CN102326309B - Electrical protection device and control method of the electrical protection device - Google Patents

Abstract

The invention relates to an electrical protective device (SCH) for being arranged between at least one load (V1, V2) and a power source, wherein the protective device (SCH) has a current-limiting function and a disconnection function. In this case, the protective device (SCH) is formed from a plurality of current-limiting or disconnecting protective elements (E1 . . . En) whose outputs are connected in parallel. Furthermore, the invention relates to a control method of an electrical protection device (SCH).

Description

Electric protection device and control method for electric protection device

technical field

The invention relates to an electrical protective device for being arranged between at least one load and a power source, wherein the protective device has a current limiting function and a disconnection function with an adjustable current limit value. Furthermore, the invention relates to a control method of an electrical protection device.

Background technique

Electrical protective devices are used everywhere where interference situations in electrical installations can lead to hazards for people and/or machines. Electrical protective devices are required in particular when a load or loads are supplied by means of a power supply. The electrical protective device is arranged between a power source and one or more loads in order to reduce the current through the one or more loads in the event of a disturbance and to open the circuit in the event of a persistent disturbance.

For example, DE 101 49 458 C1 shows a protective device between a DC source and a load. Here, two semiconductor switching elements are connected in parallel to increase the disconnection safety. Each semiconductor switching element is adjusted to half the maximum load current. As soon as one semiconductor switch is switched off, the entire load current flows through the other semiconductor switch, so that the other semiconductor switch is also switched off.

A protective device for AC applications is known from WO 96/14684 A1. The protective device here comprises two pairs of protective elements, which cause a disconnection in the event of a fault. Dividing into two protective element pairs is used to reduce the loop resistance of the protective device.

Especially in the case of power supplies for supplying a plurality of load branches, it is expedient to secure each load branch with an electrical protective device. If a disturbance occurs in a load branch, this load branch is current-limited or disconnected without endangering the power supply to the remaining load branches. In the absence of such protective precautions, a faulty load branch overloads the power supply in such a way that the set load current is exceeded. The power supply, especially the switching power supply (Schaltnetzteil), may then even be switched to current-limited mode if necessary and disconnected in the event of a persistent disturbance. All load branches are then current-free. This also occurs when the load at the output of the power supply is secured by means of a series-connected mechanical circuit breaker, since such circuit breakers require significant overcurrents for triggering. The power supply is often no longer able to supply this excess current in addition to powering the remaining load.

Such use of the electrical protective device described in the preamble entails that there must be said electrical protective device having different current limit values predetermined as tripping limits. Especially in the case of industrial plants it is a rule to supply a plurality of load branches of different powers with the aid of the power supply. Each load branch therefore includes an electrical protective device with a respectively different current limit value. It also occurs in the case of industrial plants, where there is only one load branch, which due to changing production conditions consists of one moment more and one moment less (einmal mehr und einmal weniger) load. In this case too, electrical protective devices with different current limit values must be used.

Electrical protective devices for power supplies with multiple load branches are known, for example, from WO 01/41277 A2 and EP 0933849 Al. For each load branch, evaluation or regulation electronics in the form of semiconductor switches with adjustment capabilities, current measuring elements and operational amplifiers are connected into the connecting line between the power supply and the load. The efficiency of the respective semiconductor switch is designed as a function of a defined nominal current. When a small load is connected, the triggering limit is adjusted to a value lower than the nominal current. This often leads to the unfavorable situation that the efficiency of the corresponding semiconductor switch and the corresponding driver circuit is not fully utilized. Such a solution therefore often leads to overdimensioning of the electrical protective device with poor cost-utilization relations.

Accordingly, electrical protective devices which are provided for the individual load branches are also known according to the prior art. Here, overdimensioning is prevented by offering a product series with fine nominal current grading. A corresponding electrical protective device with the required nominal current is thus connected in each load branch. The high warehouse management effort required is disadvantageous here.

Another known electrical protection device provides that a step-down converter is arranged in each load branch, which is switched on during normal operation and only clocked in a current-limited mode in the event of a fault. AT 504 528 A describes such a solution.

Contents of the invention

The invention is based on the object of specifying an improvement over the prior art for an electrical protective device of the type mentioned at the outset.

According to the invention, the object is solved by the independent claims 1 and 11 and by advantageous developments according to the dependent claims.

In this case, the protective device is formed from a plurality of current-limiting or disconnecting protective elements, and the current limit value is adjusted in such a way that in some protective elements the outputs are connected in parallel. In this way, a simple method of securing a load branch or a plurality of load branches with the respectively required current limit values is described. The corresponding current limit value is derived here from the sum of the partial current limit values of the protective elements connected in parallel on the output side.

