AU2017218925B2

AU2017218925B2 - Circuit breaker

Info

Publication number: AU2017218925B2
Application number: AU2017218925A
Authority: AU
Inventors: Jean-Mary Martel
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2016-11-24
Filing date: 2017-08-21
Publication date: 2019-02-14
Anticipated expiration: 2037-08-21
Also published as: DE102016223264A1; CN108110728B; AU2017218925A1; GB2556966B; CN108110728A; GB201712977D0; GB2556966A

Abstract

CIRCUIT BREAKER The invention relates to a circuit breaker for an electrical low voltage circuit. Said circuit breaker has an arc fault detection device function that can ascertain arcing faults in the electrical low voltage circuit and, in the event of an arcing fault limit value being exceeded, can interrupt the electrical low voltage circuit, a residual current breaker function that can ascertain fault currents in the electrical low voltage circuit and, in the event of a fault current limit value being exceeded, can interrupt the electrical low voltage circuit, and an electrical power supply for the arc fault detection device function and the residual current breaker function. The circuit breaker is configured such that the voltage in the low voltage circuit is ascertained and the arc fault detection device function is disengaged in the event of a first limit value of the voltage not being reached.

Description

CIRCUIT BREAKER [0001] The invention relates to a circuit breaker for protecting an electrical low voltage circuit according to the preamble of patent claim 1 and a method for a circuit breaker for an electrical low voltage circuit according to the preamble of patent claim 9.

[0002] Low voltage means voltages of up to 1000 volts AC or up to 1500 volts DC.

[0003] Circuit breaker means a combined switch that has an integrated residual current breaker function, as known from residual current breakers, and an integrated arc fault detection device function, as known from arc fault detection devices. Further, there may also be an integrated miniature circuit breaker function, as known for miniature circuit breakers. Furthermore, there may also be further integrated functions.

[0004] Miniature circuit breaker usually means low voltage miniature circuit breakers for currents of up to 125 amps, more specifically up to 63 amps.

[0005] Miniature circuit breakers protect the circuit against overcurrents and shorts. That is to say that if the current in the electrical circuit exceeds a current limit value, the electrical circuit can be interrupted.

[0006] Residual current breakers, RC breakers for short, are known generally. Usually, what are known as summation current transformers are used for these. In this case, two or more conductors, in most cases forward and return conductors or outer and neutral conductors in a single-phase AC system or all three outer conductors and the neutral conductor in the case of a three-phase AC system, are routed through a summation current transformer. Only the differential current, i.e. a current differing from the forward and return currents, from the conductors is converted. Usually, the total current or the differential current in an electrical circuit is equal to zero. If it is not equal to zero, these are brought about by fault currents, which can be identified in this way. If these exceed a fault current limit value or differential current limit value, the electrical circuit can be interrupted.

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2017218925 21 Aug 2017 [0007] If the summation current transformer is designed such that the secondary-side energy is sufficient for operating a tripping unit or an interruption unit or a release, then residual current breakers of this kind are termed grid voltage independent; otherwise they are termed grid voltage dependent.

[0008] Arc fault detection devices are relatively new protection devices for circuits or voltage systems and are used for identifying arcing faults, such as parallel or serial arcs. Such arcing faults, sometimes also referred to as accidental arcs, can result from poorly clamped electrical connections in splitting boxes or receptacle outlets or from poor insulation and contacts. Arc fault detection devices can be used particularly in domestic installation devices, such as fuse boxes, in order to identify such faults and, in the event of a fault being present or an arcing fault limit value being exceeded, to interrupt the electrical circuit.

[0009] Arcing faults mean particularly arcs, both serial and parallel arcs, that result from faults in the circuit. Arcs that occur regularly during switching or as a result of the operation of desired electrical loads are not meant here.

[0010] If the residual current breaker function, RCD for short, and the arc fault detection device function, AFDD for short, are integrated in a circuit breaker or device or module, e.g. in a single module having a width of 18 mm, it is necessary for many functions to be realized in a limited space. This is all the more so when still further functions are integrated.

[0011] Both RCD and AFDD parts need a low voltage supply: the electrical signals from sensors, such as summation current transformers or residual current transformers for RCDs; current sensors and high-frequency sensors for AFDDs, need to be conditioned and evaluated. This is effected using both analog and/or digital electronic components, for example. Low voltage means typically 3.3 V or 5 V DC. A power supply or power supply circuit needs to convert input voltage or system voltage, typically 230 V AC, into low output voltage (DC voltage)/low voltage.

