it affordable.

According to another preferred embodiment of the invention, said at least one coupler of the transfer switch comprises at least two said elements in the form of semiconductor elements connected between each external contact along the path of movement of the movable part and a contact closest to the later, the movable part is arranged to form in the closed state of this coupler a galvanic connection between all the contacts between and including said external contacts, this coupler comprises means for sensing the direction of the current through the coupler in the closed state, and the control unit is arranged to on the basis of information from said sensor means upon breaking the current through the coupler directing the movable part to move in either direction along its path of movement in order to open the first connector by breaking the galvanic connection between a first outer contact and a first adjacent contact thereof and then by continuing movement they open t second connector. By enabling in this way a breaking and also establishing a current path through the movement of the moving part in two different directions can in principle momentarily occur in the event of another 10 15 20 25 30 35 518 664 7 n n u. If the request for interruption of one of the alternating current supplies the moving part is accelerated to open the first contact of the coupler in question, since the direction of movement can be chosen so that the semiconductor element intended to take over the current is in a conducting state. This means that the harmful effect that a fault along the current path can cause can be reduced to a minimum while the time the load is without supply can be made very short. This is a great advantage in relation to the above-mentioned preferred embodiment, in which the direction of movement of the movable part when breaking the current path is determined and the correct current direction must be waited before operation can take place, which can cause a delay of up to half a period of alternating voltage .

According to another preferred embodiment of the invention, the movable part is connected to the load, which enables a transfer of the measurement of the load from one alternating current supply to the other by very simple means and using a minimum number of contacts.

According to another preferred embodiment of the invention, the two couplers have a common contact along the path of movement of the movable part, so that the contacts along this path of movement on one side of the common contact belong to a first of the couplers and those on the other side the other. of the couplers, and the common connector is arranged to be connected to the load.

By designing the transfer switch for connection to the load in this way, it can be made very simple and compact.

According to another preferred embodiment of the invention, the control unit is arranged to guide the movable part along a substantially circular arc-shaped path of movement along which the connector of the two couplers is arranged. As a result, in the case of an open state of one of the couplers, this can be brought to the closed state via a movement in the direction desired by rotating the movable part, so that the closed state can be achieved in the fastest possible way, so that in the case of opening and nn; || 10 15 20 25 30 35 518 664 8 closure in two different directions according to the above the direction of rotation which gives the possibility of the fastest opening with regard to the position of the alternating voltage across the coupler in question can always be selected. In this case, it is particularly advantageous if the two couplers are arranged substantially 180 ° offset relative to each other along said arc of a circle, as this enables a transfer of the supply to the load via one coupler to the other in the shortest possible maximum time regardless of the position of the alternating current. of the closed coupler has at the moment of emergence of the need for transmission. It will also be easier to operate the clutch with, for example, an electric motor.

According to another preferred embodiment of the invention, the movable part is rigidly connected to a shaft, and the control unit is arranged to control a drive device to drive the shaft for moving the movable part along said path. This way of achieving the movement of the moving part enables a simple design of the drive device as well as the possibility of a movement with a high acceleration.

According to another preferred embodiment of the invention, the transfer switch comprises means arranged to substantially continuously sense the direction and magnitude of the current through the coupler which is currently closed and send information about this to the control unit. This means that the control unit always "knows" how a transfer from one supply to the other is to take place, so that this can be done in the fastest and most flexible way possible as soon as the need arises.

According to another preferred embodiment of the invention, the coupler comprises a voltage limiting device connected in parallel with the semiconductor element, and the device is arranged to start conducting at a voltage above it in the vicinity of the maximum voltage resistance of the element. This is possible by the fact that in the closed and open state of the coupler no voltage will be present over the element and thereby also not over the device, so that this will not be heated by any leakage currents other than 15 15 20 25 30 35 518 664 9 thereby. By means of the device, which may be a varistor, but could also be of another type, for example a resistor, snubber or the like, the first voltage peak which arises across the element through the returning voltage after the opening of the first connector can be limited, which in the case of a single element means that this can be dimensioned to be able to keep a lower returning voltage in its blocking direction and thus become cheaper than otherwise. In the case of several series-connected elements, by arranging such a device in parallel with each element, the number of such series-connected elements with a given voltage resistance can be reduced. This avoids that an individual element receives a higher voltage than it can withstand, while other elements receive a lower voltage.

According to another preferred embodiment of the invention, at least one of the couplers comprises means arranged to act on raising the voltage when separating two contacts in connection with the opening of the first connector. The voltage at the contact separation is normally in the order of 12-15 V, and drives the transmission of the current to the element connected in parallel. The higher this voltage, the faster the current can be fed into the element. By arranging the said means, a smaller material wear is achieved and the contact point will also hold better in terms of insulation.

According to another preferred embodiment of the invention, said means comprise several series-connected first connectors arranged to be opened substantially simultaneously for transmitting the current to the element. Through such a series connection of several connectors, the voltage which will drive on the line of the element will be increased, as this will be formed by an addition of the voltages of the series-connected connectors with the aforementioned advantageous results as a result.

According to another preferred embodiment of the invention, said means are formed by the contacts included in the first connector having at least a part of ablating material arranged to be heated and evaporated into gases for gas blowing on a light base. by separating two contacts when opening the first connector, which also provides a higher arc voltage and faster commutation of the current to the element.

