DESCRIPTION

Technical Field

The present invention relates to the field of the electrical power transmission in power generation, conversion, and supply systems; more in particular, the object of the invention is a relay for safely disconnecting two subsequent units, such as preferably an inverter-based unit for power conversion and the distribution network or home network to which the conversion unit is connected.

State of the Art

As it is well known, in many power generation systems, such as the photovoltaic systems, DC is generated in a photovoltaic first unit, is subsequently transformed in AC via a conversion second unit such as an inverter, and is then supplied from the inverter to the grid, for instance a three-phase grid.

For reasons of operation, it shall be possible for the power generation system to be disconnected from the grid safely and reliably. To this end, a redundant number of disconnection relays is arranged downstream of the power conversion section, so that a second relay can operate in case a first relay fails.

A relay is a controlled device for reversibly interrupting the electrical power continuity of the line on which it is placed. A relay comprises, in its basic configuration, a box-shaped casing with a pair of terminals exiting from it and internally connected via a track along which a controlled switch is arranged; the terminals shall be connected with the two ends of the line disconnectable by the relay. The inner switch is comprised of a pair of opposite contacts defined along the line (and practically being the ends of the line interruption) and of an electrically conductive body moved by an actuator, usually an electromagnetic solenoid actuator, to connect/disconnect the two opposite contacts/ends of the switch; associated with the actuator there is a pair of further terminals, exiting from the box-shaped casing and controlling the actuator, supplying current to the solenoid windings.

There are relays with only one pair of terminals for the connection to the line to be disconnected; they are usually called single-contact relays (i.e. there is only one line with a single switch provided with only one pair of contacts). Multi-contact relays are also well known. They comprise a plurality of pairs of terminals for the connection to the various lines that must be simultaneously disconnected. Inside the casing a switch is arranged on each line connecting a respective pair of terminals.

The switch actuator is common to all the switches of the relay. Practically, to the body of the actuator slider are fixed all the bodies or bridges, constituting the connection or disconnection elements of the switches. Therefore, the movement of the single actuator connects or disconnects the ends of all the relay switches contemporaneously.

As mentioned above, it shall be possible for the power generation systems to be disconnected from the grid in a safe and reliable manner, hence a redundant number of disconnection relays is provided. According to a known and particularly used first configuration, each line to be disconnected has a pair of relays connected in series and controlled contemporaneously. In this way, if a relay fails and is not able to work, the other relay can disconnect the line.

From a practical viewpoint, to disconnect, for instance, an inverter from a three-phase grid, six single-contact relays are arranged on an adequate board, each pair of relays is connected in series, the input of one pair is connected with the output of the inverter and the output of the other pair is connected with the respective grid phase. Furthermore, the terminals of the six actuators shall be connected to the electronic board managing the operation thereof.

Obviously, all these connection operations entail waste both of time and resources. Furthermore, the relay arrangement is particularly bulky, and this contrasts with the current industrial needs to limit the dimensions of the various power conversion units.

According to a more compact solution, two multi-contact relays are used (for the three-phase, three pairs of terminals for each relay), connected in series at the respective output and input terminals of corresponding pairs, so as to obtain three independent lines.

Also this relay arrangement, even if allows a reduced bulk and a lower number of connections of the switch actuators than in the case with single-contact relay, is not completely satisfactory.

The patent application No. US 2010/0226160 discloses another solution, aiming at further reducing bulk. It discloses two alternate arrangements of three double-contact relays connected to one another so that each relay disconnects two lines. If a first relay fails, a second relay can therefore disconnect the remaining line. In this system the relay number is lower than in the case of the three pairs of single-contact relays; however, a careful connecting step for the various components is required, as well as adequate space to arrange the relays according to the connections.

Object and summary of the invention

The main object of the present invention is to provide a safe disconnection relay allowing the drawbacks of the known relays to be solved.

With reference to this main object, a further important object of the present invention is to provide a particularly compact safe disconnection relay.

Another important object of the present invention is to provide a safe disconnection relay allowing to reduce the installation times with respect to the known relays.

These and other objects, that will be better described below, are achieved through a safe disconnection relay comprising

- an outer box-shaped casing;

- at least one pair of electrical terminals exiting from said box-shaped casing for connecting the relay to the circuit in which it must operate;

- inside the box-shaped casing, a line for connecting the electrical terminals of said pair;

- inside the box-shaped casing, a switch arranged along the connection line to allow the interruption thereof;

- again inside the box-shaped casing, a switch control actuator.

The relay according to the invention comprises a further actuator for a further switch inside the box-shaped casing arranged along the line to allow the interruption thereof.

