An automatic transfer switch electromagnet drive circuit

Abstract

The present invention provides an automatic transfer switch electromagnet drive circuit, including a common power supply, a backup power supply, a power selection and rectification module, a current breaking module, a switching direction control module, an overcurrent protection and alarm module, and a processing module. The automatic transfer switch electromagnet drive circuit described in the present invention is reasonably designed, so that the product meets higher requirements for electrical clearance and creepage distance, has a stronger current breaking capacity, and adds overcurrent protection and overcurrent alarm functions. In addition, even if the processing module is miscontrolled due to a fault, the common power supply and the backup power supply will not be short-circuited or multiple electromagnets will not be powered at the same time, making the product safer and more reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of automatic transfer switches, and in particular relates to an automatic transfer switch electromagnet drive circuit. Background Art

[0002] At present, the common automatic transfer switches in the market are generally of the excitation type. With the increasing number of electrical equipment in the power grid, the requirements for the current breaking capacity of the automatic transfer switch are becoming higher and higher. Under the same transfer time, the driving current required by the electromagnet inside the switch with large breaking capacity is generally larger. At present, the switch controller generally uses a relay to break the electromagnet current. Due to the limitation of the relay contact breaking capacity, it is like a "small horse pulling a big cart" on a large shell switch, sacrificing the transfer time. In addition, the relay is prone to contact adhesion when the electromagnet is overcurrent or short-circuited, resulting in current breaking failure.

[0003] In addition, two double-pole single-throw relays are generally used in the automatic transfer switch controller to select the normal power supply and the backup power supply. As the application field of the product becomes wider and wider, especially in the rail transportation industry, the environment is relatively humid and the pollution level is high. Due to the limitation of the relay pin spacing, voltage breakdown often occurs due to insufficient electrical clearance and creepage distance. Summary of the invention

[0004] In view of this, the present invention aims to provide an automatic transfer switch electromagnet drive circuit to solve the deficiencies of the prior art.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] An automatic switching switch electromagnet drive circuit comprises a common power supply, a backup power supply, a power selection and rectification module, a current disconnecting module, a switching direction control module, an overcurrent protection and alarm module and a processing module, wherein the output signal of the processing module is respectively connected to the control end of the power selection and rectification module, the control end of the current disconnecting module and the control end of the switching direction control module, the input end of the power selection and rectification module is respectively connected to the common power supply and the backup power supply, the output end of the power selection and rectification module is connected to the input end of the current disconnecting module, the output end of the current disconnecting module is connected to the switching direction control module, the output signal of the current disconnecting module is connected to the control end of the overcurrent protection and alarm module, and the output signal of the overcurrent protection and alarm module is respectively connected to the control end of the current disconnecting module and the processing module.

[0007] Further, the power selection and rectification module includes a common circuit for receiving a common power supply and a standby circuit for receiving a standby power supply, the common circuit includes a power selection circuit and a rectification circuit, so the power selection circuit includes a common control circuit and a common relay circuit, the rectification circuit includes a common protection circuit and a rectifier bridge Z1, one end of the common control circuit receives a common power selection signal of the processing module, and the other end is connected to a common relay circuit, the common relay circuit is connected to the A phase and C phase circuits of the common power supply, and the common relay circuit is connected to the AC input end of the rectifier bridge Z1 through the common protection circuit, and the rectifier bridge Z1 outputs a voltage VDC;

[0008] The standby circuit has the same principle as the common circuit.

[0009] Furthermore, the common control circuit includes a resistor R1, a resistor R3, a capacitor C1 and an NPN transistor Q1, one end of the resistor R1 is connected to the common power selection signal of the processing module, and the other end is connected to the base of the NPN transistor Q1, one end of the resistor R3 is connected to the other end of the resistor R1, and the other end of the resistor R3 is grounded, one end of the capacitor C1 is connected to the other end of the resistor R1, and the other end of the capacitor C1 is grounded, the emitter of the NPN transistor Q1 is grounded, and the collector of the NPN transistor Q1 is connected to a common relay circuit.

[0010] Furthermore, the common relay circuit includes a double-pole single-throw relay K1, a double-pole single-throw relay K2 and a diode D1, the double-pole single-throw relay K1 normally open point 1 is connected to the A-phase circuit of the common power supply, the double-pole single-throw relay K1 normally open point 2 is connected to the common protection circuit, the double-pole single-throw relay K1 power supply point is respectively connected to the first power supply VCC1 and the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to the first power supply VCC1, the positive electrode of the diode D1 is also connected to the collector of the NPN transistor Q1 and the power supply point of the double-pole single-throw relay K2, the power supply point of the double-pole single-throw relay K2 is connected to the first power supply VCC1, the double-pole single-throw relay K2 normally open point 1 is connected to the C-phase circuit of the common power supply, and the double-pole single-throw relay K2 normally open point 2 is connected to the common protection circuit.

