Electronic interruption unit
By connecting a TVS diode and an RC snubber in parallel in the electronic interruption unit, the voltage protection problem of the power semiconductor in the case of a short circuit is solved, the parameter design is simplified, the cost is reduced and the reliability and compactness of the system are improved.
Patent Information
- Application Number
- CN202480015231.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-02-28
- Filing Date
- 2024-02-26
- Publication Date
- 2025-10-03
AI Technical Summary
Existing electronic interruption units are difficult to effectively protect power semiconductors from damage due to excessive voltage in the event of a short circuit, and the parameter design of the energy absorber is complex and costly.
A series circuit of a TVS diode and an RC snubber is connected in parallel with at least one transistor, the power semiconductor voltage is limited by the TVS diode, and an RC snubber is set between the gate and the drain to reduce the pulse load and simplify the parameter design.
It effectively protects power semiconductors from excessive voltage, reduces the complexity and cost of energy absorbers, and improves the reliability and compactness of the system.
Smart Images
Figure CN120752856A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to an electronic interruption unit for interrupting an electric current. Background Art
[0002] Advances in the development of semiconductor components have led to new switch concepts that can replace conventional, typically electromechanical, switches, particularly those in low-voltage technology. These new concepts involve, for example, circuit breakers or motor starters, but can also be used to switch higher currents, such as with circuit breakers. The fast response time of the semiconductor components is crucial here, as it prevents damage due to overload. In other words, the switch interrupts the current before the semiconductor components can be damaged.
[0003] In the following, low voltage refers to a voltage of up to 1000 V AC or up to 1500 V DC. Low voltage refers in particular to a voltage greater than the minimum voltage, which is 50 V AC or 120 V DC.
[0004] A low-voltage circuit, low-voltage network, or low-voltage system is understood to be a circuit with a rated or nominal current of up to 125 amperes, more particularly up to 63 amperes. A low-voltage circuit is particularly understood to be a circuit with a rated or nominal current of up to 40 amperes, 32 amperes, 25 amperes, 16 amperes, or 10 amperes. The current values mentioned are in particular the rated current, the nominal current, and / or the cut-off current, i.e., the maximum current conducted through the circuit under normal circumstances, or the current that is normally interrupted by the circuit, for example, by a protective device such as a protective switchgear, a circuit breaker, or a circuit breaker.
[0005] Circuit breakers are long-known overcurrent protection devices used in low-voltage circuits in electrical installation technology. They protect circuits from damage caused by overcurrent and / or short-circuit-induced heating. They automatically disconnect circuits in the event of an overload and / or short-circuit. Circuit breakers are typically non-self-resetting fuse elements and often have a mounting option for top-hat rails (supporting rails, DIN rails, TH35).
[0006] Conventional line circuit breakers are electromechanical. They contain mechanical switching contacts or operating current triggers within their housings for interrupting (tripping) the current. Typically, a bimetallic protective element or bimetallic element is used to trigger (interrupt) in the event of a prolonged overcurrent (overcurrent protection) or thermal overload (overload protection). An electromagnetic trigger with a coil is used for short-term triggering when an overcurrent limit is exceeded or a short circuit occurs (short-circuit protection). One or more arc extinguishing chambers or arc extinguishing devices are provided, along with connection elements for the conductors of the circuit to be protected.
[0007] Line protection switchgear with electronic interruption units is a relatively recent development. These devices have semiconductor-based electronic interruption units. This means the current in the low-voltage circuit is passed through a semiconductor component or switch, which interrupts the current or switches it into conduction mode.
[0008] The term "circuit breaker" hereinafter specifically refers not only to line circuit breakers but also to switches with a protective function in general, such as circuit breakers. In contrast to line circuit breakers, low-voltage circuit breakers are designed for currents greater than 125A, and sometimes also for currents starting at 63A. However, the term "circuit breaker" is not intended to encompass only the classic low-voltage switches used in the energy supply sector. For example, the invention described below can also be used for motor starters with short-circuit protection, other switches in industrial environments, or medium-voltage circuit breakers with a protective function.
[0009] A protective switchgear with an electronic interruption unit usually has a mechanical disconnecting contact system, which in particular has disconnecting characteristics according to the relevant standards for low-voltage circuits, wherein the contacts of the mechanical disconnecting contact system are connected in series with the electronic interruption unit, i.e. the current of the low-voltage circuit to be protected is conducted both through the mechanical disconnecting contact system and through the electronic interruption unit.