The protective device according to the invention comprises, for example, a selectable number of protective elements, which in a summative manner bring about the required protective protection for the connected load, without being overdimensioned here. Furthermore, the protective device can be subdivided into a plurality of protective device blocks in order in this way to realize a plurality of separate safety channels operating in parallel for different loads or load branches. In this case, for different loads, a different number of protective elements are connected to one another on the output side. The respective interconnected protective elements form blocks which have the required protective protection for the respectively connected loads.

A corresponding control method provides that the protective element limits the current through the protective element when the associated predetermined partial current limit value is reached until a critical parameter of the protective element exceeds a predetermined maximum value and the protective element is disconnected. In normal operation, therefore, the load current through the protective elements connected in parallel is always divided in such a way that no current greater than the partial current limit value flows through any of the protective elements. When the partial current limit value of the protective element is reached, the current through the protective element is reduced. The current through the remaining protective elements connected in parallel to this protective element increases to the same extent. In this way the tolerances of the individual protective elements are balanced.

An advantageous refinement of the invention provides that each protective element has a fixed partial current limit value, so that the protective elements are simple to construct and thus inexpensive to manufacture.

It is advantageous here if the current limiting value of the protective device or of the protective device block is designed as the sum of equally large partial current limiting values of parallel-connected protective elements. Different protective devices or protective device blocks with optionally graded current limit values are thus formed by means of protective elements of the same design. With only one protective element embodiment, it is possible to secure load branches with a maximum different power without overdimensioning the protective device.

A simple embodiment is embodied in such a way that the protective elements of the protective device are connected on the output side by means of connecting combs. Expensive wiring in the distribution box is thus dispensed with.

Advantageously, the connecting comb is welded to the output ends of the protective element, so that a reliable and predictable (berechenbar) contact is provided between the individual output ends of the protective element.

Furthermore, it is advantageous if the connecting combs between the protective elements each have at least one manually detachable separation point, in particular a rated breaking point. The protective device here comprises a preselectable number of protective elements, which are already connected on the output side. During installation, the protective device is divided into a plurality of protective device blocks as required by interrupting a connection or connections between two protective elements in each case. In this case, each of the resulting protective device blocks includes a plurality of protective elements, which are required for securing the connected load branch.

In an advantageous variant, the connecting combs between the protective elements each have a bulky separating part which can be manually detached from the connecting combs. To separate the comb, the separating part is removed, wherein the bulky shape prevents the separating part from falling unintentionally through the ventilation hole into the adjacent device housing.

It is also advantageous if a marking is provided below the separation point or the separating element, wherein the marking becomes visible after the separation process and indicates that the comb has separated.

Another embodiment provides that the protective device is integrated into the power source. This additionally simplifies the installation, in particular in the distribution box.

In a development of the invention, each protection element comprises a drive unit and a current limiting element with a variable loop resistance. In this case, the circuit resistance (Druchgangswiderstand) is determined by means of the drive unit as a function of the current flowing through the current-limiting element. The control then takes place, for example, in such a way that the conduction path of the protective element that reaches the partial current limit becomes slightly more ohmic. In this case, the regulating (abregelnd) protective element is designed with only so many (soviel mehr) resistors that the tolerances of the protective element are compensated.

In a further development of the control method it is provided that a voltage is detected at each output of the protective element and that when a predetermined voltage drop value is reached, the associated protective element limits the passage of the protective element for a predetermined limiting time interval. current, and the protection element trips after the expiration of this limiting time interval. The time-limiting elements are therefore activated only after a clear drop in the voltage at the outputs of all parallel-connected protective elements, so that slight disturbances or uneven distribution of the load current do not lead to a tripping.

Here, it is also advantageous if, after disconnection, all protective elements are reset as soon as a predetermined switch-off time interval has expired and/or a critical parameter of the respective protective element falls below a predetermined switch-on value . For example, all time-limiting elements are reset, so that all protection elements assume the same output state again independent of the momentary switching state. As a result, any protective element outputs can be interconnected and reactivated by a common reset.

Advantageously, the chip temperature of the respective protective element is detected as a critical parameter. This ensures that the protective device or the associated protective device block is only disconnected when the thermal load becomes too great due to the control process.

The invention is explained below by way of example with reference to the drawings. Schematically:

Figure 1 shows the circuit structure of a protective device with two load branches,

Figure 2 shows the connecting comb with the separation point.