[0011] Further, the common protection circuit includes a fuse FU1 and a varistor RV1, one end of the fuse FU1 is connected to the normally open point 2 of the double-pole single-throw relay K1, the other end of the fuse FU1 is connected to the AC input end of the rectifier bridge Z1, one end of the varistor RV1 is connected to the fuse FU1, and the other end of the varistor RV1 is connected to the normally open point 2 of the double-pole single-throw relay K2;

[0012] The input and output of each phase power supply of the double-pole single-throw relay K1 and the double-pole single-throw relay K2 are both selected at the diagonal position of the relay.

[0013] Furthermore, the first power supply VCC1 and the second power supply VCC2 of the current disconnection module and the overcurrent protection and alarm module 6 are connected to the isolation power supply module U4, and the current disconnection module 4 includes a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R17, a capacitor C3, a capacitor C4, an NPN transistor Q4, an optocoupler U1, an IGBT and a diode D3, one end of the resistor R7 is connected to the current disconnection signal of the processing module, and the other end of the resistor R7 is respectively connected to the base of the NPN transistor Q4 and the output end of the overcurrent protection and alarm module, one end of the resistor R8 is connected to one end of the resistor R7, and the other end of the resistor R8 is grounded, one end of the capacitor C3 is connected to the other end of the resistor R7, and the capacitor The other end of C3 is grounded, the emitter of NPN transistor Q4 is grounded, the collector of NPN transistor Q4 is connected to optocoupler U1, one end of optocoupler U1 is connected to the first power supply VCC1 through resistor R5, and the other end is respectively connected to the second power supply VCC2 and one end of resistor R6, the other end of resistor R6 is connected to the IGBT base, one end of resistor R9 is connected to one end of resistor R6, the other end of resistor R9 is grounded, one end of capacitor C4 is connected to the other end of resistor R6, the other end of capacitor C4 is grounded, the emitter of IGBT is respectively connected to resistor R17 and the input end of overcurrent protection and alarm module, resistor R17 is grounded, the collector of IGBT is divided into two paths, one is connected to the conversion direction control module, and the other is connected to VDC through diode D3.

[0014] Furthermore, the overcurrent protection and alarm module includes a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, an operational amplifier U3, a diode D4, a capacitor C5, an NPN transistor Q5, a MOS transistor Q6 and an optocoupler U2. The same-phase input terminal of the operational amplifier U3 is connected to the emitter of the IGBT, the inverting input terminal of the operational amplifier U3 is respectively connected to the resistor R11 and the resistor R16, the other end of the resistor R11 is connected to the second power supply VCC2, the other end of the resistor R16 is grounded, the output terminal of the operational amplifier U3 is connected to one end of the resistor R13 through the diode D4, the other end of the resistor R13 is connected to the MOS transistor Q6, and the resistor R One end of 15 is connected to one end of resistor R13, and the other end of resistor R15 is grounded. One end of capacitor C5 is connected to the other end of resistor R13, and the other end of capacitor C5 is grounded. One end of MOS tube Q6 is grounded, and the other end is connected to optocoupler U2. One end of optocoupler U2 is connected to the second power supply VCC2 through resistor R10, and the other end is respectively connected to the first power supply VCC1 and one end of resistor R12. When optocoupler U2 is connected to resistor R12, it sends an overcurrent alarm signal to the input end of the processing module. The other end of resistor R12 is connected to the base of NPN transistor Q5. One end of resistor R14 is connected to one end of resistor R12, and the other end of resistor R14 is grounded. The emitter of NPN transistor Q5 is grounded, and the collector of NPN transistor Q5 is connected to resistor R7.

[0015] Further, the conversion direction control module includes a first control signal circuit, a second control signal circuit and a load circuit, the input end of the first control signal circuit is respectively connected to the processing module and the IGBT collector, the output end of the first control signal circuit is respectively connected to the second control signal circuit and the load circuit, the input end of the second control signal circuit is connected to the processing module, and the output end of the second control signal circuit is connected to the load circuit;

[0016] The load circuit includes electromagnet No. 1, electromagnet No. 2 and electromagnet No. 3, one end of electromagnet No. 1 is connected to VDC, and the other end is connected to the first control signal circuit, one end of electromagnet No. 2 and one end of electromagnet No. 3 are both connected to VDC, and the other ends of electromagnet No. 2 and No. 3 are both connected to the second control signal circuit.

