A molded case circuit breaker with adaptive overcurrent protection

Abstract

This invention discloses an adaptive overcurrent protection molded case circuit breaker, belonging to the field of low-voltage electrical appliance technology. The invention includes a housing, an operating mechanism, a symmetrical double-break contact system, an arc-extinguishing chamber, a current detection unit, an electromagnetic repulsion acceleration component, an energy storage and discharge unit, and a control unit. The stationary contact is equipped with a hollowed-out groove and a permanent magnet magnetic field enhancement block, forming an adaptive composite magnetic blowout arc-extinguishing structure. The current detection unit outputs the current amplitude and rate of change signal based on the Rogowski coil. The control unit accurately distinguishes between motor starting current, overload faults, and short-circuit faults based on signal characteristics: during startup, it suppresses protection to avoid false tripping; during overload, it triggers the trip unit according to inverse-time characteristics; during short circuit, it simultaneously triggers the electromagnetic repulsion acceleration component and the trip unit, achieving ultra-fast breaking. This invention deeply integrates intelligent electronic control with a novel contact mechanical structure, achieving graded and precise response to different overcurrent levels, significantly improving the breaking capacity and protection reliability of the circuit breaker.

Description

Technical Field

[0001] This invention belongs to the field of low-voltage electrical appliance technology, specifically relating to a molded case circuit breaker with adaptive overcurrent protection. Background Technology

[0002] Molded case circuit breakers (MCCBs) are indispensable protective electrical devices in low-voltage power distribution systems, primarily used for distributing electrical energy and protecting lines and equipment from overload and short-circuit faults. Traditional MCCBs typically employ single-break or single-sided double-break contact structures. When interrupting large currents, the energy of a single arc is concentrated, placing extremely high demands on the performance of the arc-extinguishing chamber, resulting in a long arcing time and severe contact burn-out.

[0003] In existing technologies, some circuit breakers attempt to improve the static contact structure, such as using simple L-shaped or Z-shaped bends to guide the arc, but the effect is limited. More importantly, the overcurrent protection characteristics of traditional circuit breakers rely entirely on the fixed mechanical parameters of the bimetallic strip and electromagnetic trip unit. Their protection curves are fixed at the factory and cannot be adaptively adjusted according to the dynamic changes in the actual load (such as motor starting impact, seasonal load fluctuations, line aging, etc.). This leads to two common problems in practical applications: first, when the motor starts normally, the starting current (which can reach 5-7 times the rated current) is misjudged as a short circuit fault, causing the circuit breaker to malfunction and resulting in unnecessary power outages; second, under slight overload, the bimetallic strip responds slowly, the protection action time is long, and it cannot protect the line insulation in time. In addition, the integration of electronic trip units with traditional mechanical bodies in existing technologies is mostly an "additional" design. The electronic part only replaces the thermomagnetic trip unit and fails to achieve active coordinated control with the mechanical characteristics of the contact system (such as contact preload, breaking distance, breaking speed), which is insufficient in innovation.

[0004] Therefore, developing a circuit breaker that can deeply integrate a novel static contact magnetic blowout arc extinguishing structure with an adaptive electronic control system to achieve graded and precise response to different overcurrent levels, while also possessing ultra-fast short-circuit breaking capability, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a molded case circuit breaker with adaptive overcurrent protection, which deeply integrates intelligent electronic control with a novel contact mechanical structure to achieve graded and precise response to different overcurrent levels, significantly improving the breaking capacity and protection reliability of the circuit breaker, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an adaptive overcurrent protection molded case circuit breaker, comprising:

[0007] The casing consists of a base and a top cover;

[0008] Operating mechanism, including handle and linkage mechanism, is used for manual opening and closing of circuit breaker and driving the contact system.

[0009] The contact system includes a support turntable, a moving contact assembly mounted on the support turntable, and an upper stationary contact and a lower stationary contact fixed within a housing; the upper and lower stationary contacts are arranged symmetrically to form a double-break structure.

[0010] The arc-extinguishing chamber includes an upper arc-extinguishing chamber and a lower arc-extinguishing chamber, which are respectively disposed on the outside of the upper stationary contact and the lower stationary contact;

[0011] The current detection unit is used to output current signals and current change rate signals.

[0012] The electromagnetic repulsion acceleration assembly includes a repulsion armature fixed to the moving contact arm and a repulsion coil fixed to the mechanism frame;

[0013] An energy storage and discharge unit, including an energy storage capacitor and a discharge switch, is used to provide a large instantaneous current to the repulsion coil;

[0014] The control unit is electrically connected to the current detection unit, the discharge switch, and the trip unit of the operating mechanism, respectively, and is used to control the discharge switch and the trip unit according to the received signals.