Detailed ways

FIG. 1 shows a protective device SCH with a plurality of protective elements E1 . . . En. In this case, initially three protective elements E1, E2, E3 are combined to form a first protective device block B11 and the remaining protective elements E4...En are combined to form a second protective device block B12. The first load or load branch V1 is connected to the supply voltage U of the power supply via the first protective device block B11 and the second load or load branch V2 is connected to the supply voltage U of the power supply via the second protective device block B12.

Each protection element El...En includes a current limiting element Tl...Tn and a current detection unit I1...In. The corresponding current-limiting elements T1 . . . Tn are designed, for example, as transistors and the corresponding current detection units I1 . . . The current flow through the current-limiting elements Tl...Tn is controlled in dependence on the respective detected currents by means of corresponding drive units A1...Tn. Partial current limit values are predetermined for each drive unit A1...An. The partial current limit values of the protective elements E1, E2, E3 or E4 . The drive unit Al...An is designed either analogously or as a microcontroller.

For fire protection reasons, another fuse Sl...Sn is connected upstream of each current limiting element Tl...Tn. These are either fuses or circuit breakers.

The operating principle of the protective device SCH is explained on the basis of the first protective device block B11. The load or load branch V1 is connected to the output terminal K11 of the block B11. If the connection on the output side takes place by means of the connection comb Ka, the two further output terminals K12 , K13 remain free. In this case, the first connecting comb section Ka1 is connected to the output of the first block B11 and the second connecting comb section Ka2 is connected to the output of the second block B12. As an alternative thereto, the connection on the output side can take place via the corresponding terminals K11, K12, K13 or K14 . . . K1n by means of bridges.

In the case of a connection using the connecting comb Ka, each output terminal K11 . . . K1n must be designed for the largest possible current limit value. In normal operation, the load current drawn by the load or load branch V1 will not reach the current limit value of block B11. Then the load current is divided into three protection elements El, E2, E3 according to the loop resistance. Tolerances can cause the protective element El or E2 or E3 to reach part of its current limit value here. The associated drive unit A1 or A2 or A3 then reverses the current flowing through the protective element E1 or E2 or E3 so that correspondingly more current flows through the other two protective elements E1 , E2 or E2 , E3 or E1 , E3 . In order to utilize the maximum available efficiency of the current-limiting elements T1, T2, T3 with this different power division of the individual protective elements E1, E2, E3, the chip temperature of the corresponding current-limiting elements T1, T2, T3 be considered. If the maximum chip temperature of the protective element E1 or E2 or E3 is reached, the protective element is disconnected. Therefore, the protective elements E1, E2 or E2, E3 or E1, E3 connected in parallel must bear the overload. These protection elements also trip when the maximum permissible chip temperature is exceeded.

As an alternative to chip temperature detection, overloading is permitted only for the duration of a predetermined time interval. In this case, the time-limiting element can only be activated after a definite drop in the voltage at the output of the parallel-connected protection units E1 , E2 , E3 . In this case, the output voltages of the individual protective elements can be sampled sequentially by means of a superordinated control unit, since this control unit does not know which protective elements E1 . . . En are connected in parallel. The thermal load of the current limiting elements T1, T2, T3 is deduced from the output voltage.

Only thereafter, after the expiry of a defined effective limiting time during which the load voltage has effectively been reduced, is the relevant block B11 disconnected, for example by means of a higher-level control unit Signals are sent to drive units A1, A2, A3. During the subsequent switch-on process, the cooling time to limit the temperature of the components should be taken into account. In this case, all time-limiting elements are reset, for example by means of a manually triggered reset. The reset is inhibited for such a long time until either the predetermined off-time expires or the critical parameter falls below the predetermined on-value.

A further embodiment provides that the voltage drop at the respective current limiting element T1 , T2 , T3 is detected.

In addition, the ambient temperature can be detected when a specific time interval is specified for the current limitation. The permissible load duration is extended at lower ambient temperatures. However, the ambient temperature is already taken into account when detecting the corresponding chip temperature.

For a safe and predictable connection at the output of the protective elements E1 . . . En it is expedient to provide a connection comb Ka. Such a connecting comb is shown in FIG. 2 and is electrically conductively connected to the outputs of the protective elements ( E1 . . . En) by means of corresponding connections. Advantageously, this is achieved by soldering corresponding solder lugs into the printed circuit board LP. Each solder lug is connected here to an output of the protective element. With such a connecting comb Ka, there is a correspondingly large line cross section between the individual protective elements E1 . . . En, so that a large number of protective elements El . . . En can be connected in parallel. Furthermore, the installation effort is significantly reduced, especially if a manually detachable breaking point Br, preferably designed as a rated breaking point, is provided between the protective elements El...En. Depending on the load to be connected or the load branch V1 , V2 , the connecting comb Ka is interrupted at such a separation point Br, so that the connecting comb Ka is divided into a plurality of connecting comb segments Ka1 , Ka2 .

