An ftu feeder terminal magnetic control mechanism reverse potential elimination circuit

Abstract

The present application relates to the technical field of FTU feeder terminal, in particular to a kind of FTU feeder terminal magnetic control mechanism reverse potential elimination circuit, including Y=A+ unit A, isolated opto-coupler drive unit A, high-voltage electronic switch A, freewheeling diode A, Y=A+ unit B, isolated opto-coupler drive unit B, high-voltage electronic switch B and freewheeling diode B;Y=A+ unit A is carried out logic processing to the closing elimination signal and the opening signal of input;Y=A+ unit B is carried out logic processing to the opening elimination signal and the closing signal of input;To prevent the short circuit of opening and closing reverse potential elimination unit misinvestment, the present application is logically limited on hardware: when closing, opening reverse potential elimination unit is prohibited to invest;When opening, closing reverse potential elimination unit is prohibited to invest;The present application can completely eliminate the reverse potential generated by magnetic control mechanism in opening and closing moment, effectively solve the problem that product occasionally appears pole post drop, improve the operation reliability of product.

Description

Technical Field

[0001] This invention relates to the field of FTU feeder termination technology, and in particular to a magnetic control mechanism reverse potential elimination circuit. Background Technology

[0002] In 10kV distribution network systems, FTU (Feeder Terminal Unit) collects voltage and current parameters from the power grid lines to control the opening and closing of pole-mounted circuit breakers. In actual use, one type of magnetically controlled pole-mounted circuit breaker occasionally experiences spontaneous tripping while closed. Therefore, most customers are unwilling to use magnetically controlled circuit breakers and instead choose traditional spring-mechanism circuit breakers. Through testing and analysis, the reason is that the magnetic control mechanism in the magnetically controlled circuit breaker generates a reverse pulse (reverse electromotive force generated by the inductor coil) at the moment of closing. Although this reverse pulse does not directly cause the magnetic control mechanism to trip, it reduces the holding force of the magnetic control mechanism. When the consistency deviation of the magnetic control mechanism parameters is slightly large, coupled with environmental factors, the magnetic control mechanism may occasionally detach. If the detachment occurs after reclosing, it may trigger cascading tripping or even switch arcing and explosion, leading to busbar voltage loss and large-scale power outages. For dedicated lines with sensitive industrial loads, instantaneous voltage loss can cause batch product scrapping. Therefore, abnormal power outages caused by equipment defects must be avoided.

[0003] For reverse pulses generated by inductive loads such as motors, TVS diodes, freewheeling diodes, and RC snubber circuits are typically used in hardware to eliminate or weaken them. However, the following drawbacks still exist: 1. The breakdown voltage and clamping voltage of the TVS diode must be higher than the operating voltage of the motor, and it has no effect on eliminating reverse potentials with amplitudes lower than the operating voltage; 2. Using a single freewheeling diode is suitable for unidirectional motors. Connecting the diode in reverse parallel across the motor windings can quickly and effectively eliminate the reverse potential. However, for motors with both forward and reverse rotation, the reverse parallel connection will cause a power short circuit when the motor reverses; 3. Using an RC snubber circuit, connecting an RC circuit in parallel across the windings can absorb some of the peak potentials. However, for reverse potentials generated by high-power inductive loads, it can only appropriately suppress the potential amplitude and cannot completely eliminate them. At the same time, the parallel RC circuit will continuously consume power energy when the load is working. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a reverse electromotive force elimination circuit for the magnetic control mechanism of an FTU feeder terminal, which can quickly and effectively eliminate the reverse electromotive force generated by the magnetic control mechanism at the moment of closing.

[0005] The technical solution adopted in this invention is: a reverse potential elimination circuit for an FTU feeder terminal magnetic control mechanism, comprising Y=A+ Unit A, Isolation Optocoupler Driver Unit A, High Voltage Electronic Switch A, Freewheeling Diode A, Y= A+ Unit B, isolation optocoupler drive unit B, high-voltage electronic switch B, and freewheeling diode B; Y = A + Unit A performs logic processing on the input closing cancellation signal and opening signal, and outputs a control signal that meets the requirements; the isolation optocoupler drive unit A isolates the transmitted signal between the preceding and following stages and is also responsible for driving the high-voltage electronic switch A; the high-voltage electronic switch A operates in the on or off state according to the high or low potential of the control signal; the freewheeling diode A conducts unidirectionally to the reverse electromotive force generated by closing; Y = A + Unit B performs logic processing on the input tripping cancellation signal and closing signal, and outputs a control signal that meets the requirements; the isolation optocoupler drive unit B isolates the transmitted signal between the front and rear stages and is also responsible for driving the high-voltage electronic switch B; the high-voltage electronic switch B operates in the on or off state according to the high or low potential of the control signal; the freewheeling diode B conducts unidirectionally to the reverse electromotive force generated by tripping.

[0006] Preferably, Y = A + Unit A includes resistor R30, transistor Q7 (S8050), resistors R31 and R32, transistor Q8, resistor R35, and transistor Q9. The closing cancellation signal is connected to one end of resistor R30, and the other end of resistor R30 is connected to the base of transistor Q7. The collector of transistor Q7 is connected to one end of resistor R31 and one end of resistor R32. The other end of resistor R31 is connected to the power supply VCC. The other end of resistor R32 is connected to the base of transistor Q8. The collector of transistor Q8 is connected to one end of resistor R33 in the isolation optocoupler driver unit A, the anode of diode D5, and pin 3 of optocoupler U5. The emitter of transistor Q8 is connected to the collector of transistor Q9. The opening signal is connected to one end of resistor R35, and the other end of resistor R35 is connected to the base of transistor Q9. The emitters of transistors Q7 and Q9 are both connected to the power supply ground.