[0015] As a further option, the upper stationary contact and the lower stationary contact are formed by integral stamping and bending of a conductive plate, and include in sequence: a terminal, a first bent part, an arc transition part and a second bent part; a stationary contact is fixed on the end plane of the second bent part; a hollow groove is opened in the middle of the first bent part along the length direction, and the hollow groove divides the first bent part into a first side current branch and a second side current branch that are symmetrical on the left and right.

[0016] As a further option, the outer edge of the first bend near the second bend is integrally formed with an outwardly protruding arc-inducing boss, the end of which extends toward the entrance of the upper or lower arc-extinguishing chamber.

[0017] As a further option, a magnetic field enhancement block is also included, which is clamped and fixed in the angular space between the first bend and the second bend; the magnetic field enhancement block includes a magnetically conductive substrate made of soft magnetic material and a permanent magnet embedded therein, the magnetization direction of the permanent magnet being perpendicular to the plane where the stationary contact is located and pointing to the corresponding arc-extinguishing chamber.

[0018] As a further option, the electromagnetic repulsion acceleration component includes: a first repulsion armature fixed to the back of the upper moving contact arm by an insulating pad, a first repulsion coil disposed opposite to the first repulsion armature, a second repulsion armature fixed to the back of the lower moving contact arm by an insulating pad, and a second repulsion coil disposed opposite to the second repulsion armature; the first repulsion coil and the second repulsion coil are connected in parallel and then connected to the output terminal of the energy storage discharge unit.

[0019] As a further option, the current detection unit includes: a Rogowski coil mounted on the main circuit busbar, and a proportional amplifier circuit connected to the output terminal of the Rogowski coil; the proportional amplifier circuit outputs a signal S proportional to the rate of change of current di / dt. didt The output of the Rogowski coil, after integration, yields a signal S that is proportional to the instantaneous current value i(t). i .

[0020] As a further option, the control unit includes a microprocessor and a memory, configured to: receive the instantaneous current value signal i(t) and the current rate of change signal di / dt; and when it is determined that the current amplitude exceeds the short-circuit threshold I... short And the absolute value of the rate of change of current exceeds the rate of change threshold K. didt At the same time, the discharge switch (47) and the trip unit of the operating mechanism are triggered; when the current amplitude is determined to exceed the overload threshold I overload However, if the short circuit condition is not met, only the trip unit of the operating mechanism is triggered.

[0021] As a further alternative, the control unit is further configured to: identify the motor starting current by detecting the half-wave peak decay trend of the current waveform, and suppress it for a preset suppression time T. start Internal shielding overload protection.

[0022] As a further option, the control unit is further configured to estimate the short-circuit current rise rate based on the measured absolute value of the current change rate |di / dt|, and dynamically adjust the output voltage of the charging circuit accordingly to adjust the pre-charge voltage of the energy storage capacitor.

[0023] As a further option, the discharge switch in the energy storage discharge unit is a high-power thyristor, with its anode connected to the positive terminal of the energy storage capacitor, its cathode connected to the common input terminal of the first repulsion coil and the second repulsion coil, and its control electrode connected to the control unit through a drive circuit.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The control unit accurately distinguishes between motor starting current, overload faults, and short-circuit faults based on the current amplitude and rate of change. During startup, it automatically suppresses protection to prevent false tripping; during overload, it triggers only the trip unit according to the inverse-time characteristic; during short circuit, it simultaneously triggers electromagnetic repulsion to accelerate disconnection, achieving intelligent matching between protection actions and fault types.

[0026] 2. The symmetrical double-break contact and the electromagnetic repulsion acceleration component work together. When a short circuit occurs, the energy storage capacitor discharges instantaneously, actively generating a strong repulsive force to drive the moving contact to accelerate the break. This, combined with the electric repulsive force, significantly shortens the arcing time and reduces the peak short-circuit current.

[0027] 3. The hollowed-out groove forces current diversion, generating a composite magnetic field in the contact gap that is proportional to the main circuit current. At low currents, the permanent magnet dominates the arc-blowing process; at high currents, the self-generated magnetic field increases with the current, achieving an adaptive effect where the larger the fault current, the faster the arc-blowing. The arc-initiating protrusion guides the arc to quickly leave the contact, protecting the contact from burn-out.