[0012] Such a power supply requires space in the circuit breaker and generates heat. Particularly when this power supply is intended to operate over a wide input voltage range.

[0013] The demands on an arc fault detection device function or AFDD and a residual current breaker function or RCD in respect of the minimum operating voltage are different:

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- The standard for AFDDs (IEC 62606) requires the protection function to work from 85% of the rated voltage or system voltage. When the rated voltage of the system or circuit is 230 volts, this is 195 V.

- The standard for RCDs (IEC 61008) requires the protection function in 230 volt systems to work from 85 volts. In countries such as China, the demands are even higher, the protection function being required to work from 50 volts in this case.

[0014] This requires the power supply to have to operate in a wide input voltage range. This means that the current draw at lower input voltage rises. This also means that the input capacitance of the circuit (capacitor) needs to be sufficiently high to store enough energy at low input voltages. The value of the input capacitor is proportional to the circuit power consumption and inversely proportional to the input voltage.

[0015] Further, the power supply also needs to be designed to process high values of the input voltage. By way of example, a residual current breaker/RCD needs to be capable of tolerating overvoltages of the square root of 3 or 1.73 times the value of the rated voltage, e.g. 400 V for a 230 V system; this is for one hour without sustaining damage.

[0016] This means that the input capacitor also needs to have a high dielectric strength. The combination of these demands leads to a high capacitance for a high dielectric strength. These components are large and not always realizable in a compact device with limited installation space. Realizing such a circuit breaker is difficult, expensive or even impossible.

[0017] It is an object of the present invention to substantially overcome or at least ameliorate one or more disadvantages of existing arrangements.

[0018] In one aspect the present disclosure seeks to improve a circuit breaker of the type cited at the outset, particularly to allow a power supply of small size for a circuit breaker.

[0019] According to one aspect of the present invention, there is provided a circuit breaker for an electrical low voltage circuit, having:

- an arc fault detection device function that can ascertain arcing faults in the electrical low voltage circuit and, in the event of an arcing fault limit value being exceeded, can interrupt the electrical low voltage circuit,

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- a residual current breaker function that can ascertain fault currents in the electrical low voltage circuit and, in the event of a fault current limit value being exceeded, can interrupt the electrical low voltage circuit,

- an electrical power supply for the arc fault detection device function and the residual current breaker function, wherein the circuit breaker is configured such that the voltage in the low voltage circuit is ascertained, and wherein the arc fault detection device function is in a disengaged state in the event of a first limit value of the voltage not being reached.

[0020] This allows the use of a smaller power supply, since at low voltages in the system there is no need to provide power for the arc fault detection device function. Hence, the power supply or the power supply unit needs to provide only a smaller current at low voltages, as a result of which the physical size is distinctly reduced. This is advantageous particularly for system voltage dependent residual current breakers and residual current breaker functions.

[0021] Other configurations are specified below.

[0022] In one configuration, a first peripheral device of the circuit breaker is in a disengaged state in the event of the first or a second limit value of the voltage not being reached.

[0023] This has the particular advantage that a further reduction in the physical size of the power supply is made possible, since peripheral devices, such as display units, e.g. a display or an LED display, and/or communication units, are disengaged at low voltages or, respectively, are engaged only from a specific voltage. In this case, the limit values for the arc fault detection device function and peripheral device may be the same or different.

[0024] In one advantageous configuration, a second peripheral device of the circuit breaker is in a disengaged state in the event of a third limit value of the voltage not being reached.

[0025] This has the particular advantage that the disengagement can be scaled depending on the power consumption of peripheral devices depending on the voltage of the low voltage circuit, as a result of which the power supply for the circuit breaker can be reduced or optimized.

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2017218925 21 Jan 2019 [0026] In one advantageous configuration, the circuit breaker has a miniature circuit breaker function that ascertains the electric current in the electrical low voltage circuit and can interrupt the electrical low voltage circuit in the event of a current limit value being exceeded.

[0027] This has the particular advantage that a further protection function is integrated in the circuit breaker, as a result of which said circuit breaker becomes more universally usable. The reduced physical size of the power supply means that this additional function is realizable.

[0028] In one advantageous configuration, a control device (MCU) is provided that is configured such that it compares the ascertained voltage with at least one limit value and disengages and/or engages the arc fault detection device function, first or second peripheral device on the basis of the at least one limit value not being reached or being exceeded.

[0029] This has the particular advantage that the realization is advantageously performed by a microcontroller for example, which has a low power consumption and a small size, as a result of which a circuit breaker becomes realizable in a small housing or module.