[0010] For semiconductor-based protective switching devices or protective devices, new solid-state circuit breakers (SSCBs) do not convert the switching energy into an arc as with mechanical switching devices. Instead, they convert it into heat using an additional circuit, namely an energy absorber. This switching energy includes energy stored in the circuit, namely the grid impedance, line impedance, or load impedance (consumer impedance). To reduce the load on the energy absorber, the current flowing at the time of switching must be as low as possible. This also applies to short circuits. In this case, the current rises very quickly. Fast short-circuit detection allows short circuits to be detected early and excessive short-circuit currents to be avoided. Semiconductor-based protective switching devices interrupt the circuit almost immediately during the switching process, within the microsecond (μs) range. High currents do not occur, and the load on the energy absorber of the semiconductor-based protective switching device is reduced. Known short-circuit detection or shutdown criteria are usually based on determining and analyzing the actual current value. Summary of the Invention
[0011] The object of the present invention is to improve the properties of an electronic interruption unit having an energy absorber.
[0012] This object is achieved by an electronic interruption unit according to claim 1. Advantageous developments are specified in the dependent claims.
[0013] An electronic interruption unit for interrupting a current is proposed. The electronic interruption unit is formed using at least one transistor having a source terminal, a control terminal, and a low-potential terminal. The source terminal can be a source terminal or an emitter terminal, the control terminal can be a gate terminal or a base terminal, and the low-potential terminal can be a drain terminal or a collector terminal. Thus, the transistor can, in particular, be a BJT (bipolar junction transistor) having a base, a collector, and an emitter, a field-effect transistor, such as a MOSFET (metal oxide semiconductor field-effect transistor) having a gate, a source, and a drain, or an IGBT (insulated-gate bipolar transistor) having a gate, a collector, and an emitter. At least one driver can be provided, which is connected to the control terminal of the at least one transistor to drive or switch the at least one transistor on and off.
[0014] For energy absorption purposes, the electronic interruption unit is designed to have at least one TVS diode connected in parallel with at least one transistor. For example, a series circuit consisting of a plurality of TVS diodes is connected in parallel with at least one transistor, wherein the individual TVS diodes are preferably, but not necessarily, constructed identically.
[0015] Furthermore, a series circuit consisting of at least one capacitive element and at least one resistive element is provided, which is arranged between the control terminal and the low-potential terminal of at least one transistor. The electronic interruption unit, for example, comprises a first transistor and a second transistor, wherein the two transistors are connected in series in an anti-series manner, and for each transistor, a series circuit consisting of at least one capacitive element and at least one resistive element is arranged between the control terminal and the low-potential terminal. In this case, or generally for a plurality of transistors, a series circuit having a capacitive element and a resistive element can be provided for all transistors, these series circuits being arranged between the control terminal and the low-potential terminal. These series circuits are then preferably identical in terms of the individual elements and their order (e.g., the elements are of the same type and have the same rated value).
[0016] The electronic interruption unit according to the present invention provides effective protection for transistors or power semiconductors against excessive voltages by virtue of its energy absorption properties.
[0017] For a plurality of, that is, N, clamping voltages U clThe TVS diode solution can be designed with appropriate parameters as follows: the number N of TVS diodes connected in series and / or the clamping voltage U cl is chosen to satisfy the following relationship:
[0018] .
[0019] The electronic interruption unit according to the invention can be, in particular, a component of an electronic circuit breaker or a motor starter, but is not limited thereto. It is also conceivable that it can be used in a circuit breaker, for example.
[0020] The electronic interruption unit according to the present invention may be an independent structural unit, which may also be manufactured separately from the switch and then installed in the switch during its manufacturing process. However, it is also possible that a switch having the electronic interruption unit according to the present invention is constructed such that the components associated with the unit as a whole are not or cannot be separated from the switch or a component of the switch containing other components, i.e., they may be considered as a single unit only in terms of function and not in terms of construction. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be described in more detail below within the scope of an embodiment. In the accompanying drawings:
[0022] Figure 1 shows the architecture of SSCB,
[0023] Figure 2 shows the equivalent circuit diagram for a short circuit situation,
[0024] Figure 3 An electronic interruption unit or shutoff device is shown, and
[0025] Figure 4 An electronic interruption unit according to the invention is shown. DETAILED DESCRIPTION
[0026] Figure 1 A view of an SSCB for protecting low-voltage circuits is shown. The neutral conductor connection NG on the grid side, the phase conductor connection LG on the grid side, the neutral conductor connection NL on the load side, and the phase conductor connection LL on the load side are arranged in the housing GEH. An energy source is connected to the grid side GRID, and electrical consumers are connected to the load side LOAD.