According to another preferred embodiment of the invention, at least one semiconductor element of one coupler is a diode, which would often be preferable, as such a solution becomes cheap in relation to other controllable semiconductor elements and also very reliable. However, it is also conceivable that the semiconductor element is controllable, such as a thyristor, and it could also be extinguishable, such as a GTO or an IGBT, to enable a faster breaking process of the closed coupler. It could also be advantageous in some situations to arrange a bidirectional semiconductor element, i.e. a semiconductor element that can block and lead in both directions, such as a BCT (bidirectionally controlled thyristor).

If a semiconductor element is made of material with a wide energy gap between valence band and lead band, i.e. an energy gap exceeding 2.5 eV, such as SiC and diamond, relatively high voltages can be handled by both transfer switch couplers and thus by the transfer switch using a small number of semiconductor elements. .

According to another preferred embodiment of the invention, the transfer switch comprises means arranged to continuously or intermittently determine which of the two measurements is currently most suitable for the load, and the control unit is arranged to control said movable part for transmission on the basis of information from said means. of the supply of the load from one alternating current supply to the other if the alternating voltage supply connected to the load at this time does not correspond to said most suitable supply. In this way, the transfer switch can be used to always ensure that, according to certain criteria, the most suitable of two AC power supplies is connected to the load. ; i.a | The invention also relates to advantageous uses of a transfer switch as above in accordance with the appended claims, and the advantages of most of these will become apparent from all the desired clarity of the discussion above, but here It is mentioned that a particularly advantageous use of the transfer switch is for connecting electrical equipment to an alternating voltage network via two different current paths, first the first for starting the electrical equipment via closing the first of the couplers and then the second for operating it. equipment via opening of the first coupler and closing of the second, a more specific such use being the reactor start of an electric motor connected to an alternating voltage network to first connect the motor to the alternating voltage network via a reactor via the first coupler, the ie an inductor, and then connect the motor directly to the AC mains via the other switch. This avoids that a large such motor reduces the voltage level of the AC mains to impermissibly low levels at said start, and instead a soft start can take place via the reactor.

The invention also relates to a switchgear for electricity supply in industries or in distribution networks or transmission networks provided with a transfer switch according to the invention.

Additional advantages and advantageous features of the invention will become apparent from the following description and other dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are described below by way of example with reference to the accompanying drawings, in which: Figures 1 and 3-8 are simplified views illustrating a transfer switch according to a first preferred embodiment of the invention in various modes of operation between a load connected to a first alternating voltage supply and the load connected to a second alternating voltage supply, Fig. 2 is a simplified circuit diagram illustrating the principle of operation of the transfer switch according to Fig. 1, fig. Fig. 9 is a simplified view illustrating a transfer switch according to a second preferred embodiment of the invention in a parking position with the load separate from both feeds; Figs. 10 and 12-14 are simplified views illustrating a transfer switch according to a third preferred embodiment of the invention. in different operating modes between a load connected to a first AC power supply and the load connected t Fig. 11 is a simplified wiring diagram illustrating the principle of operation of the transfer switch of Fig. 10, Figs. 15-17 schematically illustrate an electrical coupler applicable in a transfer switch according to a fourth preferred embodiment of the invention at the end, temporarily closed and open, respectively. Fig. 18 and 19 illustrate electrical couplers useful in transfer switches according to further preferred embodiments of the invention, Fig. 20 illustrates how the current I through and the voltage U across the semiconductor elements of a coupler according to Fig. 19 develop over time compared to a coupler substantially according to Figs. 18, 21 and 22 illustrate a part of a coupler included in a transfer switch according to the invention in two different positions when the current is thereby broken, 14-1. Figs. 23 and 24 are schematic wiring diagrams illustrating two possible ways of arranging a transfer switch according to the invention for starting an electric motor, and Fig. 25 is a simplified wiring diagram illustrating a possible use of a transfer switch according to the invention. for connecting and disconnecting capacitors to an AC mains for reactive power compensation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 schematically illustrates a transfer switch for alternating current according to a first preferred embodiment of the invention, which comprises two electrical couplers 1, 2 arranged to establish respectively a current between a load 3 and a current. see Fig. 2) here connected to a movable contact part 4 and each of their AC power supply 5, 6 indicated by an electrical line for transmitting the supply of the load with electrical power from one AC power supply to the other. In this case, such a transfer switch is arranged per phase, so that a three-phase network has three such transfer switches in one and the same location. The movable contact part 4 is arranged on a carrier 7, which is rotatably arranged about a shaft 8.

Externally if the carrier 7 with the movable part 4 is at respective couplers three contacts 9-11 and 12-14 located along the path of movement of the movable part 4 are arranged to form good electrical contacts in abutment with the movable part 4.

The diameter of the circle along which the movable part is arranged to establish electrical contacts with the contacts 9-14 is proportional to the alternating voltage of the two measurements.

A semiconductor element 15-18 in the form of a diode connects each external contact 9, 11, 12, 14 seen in the path of movement with the middle contact 10, 13, one diode of each coupler having its conduction direction towards the middle contact and the other its direction from the latter. : The dance switch further has a drive device (not shown) arranged to drive the carrier 7 and thus the movable contact 4 for rotation about the shaft 8.

Each coupler is further provided with a sensor means 19 schematically indicated for the coupler 1, arranged to sense the direction and magnitude of the current in the current path through the currently closed coupler and to send information thereon to a unit 20 arranged to control said drive device and thereby the the movement of the movable contact part 4 due to this information. In this way, the control unit will always know what the current momentarily looks like in order to be able to instantly control the moving contact part in the desired way. Means 56 are also arranged to determine, on the basis of other parameters, such as prices of feed power of the two feeds 5, 6, which is most suitable for the feeding of the load at a given time and to send information thereon to the control unit 20.