[0030] In one advantageous configuration, the first, second or third limit value is in the range from 100 volts to 180 volts, particularly in the range from 110 volts to 170 volts. More specifically, the first, second or third limit value is in the range from 120 volts to 160 volts, in particular it has a value in the region of 120, 130, 140, 150 or 160 volts, i.e. with a tolerance of +/- 5 volts.

[0031] This has the particular advantage that there is also an arc fault detection device function below the system voltage required according to standard, the limit value being able to be stipulated depending on physical size or power supply.

[0032] In one advantageous configuration, the peripheral device is a display unit and/or a communication unit.

[0033] This has the particular advantage that particularly power-intensive units are disengaged at low voltages or are engaged only from a specific voltage level, which results in a lower power consumption and, therefore, a smaller power supply.

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2017218925 21 Jan 2019 [0034] All configurations, both in dependent form referring back to the independent patent claim and referring back just to single features or combinations of features of patent claims, bring about an improvement in a circuit breaker.

[0035] The described properties, features and advantages of this invention and the manner in which they are achieved will become clearer and more distinctly comprehensible in the junction with the description of the exemplary embodiment below, which is explained in more detail in conjunction with the drawing, in which:

[0036] Figure 1 shows a circuit diagram of an electronic circuit.

[0037] Figure 1 shows a circuit with a first and a second transistor QI, Q2; a first, second and third resistor Rl, R2, R3; an input Enable; a first power supply connection Vdcl, Ground; a power supply output Vdc2.

[0038] The input Enable is connected to the third resistor R3, which is in turn connected to the base of the first transistor QI. Said transistor is a transistor of NPN type, for example. The emitter of said transistor is connected to the connection Ground of the first power supply. The collector of said transistor is connected both to the first resistor Rl and to the second resistor R2. The first resistor Rl is connected firstly to the connection Vdcl of the first power supply, which is in turn connected to the emitter of the second transistor Q2. Said second transistor is of PNP type, for example. The base of said second transistor is connected to the other connection of the resistor R2. The collector of the second transistor Q2 forms the connection Vdc2 as a power supply output.

[0039] According to the invention, intelligent power management or power supply for a circuit breaker is proposed. The power consumption is optimized on the basis of the input voltage of the system/low voltage circuit of the circuit breaker by virtue of different switch functions or circuit parts being engaged and disengaged or activated/deactivated. The same principle is used, by way of example, in a control unit, for example in a microprocessor, in which different programs or program parts of the microprocessor are used or are not used, depending on the

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2017218925 21 Aug 2017 voltage. A microprocessor then runs with fewer functions. As such, a microprocessor can therefore operate at lower frequency, for example, or enter sleep mode, which saves energy or power. As a result, a smaller power supply or power supply unit is needed.

[0040] The functionality of the circuit breaker is divided into three parts, for example:

- The fault current function / RCD operates all the time or at voltages from 85 V or 50 V, for example.

- The arc fault detection device function / AFDD operates all the time at an input voltage from 85% of the rated voltage, e.g. 195 volts for a 230 volt system. It can actually operate at lower voltages, for example at values of 120, 130, 140, 150, 160 volts, with a tolerance of +/- 5 volts, depending on the dimensioning of the circuit breaker or the power supply.

- Peripheral devices or units, such as e.g. a display unit, LED display or communication unit, can be optionally engaged and disengaged at any voltage limit or limit value.

[0041] The circuit breaker needs to measure the voltage of the low voltage circuit and decide, by comparing the voltage with limit values, which functions or parts of the circuit breaker are disengaged and engaged.

[0042] This can be performed at least in part, for example, by a microprocessor in a control device of the circuit breaker.

[0043] Depending on the value of the voltage, the following states can be realized, for example:

1) Input voltage less than/equal to first limit value:

Only the residual current breaker function/RCD function is activated.

By way of example, the first limit value may be 120 volts.

The circuit breaker is “only” a residual current breaker. The arc fault detection device function/AFDD function and, by way of example, the display are not available.

The energy or power consumption is markedly reduced.

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2) The input voltage is between the first limit value and the second limit value:

By way of example, the second limit value may be 160 volts.

In this case, peripheral devices or the arc fault detection device function can be used, i.e. one or more further functions are engaged. By way of example, an LED display or communication means.

3) The input voltage is above the second limit value:

In this case, all functions of the circuit breaker are activated. The circuit breaker ensures RCD and AFDD functions.

Analogously, further limit values, such as a third limit value, can be stipulated and said limit value can be assigned the engagement and disengagement of specific functions of the circuit breaker.