Furthermore, the connecting comb Ka has, for example, a separating part TS which allows torque to be introduced in the region of the separating point Br. By twisting the relevant separating part TS multiple times, work hardening takes place in the region of this separating point Br and subsequently the desired fracture on both sides of the separating part TS. It is also possible to implement the separating part TS only as a removable part. In each case it should be ensured that the separating part TS is dimensioned accordingly so that it does not fall unintentionally through the ventilation openings of the device housing. This can be achieved, for example, in that the separating part TS is designed as either a larger flat part or a larger curved part compared to the other line cross sections. Furthermore, the connection comb Ka can be covered with colored markings. The markings are released when the separating part TS is removed in order to clearly indicate which protective elements E1 . . . En are connected to one another or separated from one another.

In this embodiment it can be ensured that the connection comb is only accessible when the protective device is de-energized. For this purpose, for example, a cover is provided which can only be opened when the protective device is disconnected. As an alternative, the connection combs are implemented partially insulated.

Claims (14)

1. for being arranged at least one load (V1, V2) electrical protective device (SCH) and between power supply, wherein said protective device (SCH) has current-limiting function with adjustable current limit value and cut-out function, it is characterized in that, protective device (SCH) is made up of the protection component (E1...En) of multiple current limliting and open circuit, wherein each protection component (El... En) includes current limiting element (Tl... Tn), current detecting unit (I1... In) and driver element (Al... An), and described current limit value is adjusted in the following manner, namely in a part for protection component, output is in parallel, its mode is, the protection component (E1...En) of protective device (SCH) connects by connection comb (Ka) at output end.

2. according to the electrical protective device of claim 1, it is characterized in that, each protection component (E1...En) all has fixing portion of electrical current limiting value.

3. according to the electrical protective device of claims 1 or 2; it is characterized in that; protective device (SCH) or protective device block (Bll; Bl2) current limit value is configured to the identical large portion of electrical current limiting value sum of protection component in parallel (E1...En); wherein said protective device is divided into multiple protective device block as required, and wherein said protective device block is formed by the interconnective protection component of output end.

4. according to the electrical protective device of claim 1 or 2, it is characterized in that, connect comb (Ka) and weld with the output of protection component (E1...En).

5. according to the electrical protective device of claim 1 or 2, it is characterized in that, the connection comb (Ka) between protection component (E1...En) has at least one respectively can the burble point (Br) of manual separation.

6. according to the electrical protective device of claim 5, it is characterized in that, the connection comb between protection component (E1...En) has the separation member formed bulkily respectively, and described separation member manually can be isolated from connection comb.

7. according to the electrical protective device of claim 5, it is characterized in that, under burble point or separation member, settle mark, this mark shows that comb is separated.

8. according to the electrical protective device of claim 6, it is characterized in that, under burble point or separation member, settle mark, this mark shows that comb is separated.

9. according to the electrical protective device of claims 1 or 2, it is characterized in that, protective device (SCH) is loaded in power supply.

10. according to the electrical protective device of claims 1 or 2; it is characterized in that, each protection component (El... En) comprise driver element (Al... A2) and have variable loop resistance current limiting element (Tl... Tn) and by driver element (Al... An) according to flowing through the electric current determination loop resistance of current limiting element (Tl... Tn).

11. according to the control method of the electrical protective device of one of claim 1 to 10; it is characterized in that; when reaching distributed portion of electrical current limiting value given in advance; the electric current of protection component (El... En) described in protection component (El... En) restricted passage, until the critical parameters of protection component (El... En) exceed maximum given in advance and protection component (El... En) open circuit.

12. according to the control method of claim 11; it is characterized in that; voltage is detected and when reaching voltage drop value given in advance at each output of protection component (El... En); for binding hours interval given in advance; the electric current of relevant protection component (El... En) restricted passage protection component (El... En), and protection component (El... En) open circuit after binding hours interval expires.

13. according to the control method of claim 11 or 12; it is characterized in that; once turn-off time interval given in advance expires and/or the critical parameters of corresponding protection component (El... En) drop under connection value given in advance; after open circuit, all protection components (El... En) are resetted.

14., according to the control method of claim 11, is characterized in that, the chip temperature of corresponding protection component (El... En) is detected as critical parameters.