[0007] Preferably, the isolated optocoupler driving unit A includes resistor R33, resistor R34, diode D5, optocoupler U5 (TLP250), and capacitor C10; one end of resistor R33 is connected to the anode of diode D5, pin 3 of optocoupler U5, and the collector of transistor Q8 in Y=A+B unit A; the other end of resistor R33 is connected to power supply VCC and one end of resistor R34; the other end of resistor R34 is connected to the cathode of diode D5 and pin 2 of optocoupler U5; pin 5 of optocoupler U5 is connected to negative power supply -9V4 (the fourth DC power supply provides +15V, -9V) and one end of capacitor C10; pin 6 of optocoupler U5 is connected to pin 7 of optocoupler U5, one end of resistor R43, and one end of resistor R44; pin 8 of optocoupler U5 is connected to power supply +15V4 (the fourth DC power supply provides +15V, -9V) and the other end of capacitor C10.

[0008] Preferably, the high-voltage electronic switch A includes resistors R43, R44, and R45, a TVS diode (TVS5), an IGBT (NCE40TD120BT), and a capacitor (C11). One end of resistor R43 is connected to one end of resistor R44, pins 6 and 7 of optocoupler U5 in the isolation optocoupler drive unit A, and the other end of resistor R43 is connected to the other end of resistor R44, one end of resistor R45, pin 1 of diode TVS5, and the gate G of IGBT Q5. The collector C of IGBT Q5 is connected to one end of capacitor C11 and the cathode of diode D7 in freewheeling diode A. The emitter E of IGBT Q5 is connected to the other end of resistor R45, pin 2 of diode TVS5, power ground QGND4 (the fourth DC power ground), the other end of capacitor C11, and terminal A of the magnetic control coil.

[0009] Preferably, the freewheeling diode A includes diode D7 (RHRG30120), the anode of diode D7 is connected to terminal B of the magnetic control coil, and the cathode of diode D7 is connected to the collector of IGBT transistor Q5 in high-voltage electronic switch A and one end of capacitor C11.

[0010] Preferably, Y = A + Unit B includes resistor R36, transistor Q10 (S8050), resistors R37 and R38, transistor Q11, resistor R41, and transistor Q12. The trip signal is connected to one end of resistor R36, and the other end of resistor R36 is connected to the base of transistor Q10. The collector of transistor Q10 is connected to one end of resistor R37 and one end of resistor R38. The other end of resistor R37 is connected to power supply VCC. The other end of resistor R38 is connected to the base of transistor Q11. The collector of transistor Q11 is connected to one end of resistor R39 in the isolation optocoupler driver unit B, the anode of diode D6, and pin 3 of optocoupler U6. The emitter of transistor Q11 is connected to the collector of transistor Q12. The closing signal is connected to one end of resistor R41, and the other end of resistor R41 is connected to the base of transistor Q12. The emitters of transistors Q10 and Q12 are both connected to power supply ground.

[0011] Preferably, the isolated optocoupler driving unit B includes resistor R39, resistor R40, diode D6, optocoupler U6 (TLP250), and capacitor C12; one end of resistor R39 is connected to the anode of diode D6, pin 3 of optocoupler U6, and collector of transistor Q11 in Y=A+B unit B; the other end of resistor R39 is connected to power supply VCC and one end of resistor R40; the other end of resistor R40 is connected to the cathode of diode D6 and pin 2 of optocoupler U6; pin 5 of optocoupler U6 is connected to negative power supply -9V5 (provided by the 5th DC power supply +15V, -9V) and one end of capacitor C12; pin 6 of optocoupler U6 is connected to pin 7 of optocoupler U6, one end of resistor R46, and one end of resistor R47; pin 8 of optocoupler U6 is connected to power supply +15V5 (provided by the 5th DC power supply +15V, -9V) and the other end of capacitor C12.

[0012] Preferably, the high-voltage electronic switch B includes resistors R46, R47, and R48, a TVS diode TVS6, an IGBT Q6 (NCE40TD120BT), and a capacitor C13. One end of resistor R46 is connected to one end of resistor R47, pins 6 and 7 of optocoupler U6 in the isolation optocoupler drive unit B, and the other end of resistor R46 is connected to the other end of resistor R47, one end of resistor R48, pin 1 of diode TVS6, and the gate G of IGBT Q6. The collector C of IGBT Q6 is connected to one end of capacitor C13 and the cathode of diode D8 in freewheeling diode B, and the emitter E of IGBT Q6 is connected to the other end of resistor R48, pin 2 of diode TVS6, power ground QGND5 (the fifth DC power ground), the other end of capacitor C13, and the B end of the magnetic control coil.

[0013] Preferably, the freewheeling diode B includes diode D8 (RHRG30120), the anode of diode D8 is connected to terminal A of the magnetic control coil, and the cathode of diode D8 is connected to the collector of IGBT transistor Q6 in high-voltage electronic switch B and one end of capacitor C13.

[0014] The beneficial effects of this invention are as follows: First, by separately setting up a reverse electromotive force elimination unit for closing (including Y= A+ Unit A, isolation optocoupler drive unit A, high-voltage electronic switch A, freewheeling diode A) and tripping reverse potential elimination unit (including Y= A+ Unit B, isolation optocoupler drive unit B, high-voltage electronic switch B, and freewheeling diode B enable the circuit to independently construct discharge circuits for the reverse potential generated in the closing and opening directions, respectively. Compared with the traditional single freewheeling diode solution, this invention effectively avoids the risk of power supply short circuit during forward and reverse switching, and overcomes the defect that TVS tubes cannot eliminate low-amplitude reverse potentials.

[0015] II. In this invention, the IGBT transistors (Q5, Q6) in the high-voltage electronic switches A and B remain in a conducting state during closing or opening operations, and continue to be conducting for 10ms after the operation ends. When the magnetic control coil generates a reverse electromotive force, the reverse electromotive force is directly applied to the collector of the already conducting IGBT transistor through the freewheeling diode (D7 or D8), and returns to the other end of the magnetic control coil through the emitter, forming a low-impedance discharge circuit. Since the IGBT transistor is already in a conducting state before the reverse electromotive force is generated, seamless connection can be achieved, and the reverse electromotive force energy can be quickly discharged without being limited by the amplitude of the reverse electromotive force, thus completely eliminating its influence on the holding force of the magnetic control mechanism.