As such, the power supply and functionality of a circuit breaker can be optimized on the basis of the voltage or input voltage.

Program parts of a microprocessor are activated/deactivated analogously.

[0044] According to the invention, there may be a hysteresis provided for the engagement/disengagement or switching-on/switching-off or activation/deactivation of the functions and program parts, etc. That is to say that activation and deactivation and subsequent deactivation and activation first require the threshold value to not have been reached or to have been exceeded by a further value, which is below or above the threshold value, and/or the threshold value not being reached or being exceeded must exist for a certain period before this takes place, so that constant switching-off or switching-on of functions, devices, program parts, etc. is avoided when the voltage is exactly at the limit value or fluctuates about said limit value.

[0045] The activation/deactivation of specific functions or circuit parts can be effected by virtue of the outputs of a microprocessor being used directly for activating/deactivating the power supply of the circuit parts, an inventive circuit according to figure 1 being able to be used. The activation/deactivation is effected by changing the output state of the output of the microprocessor or of the GPIO outputs of the microprocessor. As a result, a circuit/circuit part can be supplied with power directly. For higher currents, the inventive circuit according to figure 1 is used. This is a type of transformation switch. The input Enable is connected to the

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2017218925 21 Aug 2017 output of a microprocessor, the enable signal of which (low level 0 V or high level 3.3 V) results, for a high level, in the first transistor QI being turned on. As a result, the base voltage of the second transistor Q2 becomes low, and said second transistor is turned on. As a result, the voltage at Vdcl is delivered by the second transistor as an output voltage Vdc2, as a result of which circuits/circuit parts connected thereto are supplied with energy/power.

[0046] The voltage drop (collector-emitter) across the second transistor Q2, amounts to approximately 50 mV, can be disregarded in this case. By way of example, this means that the AFDD functionality can be switched on or disengaged.

[0047] The control of the power supply can also be realized alternatively, e.g. by optocoupler or relay.

[0048] The power supply for a circuit breaker or the power supply design (space, costs, efficiency) can be optimized using the present invention or the inventive power management. Different functionalities of a circuit breaker, such as RCD/AFDD, are activated depending on voltage.

[0049] The invention allows the realization of a small-design circuit breaker that complies with the relevant standards.

[0050] Although the invention has been illustrated and described in more detail by the exemplary embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

Claims

1. A circuit breaker for an electrical low-voltage circuit, having:

- a residual current breaker function that can ascertain fault currents in the electrical low voltage circuit and, in the event of a fault current limit value being exceeded, can interrupt the electrical low voltage circuit, and

2. The circuit breaker as claimed in patent claim 1, wherein a first peripheral device of the circuit breaker is in a disengaged state in the event of the first or a second limit value of the voltage not being reached.

3. The circuit breaker as claimed in patent claim 1 or 2, wherein a second peripheral device of the circuit breaker is in a disengaged state in the event of a third limit value of the voltage not being reached.

4. The circuit breaker as claimed in one of patent claims 1 to 3, wherein the circuit breaker has a miniature circuit breaker function that can ascertain the electric current in the electrical low voltage circuit and, in the event of a current limit value being exceeded, can interrupt the electrical low voltage circuit.

5. The circuit breaker as claimed in one of patent claims 1 to 4, wherein a control device (MCU) is provided that is configured such that it compares the ascertained voltage with at least one limit value and disengages and/or engages the arc fault detection device function, first or second peripheral device on the basis of the at least one limit value not being reached or being exceeded.

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6. The circuit breaker as claimed in one of patent claims 1 to 5, wherein the first, second or third limit value is in the range from 100 volts to 180 volts, particularly in the range from 110 volts to 170 volts.

7. The circuit breaker as claimed in one of patent claims 1 to 6, wherein the first, second or third limit value is in the range from 120 volts to 160 volts, particularly has a value in the region of 120, 130, 140, 150 or 160 volts.

8. The circuit breaker as claimed in one of patent claims 1 to 7, wherein the peripheral device is a display unit and/or a communication unit.

9. A method for a circuit breaker for an electrical low voltage circuit, having:

- an arc fault detection device function that ascertains arcing faults in the electrical low voltage circuit and, in the event of an arcing fault limit value being exceeded, interrupts the electrical low voltage circuit, and

- a residual current breaker function that ascertains fault currents in the electrical low voltage circuit and, in the event of a fault current limit value being exceeded, interrupts the electrical low voltage circuit, wherein the voltage in the low voltage circuit is ascertained, and in that the arc fault detection device function is engaged only in the event of a first limit value of the voltage being exceeded.