The function of this transfer switch is as follows: we assume that the transfer switch is in the position according to Fig. 1, in which the first coupler 1 is closed, so that the load is connected to the alternating current supply 5, while the alternating current supply 6 is disconnected, since the electrical coupler 2 is open. For exemplary purposes, it is assumed here that the alternating current supply 5 is the ordinary supply, while the alternating current supply 6 is a reserve supply. When a request for connection of the reserve supply 6 arises, for example by the sensor means feeling that no current flows at all in the alternating current supply 5 due to a power failure therein, then the control unit 20 first decides in which direction the movable contact part 4 must be moved so that the current path through the first coupler 1 can be broken as quickly as possible. This decision depends on the position of the current in the current path through this coupler at that time. Namely, in the closed position according to Fig. 1, the entire current passes through the coupler between the first contact 10 and the movable part 4. When the break is to take place, the current must as soon as 1.1 »- 10 15 20 25 30 35 518 664 15 possible to be transferred to go via one of the diodes 15, 16 instead. The current can be connected to a diode during the part of an alternating current period that lies between the time the diode was biased in that direction until the diode becomes reverse voltage next time. This means in a full period of 20 ms in practice that an opening of the line path parallel to the diode in question can take place, for example, about 2 ms before the zero crossing towards the forward voltage direction until the next zero crossing.

We now assume that the current in the current path 1, in the event of a break, has the direction indicated by the arrow 21 in Fig. 1 and is within the range that allows the current to be transmitted to the diode 15. The control unit 20 then controls the movable contact 4 to rotate clockwise to open a first connector lying parallel to the diode 15, which here consists of the contacts 10, 11 and the movable part 4. Then the temporarily closed position shown in Fig. 4 is reached.

When this happens, a small spark is formed in the gap 22 between the movable part 4 and the contact 10, which results in a voltage of usually 12-15 V, which will drive the transmission of the current through the diode 15, so that the current now instead will go via the moving part 4, the contact 11 and the diode 15. The transmission of the current to the semiconductor element can also be accelerated by connecting a resistor in the ordinary current path and thereby raising the voltage also across the semiconductor element.

When then the current through the coupler 1 changes direction, the diode blocks the current through it, since a voltage will build up over the then reverse voltage diode 15 and now the rotational movement of the movable contact part 4 continues in the same direction as before, so that the galvanic connection between the contact 11 and the movable part 4 are broken, whereby this refraction can take place arc-free, as no current passes through the contact point at the time of breaking. As a result, the fully open position shown in Fig. 8 is achieved. It is important in this break that it takes place so fast that the voltage across the diode 15 does not have time to change direction again and this begins to conduct. Should the voltage across: wife 10 15 20 25 30 35 518 664 16 the coupler 1 be during the second half period when the need for breaking of the current path through the coupler is detected, the control unit would instead control the movable contact part 4 to rotate in the figures seen counterclockwise for utilizing the diode 16 in the refraction instead. In this way the possibility of a very rapid break of the current path arises, and even at the most unfavorable position of the alternating voltage when detecting breaking demand can be switched between the closed position and the fully open position according to Fig. 8 in a substantially shorter time than a period , usually always within 15 ms at a frequency of 50 Hz of the AC voltage. The position shown in Fig. 8 also constitutes a possible parking position, which can be assumed for a longer period of time if the load must be separated from the measurements, for example for carrying out repair work between the load and the transfer switch.

Because in the closed position of the coupler the current never passes through the diodes, only the contacts 10, 13 and 4 must be dimensioned for the current, which can for example be 1000 A, while the diodes 15, 16 are dimensioned for a possible short-circuit current, which in such a case can be 25 kA. However, they must only withstand this for a very short time and the dimensioning of the diode can be done without any consideration of any constant operating current through the coupler. Furthermore, the diodes must be dimensioned for a return voltage which is applied across them for a short period of time after the opening of said first connector. This can in the case of a mains voltage of 12 kV, for example, be about 20 kV. The contact gap 23 in Fig. 8 must, however, be able to withstand a significantly higher so-called impulse voltage, which in this case could be 75 kV.

When the position according to Fig. 5 is reached, the backup supply 2 is immediately switched on, in which case the current direction thereof is such that a temporary current path can be established through the diode 17, and otherwise the connection of the backup supply is delayed until the position according to Fig. 6 is reached. the movable part 4 establishes a galvanic contact connection with the middle contact 13 of the second electrical coupler 2. Thereafter, the movement of the movable part is continued to the position according to Fig. 7, so that the transfer switch has entered a standby mode for the fastest possible return to supply of the load via the ordinary AC supply 5 when the request arises. It is pointed out that it may in itself be advantageous, when the movable part 4 reaches the contact 14, to have the diodes 17 and 18 directed as shown relative to the diodes 15 and 16, but they could also be in the opposite direction. The opening of the first coupler 1 and the closing of the second coupler 2 takes place by a single mechanical movement of a single moving part, which entails the advantages which are stated further up.

Additional advantages of this embodiment of the transfer switch worth mentioning are very low manufacturing costs, as it is easy to produce and the material consumption is low and the number of components contained therein is low. Furthermore, a small amount of maneuvering energy is required thanks to a slightly mobile mass. The diodes can be used without cooling. Fig. 2 very schematically illustrates the principle of the transfer switch according to Fig. 1.

