DE102011083680B4 - Circuit breaker, circuit arrangement and method for regulating a voltage in a circuit breaker - Google Patents

Abstract

Circuit breaker with a switching contact and a magnetic tripping unit with two terminals (10a, 10b), the tripping unit opening the switching contact when a voltage is applied to the terminals (10a, 10b), and with a first capacitor (16) for providing this voltage and with a signal input (20) for causing the voltage provided by the first capacitor (16) to be applied to the terminals (10a, 10b), and having an electronics unit for sending a signal to the signal input (20), the electronics unit having a second capacitor (44), which is used to provide a constant DC voltage for the electronics unit and is charged by means of a current converter via a rectifier (32) and a diode (43), and with a control unit which responds to the one at a tap (42a). the rectifier controls the voltage (P_FET) that can be tapped, this tap (42a) via a diode (46) in the control unit and an RC combination Nation is coupled from a resistor (48) and a capacitor (50) to ground (GND), characterized in that a control unit tap (60) between the diode (46) and the RC combination (48, 50) via a coupling diode ( 64) is coupled to the first capacitor (16).

Description

The invention relates to a circuit breaker according to the preamble of patent claim 1 and a circuit arrangement according to the preamble of patent claim 4. It also relates to a method for controlling the voltage provided for an electronic unit of a circuit breaker by means of a control unit.

The invention is based on the circuit for a power supply for generating a DC voltage from the DE 10 2008 027 583 B4 and includes this circuit in a preferred embodiment. While at the circuit from the DE 10 2008 027 583 B4 the direct voltage generated is suitable for an electronic unit in a circuit breaker, the present invention is also concerned with the magnetic tripping unit. A circuit breaker is designed to interrupt the flow of current through a power line when the current exceeds a certain threshold. A switching contact is used to interrupt. A tripping unit is assigned to this, which separates the switching contact. In the present case, it is supposed to be a magnetic release unit, a so-called “maglatch”. Such a maglatch has a permanent magnet that is biased against a spring. It has two terminals and when a voltage is applied to the terminals, a current flows which creates a magnetic field which opposes the field of the permanent magnet and thus causes the spring to relax; and this results in the movement of a mechanical element acting on the switching contact, such as a plunger. The voltage applied to the terminals of the magnetic trip unit can decrease while this current is flowing, since a first capacitor is typically provided to provide this voltage. There is also a signal input for causing the voltage provided by the capacitor to be applied to the terminals, with application of a specific signal to the signal input driving a transistor, for example, to connect one of the terminals of the magnetic trip unit to ground and thus the capacitor parallel to the connections. Now this signal must be provided by a specific entity. There is typically an electronics unit for sending a signal to the signal input, with the electronics unit generally having a microcontroller or some other data processing device in addition to other electronic components. In a circuit breaker there is usually a measuring device such as a Rogowski coil whose output signals are fed to the electronics unit; this aspect plays no role in the present invention. However, it is essential for the operation of the electronic unit that it is supplied with a (substantially) constant DC voltage of 12 V, for example. A second capacitor is used to provide this essentially constant DC voltage. Here the invention also ties in with the DE 10 2008 027 583 B4 because there a similar capacitor is mentioned together with another circuit. To understand the basic idea of the present invention, it is sufficient to know that the second capacitor is charged by means of a current transformer (an induction coil) and a rectifier connected to it.

With regard to the second capacitor, a regulation unit can be provided which ensures that a constant voltage is applied to it within a predetermined interval. There is no such control unit for the first capacitor. Although the first capacitor is also coupled in some way to the induction coil and the rectifier in conventional circuit breakers, it remains unaffected by the regulation of the voltage across the second capacitor. When the tripping unit is tripped, the voltage across the first capacitor drops sharply, but is not restored quickly enough after the tripping has ended. In the current molded case circuit breakers, no additional monitoring of the tripping voltage is provided.

The American Disclosure U.S. 2002/0191361 A1 discloses an electronic trip device having a capacitor for powering a trip coil. The trip device includes a system powered power supply circuit that includes a capacitor for powering a trip coil. When the trip device is switched on, the capacitor charges and its voltage is regulated according to a first reference voltage sufficient to activate the trip coil when required. After a preset period of time, the regulation of the voltage at the terminals of the capacitor is performed according to a second reference voltage that is lower than the first voltage. The reference voltage returns to the first value during the same preset period when the sensed current reaches a preset threshold, which is an indication of the presence of a fault resulting in a required trip. The capacitor is therefore generally charged to a lower voltage than required for tripping, which allows its size to be reduced.