[0027] The main components of the switch are the power supply unit NT, the control unit SE, the electronic interruption unit EU, and the mechanical disconnection contact unit MK. The control unit SE switches on the electronic interruption unit EU, which, for example, comprises a pair of MOSFETs designed to switch phase conductors, and sends a release (Enable) signal to the mechanical disconnection contact unit. The mechanical disconnection contact unit MK comprises contacts KKN and KKL for opening and closing the phase and neutral conductors.
[0028] In order to detect current values or voltage values, a current sensor unit SI is arranged in the path of the phase conductor, a first voltage sensor unit SU1 for determining the voltage between the grid-side connection point EUG and the load-side connection point EUL of the electronic interruption unit EU, and a second voltage sensor unit SU2 for determining the voltage between the grid-side neutral conductor connection NG and the grid-side phase conductor connection LG.
[0029] about Figure 1 Further details of the switch shown can be found in German application No. DE 10 2021 210 820.2.
[0030] The MOSFET of the electronic interruption unit EU, like general power semiconductors, is designed for a specific reverse voltage, which should not be exceeded during operation.
[0031] The challenge for the electronic interruption unit EU is therefore to protect the power semiconductors from excessive voltages. This applies in particular in the event of a short circuit, when the disconnection device EU interrupts the circuit protected by the SSCB.
[0032] Figure 2 The equivalent circuit diagram in the case of a short circuit is shown. The grid voltage U is applied on the grid side. netz , which supplies power to the electrical consumer (not shown) through the circuit. Figure 1 The electronic disconnection unit or disconnection device EU is protected by a switch, of which only its electronic interruption unit is shown. On the grid side, there is a grid impedance and a line impedance NLI, and on the consumer side, there is a line impedance. These impedances typically have resistive and inductive components (indicated by the letters R and L). If the electronic disconnection device interrupts the circuit in the event of a short circuit KS at the consumer, the energy stored in the system in the grid impedance and the line impedance causes the voltage across the electronic disconnection device or the power semiconductor to rise. Therefore, an energy absorber is required to prevent sufficient energy in the system from exceeding the reverse voltage of the power semiconductor and damaging it. The energy absorber's task is to limit the voltage across the power semiconductor.
[0033] An energy absorber is understood here to mean a circuit which protects the semiconductor components of the electronic interruption unit by reducing the voltage load on the semiconductor, in particular in the event of a short circuit. Figure 3 The electronic interruption unit EU with the energy absorber EA is shown schematically. The electronic interruption unit EU is represented by two MOSFETs M1 and M2 with opposite conduction directions. As is well known, the MOSFETs M1 and M2 each have an (inherent) reverse diode, which conducts in the source-drain direction. MOSFETs with opposite conduction directions are required to interrupt alternating currents or direct currents of different directions. For direct current switching in only one direction, one MOSFET may be sufficient. The switching of the MOSFETs M1 and M2 is achieved by means of drivers T1 and T2, which are triggered by the control signal SIG. Figure 1 In the illustrated SSCB, the control signal SIG originates, for example, from the control unit SE. The energy absorber EA, shown in the figure and connected in parallel with the MOSFET, can be implemented, for example, using a varistor. While the corresponding circuit is relatively simple and therefore cost-effective, a disadvantage is that the characteristic curve of the varistor is very flexible, making parameter design very difficult and, for some applications, almost impossible.
[0034] Therefore, German patent application DE 10 2022 208 528.0 proposes another solution, in which the energy absorber EA is implemented using a TVS diode in combination with an RC snubber on the power semiconductor. This has the advantage of simplifying the parameterization of the clamping voltage and potentially reducing the reverse voltage of the MOSFET. However, it has been shown that the pulse load of the RC snubber is significant during shutdown. This makes the parameterization of the energy absorber circuit difficult or very complex at higher voltages (>600V) (requiring multiple parallel and series connections of resistors and capacitors).
[0035] Figure 4 A solution that overcomes the previous shortcomings is shown. To this end, TVS diodes are still used to limit the voltage across the power semiconductor. A series circuit consisting of five TVS diodes TV1-TV5 is shown, connected in parallel with two MOSFETs M1 and M2. The two MOSFETs have source S, drain D, and gate G connections, with a driver (not shown) driving them via a resistor R at gate G.
[0036] Unlike German patent application DE 10 2022 208 528.0, the RC snubber is not placed at the corresponding power terminals (drain and source) of the power semiconductor, but rather from the drain D to the gate G. In the figure, two RC snubbers are each implemented by a series connection of an ohmic resistor R1 or R2 and a capacitor C1 or C2 between the corresponding gate terminal G and drain terminal D. The energy absorber EA comprises the components shown in the area surrounded by dashed lines, namely the TVS diodes TV1-TV5 and the snubber elements R1, C1, R2, and C2 arranged between the gate G and drain D.