[0016] III. The Y= A+ of the present invention Unit A performs logical operations on the closing cancellation signal and the opening signal, Y = A + Unit B performs logical operations on the tripping cancellation signal and the closing signal. According to the truth table, when closing cancellation is required (closing cancellation signal is low, tripping signal is high), the tripping reverse electromotive force cancellation unit is prohibited from being activated because the tripping cancellation signal is high. When tripping cancellation is required, the closing reverse electromotive force cancellation unit is also prohibited. This hardware logic interlock design ensures that the two cancellation units will not be activated simultaneously under any operating conditions, thus avoiding the potential for power short circuits from a physical perspective.

[0017] IV. When the control signal is valid, the isolation optocoupler driving units A and B (using TLP250) of this invention output a +15V positive power supply to drive the IGBT to conduct; when the control signal is invalid, they output a -9V negative power supply to apply a negative bias voltage to the gate of the IGBT, achieving rapid turn-off. The reverse electromotive force elimination process only lasts for 10ms after the closing or opening action. After 10ms, the closing elimination signal or opening elimination signal turns high, the optocoupler stops conducting, the IGBT quickly turns off, and the elimination unit exits the working state. Compared with the RC absorption circuit, which continuously consumes energy when the load is working, this invention only operates within a short window period after the reverse electromotive force is generated, resulting in extremely low power consumption and not affecting the long-term operating efficiency of the system.

[0018] V. The invention is designed for the special operating conditions of magnetically controlled circuit breakers in FTU feeder terminals. It adopts IGBTs (NCE40TD120BT) with a withstand voltage of 1200V and ultra-fast recovery diodes (RHRG30120) to adapt to high-voltage DC power supply environments (+15V / -9V drive power supply). By completely eliminating the reverse electromotive force at the moment of closing, it ensures that the holding force of the magnetic control mechanism is not weakened by the reverse pulse. Even if there are deviations in the parameters of the magnetic control mechanism or changes in environmental factors, it can still stably maintain the closed state, fundamentally eliminating the phenomenon of pole detachment, greatly improving the operational reliability of the circuit breaker on the distribution network pole, and reducing the risk of unplanned power outages. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 This is the general block diagram of the electrical principle of the present invention.

[0021] Figure 2 This is a block diagram of the reverse potential elimination unit for closing the circuit in this invention.

[0022] Figure 3 This is a block diagram of the reverse potential elimination unit for circuit breaking in this invention.

[0023] Figure 4 This is a schematic diagram of the reverse electromotive force elimination circuit for opening / closing of the present invention connected to the drive bridge arm. Detailed Implementation

[0024] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0025] like Figure 2 As shown, the reverse electromotive force elimination unit for closing in this embodiment includes Y = A + Unit A, isolation optocoupler drive unit A, high-voltage electronic switch A, freewheeling diode A; the Y = A + Input terminal a of unit A is connected to the closing cancellation signal, input terminal b is connected to the opening signal, and output terminal c is connected to input terminal a of the isolation optocoupler drive unit A.

[0026] The input terminal a of the isolated optocoupler driving unit A is connected to Y = A + The output terminal c of unit A and the output terminal b of the isolation optocoupler drive unit A are connected to the input terminal a of the high-voltage electronic switch A; the input terminal a of the high-voltage electronic switch A is connected to the output terminal b of the isolation optocoupler drive unit A; the input terminal b of the high-voltage electronic switch A is connected to the output terminal a of the freewheeling diode A; the output terminal c of the high-voltage electronic switch A is connected to the terminal a of the magnetic control coil; the output terminal a of the freewheeling diode A is connected to the input terminal b of the high-voltage electronic switch A; and the input terminal b of the freewheeling diode A is connected to the terminal b of the magnetic control coil.

[0027] Y = A+ Unit A performs logic processing on the input closing cancellation signal and opening signal, and outputs a control signal that meets the requirements. The isolation optocoupler drive unit A isolates the transmitted signal between the front and rear stages, and is also responsible for driving the high-voltage electronic switch A. The high-voltage electronic switch A operates in the on or off state according to the high or low potential of the control signal. The freewheeling diode A conducts unidirectionally to the reverse electromotive force generated by closing.

[0028] like Figure 3As shown, the reverse potential elimination unit for tripping in this embodiment includes Y = A + Unit B, isolation optocoupler drive unit B, high-voltage electronic switch B, freewheeling diode B; Y = A + Input terminal a of unit B is connected to the tripping cancellation signal, input terminal b is connected to the closing signal, and output terminal c is connected to input terminal a of the isolation optocoupler drive unit B.

[0029] The input terminal a of the isolated optocoupler driving unit B is connected to Y = A + The output terminal c of unit B and the output terminal b of the isolation optocoupler drive unit B are connected to the input terminal a of the high-voltage electronic switch B; the input terminal a of the high-voltage electronic switch B is connected to the output terminal b of the isolation optocoupler drive unit B; the input terminal b of the high-voltage electronic switch B is connected to the output terminal a of the freewheeling diode B; the output terminal c of the high-voltage electronic switch B is connected to the b terminal of the magnetic control coil; the output terminal a of the freewheeling diode B is connected to the input terminal b of the high-voltage electronic switch B; and the input terminal b of the freewheeling diode B is connected to the a terminal of the magnetic control coil.

[0030] Y = A+ Unit B performs logic processing on the input tripping cancellation signal and closing signal, and outputs a control signal that meets the requirements. The isolation optocoupler drive unit B isolates the transmitted signal between the front and rear stages, and is also responsible for driving the high-voltage electronic switch B. The high-voltage electronic switch B operates in the on or off state according to the high or low potential of the control signal. The freewheeling diode B conducts unidirectionally to the reverse electromotive force generated by tripping.

