CIRCUIT BREAKER AND METHOD FOR OPERATION THEREOF

Abstract

A circuit breaker having, in a current path, a switching device having a thermal and/or magnetic tripping device for interruption of a current circuit having the current path comprehensive in an event of overcurrent or short-circuit, wherein a functional component of the switching device connected into the current path is bridged by means of a bypass which carries the load current detected by means of a current sensor when the current is below a current threshold, and is shut off when the current threshold is exceeded.

Claims

1. A circuit breaker comprising: an input terminal; a load terminal; a switching device arranged in a current path between the input terminal and the load terminal, the switching device having a thermal and/or magnetic tripping device for an interruption of a current circuit, which comprises the current path, in an event of an overcurrent or a short-circuit, wherein a functional component of the switching device is connected in the current path and is bridged via a bypass, which carries a current detected via a current sensor when the current is below a current threshold and is shut off when the current threshold is exceeded, and wherein the current and/or voltage supply of the switching device and/or of the control circuit is provided via a function component based on a principle of energy harvesting.

2. The circuit breaker according to claim 1, wherein the bypass is a switching element connected in parallel to the functional component.

3. The circuit breaker according to claim 2, wherein the switching element is a semiconductor switch, a relay, and/or a reed contact with an associated control circuit that is connected to the current sensor.

4. The circuit breaker according to claim 1, wherein the functional component based on the principle of energy harvesting comprises an energy converter for converting the energy supplied by a switch-internal or external source into a supply voltage or into a supply current for the control circuit.

5. The circuit breaker according to claim 4, wherein the functional component based on the principle of energy harvesting comprises a current and/or a voltage regulator.

6. The circuit breaker according to claim 1, wherein the functional component based on the principle of energy harvesting comprises an energy store.

7. A method for a low power-loss operation of a circuit breaker, which comprises a switching device with a thermal and/or magnetic tripping device for an interruption of a current path in an event of an overcurrent or a short-circuit, and with a comparatively low-resistance bypass to a functional component of the switching device that is connected in the current path, the method comprising: detecting a load current flowing through the current path; and comparing the detected load current to a threshold value, the load current being carried via the bypass when the current falls below the threshold value and the bypass being shut off when the threshold value is exceeded, wherein the supply of a control circuit of the switching device and/or of a switching element switched into the bypass is based on a principle of energy harvesting from an energy source located in an operational range of the circuit breaker, and wherein the harvested energy is converted into a supply voltage and/or a supply current for the control circuit.

8. The method according to claim 7, wherein the functional component of the thermal tripping device is short-circuited with a transistor as the switching element as long as the load current falls below a limit value that is lower than the threshold value, and wherein a reed contact interacting with the functional component of the electromagnetic tripping device is closed as a further switching element and the switching element bridging the functional component of the thermal tripping device is opened when the load current exceeds the limit value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0019] FIG. 1 illustrates a thermal-magnetic circuit breaker with a semiconductor connected to a control circuit in a bypass to the thermal tripping device,

[0020] FIG. 2 illustrates a circuit breaker with a relay wired to a control circuit in the bypass to the thermal tripping device,

[0021] FIG. 3 illustrates a circuit breaker with a reed contact in the bypass to the thermal/magnetic tripping device, and

[0022] FIG. 4 is a current/time diagram or a typical current profile with optimal bypass and tripping mode.

DETAILED DESCRIPTION

[0023] FIG. 1 schematically shows a circuit breaker 1 with thermal-magnetic tripping and a bypass operation. For this purpose, the circuit breaker 1 comprises, between an input terminal 2 and a load terminal 3, a current path 4 with a disconnect switch 5 in the form of a fixed and a moving contact. A thermal tripping device 6 with or in the form of a bimetal 6a heated, for example, by means of a heating wire, is arranged downstream of the disconnect switch 5 within the current path 4. A magnetic tripping device 7 in the form of a magnetic coil 7a with an iron core 7b (FIG. 3) for tripping an impact armature is arranged downstream of this thermal tripping device 6. Both the thermal tripping device 6 and the magnetic tripping device 7 act via a switch lock 8 in the form of a releasable latching mechanism on the disconnect switch 5 in order to open the latter with a time delay or instantaneously when overcurrent or a short-circuit occurs. The row arrangement of the thermal tripping device 6 and the magnetic tripping device 7 within the current path 4 can also be interchanged.

[0024] In the event of overload and short circuit, the thermal-magnetic circuit breaker 1 thus leads to the disconnection of the circuits connected to the current path 4 via the input terminal 2 and the load terminal 3. In the case of thermal tripping, the force for tripping the switch lock 8 is obtained from the expansion, for example, of the bimetal of the thermal tripping device 6 as a result of heating due to ohmic heating power. In the case of magnetic tripping, the electromagnetic force effect of the current-conducting coil of the magnetic (electromagnetic) tripping device 7 acts on the impact armature.

[0025] In the case of a shown thermal-magnetic circuit breaker 1, heat losses occur due to the operating current, which is hereinafter also referred to as load current I.sub.L, which flows via the ohmic resistors, which essentially includes the bimetal of the thermal tripping device 6 and the coil of the magnetic-electromagnetic tripping device 7. If a current, which is below the respective rated current I.sub.N and thus is smaller than this, flows through the current path 4 and thus through the circuit breaker 1, then the power loss is to be reduced by decreasing the ohmic resistance of the circuit breaker 1. This is achieved by the fact that the functional component of the respective tripping device, in this case the bimetal of the thermal tripping device 6 and/or the coil of the magnetic/electromagnetic tripping device 7, is bridged in a manner of low-resistance. This bypass 9 represents a low-resistance connection, which is realized with the aid of a switching element.