[0037] As a result, the switching edges of the power semiconductor are reduced at the time of switching off and switching on, so that the current in the power semiconductor has sufficient time to commutate to the TVS diode. This has the advantage that the RC snubber is not affected by the high pulse load in terms of power in this case.
[0038] This circuit has the following advantages:
[0039] • Since the pulse load of the RC snubber is very low, the parameters of the RC snubber can be designed very easily.
[0040] • In particular, component selection is simpler, since no special pulse-proof resistors or capacitors need to be used, which results in lower costs and smaller space requirements.
[0041] Compared to varistor solutions, the clamping voltage can be parameterized more easily, potentially reducing the reverse voltage of the power semiconductor (for example, when using 600V power semiconductors in a three-phase AC grid). This allows the use of lower-cost power semiconductors. A possible parameterization approach is further described below.
[0042] • For smaller reverse voltages, it may be possible to use power semiconductors with even lower on-resistance RDSon. This can result in reduced system losses or a more compact design.
[0043] The parameter design of the clamping voltage given in the German patent application with application number DE 10 2022 208 528.0 can also be used according to Figure 4 Here, the sum of the clamping voltages of the TVS diodes is selected so that, taking into account the safety factor, it is less than the maximum reverse voltage U of the power semiconductor. T,max As an additional parameter, the design stipulates that even after a diode failure (breakdown), the sum of the clamping voltages should be greater than the peak voltage of the AC system. This ensures that even if the diode breaks down, no current flows through the diode when the switching module is in the off state.
[0044] Expressed in equation form:
[0045]
[0046] Among them U max is the peak voltage of the AC system, N is the number of TVS diodes connected in series, U cl is the clamping voltage of each individual TVS diode, and wherein TVS diodes with the same parameters, in particular the same clamping voltage, are used.
[0047] At the same time, the sum of the clamping voltages should be lower than the maximum permissible reverse voltage or rated voltage of the power semiconductor by a safety factor, i.e.:
[0048]
[0049] where f = 0.5 .. 0.9, and U T,max For example, it is 600V, 650V or 750V.
Claims
1. An electronic interruption unit (EU) for interrupting an electric current, the electronic interruption unit comprising: - at least one transistor (M1, M2) having a source terminal (S), a control terminal (G) and a low-potential terminal (D), wherein: The source connection (S) is a source connection or an emitter connection, the control connection (G) is a gate connection or a base connection, and the low potential terminal connection (D) is a drain connection or a collector connection, - at least one TVS diode (TVS1-TVS5) connected in parallel with the at least one transistor (M1, M2), and - a series circuit consisting of at least one capacitive element (C1, C2) and at least one resistive element (R1, R2), said series circuit being arranged between a control terminal (G) and a low potential terminal (D) of said at least one transistor (M1, M2).
2. The electronic interruption unit (EU) according to claim 1, characterized in that The electronic interruption element comprises a first transistor (M1) and a second transistor (M2), wherein the two transistors (M1, M2) are connected in series in an anti-series manner, and for each transistor (M1, M2) a series circuit consisting of at least one capacitive element (C1, C2) and at least one resistive element (R1, R2) is arranged between a control terminal (G) and a low-potential terminal (D).
3. The electronic interruption unit (EU) according to claim 1, characterized in that The at least one transistor (M1, M2) is a MOSFET or an IGBT.
4. The electronic interruption unit (EU) according to claim 1, characterized in that The electronic interruption unit is designed to have at least one driver (SIG) which is connected to a control terminal (G) of the at least one transistor (M1, M2) in order to drive (switching) the at least one transistor.
5. Electronic interruption unit (EU) according to any one of the preceding claims, characterized in that All capacitive elements (C1, C2) have the same nominal value C, and all resistive elements (R1, R2) have the same nominal value R.
6. Electronic interruption unit (EU) according to any of the preceding claims, characterized in that The electronic interruption unit is a component of a protective switch for AC voltage and has N series-connected TVS diodes connected in parallel with transistors (M1, M2) and having the same clamping voltage U cl , and the number N of TVS diodes in series and / or the clamping voltage U cl is chosen to satisfy the following relationship: ， Among them, U max It is the peak voltage of the AC voltage in the circuit that is switched on and off by the protection switch.
7. An electronic circuit breaker having an electronic interruption unit (EU) according to any one of the preceding claims.
8. A motor starter having an electronic interruption unit (EU) according to any one of the preceding claims.