[0031] like Figure 1 As shown, when the magnetic control mechanism closes the circuit, the upper arm of the closing drive, the lower arm of the closing drive, and the closing reverse electromotive force elimination unit are turned on, while the upper arm of the opening drive, the lower arm of the opening drive, and the opening reverse electromotive force elimination unit are turned off. High-voltage DC current is applied to terminal a of the magnetic control coil via the upper arm of the closing drive, and then to terminal b of the magnetic control coil via the lower arm of the closing drive. Because current flows through the magnetic control coil, the magnetic control mechanism completes the closing action. Simultaneously, the upper arm of the closing drive and the lower arm of the closing drive are turned off. The reverse electromotive force generated by the magnetic control coil is applied from terminal b of the magnetic control coil to the input terminal d of the closing reverse electromotive force elimination unit, and then to terminal a of the magnetic control coil via the output terminal c of the closing reverse electromotive force elimination unit, forming a discharge circuit. The reverse electromotive force is eliminated, and the closing reverse electromotive force elimination unit turns off after 10ms.

[0032] The operating modes of the closing signal, closing cancellation signal, opening signal, and opening cancellation signal used for control are: high level - no action, low level - action.

[0033] like Figure 1As shown, when the magnetic control mechanism trips, the upper tripping drive arm, the lower tripping drive arm, and the tripping reverse electromotive force elimination unit are turned on, while the upper closing drive arm, the lower closing drive arm, and the closing reverse electromotive force elimination unit are turned off. The DC high voltage is applied to the b end of the magnetic control coil through the upper tripping drive arm, and then to the lower tripping drive arm through the a end of the magnetic control coil. Since there is current flowing through the magnetic control coil, the magnetic control mechanism completes the tripping action. At the same time, the upper tripping drive arm and the lower tripping drive arm are turned off. The reverse electromotive force generated by the magnetic control coil is applied from the a end of the magnetic control coil to the input d end of the tripping reverse electromotive force elimination unit, and then to the b end of the magnetic control coil through the output c end of the tripping reverse electromotive force elimination unit, forming a discharge circuit. The reverse electromotive force is eliminated. The tripping reverse electromotive force elimination unit is turned off after 10ms.

[0034] like Figure 4 As shown, in this embodiment, Y = A + Unit A includes resistor R30, transistor Q7, resistor R31, resistor R32, transistor Q8, resistor R35, and transistor Q9. The closing cancellation signal is connected to one end of resistor R30, and the other end of resistor R30 is connected to the base of transistor Q7. The collector of transistor Q7 is connected to one end of resistor R31 and one end of resistor R32. The other end of resistor R31 is connected to the power supply VCC. The other end of resistor R32 is connected to the base of transistor Q8. The collector of transistor Q8 is connected to one end of resistor R33 in the isolation optocoupler driver unit A, the anode of diode D5, and pin 3 of optocoupler U5. The emitter of transistor Q8 is connected to the collector of transistor Q9. The opening signal is connected to one end of resistor R35, and the other end of resistor R35 is connected to the base of transistor Q9. The emitters of transistors Q7 and Q9 are both connected to the power supply ground.

[0035] When there is no closing control, the closing signal, closing cancellation signal, opening signal, and opening cancellation signal are all high level. The high-level closing cancellation signal is applied to the base of transistor Q7 through resistor R30, turning on transistor Q7. The collector of transistor Q7 is at a low level, so the base of transistor Q8 is at a low level, and transistor Q8 is cut off, with its collector at a high level. The high-level opening signal is applied to the base of transistor Q9 through resistor R35, turning on transistor Q9. Since transistor Q8 is cut off, whether transistor Q9 is on or off does not affect the high potential state of the collector of transistor Q8, and the subsequent isolation optocoupler U5 is not turned on; the closing reverse electromotive force cancellation unit does not work.

[0036] When closing control is required, the closing signal and closing cancellation signal are low, while the opening signal and opening cancellation signal are high. Since the closing cancellation signal is low, there is no bias voltage at the base of transistor Q7, so transistor Q7 is cut off. The power supply VCC is applied to the base of transistor Q8 through resistors R31 and R32, and transistor Q8 is turned on. The high-level opening signal is applied to the base of transistor Q9 through resistor R35, and transistor Q9 is turned on. Since both transistors Q8 and Q9 are turned on, the collector of transistor Q8 is low at this time, and the subsequent isolation optocoupler U5 is turned on. The closing reverse electromotive force cancellation unit is in working condition.

[0037] When the closing operation ends, the closing signal changes from low to high, while the closing cancellation signal remains low, still in the 10ms reverse EMF cancellation phase. After 10ms, the EMF cancellation ends, the closing cancellation signal turns high, transistor Q7 turns on, the base of transistor Q8 is low, transistor Q8 is cut off, and the closing reverse EMF cancellation unit does not work. If an emergency tripping command suddenly occurs during the 10ms reverse EMF cancellation phase, the tripping signal is low, the base of transistor Q9 loses its bias voltage, transistor Q9 is cut off, and the subsequent isolation optocoupler U5 loses its conduction circuit and is cut off; the closing reverse EMF cancellation unit does not work.

[0038] When tripping control is required, both the tripping signal and the tripping cancellation signal are low, while both the closing signal and the closing cancellation signal are high. The high-level closing cancellation signal is applied to the base of transistor Q7 through resistor R30, turning on transistor Q7. Since the collector of transistor Q7 is low, the base of transistor Q8 is low, and transistor Q8 is cut off, with its collector at a high level. With the tripping signal low, there is no bias voltage at the base of transistor Q9, so transistor Q9 is cut off. Because both transistors Q8 and Q9 are in the cutoff state, the subsequent isolation optocoupler U5 is not conducting; the closing reverse electromotive force cancellation unit does not operate.