[0028] 4. The electromagnetic repulsion components are symmetrically arranged vertically, with superimposed driving torques and zero radial resultant force, ensuring smooth and reliable movement. The control unit can dynamically adjust the pre-charge voltage of the energy storage capacitor according to the current change rate, so that the electromagnetic repulsion and electric repulsion are optimally superimposed, further improving the breaking performance. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0030] In the attached diagram:

[0031] Figure 1 This is a schematic diagram of the internal structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the overall appearance and structure of the present invention;

[0033] Figure 3 This is a schematic diagram of the upper stationary contact structure of the present invention;

[0034] Figure 4 This is a schematic diagram of the magnetic field enhancement block mounting structure of the present invention;

[0035] Figure 5 This is a schematic diagram of the electromagnetic repulsion acceleration component system architecture of the present invention;

[0036] Figure 6 This is a schematic diagram of the overcurrent protection system architecture of the present invention.

[0037] In the diagram: 10: Base; 11: Top cover; 12: Support turntable; 13: Moving contact assembly; 14: Upper stationary contact; 15: Lower stationary contact; 16: Upper arc-extinguishing chamber; 17: Lower arc-extinguishing chamber; 18: Magnetic field enhancement block; 21: Mechanism frame; 23: Handle; 24: Linkage mechanism; 30: Rogowski coil; 31: Proportional amplifier circuit; 40: Control unit; 41: Microprocessor; 42: Memory; 43: Signal conditioning circuit; 44: Drive circuit; 45: Communication module; 46: Energy storage capacitor; 47: Discharge switch; 48: Charging circuit; 71: First 72: First repulsion armature; 73: Second repulsion armature; 74: Second repulsion coil; 121: Drive handle; 131: Upper moving contact arm; 132: Lower moving contact arm; 133: Moving contact; 141: Terminal; 142: First bend; 143: Arc transition; 144: Second bend; 145: Stationary contact; 711: Insulating gasket one; 731: Insulating gasket two; 1411: Wiring hole; 1421: Hollowed-out groove; 1422: First side current branch; 1423: Second side current branch; 1424: Arc-initiating boss. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: As Figures 1-2 As shown, the present invention provides an adaptive overcurrent protection molded case circuit breaker, comprising:

[0040] Housing: Composed of a base 10 and a top cover 11, made of thermosetting plastic injection molding, providing support and protection for internal components.

[0041] Operating mechanism: includes handle 23 and linkage mechanism 24. Handle 23 is rotatably mounted at the front end of the upper cover 11 and is connected to the support turntable 12 via linkage mechanism 24. This operating mechanism is used for manual opening and closing of the circuit breaker and for driving the contact system.

[0042] The contact system includes a support turntable 12, a moving contact assembly 13, an upper stationary contact 14, and a lower stationary contact 15. The moving contact assembly 13 is mounted on the support turntable 12 and rotates coaxially with it; the upper stationary contact 14 is fixed inside the upper part of the housing, and the lower stationary contact 15 is fixed inside the lower part of the housing, arranged symmetrically to form a double-break structure. During breaking, two series arcs are generated, and the arc voltages are superimposed, which is beneficial for rapid current limiting; the symmetrical structure ensures that the moving contact is subjected to balanced forces and moves smoothly.

[0043] Arc extinguishing chamber: includes an upper arc extinguishing chamber 16 and a lower arc extinguishing chamber 17, which are respectively located on the outside of the upper stationary contact 14 and the lower stationary contact 15, and are used to extinguish the electric arc.

[0044] Current detection unit: mounted on the main circuit bus, outputting current signal and current change rate signal.

[0045] Electromagnetic repulsion acceleration component: includes a first repulsion armature 71, a first repulsion coil 72, a second repulsion armature 73, and a second repulsion coil 74. This component can actively apply additional repulsion force during short-circuit faults, significantly improving the breaking speed.

[0046] Energy storage and discharge unit: includes energy storage capacitor 46 and discharge switch 47, which provides instantaneous large current to the repulsion coil.

[0047] Control unit 40: Receives signals from the current detection unit, controls the discharge switch 47 and the trip unit of the operating mechanism, and realizes intelligent hierarchical protection.

[0048] II. Contact System and Composite Magnetic Blowout Arc Extinguishing Structure

[0049] (a) Supporting turntable and moving contact assembly

[0050] The support turntable 12 is a disc-shaped component with a central pivot hole, and is rotatably supported on the pivot seat of the base 10 via bearings. A radially extending drive handle 121 is provided on the outer circumference of the support turntable 12, and a pin hole for connecting to the linkage mechanism 24 is provided on the drive handle 121.

[0051] A flat mounting surface is provided on each of the radial sides of the supporting turntable 12. The moving contact assembly 13 includes:

[0052] Upper moving contact arm 131: a long strip of copper component that extends upward from the mounting plane of the supporting turntable 12, with a moving contact 133 fixed at its free end.