The relay according to the invention can be a single-contact relay, i.e. a relay with a single connection line and a single switch, or a multi-contact relay, i.e. with more connection lines provided with respective switches, all associated with a single common actuator. Both in the case of a single-contact relay and in the case of a multi-contact relay, according to the invention a further actuator controls one switch (in the case of single-contact relay) or more redundant switches (in the case of multi- contact relay) each arranged on a respective line. All this arrangement is contained inside a single dimensionally optimized box-shaped casing; from it only the necessary terminals exit for the connections of the system in which the relay shall be arranged to interrupt one or more lines. The relay according to the invention is practically a "customized" relay performing a superabundant interruption thanks to the presence of a second actuator for a second group of switches, all packed tight in a single box-shaped casing that can be dimensioned as small as possible, maintaining, if necessary, standardized positions and distances for the terminals connecting to the external lines and to the actuator control board.

The relay according to the invention is practically a "ready-to-use" relay when superabundant disconnections are required.

According to a preferred embodiment, the relay comprises a plurality of pairs of electrical terminals, exiting from the box-shaped casing, and a corresponding plurality of lines for connecting said pairs, one line for each pair. On each line a pair of switches is arranged in series. The invention provides for two single actuators, each of which simultaneously controls a respective group of switches arranged on different connection lines, practically obtaining a multi-contact superabundant relay.

In general, actuator means any device able to put into contact the contacts/ends of a switch; in the present description the meaning of actuator is not limited to a mechanical actuator driven by an electromagnetic force. However, in a preferred embodiment the two actuators in the box-shaped casing are electromagnetic, preferably solenoid actuators.

According to an advantageous preferred first embodiment of the invention, the two actuators are independently powered; from the box-shaped casing exit therefore two pairs of power terminals for the actuators, one pair for each actuator, shaped and spaced preferably according to standard configurations.

According to an advantageous second embodiment of the invention, two control actuators have at least one common supply polarity; from the box-shaped casing can therefore exit two or three power terminals for the actuators.

According to a particularly advantageous embodiment of the invention, an external electrical terminal of the relay and the corresponding segment of the line connecting an end of a respective switch are substantially produced in a single piece, at least up to the respective opposite contact areas of the switches; this greatly simplifies the production of the relay and allows particularly compact configurations.

Again to optimize the compactness and simplify the production, on each connection line (or on the only connection line, in the case of a single-contact relay) associated with a pair of terminals outside of the box-shaped casing, the line segment connecting the ends of the two respective switches arranged in series along the same line is made "continuous", i.e. without intermediate joining point. This segment is more preferably a single piece, at least up to the respective opposite contact areas of the switches, where there can be, if necessary, contact plates or special coatings.

In a preferred embodiment of the invention, at least one part of the housing for at least one actuator, and preferably for both the actuators, is defined on the outside of the casing. This allows to maximize the relay compactness and to increase the sturdiness thereof. More preferably, also at least one part of the housing for one or more switches is defined on the outside of the casing.

The box-shaped casing can be comprised of more parts, and the housings for the actuator/s and for the switches can be obtained on common or distinct parts of the casing.

According to an embodiment, each terminal for the connection to the circuit, in which the relay must operate, is produced in a single piece with the respective end segment forming an end of a respective inner switch, in the form of an elastically flexible element suitable to be flexed by one of the two actuators towards the opposite end of the switch to obtain the closure of this latter; the respective intermediate segment between two switches of a same line is preferably in the shape of U-shaped element, whose lateral arms define the contact ends of the switches; in the area between the wings there is preferably a separating bulkhead. In this embodiment, the actuators are preferably arranged at opposite sides with respect to the area occupied by the intermediate segments between the switches; more preferably, each actuator provides for a movable slider interacting with a plate able to oscillate to push and flex the end closing segments of the switches.

A further object of the present invention is a power generation system, preferably a photovoltaic system with a generator, a DC-AC current converter (such as preferably an inverter) connected to an electrical line, where there is a relay according to one of the embodiments described above.

A further object of the present invention is an inverter with a relay, according to one or more of the embodiments described above, housed inside its casing or on an adequate space provided on the inverter itself. Obviously, a relay according to the present invention can also be used in different fields than that of power generation, every time it is necessary to obtain a safe and reliable disconnection from the line.

Brief description of the drawings

Further characteristics and advantages of the invention will be more apparent from the description of some preferred, although not exclusive, embodiments, illustrated by way of non limiting example in the attached tables of drawings, wherein:

figure 1 shows the diagram of a power generation system where a relay according to the invention is arranged to disconnect an inverter from a distribution network or home network;

figure 2 shows the diagram of a first embodiment of a relay according to the invention;

figure 3 shows the diagram of a second embodiment of a relay according to the invention;

figures 4a, 4b, and 4c show a third schematic embodiment of a relay according to the invention, according respectively to a plan section according to the line b-b, a side section according to the line a-a- and a bottom plan view;

figures 5 a and 5b show a fourth schematic embodiment of a relay according to the invention, according to respectively a side section along the line b-b- and a plan section along the line a-a.

Detailed description of an embodiment of the invention

With reference to the previously cited figures, analogous components of different embodiments will be cited with the same reference number.

As shown in figure 1, in the described examples a relay according to the invention is inserted in a power generation system comprising a generator G connected to a unit for converting DC into three-phase AC, such as an inverter I, which is in turn connected to a three-phase grid R; a relay according to the invention is used to disconnect the output of the inverter I from the input of the grid R; it is preferably housed inside the space Γ defined inside or onto the inverter casing. The relay may also be arranged outside of the inverter in other embodiments.