[0039] The isolated optocoupler driving unit A includes resistor R33, resistor R34, diode D5, optocoupler U5, and capacitor C10; one end of resistor R33 is connected to the anode of diode D5, pin 3 of optocoupler U5, and Y= A+ In Unit A, the collector of transistor Q8, the other end of resistor R33 is connected to power supply VCC and one end of resistor R34, the other end of resistor R34 is connected to the cathode of diode D5, pin 2 of optocoupler U5, pin 5 of optocoupler U5 is connected to the negative power supply -9V4 (the 4th DC power supply provides +15V, -9V), one end of capacitor C10, pin 6 of optocoupler U5 is connected to pin 7 of optocoupler U5, one end of resistor R43, one end of resistor R44, and pin 8 of optocoupler U5 is connected to power supply +15V4 (the 4th DC power supply provides +15V, -9V), and the other end of capacitor C10; when Y = A + In circuit unit A, when transistors Q8 and Q9 are simultaneously turned on, the power supply VCC is applied to pin 2 of optocoupler U5 via resistor R34, then to the collector of transistor Q8 via pin 3 of optocoupler U5, then to the collector of transistor Q9 via the emitter of transistor Q8, and finally to ground via the emitter of transistor Q9. Optocoupler U5 is then turned on, and pins 6 and 7 of optocoupler U5 are connected to the positive power supply +15V4 at pin 8 (the internal output of the optocoupler is a push-pull circuit). Pins 6 and 7 of optocoupler U5 have a positive power supply of +15V4. When Y = A + When neither transistor Q8 nor transistor Q9 is conducting, or when one of them is not conducting, the power supply VCC cannot form a loop through optocoupler U5 to the power supply ground. When optocoupler U5 is not conducting, pins 6 and 7 of optocoupler U5 are connected to the negative power supply -9V4 at pin 5 of optocoupler U5 (the internal output of the optocoupler is a push-pull circuit), and pins 6 and 7 of optocoupler U5 have the negative power supply -9V4.

[0040] The high-voltage electronic switch A and freewheeling diode A include resistors R43, R44, and R45, a TVS diode TVS5, an IGBT Q5, a capacitor C11, and a freewheeling diode D7. One end of resistor R43 is connected to one end of resistor R44, pins 6 and 7 of optocoupler U5 in the isolation optocoupler drive unit A. The other end of resistor R43 is connected to the other end of resistor R44, one end of resistor R45, pin 1 of diode TVS5, and the gate G of IGBT Q5. The collector C of IGBT Q5 is connected to one end of capacitor C11 and the cathode of diode D7. The emitter E of IGBT Q5 is connected to the other end of resistor R45, pin 2 of diode TVS5, power ground QGND4 (the fourth DC power ground), the other end of capacitor C11, and terminal A of the magnetic control coil. The anode of diode D7 is connected to terminal B of the magnetic control coil.

[0041] When the circuit breaker closes, optocoupler U5 conducts synchronously. Pins 6 and 7 of optocoupler U5 receive a positive power supply of +15V4. This +15V4 power supply is applied to the gate G of IGBT Q5 through current-limiting resistors R43 and R44 (R43‖R44), causing IGBT Q5 to conduct. During closing, terminal A of the magnetic control coil is a high-voltage DC +, and terminal B is a high-voltage DC -. Due to the unidirectional characteristic of diode D7, the high-voltage DC at terminal A of the magnetic control coil cannot pass through the freewheeling diode inside IGBT Q5 to form a circuit at terminal B, thus not affecting the operation of the magnetic control mechanism. After the closing operation ends, optocoupler U5 continues to conduct for 10ms, and IGBT Q5 remains in the conducting state. At this time, the magnetic control coil generates a reverse electromotive force, with terminal B receiving a high-voltage DC + and terminal A receiving a high-voltage DC -. The DC high voltage at terminal B is applied to the collector C of IGBT Q5 via diode D7, and then to terminal A of the magnetic control coil via the emitter E of the IGBT, forming a discharge circuit. Since IGBT Q5 is always in the conducting state when the circuit is closed, it can achieve seamless connection and quickly eliminate the reverse potential when the magnetic control coil generates a reverse potential. After 10ms, optocoupler U5 is de-conducting, and pins 6 and 7 of optocoupler U5 are negative power supply -9V4. IGBT Q5 is quickly turned off due to the negative bias of the gate voltage G, and the reverse potential elimination unit stops working.

[0042] For ease of understanding, let Y = A + Truth-value interpretation of the logical principle of Unit A:

[0043] A represents the closing cancellation signal, B represents the opening signal, and Y represents the control output of the closing reverse electromotive force cancellation unit. In this circuit, the control signal adopts the definition of active low level, that is, when the signal is logic "0", it means that the operation is valid, and when the signal is logic "1", it means that the operation is invalid.

[0044] When A=0 and B=0, it indicates that the closing cancellation signal is valid, but the opening signal is also valid at the same time, meaning the system is performing an opening operation. To prevent conflict between the closing reverse EMF cancellation unit and the opening drive circuit, the output Y=1, disabling the closing reverse EMF cancellation unit and ensuring priority for the opening operation. When A=0 and B=1, it indicates that the closing cancellation signal is valid, but there is no opening operation. The output Y=0, allowing the closing reverse EMF cancellation unit to operate, and the subsequent isolation optocoupler drive unit A and high-voltage electronic switch A are turned on, preparing for the elimination of the reverse EMF generated at the moment of closing. When A=1 and B=0, it indicates that the closing cancellation signal is invalid, and the system is performing an opening operation. The output Y=1, disabling the closing reverse EMF cancellation unit to avoid unnecessary interference with the opening process. When A=1 and B=1, it indicates that the closing cancellation signal is invalid, and there is no opening operation; the system is in idle standby mode. The output Y=1, and the closing reverse EMF cancellation unit is not working.