Fig. 9 schematically illustrates a transfer switch according to a second preferred embodiment of the invention, in which the two couplers 1, 2 are arranged offset relative to each other along an arc of a circle with an angle of substantially 120 °, which means that the insulation distances 23 between the movable part 4 and the contacts 11, 14 can be increased in the parking position of the transfer switch shown in Fig. 9. As a result, the transfer switch in the broken parking position can withstand higher impulse voltages than in the embodiment according to Fig. 1. However, this embodiment means that the movable part has a longer distance to travel when rotating the movable part 4 in Fig. 9 clockwise for transferring the load. from one feed to the other. Another possibility for increasing said insulation distance is to arrange the two couplers offset relative to each other in the direction of the shaft 8. Figs. 10 and 12-14 illustrate a transfer switch for alternating current according to a another preferred embodiment of the invention, which operates according to the same principles as the one just described, but here instead the movable contact part 4 is movable along a rectilinear path of movement. Here, the two couplers 1 and 2 have a common fixed contact 24 along the rectilinear path of movement of the movable part 4, and to this common contact 24 the load 3 which the transfer switch is intended to provide supply for is intended to be connected. The two other contacts 25, 26 and 27, 28 of the respective couplers are each connected to a semiconductor element 29, 30 in the form of a diode, which is directed with its conduction direction towards the interior of the contacts 26, 27. However, all diodes could be opposite instead. When the alternating current supply 5 is connected to the load 3, but for some reason a wish arises for connecting the alternating current supply 6 to the load instead, then movement of the moving part 4 in Fig. 10 begins to the right. Here, however, the opening of the current path through the contact 25, the movable part 4 and the contact 24 may have to be delayed somewhat, in which case the current does not have such a direction when the need for refraction arises that the refraction process can be started immediately. Instead, costs are saved by halving the number of required semiconductor elements in relation to the embodiment according to Fig. 1. The equivalent circuit for this embodiment is shown in Fig. 11, where the load 3 is also plotted. It is shown in Figs. 12, 13 and 14 how first the movable part 4 is moved along a rectilinear path of movement to reach the temporarily closed position according to Fig. 12, in which the current is transferred to the semiconductor element 29, to the fully open position according to Fig. 13. of the first coupler 1 and then on to the second completely closed position according to Fig. 14 of the coupler 2, so that when the spare supply 6 is connected to the load 3 via the contact 28, the movable part 4 and the contact 24. 1 Fig. 15 schematically illustrates a modified electrical coupler, which in combination with a similar one could form a transfer switch according to a further preferred embodiment of the invention. Here, however, only this coupler will be manned: 10 15 20 25 30 35 518 664 19 is written, and it is obvious to a person skilled in the art how two such couplers could be combined to achieve a transfer switch using one and the same variable part 4.

The coupler has an inner cylinder 31, which is rotatably arranged at a shaft 32 and has a movable contact part 4. A second cylinder 33 is arranged outside the cylinder 31 and has four contacts 34-37 arranged along the path of movement of the movable part 4 arranged to in contact with the movable part 4 form good electrical contacts. The coupler is connected in a current path 38 thereby via the two external contacts 34 and 37, respectively.

Between the two outer contacts and the nearest inner contacts, a semiconductor element in the form of a diode 39, 40 is connected with the conduction direction from the outer to the adjacent contact, but it could instead be connected with the opposite conduction direction.

The coupler further has a drive device arranged to drive the inner cylinder 31 into rotation for movement of the movable contact part 4 relative to the other contacts 34-37. In this case, the drive device consists of a schematically indicated integrated electric motor 41, which can be of a number of different types, such as PM motor, reluctance motor, stepper motor, DC motor. The motor here is not in the same plane as the contacts, but can do so, and will thus not affect the voltage strength. It is pointed out, however, that the drive may well take place in another way, such as by a motor which is arranged to act directly on the shaft 32. As regards the dimensioning of the cylinders with respect to diameter and height, this is carried out according to the same criteria as in the embodiment according to fig 1.

The function of the electrical coupler will now be briefly described, and the decisions made about the direction of rotation of the inner cylinder in the event of a request for breaking are based on the same considerations regarding the position of the alternating current as in the embodiment according to Fig. 1. now assume that the current in the current path 'lszn 10 15 20 25 30 35 s 1 s 664 20. 38 in the case of a break request has a direction indicated by the arrows 42 in Fig. 15 and is within the range which allows the transmission of current to the diode 39. The control unit 20 then controls via the motor 41 the movable contact 4 to rotate clockwise to open a first connector lying parallel to the diode 39, which here consists of the contacts 34, 35 and the movable part 4.

Then the temporarily closed position shown in Fig. 14 is reached. When this happens, a small spark is formed in the gap 43 between the movable part 4 and the contact 34, which results in a voltage of usually 12-15 V, which will drive the transmission of the current through the diode 39, so that the current now instead will go via the diode 39, the connector 35, the moving part 4 and the connector 37.

When then the current through the coupler changes direction, no current will flow through it, but a voltage will build up over the then reverse voltage diode 39 and now the rotational movement of the movable contact part 4 continues in the same direction as before, so that the galvanic connection between the contact 35 and the contact 37 are broken, whereby this breaking can take place arc-free, as no current passes through the contact point at the time of breaking. As a result, the fully open position shown in Fig. 17 is achieved.