[0017] Furthermore, the first control signal circuit includes a resistor R18, a resistor R19, a capacitor C8, an NPN transistor Q7, a diode D5 and a single-pole double-throw relay K5, one end of the resistor R18 receives a No. 1 conversion direction control signal of the processing module, the other end of the resistor R18 is connected to the base of the NPN transistor Q7, one end of the resistor R19 is connected to the other end of the resistor R18, the other end of the resistor R19 is grounded, one end of the capacitor C8 is connected to the other end of the resistor R18, the other end of the capacitor C8 is grounded, the emitter of the NPN transistor Q7 is grounded, and the collector of the NPN transistor Q7 is divided into two paths, one path is connected to the first power supply VCC1 through the diode D5, and the other path is connected to the power supply point of the single-pole double-throw relay K5, the power supply point of the single-pole double-throw relay K5 is connected to the first power supply VCC1, the normally closed point of the single-pole double-throw relay K5 is respectively connected to the IGBT collector and the No. 1 electromagnet, and the normally open point of the single-pole double-throw relay K5 is connected to the second control signal circuit.

[0018] Furthermore, the second control signal circuit includes a resistor R20, a resistor R21, a capacitor C9, an NPN transistor Q8, a diode D6 and a single-pole double-throw relay K6, one end of the resistor R20 receives the No. 2 conversion direction control signal of the processing module, the other end of the resistor R20 is connected to the base of the NPN transistor Q8, one end of the resistor R21 is connected to the other end of the resistor R20, the other end of the resistor R21 is grounded, one end of the capacitor C9 is connected to the other end of the resistor R20, the other end of the capacitor C9 is grounded, the emitter of the NPN transistor Q8 is grounded, and the collector of the NPN transistor Q8 is divided into two paths, one path is connected to the first power supply VCC1 through the diode D6, and the other path is connected to the power supply point of the single-pole double-throw relay K6, the power supply point of the single-pole double-throw relay K6 is connected to the first power supply VCC1, the normally closed point of the single-pole double-throw relay K6 is respectively connected to the normally open point of the single-pole double-throw relay K5 and the second electromagnet, and the normally open point of the single-pole double-throw relay K6 is connected to the third electromagnet.

[0019] Compared with the prior art, the automatic transfer switch electromagnet drive circuit of the present invention has the following advantages:

[0020] (1) The automatic transfer switch electromagnet drive circuit described in the present invention is reasonably designed, so that the product meets higher requirements for electrical clearance and creepage distance, has stronger current breaking capacity, and adds overcurrent protection and overcurrent alarm functions. In addition, even if the processing module is miscontrolled due to a fault, there will be no short circuit between the normal power supply and the backup power supply or multiple electromagnets will not be powered at the same time, making the product safer and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 This is a schematic diagram of the overall structure of an automatic transfer switch electromagnet drive circuit according to an embodiment of the present invention;

[0023] Figure 2 A circuit diagram of a power selection and rectification module of an automatic transfer switch electromagnet drive circuit according to an embodiment of the present invention;

[0024] Figure 3 A schematic diagram of double-pole single-throw relay connection in an automatic transfer switch electromagnet drive circuit according to an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of the connection of an existing double-pole single-throw relay in an automatic transfer switch electromagnet drive circuit according to an embodiment of the present invention;

[0026] Figure 5 A circuit diagram of a current breaking module, an overcurrent protection and alarm module of an automatic transfer switch electromagnet drive circuit according to an embodiment of the present invention;

[0027] Figure 6 A circuit diagram of a direction-changing control module of an automatic transfer switch electromagnet drive circuit according to an embodiment of the present invention;

[0028] Figure 7 The present invention is a flowchart of the conversion of an automatic transfer switch electromagnet drive circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0032] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0033] Glossary:

[0034] IGBT (Insulated Gate Bipolar Transistor): Insulated Gate Bipolar Transistor, is a composite fully controlled voltage-driven power semiconductor device composed of BJT (bipolar transistor) and MOS (insulated gate field effect transistor), which has the advantages of both MOSFET's high input impedance and GTR's low on-state voltage drop. GTR has low saturation voltage drop and high current density, but large driving current; MOSFET has low driving power and fast switching speed, but large on-state voltage drop and low current density. IGBT combines the advantages of the above two devices, with low driving power and low saturation voltage drop. It is very suitable for use in converter systems with DC voltage of 600V and above, such as AC motors, inverters, switching power supplies, lighting circuits, traction drives and other fields.

[0035] Sampling resistor: used for current sampling, a small resistor connected in series in the circuit, with the characteristics of low resistance and high precision.