[0045] As shown in Table 1 below, the closing reverse EMF elimination unit is only allowed to work when the closing cancellation signal is valid and the opening signal is invalid, i.e., A=0 and B=1. Once the opening signal is valid, regardless of the state of the closing cancellation signal, the output Y is always 1, and the closing reverse EMF elimination unit is forcibly disabled. This logic relationship realizes the hardware interlock function of opening priority, ensuring that the closing reverse EMF elimination unit will not be mistakenly activated during the opening process.

[0046] Table 1

[0047] The Y = A+ Unit B includes resistor R36, transistor Q10, resistor R37, resistor R38, transistor Q11, resistor R41, and transistor Q12. The trip signal is connected to one end of resistor R36, and the other end of resistor R36 is connected to the base of transistor Q10. The collector of transistor Q10 is connected to one end of resistor R37 and one end of resistor R38. The other end of resistor R37 is connected to the power supply VCC. The other end of resistor R38 is connected to the base of transistor Q11. The collector of transistor Q11 is connected to one end of resistor R39 in the isolation optocoupler driver unit B, the anode of diode D6, and pin 3 of optocoupler U6. The emitter of transistor Q11 is connected to the collector of transistor Q12. The closing signal is connected to one end of resistor R41, and the other end of resistor R41 is connected to the base of transistor Q12. The emitters of transistors Q10 and Q12 are both connected to the power supply ground.

[0048] When there is no tripping control, the closing signal, closing cancellation signal, tripping signal, and tripping cancellation signal are all at high level. The high-level tripping cancellation signal is applied to the base of transistor Q10 through resistor R36, turning on transistor Q10. The collector of transistor Q10 is at low level, so the base of transistor Q11 is at low level, and transistor Q11 is cut off, with its collector at high level. The high-level closing signal is applied to the base of transistor Q12 through resistor R41, turning on transistor Q12. Since transistor Q11 is cut off, whether transistor Q12 is on or off does not affect the high potential state of the collector of transistor Q11, and the subsequent isolation optocoupler U6 is not turned on; the tripping reverse electromotive force cancellation unit does not work.

[0049] When tripping control is required, the tripping signal and tripping cancellation signal are at low level, while the closing signal and closing cancellation signal are at high level. Since the tripping cancellation signal is low, there is no bias voltage at the base of transistor Q10, so transistor Q10 is cut off. The power supply VCC is applied to the base of transistor Q11 through resistors R37 and R38, and transistor Q11 is turned on. The high-level closing signal is applied to the base of transistor Q12 through resistor R41, and transistor Q12 is turned on. Since both transistors Q11 and Q12 are turned on, the collector of transistor Q11 is at low level, and the subsequent isolation optocoupler U6 is turned on. The tripping reverse electromotive force cancellation unit is in working state.

[0050] When the tripping ends, the tripping signal changes from low to high, while the tripping cancellation signal remains low, still in the 10ms reverse EMF cancellation phase. After 10ms, the EMF cancellation ends, the tripping cancellation signal goes high, transistor Q10 turns on, the base of transistor Q11 is low, transistor Q11 is off, and the tripping reverse EMF cancellation unit does not work. If a closing command suddenly appears during the 10ms reverse EMF cancellation phase, the closing signal is low, the base of transistor Q12 loses its bias voltage, transistor Q12 is off, and the subsequent isolation optocoupler U6 loses its conduction circuit and is also off; the tripping reverse EMF cancellation unit does not work.

[0051] When closing control is required, both the closing signal and the closing cancellation signal are low, while both the opening signal and the opening cancellation signal are high. The high-level opening cancellation signal is applied to the base of transistor Q10 through resistor R36, turning on transistor Q10. Since the collector of transistor Q10 is low, the base of transistor Q11 is low, and transistor Q11 is cut off, with its collector at a high level. With the closing signal low, there is no bias voltage at the base of transistor Q12, so transistor Q12 is cut off. Because both transistors Q11 and Q12 are in the cut-off state, the subsequent isolation optocoupler U6 is not turned on; the opening reverse electromotive force cancellation unit does not operate.

[0052] The isolated optocoupler driving unit B includes resistor R39, resistor R40, diode D6, optocoupler U6, and capacitor C12; one end of resistor R39 is connected to the anode of diode D6, pin 3 of optocoupler U6, and Y= A+ In Unit B, the collector of transistor Q11, the other end of resistor R39 is connected to power supply VCC and one end of resistor R40, the other end of resistor R40 is connected to the cathode of diode D6, pin 2 of optocoupler U6, pin 5 of optocoupler U6 is connected to the negative power supply -9V5 (the 5th DC power supply provides +15V, -9V), one end of capacitor C12, pin 6 of optocoupler U6 is connected to pin 7 of optocoupler U6, one end of resistor R46, one end of resistor R47, and pin 8 of optocoupler U6 is connected to power supply +15V5 (the 5th DC power supply provides +15V, -9V), and the other end of capacitor C12; when Y = A + In circuit unit B, when transistors Q11 and Q12 are simultaneously turned on, the power supply VCC is applied to pin 2 of optocoupler U6 via resistor R40, then to the collector of transistor Q11 via pin 3 of optocoupler U6, then to the collector of transistor Q12 via the emitter of transistor Q11, and finally to ground via the emitter of transistor Q12. Optocoupler U6 is then turned on, and pins 6 and 7 of optocoupler U6 are connected to the positive power supply +15V4 at pin 8 (the internal output of the optocoupler is a push-pull circuit). Pins 6 and 7 of optocoupler U6 have a positive power supply of +15V4. When Y = A + When transistors Q11 and Q12 are both off or one of them is off, the power supply VCC cannot form a loop through optocoupler U6 to the power supply ground. When optocoupler U6 is off, pins 6 and 7 of optocoupler U6 are connected to the negative power supply -9V4 at pin 5 of optocoupler U6 (the internal output of the optocoupler is a push-pull circuit), and pins 6 and 7 of optocoupler U6 have the negative power supply -9V4.