[0053] Lower moving contact arm 132: a long strip of copper component that extends downward from the mounting plane of the supporting turntable 12, with a moving contact 133 fixed at its free end.

[0054] The upper moving contact arm 131 and the lower moving contact arm 132 are arranged symmetrically. The moving contact arms rotate synchronously with the support turntable to ensure that the two break points close or break simultaneously; the symmetrical structure makes the center of mass of the moving contact assembly located at the center of the rotation axis, resulting in a small inertial torque and fast response speed when breaking.

[0055] (ii) Static contact assembly (composite magnetic blowout structure)

[0056] The upper stationary contact 14 and the lower stationary contact 15 have the same structure and are symmetrical. The following is a detailed description using the upper stationary contact 14 as an example (see...). Figure 3 ).

[0057] The upper stationary contact 14 is formed by integral stamping and bending of a conductive plate, and includes, in sequence:

[0058] Terminal 141: A rectangular flat plate with a wiring hole 1411 for connecting external wires.

[0059] The first bend 142: Starting from the end of the terminal 141, it bends vertically away from the moving contact, then extends obliquely outward. The width of the first bend 142 is greater than that of the subsequent second bend 144. A perforated groove 1421 is formed along the length of the first bend 142 in the middle. The perforated groove 1421 is a long strip-shaped through hole that completely penetrates the thickness of the plate. The perforated groove 1421 divides the first bend 142 into two symmetrical current branches: a first side current branch 1422 and a second side current branch 1423, with equal cross-sectional areas. The perforated groove forces the current to be split, forming a ring-shaped magnetic field around the perforated groove in the contact area. Because the two branches are symmetrical, the magnetic field is evenly distributed, and the strength of the self-generated magnetic field is proportional to the main circuit current, thus achieving automatic enhancement of the arc-blowing force with the current. An outwardly protruding arc-initiating boss 1424 is integrally formed on the outer edge of the first bend 142 near the second bend. The end of the arc-initiating boss 1424 extends toward the entrance of the upper arc-extinguishing chamber 16, with a gap between them. As a priority point for arc transfer, the arc-initiating boss guides the arc to quickly leave the stationary contact, protecting the contact from ablation.

[0060] Arc transition section 143: Connects the first bend section 142 and the second bend section 144, with a smooth radius of curvature. The smooth transition reduces stress concentration and localized heating, while also avoiding current distortion.

[0061] The second bend 144 bends inward first, then bends upward and extends, with its end plane tangent to the movement trajectory of the upper moving contact 136. An upper stationary contact 145 is fixed to this end plane. The width of the second bend 144 is smaller than the width of the first bend 142, allowing current to converge from the wider first bend and enter the narrower second bend, further increasing the current density in the contact area and enhancing the magnetic field.

[0062] Magnetic field enhancement block 18 (see Figure 4The magnetic field enhancing block 18 is clamped and fixed within the angular space between the first bent portion 142 and the second bent portion 144. It comprises a magnetically conductive substrate made of soft magnetic material and a permanent magnet embedded therein. The magnetization direction of the permanent magnet is perpendicular to the plane of the stationary contact and points towards the arc-extinguishing chamber (for the upper stationary contact 14, the magnetization direction points towards the upper arc-extinguishing chamber 16 on the right; for the lower stationary contact 15, the magnetization direction points towards the lower arc-extinguishing chamber 17 on the left). The surface of the magnetically conductive substrate is bonded to the stationary contact through an insulating adhesive layer to ensure electrical insulation. The permanent magnet provides a constant basic magnetic field, ensuring that the arc can be effectively driven away even under small current overload; the magnetically conductive substrate concentrates magnetic lines of force, improving magnetic field utilization efficiency.

[0063] (III) Principle and Effect of Composite Magnetic Blowout Arc Extinguishing

[0064] When current flows through the stationary contact, the permanent magnet generates a constant magnetic field B. const Simultaneously, the hollowed-out groove 1421 forces the current to split into two paths, forming a combined magnetic field B pointing towards the arc-initiating boss in the contact gap region. self The strength of this magnetic field is proportional to the main circuit current I, and its direction is parallel to B in the contact gap region. const The same. The arc current I generated by the separation of the moving and stationary contacts. arc The electromagnetic force F=I in the combined magnetic field arc ×(B const +B self The force points towards the arc-starting boss 1424 and the arc-extinguishing chamber. At low current, B... const Maintain arc extinguishing to ensure reliable arc suppression; B under high current. self As the current increases sharply, the arc-blowing force increases significantly, achieving an adaptive effect where the larger the fault current, the faster the arc-blowing, without the need for any external sensors or actuators.