It would of course be quite possible, by suitable modification of the outer cylinder, to provide an additional coupler of this kind with four fixed contacts arranged along the path of movement of the movable part 4 in the same way as in the coupler shown to provide a transfer switch. In this case, for example, in the event that we assume that the contact 34 would be connected to the load, this contact could be common to the two couplers. otherwise, three further fixed contacts would be arranged in the counterclockwise direction one after the other from the contact 34 with semiconductor elements connected in the same way as for the contacts shown and the last contact in this direction would be connected to a further alternating current supply, such as a re - service feed. Fig. 18 schematically illustrates how several semiconductor elements 44-46 can be connected in series with each other in order to be able to cope with a given return voltage after breaking the current path of a coupler included in a transfer switch according to the invention. .

Thus, in all the embodiments shown above, each diode symbol can be replaced by a number of diodes connected in this way in series. Here it is also possible, by choosing a material with a wide band gap between the valence band and the lead band, such as SiC or diamond, to achieve that the number of semiconductor elements required for a given voltage becomes low. It is further shown in this figure how it is possible to connect semiconductor elements in parallel by arranging here two packets of series-connected diodes in parallel with each other, and this is done to cope with a certain short-circuit current or simply for redundancy reasons, so that the coupler can operate on the desired even if a diode in one package of series-connected diodes breaks down. Fig. 19 further illustrates how a varistor 47, preferably of ZnO, can be connected in parallel with the respective semiconductor element 48, the varistor being arranged to conduct at a voltage above it in the vicinity of the maximum voltage resistance of the semiconductor element.

This can be achieved by the varistors not normally conducting any current at all, as no voltage will be applied across them, but they will only receive a voltage across them in connection with the transition between the temporarily closed and the completely open the situation. Fig. 18 illustrates how the voltage U across the semiconductor elements 48 in their reverse direction develops over time t when the voltage rises above them in the temporarily closed position at time zero. The dashed line shows how the voltage across the diodes develops in the absence of varistors and the solid line with varistors. It thus appears that the varistors cut off the first voltage peak. If, for example, four 5 kV diodes are arranged in series in a system with a mains voltage of 12 kV and a normal return voltage of 22 kV, the varistors can in this way begin to conduct a small current during the short time (approx. 10 ps) which the peak of the return voltage lasts, so that this voltage peak could be brought down snus 10 15 20 25 30 35 518 664 22 n ~ ø nn. u to 18 kV. To the left of (before) time 0 is changed the change of the current I. This means that five series-connected diodes are not required, but only four, in order to cope with the return voltage. By connecting a separate varistor with each semiconductor element in parallel in this way, it is avoided that an individual semiconductor element has a higher voltage than it can withstand, while other semiconductor elements have a lower voltage across them. It is also possible to arrange resistors or capacitances connected in parallel with the semiconductor elements in order to distribute the voltage substantially evenly over the semiconductor elements. Fig. 21 illustrates what means arranged to influence the raising of the voltage when separating two contacts in connection with the opening of the first connector of one of the couplers could look like. Here we imagine that the first connector has two fixed contacts 56, 57, which are arranged to be galvanically connected in the closed state by a movable part 58. The movable part 58 is provided at one end with a portion 59 of a material with a relatively high resistivity, so that the resistance between the movable part 58 and the contact 56 and thus between the two contacts 56 and 57 is increased at the beginning of said separation (the position according to Fig. 22) while allowing a current between these contacts thereby, so that a voltage which will drive on the transmission of the current through the semiconductor element will increase. The portion 58 may, for example, be made of graphite.

Furthermore, Figs. 23 and 24 illustrate a possible application of a transfer switch according to the invention for motor starters. It is illustrated in Fig. 23 how a transfer switch of the type according to the invention (see the principle diagram according to Fig. 2) is connected between a motor 49 and an alternating voltage network 50. Here we can consider the alternating voltage supply via one coupler 1 directly to the motor 49 as a main supply , while the alternating current supply via the second coupler 2 through a reactor 51 as a backup supply. This view is even better understood when studying the embodiment of Fig. 24, which differs from that of Fig. 23 in that the transfer switch 52 is arranged there in direct connection with the motor.

Most power grids are not rigid enough to allow the start of large motors directly connected to them, as these draw so much power that the voltage on the grid would drop far too much.

This problem can be solved by starting the engine according to different starting methods, such as reactor start, capacitor start or transformer start, whereby reactor start is illustrated here. When the engine is to be started, the left clutch 2 shown in Fig. 23 is brought into a closed position, so that the engine receives its supply via the reactor 51.

Should you now for any reason want to interrupt the start, the contacts 53-55 of this coupler can be opened according to the sequence 55, 54, 53. When the motor has then reached synchronous speed, the reactor 51 can be bypassed by bringing the coupler 2 into the open position while the coupler 1 is brought to the closed position.

Should a short circuit occur in any equipment connected to the AC mains 50, then the motor 49 will start running as a generator and contribute power to the fault steel before the fault is disconnected. Here it is possible to limit the effect of this by closing the clutch 2 in such a case and opening the clutch 1, so that the short-circuit contribution from the motor to the fault position is limited and at the same time the braking of the motor is reduced.

Should a short circuit occur in the motor or a planned stop is made, then switch 1 opens.