With reference to figure 2, a relay 10 according to the invention comprises an outer box-shaped casing 11, inside which there are three distinct electrical power lines 12 (indicated respectively with 12A, 12B, and 12C) between respective electrical terminals 13' and 13" (more in particular between the pairs of terminals 13A'-13A", 13B*-13B", 13C-13C") exiting from the casing 1 1, for instance for the connection to the output of the inverter I and to the input of the three-phase grid R.

On each line 12 there are two switches 14' and 14" (respectively 14A'-14",

14B'-14B") allowing the line to be disconnected.

Inside the box-shaped casing 11 there are also two independent actuators 15' and 15", each of which controls a respective switch 14 of a line 12. Practically, the first actuator 15' controls the group of the switches 14A', 14B', and 14C, and the second actuator 15" controls the group of the switches 14A", 14B", and 14C". The actuators 15' and 15" are preferably electromagnetic solenoid actuators, and have a moving rod, with which are associated the conductive bodies 16 (bridges) forming the connection of the ends/contacts 17 of the respective switch.

The actuators 15' and 15" are independently powered. Each actuator is connected to a pair of terminals 18'- 19' and 18"- 19" exiting from the box-shaped casing 11, and allows power connection, i.e. connection to an electronic board (not shown in the figures) allowing the operation thereof.

Figure 3 shows a relay variant, wherein the actuators 15' and 15" have a common supply polarity. There are preferably only three terminals 18', 19', and 19" for the connection to the power supply, that in this case is therefore common to the two actuators.

According to the preferred embodiment, on each line 12 the intermediate segment 12"' (i.e. 12A'", 12B'", 12C" respectively), connecting the ends of the two respective switches 14'- 14" arranged in series along the same line, is substantially continuous (i.e. devoid of intermediate joining points), preferably in a single piece, at least up to the respective opposite contact areas of the switches, where there can be elements for optimizing the electric contact between the two ends.

Analogously, also the two end segments 12' and 12" (i.e. 12A'-12A", 12B'- 12B", 12C-12C" respectively) of a line 12 connecting the outer terminals 13'-13" (13A'-13A", 13B'-13B", 13C-13C" respectively) to the ends of the two respective switches 14'- 14" arranged in series along the same line are continuous (i.e. they are devoid of intermediate joining points) and are preferably produced in a single piece. These segments are advantageously produced in a single piece also with the respective outer terminals 13'- 13".

Figure 4 shows a schematized embodiment of a relay according to the invention, wherein each actuator 15' and 15" has a rod 20, which can be linearly translated and with which bridges 16 A, 16B, 16C (respectively for each rod 16A'- 16B'-16 , 16A'-16B"-16C") are constrained to translate linearly; these bridges are able contemporaneously to put into contact two distinct ends of a switch 14, i.e. the parts of the external terminals 13 that are inside the box-shaped casing 11 (matching the end segments 12' and 12" of the lines 12) and the intermediate segments 12 A"', 12B'", and 12C".

The solenoid 21 moving the rod 20 is arranged above the same rod, and the solenoid slider 23 is cinematically connected to the rod 20 via a return 24, according to a known configuration, so that the motion of the slider 23, moved by the solenoid, moves the rod 20.

It should be noted that the box-shaped casing 11 is substantially comprised of two coupled semi-shells, respectively defining two housings, one upper housing 25 for the solenoid 21 and one lower housing 26 for the rod 20 and the switches 14. Between switches and solenoids there is a separating wall 27.

Figures 5a and 5b show a fourth embodiment of the relay according to the invention. In this case the switches 14 (i.e. 14A', 14A", 14B', 14B", 14C, 14C") comprise the end parts inside the casing 11 of the external terminals 13 (matching the end segments 12' and 12" of the lines 12) formed by flexible foils through the actuators 15, as shown in figure 5a. The intermediate segments 12A'", 12B'", and 12C" of the lines 12 A, 12B, and 12C are formed by U-shaped bodies, whose ends act as contact ends for the respective switches 14', 14". Between the arms of the U a separating bulkhead 28 is arranged, separating the two switches of a same line.

Each actuator 15', 15" comprises a solenoid 21 with wiper 23 connected to a plate 124 acting as a lever, which is in turn able to push the three respective end segments 12' and 12" to bend them and close the respective switch 14, according to a known configuration.

It should be noted that the box-shaped casing 11 is comprised, in this case, of a main shell 129 defining the housings 125 for the actuators 15', 15" and the switches 14, and a lid 130.

Obviously, the examples above can be combined together so as however to remain within the protective scope of the invention.

It is understood that what illustrated purely represents possible non-limiting embodiments of the present invention, which may vary in forms and arrangements without departing from the scope of the concept on which the invention is based. Any reference numbers in the appended claims are provided for the sole purpose of facilitating the reading thereof in the light of the description before and the accompanying drawings and do not in any way limit the scope of protection of the present invention.