[0065] III. Electromagnetic repulsion acceleration assembly (as a further optional reinforcement mechanism, see...) Figure 5 )

[0066] The electromagnetic repulsion acceleration component is used to actively drive the moving contact arm to accelerate the breaking process during a short-circuit fault. Its specific structure is as follows:

[0067] The first repulsive armature 71 is made of a high magnetic permeability material and is fixed to the back of the upper moving contact arm 131 (i.e. the side away from the upper stationary contact 145) by an insulating pad 711.

[0068] First repulsion coil 72: A multi-layered coil wound with enameled wire and covered with an insulating layer. The first repulsion coil 72 is fixedly mounted on the mechanism frame 21, with its end face facing the end face of the first repulsion armature 71, and an air gap between them. This air gap remains in a non-contact state during the closing and opening of the moving contact arm, and a limiting structure is provided to prevent the armature from excessively moving and colliding with the coil.

[0069] The second repulsive armature 73 has the same structure as the first repulsive armature 71 and is fixed to the back of the lower moving contact arm 132 by an insulating pad 731.

[0070] The second repulsion coil 74 has the same structure as the first repulsion coil 72 and is fixedly mounted on the mechanism frame 21, opposite to the second repulsion armature 73. Similarly, a limiting structure is provided at this air gap.

[0071] The first repulsion coil 72 and the second repulsion coil 74 are connected in parallel and are both connected to the output terminal of the energy storage and discharge unit. When both coils are energized simultaneously, the generated magnetic field causes the two repulsion armatures to be subjected to an outward pushing force (in the direction of the opening of the moving contact arm). Due to the vertical symmetry, this pushing force generates two driving torques in the same direction on the rotating shaft of the supporting turntable 12. The superposition of these two torques drives the moving contact assembly 13 to break more quickly. At the same time, the symmetrical structure makes the radial resultant force acting on the supporting turntable 12 zero, avoiding the tilting and vibration of the turntable caused by unilateral force, thus making the movement more stable.

[0072] This component is triggered by the control unit only in the event of a short-circuit fault, providing a driving force that is much greater than that of traditional electric repulsion, enabling the moving contact to begin breaking in a very short time, thus significantly improving the current limiting capability; the symmetrical arrangement avoids the deflection and vibration caused by unilateral repulsion.

[0073] IV. Current Detection Unit (see below) Figure 6 )

[0074] The current detection unit includes:

[0075] Rogowski coil 30: It is installed on the main circuit bus, and its output voltage e(t) is proportional to the rate of change of current di / dt, that is, e(t) = −M⋅di / dt, where M is the mutual inductance coefficient.

[0076] Proportional amplifier circuit 31: Connected to the output terminal of Rogowski coil 30, it amplifies the signal without phase shift, and outputs a signal S proportional to di / dt. didt This circuit avoids the noise amplification and phase distortion introduced by the differentiating circuit.

[0077] Meanwhile, the output of the Rogowski coil 30 is integrated to obtain a signal S that is proportional to the instantaneous current value i(t). i This integration process can be performed by an analog integrating circuit or by a microprocessor within the control unit 40 using a digital integrating algorithm. Considering small-signal accuracy and phase compensation, an active integrating circuit with an automatic reset function is preferred.

[0078] The Rogowski coil is free from magnetic saturation and has a wide dynamic range, enabling precise measurement of current waveforms from overload to extreme short circuits. It also outputs two signals, i(t) and di / dt, providing ample information for rapid fault type identification.

[0079] The two output signals S of the current detection unit didt and S i The signal is transmitted to the control unit 40 via a shielded cable.

[0080] V. Energy Storage and Discharge Unit (see) Figure 6 )

[0081] The energy storage and discharge unit includes:

[0082] Energy storage capacitor 46: Used to store electrical energy.

[0083] Charging circuit 48: The input terminal is connected to the auxiliary power supply, and the output terminal is connected to both ends of the energy storage capacitor 46. The charging circuit 48 is controlled by the control unit 40 and charges the energy storage capacitor 46 to a preset voltage when the circuit breaker is operating normally. This charging circuit can adopt a switching power supply topology, and the control unit 40 can dynamically adjust its output voltage through control signals, thereby regulating the pre-charge voltage of the energy storage capacitor.

[0084] Discharge switch 47: Employs a high-power thyristor. Its anode is connected to the positive terminal of the energy storage capacitor 46, its cathode is connected to the common input terminal of the first repulsion coil 72 and the second repulsion coil 74, and the other end of the coil is connected to the negative terminal of the energy storage capacitor 46. The control terminal of discharge switch 47 is connected to control unit 40 via a drive circuit.