The American disclosure document U.S. 2008/0180071 A1 discloses a method and apparatus for correcting overshoot and undershoot errors in analog Low dropout controls. The application provides a method and apparatus for dynamically correcting overshoot and undershoot errors in an analog integrated circuit by improving the response time of the analog integrated circuit. Accordingly, an error correction circuit is disclosed that includes an overshoot correction circuit and an undershoot correction that are activated only to reduce overshoot and undershoot errors by increasing the bandwidth of the integrated circuit when either undershoot or overshoot errors are detected.

It is an object of the present invention to provide greater reliability for a circuit breaker of the type described in the opening paragraph.

The object is achieved in one aspect by a circuit breaker having the features according to patent claim 1, in another aspect by a circuit arrangement having the features according to patent claim 4 and finally by a method according to patent claim 7.

In the case of the invention, the circuit breaker has a control unit which controls the voltage present at the second capacitor. The second capacitor is coupled to an RC combination via a diode in the control unit, for example coupled to ground via a diode and a series combination of a resistor and a capacitor. A control unit tap between the diode and the circuit with the capacitor (ie in the example of the series circuit) is now inventively coupled to the first capacitor via a coupling diode.

In this case we are dealing with two diodes. If the coupling diode is connected in the forward direction between the tap and the first capacitor, it is able to allow charge from the RC combination (in particular the capacitor contained therein) to flow into the first capacitor. Through the coupling diode, the circuit from the DE 10 2008 027 583 B4 supplemented, so a quick response to a self-discharging of the first capacitor allows. This is especially true if the capacitor in the RC combination is designed to match the resistor in the RC combination in such a way that a time constant, which indicates the rate at which said capacitor is discharged, is less than the period of the mains current, i.e of the primary current in the current transformer, i.e. that the discharge of charge from the control unit takes place faster than a change in the voltage across the second capacitor.

In a preferred embodiment, the embodiment with the control unit, it is provided that the tap is coupled to ground on the one hand via a series connection of capacitor and resistor and on the other hand also via a series connection of two resistors, with a further tap between the resistors having a first input of a comparator, at whose second input there is a constant potential, and whose output is coupled to the control input or the gate of a transistor, via which the induction coils (iron core converters) can be short-circuited. This measure creates a stably running control unit, as is known per se.

It is preferably also provided in the control unit, optionally according to patent claim 2, that the tap between the RC combination and the (first) diode is coupled to the second capacitor via a further coupling diode. In this way, a return flow of charge from the control unit into the second capacitor is made possible to a certain extent when the coupling diode is connected in the forward direction from the tap to the second capacitor; this measure is advantageous so that short-term fluctuations can be reacted to very quickly; Here, too, it is advantageous if the discharge time of the RC combination is (much) shorter than the period of the primary current in the current transformer.

The circuit arrangement according to the invention relates to those components of the circuit breaker according to the invention that can be arranged on a printed circuit board. Accordingly, it has connections for connecting a magnetic tripping unit and a first capacitor assigned to these connections, in which case the microcontroller could be connected here, and it has a second capacitor assigned to this voltage tap. It also includes the control unit on the printed circuit board. According to the invention, the tapping point for the current converter or the rectifier arranged downstream of it is therefore coupled to the first capacitor via a diode and a coupling diode so that the capacitor of the RC combination can discharge into the first capacitor.

The other preferred embodiments are also those mentioned for the circuit breaker according to the invention.

The inventive method for controlling the voltage provided for an electronic unit of a circuit breaker by means a control unit is characterized in that the control unit is also used to control the voltage applied to a capacitor, which is used to provide electric current for a magnetic trip unit of the circuit breaker.

Here, the method shows that one and the same control unit can be used for two purposes, namely for controlling the voltage of the capacitor for providing the DC voltage for the electronic unit on the one hand and for controlling the additional capacitor in the tripping circuit on the other.

The invention is described in more detail with reference to the drawing, in which the only 1 shows a circuit arrangement according to the invention for a circuit breaker, on the basis of which a circuit breaker according to the invention is also described.