Fig. 25 illustrates a possible application of a transfer switch according to the invention for connecting capacitors 60 to a three-phase alternating voltage network 61 for reactive power compensation. In this case, a transfer switch according to the invention can replace two switches 62, 63, as illustrated in Fig. 25. When the capacitor 60 is connected to the phase in question of the alternating voltage network, the switch 62 can first be closed. Thereafter, the switch 62 for the phase in question connecting thyristors 64 is turned on so that the capacitor 60 is turned on at the desired time. Then the switch 63 is also closed. Then the switch 62 is opened, so that the thyristors do not have to lead any further, while the switch 63 is: anus 10 15 20 25 30 35 518 664 24 «| ~ n n. closed and the connection of the capacitor is completed. This advantageous sequence, for switching on reactive power compensation, can be conveniently realized by appropriately designing a transfer switch according to the invention.

Another advantage of a transfer switch according to the invention is achieved thanks to the fact that in the case of a three-phase voltage, which is the most common, the three transfer switches for each phase are arranged controllably completely independently of each other, which is not the case with previously known such switches, which are mechanically interconnected with each other, so that they must all be opened or closed at the same time. In the event of a fault near a generator connected to an AC network, it is possible that an asymmetry of the voltage may occur in one of the phases and that it takes several periods before it becomes zero, which is why in previously known transfer switches one must wait with the break until you are sure that a zero crossing has been reached for all phases, which may mean a delay of the order of 100 ms. By means of the device according to the invention of independently controlled transfer switches, the refraction of the phases where symmetry is present can take place considerably earlier than for a phase with said asymmetry, so that the harmful consequences of the error-induced currents can be considerably reduced.

The invention is of course not in any way limited to the preferred embodiments described above, but a number of possibilities for modifications thereof should be obvious to a person skilled in the art, without this departing from the basic idea of the invention as defined in the claims.

For example, in the embodiment according to Fig. 1, it would be entirely possible to remove an external contact of each coupler and the semiconductor element connected thereto, but then the couplers could only be opened by movement in one direction and the breaking time would be longer. Similarly, in the embodiment of Fig. 13, one of the internal contacts and the semiconductor element connected thereto could be removed at each coupler with the same result as a result. : anno 10 15 20 25 518 664 f. 25 The embodiments which above show a rotational movement could be modified to a rectilinear movement of the moving part instead, while in the embodiment according to Fig. 8 a change in the other direction could take place.

It would also be possible to replace the diodes shown above with other elements which have the ability to block in at least one direction in accordance with what has been said previously.

It is also pointed out that it is per se conceivable to design the two switches of the transfer switch in different ways, such as one with three fixed contacts and two semiconductor elements according to Fig. 1 and the other with two fixed contacts and a semiconductor element according to the lower part of Figs. 1 without, for example, the contact 12 and the semiconductor element 18, in which case, for example, the requirement for speed is set differently depending on the direction in which the switch is operated.

Most often, however, the two couplers should be designed equally. Possibly the electrical quantities, such as voltage and current, would have slightly different levels of, for example, a backup supply and therefore the couplers could be slightly differently designed.

Furthermore, it has been shown above how the "second measurement" has been connected, ie the second coupler has been closed, only after the first supply has been completely disconnected, but it would be quite possible to design the transfer switch so that the second supply is already connected before the first supply is completely disconnected, ie the moving part then bridges the gap between the couplers. The patent claims are to be interpreted as including this case as well.

Claims (51)