[0085] Under normal conditions, the discharge switch 47 is off. When the control unit 40 sends a trigger pulse, the discharge switch 47 is turned on, and the energy storage capacitor 46 quickly discharges to the parallel repulsion coil, generating a pulse current with extremely high amplitude.

[0086] The energy storage capacitor is pre-charged to ensure that a large current pulse can be provided immediately when a short circuit occurs; the thyristor conduction time is extremely short to ensure that the electromagnetic repulsion force is synchronized with the short circuit current.

[0087] VI. Control Unit (see...) Figure 6 )

[0088] The control unit 40 is integrated into a metal shielded box and fixed to one side of the base 10. Its internal components include: a microprocessor 41, a memory 42, a signal conditioning circuit 43, a drive circuit 44, and a communication module 45.

[0089] The core function of the control unit 40 is to receive the i(t) and di / dt signals output by the current detection unit, determine the fault type through an internal algorithm, and then control the discharge switch 47 and the trip unit of the operating mechanism according to the fault level to achieve graded protection. Its basic principle and coordination are as follows.

[0090] (I) Signal Acquisition and Fault Diagnosis

[0091] The microprocessor 41 continuously acquires the instantaneous values ​​of i(t) and di / dt. It then compares i(t) with a preset overload threshold I. overload Short-circuit current threshold I short , and |di / dt| and the rate of change threshold K didt It can distinguish three working conditions:

[0092] Normal startup current: The current amplitude is relatively high, but the waveform exhibits an exponential decay characteristic, and |di / dt| decreases rapidly after the initial peak. The microprocessor 41 identifies the startup process by detecting the decay trend of several consecutive half-wave peaks and suppresses it for a preset suppression time T. start Internal shielding overload protection.

[0093] Overload fault: Current amplitude exceeds I overload However, the short-circuit condition was not met, and the duration exceeded the time allowed by the inverse time characteristic.

[0094] Short circuit fault: Current amplitude exceeds I short And |di / dt| exceeds K didt If both conditions are met, it is considered a short circuit.

[0095] (II) Hierarchical protection and coordinated control

[0096] Based on the judgment result, the control unit 40 executes different cooperative actions:

[0097] In the event of a short circuit: the microprocessor 41 immediately triggers the discharge switch 47 via the drive circuit 44, causing the energy storage capacitor 46 to discharge to the first repulsion coil 72 and the second repulsion coil 74, generating a strong instantaneous repulsive force to accelerate the opening of the moving contact arm. Simultaneously, the microprocessor 41 triggers the trip unit of the operating mechanism, causing the support turntable 12 to rotate to the disconnected position and remain there. During this process, the electromagnetic repulsion acceleration component and the stationary contact composite magnetic blow-out structure work together: the repulsion component ensures rapid initial contact separation, and the magnetic blow-out structure ensures the arc is quickly blown into the arc-extinguishing chamber and extinguished.

[0098] It should be noted that the moving contact arm itself generates an electrodynamic repulsion force under short-circuit current, with its peak value appearing in the first half-wave of the short-circuit current. The electromagnetic repulsion component has an inherent delay in its operation (including signal processing, thyristor conduction, capacitor discharge, and coil magnetization). This delay, after optimization, naturally overlaps with the peak value of the electrodynamic repulsion force in time, thus eliminating the need for artificially adding additional delay. Simultaneously, the control unit 40 estimates the short-circuit current rise rate based on the measured |di / dt| and dynamically adjusts the output voltage of the charging circuit 48 through control signals. This ensures that the pre-charge voltage of the energy storage capacitor 46 matches the expected amplitude of the electrodynamic repulsion force, thereby achieving the maximum combined acceleration during the initial contact breaking stage.

[0099] In case of overload fault: Microprocessor 41 does not trigger discharge switch 47, but only initiates inverse-time integral oscillation. After the integral reaches the action threshold, it triggers the trip unit, causing the support turntable 12 to rotate and disconnect. At this time, the fault current is relatively small, and the constant magnetic field of the permanent magnet in the stationary contact is sufficient to reliably drive the arc into the arc-extinguishing chamber without the need for repulsive force assistance. If microprocessor 41 detects that the overload current is close to the short-circuit threshold and di / dt is large, it automatically switches to short-circuit protection logic and triggers discharge switch 47 to ensure reliable disconnection.

[0100] When the motor starts normally: after the microprocessor 41 identifies the starting current, it sets the starting flag and starts the suppression timer. During the suppression time T... start Even if the current exceeds the overload threshold, no protection will be triggered. After the suppression period ends, normal monitoring will automatically resume. This function completely solves the problem of traditional circuit breakers tripping falsely due to starting current.