In the present case, a circuit breaker should have a magnetic tripping unit for opening a switching contact, a so-called “maglatch”. The maglatch is coupled to the circuit arrangement via connections 10a, 10b. The terminals 10a and 10b are internally coupled to one another via a diode 12. The terminal 10a is coupled to a capacitor 16 via a diode 14 in such a way that the conducting direction of the diode 14 enables the capacitor 16 to be discharged towards the terminal 10a. Discharging takes place in particular when a transistor 18, which is in the form of a MOSFET, is switched to conduct, ie short-circuits the connection 10b to ground “GND”. This is the case when a corresponding control signal is applied to the gate G of the transistor 18 via a connection 20 . Resistors 22, 24, 26 and the capacitor 28 are used for the stability of the circuit.

The signal at input 20 is controlled in the power switch by a microcontroller (which is shown in 1 not shown) produced when current flows through a conductor (also shown in Fig 1 not shown) exceeds a certain current value. The evaluation unit and associated electronics require a substantially constant voltage of 12 V. This voltage is provided from the power line to be monitored itself by the alternating current in a current transformer, not shown, indicating a voltage that is connected via terminals 30a, 30b of the circuit arrangement of 1 is supplied and a rectifier stage 32 with diodes 34, 36, 38, 40 passes through. The potential P_FET is therefore present at a tapping point 42a, and this tapping point 42a is coupled via a diode 43 to one side of a further capacitor 44 and at the same time to a tapping point 42b, at which the 12 V should essentially be present. The capacitor 44 is charged due to the voltage induced in the current transformer. With a sufficiently high capacitance, there are only slight fluctuations in the value of 12 V at the tapping point 42b. This applies in particular because a control unit is provided which prevents excessive fluctuations in the potential P_FET, which is higher by the forward voltage of the diode 43 . The potential P_FET, ie the tapping point 42a, is coupled to a diode 46. Downstream of this diode 46 is an RC combination with, in this case, a series connection made up of a resistor 48 and a capacitor 50 and, parallel thereto, a series connection made up of a resistor 52 and a further resistor 54.

A tapping point 56 between the two resistors 52 and 54 is fed to a first input E1 of a comparator K, whose second input E2 is coupled to a potential of 2.5V. The output A of the comparator K is fed to the gate G of a MOSFET transistor 58, which may cause a short circuit between the tapping point 42a and ground “GND”.

In the present case, for example, the value of the resistor 52 is 47 kΩ and the value of the resistor 54 is 13 kΩ. Then there is a potential of greater than 2.5 V at tap point 56 precisely when the potential P_FET is too much above 12 V, so that the transistor 58 is short-circuited and the potential P_FET is reduced again by the capacitor 44 is discharged until the voltage of 12 V reaches the correct value again. Conversely, the voltage across the capacitor 44 then steadily increases again due to the supply of charge from the current transformer.

In the present case, the capacitor 50 should have a capacitance of 470 nF, and the resistor 48 should have a resistance of 10 Ω. The discharge time of the capacitor 50 is therefore considerably less than that of the capacitor 44, which has a capacitance in the μF range, for example 47 μF.

The capacitor 16 also has a rather higher capacitance of 100 μF, for example.

The regulation to the potential P FET and thus indirectly the voltage across the capacitor 44 is now also used in the present case to stabilize the voltage across the capacitor 16 . For this purpose, the tapping point 42a is coupled to the positive pole of the capacitor 16 via a diode 59. FIG. For this purpose, there is also the tap point 60 between the diode 46 and the RC combination, in this case the series connection of the resistor 48 and the capacitor 50, via a further resistor 62 and a coupling diode 64 is coupled to the positive terminal of capacitor 16 so that a discharge current from capacitor 50 can offset a variation in the voltage across capacitor 16 across the power supply. The rapid discharging of the capacitor 50 via the activated maglatch is used in particular to quickly reduce the voltage at the input E1 of the comparator K. This puts the power pack into the recharging state more quickly. The purpose of the diodes 64 and 66, respectively, is to shorten the discharge time of the capacitor 50 in the event of a rapid voltage drop (faster than the discharge time of the capacitor 50 via the resistors 48, 52 and 54) across the capacitors 44 and 16. The potential 56 thus falls below the reference potential P2V5 more quickly and the comparator K switches to the recharging mode more quickly. Transistor 58 is nonconductive in this condition. This means that the capacitors 44 and 16 are recharged.