[0053] The high-voltage electronic switch B and freewheeling diode B include resistors R46, R47, and R48, a TVS diode TVS6, an IGBT Q6, a capacitor C13, and a freewheeling diode D8. One end of resistor R46 is connected to one end of resistor R47, pins 6 and 7 of optocoupler U6 in the isolation optocoupler drive unit B, and the other end of resistor R46 is connected to the other end of resistor R47, one end of resistor R48, pin 1 of diode TVS6, and the gate G of IGBT Q6. The collector C of IGBT Q6 is connected to one end of capacitor C13 and the cathode of diode D8. The emitter E of IGBT Q6 is connected to the other end of resistor R48, pin 2 of diode TVS6, power ground QGND5 (the 5th DC power ground), the other end of capacitor C13, and the B end of the magnetic control coil. The anode of diode D8 is connected to the A end of the magnetic control coil.

[0054] When the circuit breaker is tripped, optocoupler U6 conducts synchronously. Pins 6 and 7 of optocoupler U6 receive a positive power supply of +15V4. This +15V4 power supply is applied to the gate G of IGBT Q6 through current-limiting resistors R46 and R47 (R46‖R47), causing IGBT Q6 to conduct. During tripping, the B terminal of the magnetic control coil receives a high-voltage DC positive, and the A terminal receives a high-voltage DC negative. Due to the unidirectional characteristic of diode D8, the high-voltage DC at the B terminal of the magnetic control coil cannot form a circuit through the freewheeling diode inside IGBT Q6 to the A terminal of the magnetic control coil, thus not affecting the operation of the magnetic control mechanism. After the tripping operation ends, optocoupler U6 continues to conduct for 10ms, and IGBT Q6 remains in the conducting state. At this time, the magnetic control coil generates a reverse electromotive force, with the A terminal of the magnetic control coil receiving a high-voltage DC positive and the B terminal receiving a high-voltage DC negative. The high DC voltage at terminal A is applied to the collector C of IGBT Q6 via diode D8, and then to terminal B of the magnetic control coil via the emitter E of IGBT Q6, forming a discharge circuit. Since IGBT Q6 is always in the conducting state when the circuit is closed, it can seamlessly connect and quickly eliminate the reverse potential when the magnetic control coil generates a reverse potential. After 10ms, optocoupler U6 stops conducting. Pins 6 and 7 of optocoupler U6 are negative power supplies -9V4. IGBT Q6 is quickly turned off due to the negative bias of the gate voltage G, and the reverse potential elimination unit stops working.

[0055] For ease of understanding, let Y = A + Truth-value interpretation of the logical principle of Unit B:

[0056] A represents the tripping cancellation signal, B represents the closing signal, and Y represents the control output of the tripping reverse electromotive force cancellation unit. In this circuit, the control signal adopts the definition of active low level, that is, when the signal is logic "0", it means that the operation is valid, and when the signal is logic "1", it means that the operation is invalid.

[0057] When A=0 and B=0, it indicates that the tripping cancellation signal is valid, but the closing signal is also valid at the same time, meaning the system is performing a closing operation. To prevent conflict between the tripping reverse EMF cancellation unit and the closing drive circuit, the output Y=1, disabling the tripping reverse EMF cancellation unit and ensuring priority for the closing operation. When A=0 and B=1, it indicates that the tripping cancellation signal is valid, but there is no closing operation. The output Y=0, allowing the tripping reverse EMF cancellation unit to operate. The subsequent isolation optocoupler drive unit B and the high-voltage electronic switch B are turned on, preparing for the elimination of the reverse EMF generated at the moment of tripping. When A=1 and B=0, it indicates that the tripping cancellation signal is invalid, but the system is performing a closing operation. The output Y=1, disabling the tripping reverse EMF cancellation unit to avoid unnecessary interference with the closing process. When A=1 and B=1, it indicates that the tripping cancellation signal is invalid, and there is no closing operation; the system is in idle standby mode. The output Y=1, and the tripping reverse EMF cancellation unit is not working.

[0058] As shown in Table 2 below, the tripping reverse EMF elimination unit is only allowed to operate when the tripping cancellation signal is valid and the closing signal is invalid, i.e., A=0 and B=1. Once the closing signal is valid, regardless of the state of the tripping cancellation signal, the output Y is always 1, and the tripping reverse EMF elimination unit is forcibly disabled. This logic relationship realizes the hardware interlock function of closing priority, ensuring that the tripping reverse EMF elimination unit will not be mistakenly activated during the closing process.

[0059] Table 2

[0060] In summary, to prevent short circuits caused by erroneous activation of the reverse electromotive force elimination unit during closing and tripping, this invention implements logical restrictions in hardware: when closing, the reverse electromotive force elimination unit during tripping is prohibited from being activated; when tripping, the reverse electromotive force elimination unit during tripping is prohibited from being activated.

[0061] Compared with existing technologies, this invention can completely eliminate the reverse electromotive force generated by the magnetic control mechanism at the moment of opening and closing, effectively solving the problem of occasional pole detachment and improving the operational reliability of the product. This invention is particularly suitable for eliminating the reverse electromotive force of high-voltage DC inductive loads.

[0062] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A reverse electromotive force elimination circuit for an FTU feeder terminal magnetic control mechanism, characterized in that, Including Y=A+ Unit A, Isolation Optocoupler Driver Unit A, High Voltage Electronic Switch A, Freewheeling Diode A, Y=A+ Unit B, isolation optocoupler drive unit B, high-voltage electronic switch B, and freewheeling diode B; Y=A+ Unit A performs logic processing on the input closing cancellation signal and opening signal, and outputs a control signal that meets the requirements; the isolation optocoupler drive unit A isolates the transmitted signal between the preceding and following stages and is also responsible for driving the high-voltage electronic switch A; the high-voltage electronic switch A operates in the on or off state according to the high or low potential of the control signal; the freewheeling diode A conducts unidirectionally to the reverse electromotive force generated by closing; Y=A+ Unit B performs logical processing on the input tripping cancellation signal and closing signal, and outputs a control signal that meets the requirements. The isolation optocoupler drive unit B isolates the transmitted signal between the preceding and following stages and is also responsible for driving the high-voltage electronic switch B; the high-voltage electronic switch B operates in the on or off state according to the high or low potential of the control signal; the freewheeling diode B conducts unidirectionally to the reverse electromotive force generated by the circuit breaker tripping.

2. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 1, characterized in that, The Y=A+ Unit A includes resistor R30, transistor Q7, resistor R31, resistor R32, transistor Q8, resistor R35, and transistor Q9. The closing cancellation signal is connected to one end of resistor R30, and the other end of resistor R30 is connected to the base of transistor Q7. The collector of transistor Q7 is connected to one end of resistor R31 and one end of resistor R32. The other end of resistor R31 is connected to the power supply VCC. The other end of resistor R32 is connected to the base of transistor Q8. The collector of transistor Q8 is connected to one end of resistor R33 in the isolation optocoupler driver unit A, the anode of diode D5, and pin 3 of optocoupler U5. The emitter of transistor Q8 is connected to the collector of transistor Q9. The opening signal is connected to one end of resistor R35, and the other end of resistor R35 is connected to the base of transistor Q9. The emitters of transistors Q7 and Q9 are both connected to the power supply ground.

3. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 1, characterized in that, The isolated optocoupler driving unit A includes resistor R33, resistor R34, diode D5, optocoupler U5, and capacitor C10; one end of resistor R33 is connected to the anode of diode D5, pin 3 of optocoupler U5, and Y=A+. In Unit A, the collector of transistor Q8 is connected to the power supply VCC and one end of resistor R34. The other end of resistor R34 is connected to the cathode of diode D5 and pin 2 of optocoupler U5. Pin 5 of optocoupler U5 is connected to the negative power supply -9V4 and one end of capacitor C10. Pin 6 of optocoupler U5 is connected to pin 7 of optocoupler U5, one end of resistor R43, and one end of resistor R44. Pin 8 of optocoupler U5 is connected to the power supply +15V4 and the other end of capacitor C10.

4. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 1, characterized in that, The high-voltage electronic switch A includes resistors R43, R44, and R45, a TVS diode (TVS5), an IGBT (IgB) transistor Q5, and a capacitor C11. One end of resistor R43 is connected to one end of resistor R44, pins 6 and 7 of optocoupler U5 in the isolation optocoupler drive unit A. The other end of resistor R43 is connected to the other end of resistor R44, one end of resistor R45, pin 1 of diode TVS5, and the gate G of IGBT transistor Q5. The collector C of IGBT transistor Q5 is connected to one end of capacitor C11 and the cathode of diode D7 in freewheeling diode A. The emitter E of IGBT transistor Q5 is connected to the other end of resistor R45, pin 2 of diode TVS5, power ground QGND4, the other end of capacitor C11, and terminal A of the magnetic control coil.

5. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 1, characterized in that, The freewheeling diode A includes diode D7. The anode of diode D7 is connected to terminal B of the magnetic control coil, and the cathode of diode D7 is connected to the collector of IGBT transistor Q5 in high-voltage electronic switch A and one end of capacitor C11.

6. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 5, characterized in that, The Y=A+ Unit B includes resistor R36, transistor Q10, resistor R37, resistor R38, transistor Q11, resistor R41, and transistor Q12. The trip signal is connected to one end of resistor R36, and the other end of resistor R36 is connected to the base of transistor Q10. The collector of transistor Q10 is connected to one end of resistor R37 and one end of resistor R38. The other end of resistor R37 is connected to power supply VCC. The other end of resistor R38 is connected to the base of transistor Q11. The collector of transistor Q11 is connected to one end of resistor R39 in the isolation optocoupler driver unit B, the anode of diode D6, and pin 3 of optocoupler U6. The emitter of transistor Q11 is connected to the collector of transistor Q12. The closing signal is connected to one end of resistor R41, and the other end of resistor R41 is connected to the base of transistor Q12. The emitters of transistors Q10 and Q12 are both connected to power supply ground.

7. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 1, characterized in that, The isolated optocoupler driving unit B includes resistor R39, resistor R40, diode D6, optocoupler U6, and capacitor C12; one end of resistor R39 is connected to the anode of diode D6, pin 3 of optocoupler U6, and Y=A+. In Unit B, the collector of transistor Q11 is connected to the power supply VCC and one end of resistor R39. The other end of resistor R40 is connected to the cathode of diode D6 and pin 2 of optocoupler U6. Pin 5 of optocoupler U6 is connected to the negative power supply -9V5 and one end of capacitor C12. Pin 6 of optocoupler U6 is connected to pin 7 of optocoupler U6, one end of resistor R46, and one end of resistor R47. Pin 8 of optocoupler U6 is connected to the power supply +15V5 and the other end of capacitor C12.

8. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 7, characterized in that, The high-voltage electronic switch B includes resistors R46, R47, and R48, a TVS diode (TVS6), an IGBT (Ionizing Power Transistor) Q6, and a capacitor C13. One end of resistor R46 is connected to one end of resistor R47, pins 6 and 7 of optocoupler U6 in the isolation optocoupler drive unit B. The other end of resistor R46 is connected to the other end of resistor R47, one end of resistor R48, pin 1 of diode TVS6, and the gate G of IGBT Q6. The collector C of IGBT Q6 is connected to one end of capacitor C13 and the cathode of diode D8 in freewheeling diode B. The emitter E of IGBT Q6 is connected to the other end of resistor R48, pin 2 of diode TVS6, power ground QGND5, the other end of capacitor C13, and terminal B of the magnetic control coil.

9. The reverse potential elimination circuit of the FTU feeder terminal magnetic control mechanism according to claim 8, characterized in that, The freewheeling diode B includes diode D8. The anode of diode D8 is connected to terminal A of the magnetic control coil, and the cathode of diode D8 is connected to the collector of IGBT transistor Q6 in the high-voltage electronic switch B and one end of capacitor C13.

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