[0101] (iii) Overload inverse time characteristic

[0102] Overload protection uses standard inverse time characteristics. The relationship between the action delay time t and the overload multiple is as follows:

[0103]

[0104] Where I is the measured effective value of the current, I n The rated current is K, and the time constant (adjustable) is t. min This is the minimum operating time. The microprocessor 41 performs discrete integration based on this characteristic, and triggers the trip unit when the integral value reaches the operating threshold.

[0105] (iv) Dynamic adjustment of discharge voltage

[0106] To achieve the optimal superposition of electromagnetic and electrodynamic repulsion forces, the control unit 40 estimates the expected short-circuit current rise rate based on the current peak value of |di / dt| each time a short-circuit fault occurs. The larger this value, the greater the required electromagnetic repulsion force. Based on this, the microprocessor 41 adjusts the output voltage of the charging circuit 48 via control signals, thereby increasing the pre-charge voltage of the energy storage capacitor 46 accordingly from its rated value (the upper limit is determined by the capacitor's withstand voltage). This dynamic adjustment process is completed during the normal operation intervals of the circuit breaker, ensuring that the energy storage capacitor is in an optimal voltage state when a short circuit occurs.

[0107] VII. System Collaboration Workflow

[0108] (a) Short-circuit fault disconnection process

[0109] Detection: The current detection unit detected i(t) > I short And |di / dt|>K didt The signal is sent to the control unit 40.

[0110] Decision and triggering: Microprocessor 41 immediately triggers discharge switch 47 without additional delay.

[0111] Active repulsion: When the discharge switch 47 is turned on, the energy storage capacitor 46 discharges to the first repulsion coil 72 and the second repulsion coil 74, generating a transient strong magnetic field. The first repulsion armature 71 and the second repulsion armature 73 are subjected to strong repulsion, which forces the upper moving contact arm 131 and the lower moving contact arm 132 to move at high speed in the breaking direction.

[0112] Composite magnetic blowout arc extinguishing: An electric arc is generated when the moving and stationary contacts separate. The constant magnetic field of the permanent magnet on the stationary contact is superimposed with the self-generated magnetic field of the hollow groove, generating a strong electromagnetic force pointing towards the arc extinguishing chamber, which quickly drives the arc into the upper arc extinguishing chamber 16 and the lower arc extinguishing chamber 17 to extinguish it.

[0113] Trip holding: The control unit 40 simultaneously triggers the trip unit of the operating mechanism to keep the support turntable 12 in the disconnected position.

[0114] The total time from detection to arc extinction is extremely short, resulting in significant current limiting and effective protection of lines and equipment.

[0115] (II) Overload Fault Disconnection Process

[0116] Detection: The current detection unit detected i(t) > I overload However, |di / dt| is low and does not meet the short-circuit condition.

[0117] Inverse time delay: Microprocessor 41 starts inverse time integration, without triggering discharge switch 47.

[0118] Interruption and Arc Extinguishing: When the integral reaches the operating value, only the trip unit is triggered, causing the support turntable 12 to rotate and interrupt the arc. At this time, the current is small, and the constant magnetic field of the permanent magnet is sufficient to drive the arc into the arc extinguishing chamber.

[0119] The overload protection operates reliably based on the inverse-time characteristic and does not activate electromagnetic repulsion, thus avoiding unnecessary mechanical impact and extending the circuit breaker's lifespan.

[0120] Normal start-up process of electric motor

[0121] Detection: The starting current reaches a high amplitude, but the waveform exhibits an exponential decay characteristic.

[0122] Identification: The microprocessor 41 identifies the normal startup by the half-wave peak sequence, sets the startup flag, and starts the suppression timer.

[0123] Inhibition protection: During inhibition time T start Within this timeframe, protection will not be triggered even if the current exceeds the overload threshold. Normal monitoring will resume after the suppression period ends.

[0124] Result: The circuit breaker remained closed, preventing accidental tripping.

[0125] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A molded case circuit breaker with adaptive overcurrent protection, characterized in that, include: The housing consists of a base (10) and a top cover (11); The operating mechanism includes a handle (23) and a linkage mechanism (24) for manually opening and closing the circuit breaker and driving the contact system. The contact system includes a support turntable (12), a moving contact assembly (13) mounted on the support turntable (12), and an upper stationary contact (14) and a lower stationary contact (15) fixed in the housing; the upper stationary contact (14) and the lower stationary contact (15) are arranged symmetrically in the upper and lower parts to form a double-break structure; The arc-extinguishing chamber includes an upper arc-extinguishing chamber (16) and a lower arc-extinguishing chamber (17), which are respectively disposed on the outside of the upper stationary contact (14) and the lower stationary contact (15); The current detection unit is used to output current signals and current change rate signals. The electromagnetic repulsion acceleration assembly includes a repulsion armature fixed to the moving contact arm and a repulsion coil fixed to the mechanism frame; The energy storage and discharge unit includes an energy storage capacitor (46) and a discharge switch (47) for providing a large instantaneous current to the repulsion coil; The control unit (40) is electrically connected to the current detection unit, the discharge switch (47) and the trip unit of the operating mechanism, respectively, and is used to control the discharge switch (47) and the trip unit according to the received signal.