In addition to the coupling diode 64, a further coupling diode 66 can optionally also be provided, which again couples the tapping point 60 to the capacitor 44 or the tapping point 42b. This allows charge to flow back from the capacitor 50 into the capacitor 44, which is particularly helpful in the event of short-term fluctuations in the voltage across the capacitor 44, in order to ensure that the voltage of 12 V at the tapping point 42b is largely constant.

The trigger circuit, which is known per se, with the first capacitor 16 is therefore coupled by the coupling diode 64 to the control unit made up of the elements 46, 48, 50, 52, 54, K, and 58 and is coupled directly to the tapping point 42a by the diode 59, see above that at least indirectly, in addition to the regulation to the potential P FET, the voltage across the capacitor 16 is also regulated.

Claims (7)

Circuit breaker with a switching contact and a magnetic tripping unit with two terminals (10a, 10b), the tripping unit opening the switching contact when a voltage is applied to the terminals (10a, 10b), and with a first capacitor (16) for providing this voltage and with a signal input (20) for causing the voltage provided by the first capacitor (16) to be applied to the terminals (10a, 10b), and having an electronics unit for sending a signal to the signal input (20), the electronics unit having a second capacitor (44), which is used to provide a constant DC voltage for the electronics unit and is charged by means of a current transformer via a rectifier (32) and a diode (43), and with a control unit which responds to the one at a tap (42a). the rectifier controls the voltage (P_FET) that can be tapped, this tap (42a) via a diode (46) in the control unit and an RC combination Nation is coupled from a resistor (48) and a capacitor (50) to ground (GND), characterized in that a control unit tap (60) between the diode (46) and the RC combination (48, 50) via a coupling diode ( 64) is coupled to the first capacitor (16). circuit breaker after claim 1 , characterized in that the control unit tap (60) is coupled to ground (GND) on the one hand via a series connection of capacitor (50) and resistor (48) and on the other hand via a series connection of resistors (52, 54), with a further tap (56 ) is coupled between the resistors (52, 54) to a first input (E1) of a comparator (K), at whose second input (E2) there is a constant potential, and whose output is connected to the control input or the gate of a transistor (58 ) is coupled via which the current transformer can be short-circuited. circuit breaker after claim 1 or 2 , characterized in that the control unit tap (60) is coupled to the second capacitor (44) via a further coupling diode (66). Circuit arrangement with connections (10a, 10b) for connecting a magnetic tripping unit and a first capacitor (16) assigned to these connections (10a, 10b), a potential tap (42b) for an electronic unit and a second capacitor (44) assigned to this potential tap, and with a control unit that controls the potential (P_FET) present at a tapping point (42a), which is coupled to the second capacitor via a diode (43), so that the control unit indirectly controls the voltage present at the second capacitor (44). , wherein the tapping point (42a) is coupled to ground (GND) via a diode (46) in the control unit and an RC combination (48, 50) of a resistor (48) and a capacitor (50), characterized in that a control unit tap (60) between the diode (46) and the RC combination (48, 50) is coupled to the first capacitor (16) via a coupling diode (64). Circuit arrangement according to claim 4 , characterized in that the control unit tap (60) is coupled to ground (GND) via a series circuit made up of the resistor (48) and the capacitor (50) and via a series circuit made up of resistors (52, 54), with a further tap (56 ) is coupled between the resistors (52, 54) to a first input (E1) of a comparator (K), at whose second input (E2) there is a constant potential, and whose off output is coupled to the control input or the gate of a transistor (58) via which the tapping point (42a) can be short-circuited. Circuit arrangement according to claim 4 or 5 , characterized in that the control unit tap (60) is coupled to the second capacitor (44) via a further coupling diode (66). Method for controlling the voltage provided for an electronic unit of a circuit breaker by means of a control unit (46, 48, 50, 52, 54, K, 58), characterized in that the control unit (46, 48, 50, 52, 54, K, 58 ) is also used to regulate the voltage across a capacitor (16) which is used to provide electrical power to a magnetic trip unit of the circuit breaker.

Images