[0026] Whereas in FIG. 1, a transistor or power semiconductor 10, as a switching element, forms the bypass 9 or is switched on in this circuit, in the embodiment of the otherwise similarly constructed circuit breaker 1 shown in FIG. 2, a relay contact 11a of a relay 11 activated via a relay coil 11b is wired into the bypass 9. To both switching elements 10, 11, a control circuit 12 is assigned, to which a sensor signal S.sub.L, which corresponds or is proportional to the current load current I.sub.L, is fed. This is generated by a current sensor 13, which detects the effective load current I.sub.L in the current path 4.

[0027] Depending on the magnitude of the detected load current I.sub.L, the control device 12 generates a control signal S.sub.C for activating the switching element 10, 11. As a result, the bypass 9 is switched on at a load current I.sub.L, which falls below a threshold value I.sub.Nenn (FIG. 4), and is thus activated, or shut off or deactivated by opening the respective switching element 10, 11 when the detected load current I.sub.L exceeds the threshold value I.sub.Nenn. In this case, the load current I.sub.L is exclusively routed via the tripping devices 6, 7, so that these trip, if necessary, in the event of overcurrent or short-circuit.

[0028] In the case of the circuit breaker 1 shown schematically in FIG. 3, on the one hand, a transistor 10 is connected as a switching element in the bypass 9, parallel to the thermal tripping device 6 or the bimetal 6a thereof, and, as a further switching element, a reed contact 14. This is preferably integrated into the magnetic tripping device 7, i.e., preferably into the coil body of the magnetic coil 7a. The reed contact 14 is activated by the magnetic coil 7a of the magnetic tripping device 7 of the circuit breaker 1 and responds when a predetermined threshold value is exceeded, preferably when the load current I.sub.L has reached a limit value I′.sub.N of, for example, 80% of the rated current I.sub.N (I′.sub.N=0.8.Math.I.sub.N).

[0029] As long as the load current I.sub.L falls below this threshold value I′.sub.N, which is smaller than the threshold value (I.sub.Nenn), the bimetallic element 6a as a functional component of the thermal tripping device 6 is shorted with the transistor 10 as a switching element, while the reed contact 14 is open. This is closed, and the transistor bridging the bimetal 6a is opened when the load current I.sub.L exceeds the threshold value I′.sub.N.

[0030] The control circuit 12 retrieves the switching state of the reed contact 14. At the same time, the control circuit 12 turns on the transistor 10, which is connected in the bypass 9 and which short circuits the thermal tripping device 6 of the circuit breaker 1 or the bimetal 6a thereof. As soon as the load current I.sub.L exceeds the threshold value I′.sub.N and the reed contact 14 responds, the transistor 10 is opened via the thermal tripping device 6 or via the bimetal 6a thereof, and the load current I.sub.L flows exclusively through the current path 4 so that the circuit breaker 1 operates as a regular thermal-magnetic circuit breaker 1. If the load current I.sub.L again falls below the threshold value I′.sub.n=0.8.Math.I.sub.Nenn, the reed contact 14 opens and the process runs in reverse.

[0031] FIG. 4 shows, in a current-time diagram I, t, an idealized current profile I.sub.B via the bypass 9 as well as the current profile (trip current) I.sub.A over the functional component bridged via the bypass 9, in the present case over the bimetal of the thermal tripping device 6. This current profile I.sub.A is shown as a solid line, while the current profile I.sub.B via the bypass 9 is displayed as a dotted line.

[0032] The control circuit 12 controls the respective switching element 10, 11 in dependence on the current I.sub.L detected by means of the current sensor 13 such that the bypass 9, which is low-resistance in comparison with the current path 4, is activated and the corresponding functional element 6a, 7a is bridged in the current path 4 until the threshold value I.sub.Nenn, hereinafter also referred to as the current threshold, is reached, which in the exemplary embodiment corresponds to the rated current I.sub.N of the circuit breaker 1. If this current threshold I.sub.Nenn is reached or exceeded, for example, at a time t.sub.1, the bypass 9 is deactivated in that the respective switching element 10, 11, 14 is opened or opens, resulting in solely the load current I.sub.L flowing through the current path 4.

[0033] Hence, the circuit breaker 1 assumes its typical protective function and, in the event of overcurrent, trips thermally with a time-delay or, in the case of a short-circuit, trips magnetically/electromagnetically without delay. If at a later time the detected load current I.sub.L again falls below the current threshold I.sub.Nenn, the bypass 9 is activated with a certain hysteresis current limit I.sub.Hys at time t.sub.2, and the respective switching element 10, 11, 14 is closed by the appropriate control.

[0034] The current and/or voltage supply of the control circuit 12 advantageously takes place by means of a functional component 15 according to the principle of energy harvesting. This functional component 15, which in the exemplary embodiment is assigned to the control circuit 12, comprises an energy converter 16 for converting the energy supplied by a switch-internal or else switch-external source 17 into the supply voltage or into the supply current for the control circuit 12. In addition, the functional component 15 based on the principle of energy harvesting comprises a current and/or voltage regulator 18 and an energy store 19.

[0035] In addition to or instead of the thermal or magnetic tripping device, the switching device may also have an electronic trip unit for interrupting the current circuit, which comprises the current path 4, in the event of overcurrent or short-circuit. The functional component bridged by means of the bypass can then be a shunt, which is used for current measurement, or another electrical or electronic component of the circuit breaker. The function component 15 for the utilization or realization of energy harvesting in combination with an electronic circuit breaker is also advantageous in that the harvested energy is used by the switch-internal or external source 17 for the self-supply of the control circuit usually associated with this type of electronic circuit breaker, and is converted in particular by means of the converter 16 into a supply voltage and/or a supply current, or, if necessary, is controlled by means of the current or voltage regulator 18, and when necessary, is temporarily stored by means of the accumulator 19.

[0036] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.