2. The molded case circuit breaker with adaptive overcurrent protection according to claim 1, characterized in that, The upper stationary contact (14) and the lower stationary contact (15) are formed by integral stamping and bending of conductive plates, and include in sequence: terminal (141), first bent part (142), arc transition part (143) and second bent part (144); a stationary contact (145) is fixed on the end plane of the second bent part (144); a hollow groove (1421) is provided in the middle of the first bent part (142) along the length direction, and the hollow groove (1421) divides the first bent part (142) into a first side current branch (1422) and a second side current branch (1423) that are symmetrical on the left and right.

3. A molded case circuit breaker with adaptive overcurrent protection according to claim 2, characterized in that, The outer edge of the first bend (142) near the second bend has an outwardly protruding arc-inducing boss (1424), the end of which extends toward the entrance of the upper arc-extinguishing chamber (16) or the lower arc-extinguishing chamber (17).

4. A molded case circuit breaker with adaptive overcurrent protection according to claim 2, characterized in that, It also includes a magnetic field enhancement block (18), which is clamped and fixed in the angle space between the first bending part (142) and the second bending part (144); the magnetic field enhancement block (18) includes a magnetic conductive substrate made of soft magnetic material and a permanent magnet embedded therein, the magnetization direction of the permanent magnet is perpendicular to the plane where the stationary contact is located and points to the corresponding arc extinguishing chamber.

5. A molded case circuit breaker with adaptive overcurrent protection according to claim 1, characterized in that, The electromagnetic repulsion acceleration assembly includes: a first repulsion armature (71) fixed to the back of the upper moving contact arm (131) by an insulating pad (711), a first repulsion coil (72) disposed opposite to the first repulsion armature (71), a second repulsion armature (73) fixed to the back of the lower moving contact arm (132) by an insulating pad (731), and a second repulsion coil (74) disposed opposite to the second repulsion armature (73); the first repulsion coil (72) and the second repulsion coil (74) are connected in parallel and then connected to the output terminal of the energy storage discharge unit.

6. A molded case circuit breaker with adaptive overcurrent protection according to claim 1, characterized in that, The current detection unit includes: a Rogowski coil (30) mounted on the main circuit busbar, and a proportional amplifier circuit (31) connected to the output terminal of the Rogowski coil (30); the proportional amplifier circuit (31) outputs a signal S proportional to the rate of change of current di / dt. didt The output of the Rogowski coil (30) is integrated to obtain a signal S that is proportional to the instantaneous current value i(t). i .

7. A molded case circuit breaker with adaptive overcurrent protection according to claim 1, characterized in that, The control unit (40) includes a microprocessor (41) and a memory (42), and is configured to receive a current instantaneous value signal i(t) and a current rate of change signal di / dt; When the current amplitude exceeds the short-circuit threshold I short And the absolute value of the rate of change of current exceeds the rate of change threshold K. didt At the same time, the discharge switch (47) and the trip unit of the operating mechanism are triggered; when the current amplitude is determined to exceed the overload threshold I overload However, if the short circuit condition is not met, only the trip unit of the operating mechanism is triggered.

8. A molded case circuit breaker with adaptive overcurrent protection according to claim 7, characterized in that, The control unit (40) is further configured to: identify the motor starting current by detecting the half-wave peak decay trend of the current waveform, and suppress it for a preset suppression time T. start Internal shielding overload protection.

9. A molded case circuit breaker with adaptive overcurrent protection according to claim 7 or 8, characterized in that, The control unit (40) is further configured to estimate the short-circuit current rise rate based on the measured absolute value of the current change rate |di / dt|, and dynamically adjust the output voltage of the charging circuit (48) accordingly to adjust the pre-charge voltage of the energy storage capacitor (46).

10. A molded case circuit breaker with adaptive overcurrent protection according to claim 1, characterized in that, The discharge switch (47) in the energy storage discharge unit is a high-power thyristor. Its anode is connected to the positive terminal of the energy storage capacitor (46), and its cathode is connected to the common input terminal of the first repulsion coil (72) and the second repulsion coil (74). The control electrode is connected to the control unit (40) through the drive circuit (44).

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