: from 10 15 20 25 30 35 518 664 26. | o - n; Patent claims A transfer switch for alternating current comprising two electrical couplers (1, 2) arranged to establish and break a current path between a load (3) and each alternating current supply (5, 6) for transmitting the supply of the load with electric power from one the AC power supply to the second, each coupler comprising two branches connected in parallel in a current path, the first of the branches comprising a first connector (4, 10) with two relative to each other for opening and closing movable contacts (4, 10) and the second comprising an element (15) capable of blocking current therethrough in at least a first blocking direction and conducting current therethrough in at least one direction, a second connector (4, 11) having two relative to each other for opening and closing movable contacts (4, 11 ) is connected in series with the element, and wherein the transfer switch comprises a unit (20) arranged to control the opening of said current path through the coupler which is closed by controlling it. the first connector of this coupler to open for transmitting the current to the element when it is in or on its way into the conducting state and then the second connector to open when the element is in a state of blocking current through it for breaking of the current through the coupler and the second electrical coupler to be closed, characterized in that it comprises at least one movable part (4) and that the unit (20) is arranged to control this part to perform a single mechanical movement to open the two connectors at the first coupler and disconnect the two connectors of the second coupler. Transfer switch according to claim 1, characterized in that each coupler comprises at least two contacts (10, 11) arranged one after the other along the path of the movable part for said mechanical movement, that the movable part (4) is arranged to be in the respective coupler closed states form a galvanic connection between said two contacts, that each coupler is arranged to be connected via one (10, 13) of the contacts and the movable part in a current path leading through the coupler, that at the respective cup coon »10 15 20 25 The element (15) connects the two contacts to each other, and that the control unit is arranged to control the opening of the current path through the respective coupler by controlling the movable part (4) to move along such path and in such a direction that first the galvanic connection between one (10) of said two contacts and the movable part is broken to open the first connector and then the galvanic connection between the second (11) of said two contacts and the movable part is broken to open the second connector. Transfer switch according to claim 1 or 2, characterized in that at least one of said couplers comprises at least three contacts (24-26) arranged successively with the path of the movable part for said mechanical movement, and that the element (29) thereof couplers connect a first and a second adjacent of these three contacts to each other. A transfer switch according to claim 3, independently of claim 2, characterized in that the movable part is arranged to form a galvanic connection between said three contacts (24-26) in the closed state of said at least one coupler, and that the control unit (20) is arranged to control the moving part to move along such a path in order to break the current through this coupler and in such a direction that first the galvanic connection between the first contact (25) is most distant from the third of the contacts and the other two contacts are broken to open the first connector and then the galvanic connection between the second (26) and third (24) contacts is broken to open the second connector. Transfer switch according to one of Claims 1 to 4, characterized in that the element is a semiconductor element (15), and in that the unit (20) is arranged to control the first connector to open when the semiconductor element is in or on a wave into a conducting state. Transfer switch according to claims 3 and 5 or 4 and 5, characterized in that said at least one coupler comprises at least two said semiconductor elements (15-18, 39, 40) connected between each along the path of movement of the movable part (4) external contact and a contact closest to the latter, that the movable part is arranged to form in the closed state of this coupler a galvanic connection between all the contacts between and including said external contacts, that this coupler comprises means (19) for sensing the direction of the current through the coupler in the closed state, and that the control unit (20) is arranged to, on the basis of information from said sensing means when breaking the current through the coupler, control the moving part to move in either direction. along its path of movement to open the first contact by breaking the galvanic connection between a first external contact and a first adjacent contact. open and then open the other connector by continuing to move 7. Transfer switch according to claim 6, independent of claim 2, characterized in that the at least one coupler is arranged to be connected via said two external contacts (34, 37) in a current path leading through the coupler, that the contacts along the movable part ( 4) the path of the mechanical movement of this coupler is four in number, that in each coupler the semiconductor elements (39, 40) are arranged to block against current thereby either both to or both from the respective external contact (34, 37), and to control the unit is arranged to control the movable part so that after opening the first connector the galvanic connection between said first adjacent contact (35) and the contact (36) adjacent to the second outer contact is broken to open the second connector. 8. A transfer switch according to claim 6, independently of claim 4, characterized in that in said at least one coupler the contacts arranged along the path of movement of the movable part (4) are three in number (9-11), that this coupler is arranged to via the middle contact (10) and the movable part be connected in a current path conducting through the coupler, that one semiconductor element (16) is arranged to block against current thereby to the other 10 15 20 25 30 35 518 664 29 ø no a. the middle contact and the second (15) to block against current therethrough from the middle contact, and that the control unit is arranged to control the movable part so that after the opening of the first connector of this coupler the galvanic connection the part between the first outer contact (11) and the movable part (4) is broken to open the second connector. Transfer switch according to Claim 2 or 8, characterized in that the movable part (4) is connected to the load (3). Transfer switch according to one of Claims 3 to 7, characterized in that the two couplers have a common contact (24) along the path of movement of the movable part, so that the contacts along this path of movement on one side of the common contact belong to a first of the couplers and those on the other side of the couplers, and that the common contact is arranged to be connected to the load (3). Transfer switch according to one of Claims 1 to 10, characterized in that the control unit is arranged to control the movable part (4) along a substantially rectilinear path of movement along which the connectors of the two couplers are arranged. Transfer switch according to one of Claims 1 to 10, characterized in that the control unit is arranged to control the movable part (4) along a substantially circular arc-shaped path of movement along which the connectors of the two couplers are arranged. Transfer switch according to claim 12, characterized in that the two couplers (1, 2) are arranged substantially 180 ° offset relative to each other along said arc of a circle. Transfer switch according to claim 12, characterized in that the two couplers (12) are arranged offset relative to each other along said circular arc at an angle between 100 ° and 140 °, preferably substantially 120 °, and that a rest position for the movable part (4 ) with both measurements separated relative to the load is: anno 10 15 20 25 30 35 518 664 30 arranged along the portion of the arc of the circle where the angular distance between the two couplers is greatest. Transfer switch according to any one of claims 12-14, characterized in that the movable part is rigidly connected to a shaft (8, 32), and that the control unit is arranged to control a drive device to drive the shaft for moving the movable part along said path. Transfer switch according to one of Claims 11 to 15, characterized in that it comprises a first piece (31) rotatably received in a second piece (33), and in that the movable part (4) is arranged on one of the pieces and contacts of the two couplers along said path of movement are arranged on another of the pieces. Transfer switch according to Claim 16, characterized in that the two pieces (31, 33) through the contacts each form in whole or in part a cylinder with the height and diameter thereof adapted to the operating current through the respective coupler in the closed state and the voltage it has to hold. the open state. Transfer switch according to Claim 16 or 17, characterized in that the movable part (4) is arranged on the first piece (31), and in that a motor (41) is integrated in the pieces in order to drive them to rotate relative to one another. Transfer switch according to any one of the preceding claims, characterized in that it comprises means (19) arranged to substantially continuously sense the direction and magnitude of the current through the coupler which is currently closed and to transmit information thereon. to the control unit (20). Transfer switch according to any one of the preceding claims, characterized in that at least one of said couplers comprises several series-connected said elements (44-46) arranged to together hold a voltage across this coupler in the blocking state. Inna: 10 15 20 25 30 35 518 664 31 21. A transfer switch according to any one of the preceding claims, characterized in that at least one of the couplers comprises several elements (44-46) connected in parallel arranged to together take care of the current through that coupler when opening the first connector. Transfer switch according to any one of the preceding claims, characterized in that a voltage limiting device (47) is connected in parallel with the element (48), and that said device is arranged to start conducting at a voltage above it in the vicinity of the maximum voltage resistance of the element. . Transfer switch according to claims 20 and 22, characterized in that each element has its own said voltage limiting device (47) connected in parallel with it for substantially even distribution of the voltage over the series connection of elements on the individual elements. Transfer switch according to Claim 22 or 23, characterized in that the voltage limiting device is a varistor. 25. A transfer switch according to any one of the preceding claims, characterized in that at least one of the couplers comprises means arranged to act on raising the voltage when separating two contacts in connection with opening of the first contactor. 26. A transfer switch according to claim 25, characterized in that said means comprises several series-connected first connectors arranged to be opened substantially simultaneously for transmitting the current to the element. Transfer switch according to claim 25 or 26, characterized in that said means comprise an element (59) arranged to increase the resistance between said two contacts (56, 58) at the initial 10 15 20 25 30 35 518 664 32 ø w | n. now of said separating them while allowing a current between these contacts therethrough. A transfer switch according to claim 25 or 26, characterized in that said means is formed by a contacts included in the first connector having at least a part of ablating material arranged to be heated and evaporated into gases for gas blowing on an arc when separating two contacts when opening the first connector. Transfer switch according to Claim 5 or 5 and one of the preceding claims, characterized in that the semiconductor element of at least one coupler is a diode. Transfer switch according to claim 5 or claim 5 and any one of claims 1-29, characterized in that at least one semiconductor element of one coupler is controllable. Transfer switch according to Claim 5 or 5 and one of Claims 1 to 29, characterized in that the semiconductor element of at least one coupler is extinguishable. Transfer switch according to Claim 30, characterized in that the semiconductor element of at least one coupler is a thyristor. Transfer switch according to Claim 31, characterized in that the semiconductor element of at least one coupler is bidirectional, i.e. can block and lead in both directions. Transfer switch according to claim 5 or claim 5 and any one of the preceding claims, characterized in that the semiconductor element of at least one coupler is of a material with an energy gap between valence band and lead band exceeding 2.5 eV, such as SiC and diamond. 10 15 20 25 30 35 518 664 33 Transfer switch according to one of the preceding claims, characterized in that the system voltage at which its two couplers are designed to operate is between 1-52 kV. Transfer switch according to one of the preceding claims, characterized in that its two couplers are arranged to withstand at least one operating current of 1 kA, preferably at least 2 kA, in their closed state. Transfer switch according to one of the preceding claims, characterized in that one, the first of the switches is arranged to be connected to an ordinary AC supply and to be closed in the normal state of the transfer switch, and that the second switch is arranged to be connected. to a backup feed and in the normal state be open. Transfer switch according to one of the preceding claims, characterized in that it has a rest position for the movable part (4) with the two couplers (1, 2) opened and the load separated from both measurements. A transfer switch according to any one of claims 1-36, characterized in that it comprises means (56) arranged to continuously or intermittently determine which of the two feeds is currently most suitable for the load, and that the control unit (20) is arranged controlling, on the basis of information from said means, said movable part (4) for transferring the measurement of the load from one alternating current supply to the other if the alternating current supply connected to the load at this time does not correspond to said most suitable supply. Use of a transfer switch according to any one of the preceding claims for connecting electrical equipment to an AC mains supply via two different current paths, first the first for starting the electrical equipment via closing the first (2) of the couplers and then the second for operation of this equipment by opening the first coupler and closing the second (1). rann »10 15 20 25 30 35 518 664 34 Use according to claim 40, characterized in that the first current path has a current limiting function. Use according to Claim 41 or 42, characterized in that the transfer switch is arranged for starting an electric motor (49) connected to an AC mains (50). Use according to Claim 42, characterized in that the transfer switch is used for starting the motor (49) by first connecting the motor to the AC mains via the first switch via a reactor (51) and then connecting the motor directly via the second switch. to the AC mains. Use of a transfer switch according to any one of claims 1-39 for connecting a backup alternating current supply to said load in the event of a power failure or failure of the ordinary alternating current supply. Use of a transfer switch according to any one of claims 1-39 in switchgear for power supply in industry or at distribution networks or transmission networks. Use of a transfer switch according to any one of claims 1-39 for switching on and disconnecting a device for reactive power compensation relative to an alternating voltage line. Use according to claim 46, characterized in that a connector of each of the two parallel-connected branches is intended to be connected to the alternating voltage line and the two other connectors of these branches are intended to be connected to components included in the device (60). for reactive power compensation. Use according to Claim 46 or 47, characterized in that the coupler is used for connecting and disconnecting capacitors (60) to the alternating voltage line. Ilußu 10 15 20 518 664 35 A system for a multiphase network with a plurality of transfer switches according to any one of claims 1-39, one for each phase, characterized in that the transfer switches are controllable independently of each other. 50. Switchgear for power supply in industry or at distribution networks or transmission networks, characterized in that it includes a transfer switch according to any one of claims 1-39. 51. A method of transferring a supply of a load of alternating current from one alternating current supply to another by opening a current path between a first alternating current supply and the load through a first electrical coupler and then closing a current path between a second alternating current supply and the load through a second electrical coupler, wherein an ordinary current path through the first coupler is opened and the current is transferred to a temporary current path through an element capable of blocking current therethrough in at least a first blocking direction and then the temporary current path is broken and thereby the current through it the first coupler is broken, and the second electrical coupler is closed, characterized in that one and the same movable part (4) opens the ordinary and the temporary current path and closes the current path through the second coupler by performing a single mechanical movement.