[0036] like Figures 1 to 7As shown, an automatic transfer switch electromagnet drive circuit includes a common power supply, a backup power supply, a power selection and rectification module, a current breaking module, a conversion direction control module, an overcurrent protection and alarm module and a processing module, the output signal of the processing module is respectively connected to the control end of the power selection and rectification module, the control end of the current breaking module, and the control end of the conversion direction control module, the input end of the power selection and rectification module is respectively connected to the common power supply and the backup power supply, the output end of the power selection and rectification module is connected to the input end of the current breaking module, the output end of the current breaking module is connected to the conversion direction control module, the output signal of the current breaking module is connected to the control end of the overcurrent protection and alarm module, and the output signal of the overcurrent protection and alarm module is respectively connected to the control end of the current breaking module and the processing module. The automatic transfer switch electromagnet drive circuit described in the present invention is reasonably designed, so that the product meets the higher requirements of electrical clearance and creepage distance, has a stronger current breaking capacity, and increases the overcurrent protection and overcurrent alarm functions. In addition, even if the processing module is miscontrolled due to a fault, the common power supply and the backup power supply will not be short-circuited or multiple electromagnets will not be energized at the same time, making the product safer and more reliable.

[0037] The power selection and rectification module includes a common circuit for receiving a common power supply and a standby circuit for receiving a standby power supply. The common circuit includes a power selection circuit and a rectification circuit, so the power selection circuit includes a common control circuit and a common relay circuit. The rectification circuit includes a common protection circuit and a rectifier bridge Z1. One end of the common control circuit receives the common power selection signal of the processing module, and the other end is connected to the common relay circuit. The common relay circuit is connected to the A-phase and C-phase circuits of the common power supply, and the common relay circuit is connected to the AC input end of the rectifier bridge Z1 through the common protection circuit. The rectifier bridge Z1 outputs a voltage VDC. The standby circuit and the common circuit have the same principle.

[0038] In this embodiment, the power selection and rectification module includes a common circuit and a standby circuit for receiving a common power supply. The common circuit includes a fuse FU1, a varistor RV1, a double-pole single-throw relay K1, a double-pole single-throw relay K2, a rectifier bridge Z1, a diode D1, an NPN transistor Q1, a resistor R1, a resistor R3 and a capacitor C1. One end of the resistor R1 is connected to a common power selection signal, and the other end is connected to the base of the NPN transistor Q1. One end of the resistor R3 is connected to the other end of the resistor R1, and the other end of the resistor R3 is grounded. One end of the capacitor C1 is connected to the other end of the resistor R1, and the other end of the capacitor C1 is grounded. The emitter of the NPN transistor Q1 is grounded, and the collector of the NPN transistor Q1, the double-pole single-throw relay K2, the double-pole single-throw relay K3, and the double-pole single-throw relay K3. One end of the power supply point of the double-pole single-throw relay K1 and one end of the power supply point of the double-pole single-throw relay K2 are connected to the positive electrode of the diode D1, the negative electrode of the diode D1, the other end of the power supply point of the double-pole single-throw relay K1, and the other end of the power supply point of the double-pole single-throw relay K2 are connected to the first power supply VCC1, the double-pole single-throw relay K1 is also connected to the A-phase circuit of the common power supply, the double-pole single-throw relay K2 is also connected to the C-phase circuit of the common power supply, the double-pole single-throw relay K1 is also connected to one end of the varistor RV1 through the fuse FU1, the double-pole single-throw relay K2 is connected to the other end of the varistor RV1, and the two ends of the varistor RV1 are respectively connected to the two AC voltage input ends of the rectifier bridge Z1, and the rectifier bridge Z1 outputs the voltage VDC.

[0039] The commonly used control circuit includes a resistor R1, a resistor R3, a capacitor C1 and an NPN transistor Q1. One end of the resistor R1 is connected to the commonly used power selection signal of the processing module, and the other end is connected to the base of the NPN transistor Q1. One end of the resistor R3 is connected to the other end of the resistor R1, and the other end of the resistor R3 is grounded. One end of the capacitor C1 is connected to the other end of the resistor R1, and the other end of the capacitor C1 is grounded. The emitter of the NPN transistor Q1 is grounded, and the collector of the NPN transistor Q1 is connected to a commonly used relay circuit.

[0040] The common relay circuit includes a double-pole single-throw relay K1, a double-pole single-throw relay K2 and a diode D1. The normally open point 1 of the double-pole single-throw relay K1 is connected to the A-phase circuit of the common power supply, the normally open point 2 of the double-pole single-throw relay K1 is connected to the common protection circuit, the power supply point of the double-pole single-throw relay K1 is respectively connected to the first power supply VCC1 and the positive electrode of the diode D1, the negative electrode of the diode D1 is connected to the first power supply VCC1, the positive electrode of the diode D1 is also connected to the collector of the NPN transistor Q1 and the power supply point of the double-pole single-throw relay K2, the power supply point of the double-pole single-throw relay K2 is connected to the first power supply VCC1, the normally open point 1 of the double-pole single-throw relay K2 is connected to the C-phase circuit of the common power supply, and the normally open point 2 of the double-pole single-throw relay K2 is connected to the common protection circuit.

[0041] The commonly used protection circuit includes fuse FU1 and varistor RV1, one end of the fuse FU1 is connected to the normally open point 2 of the double-pole single-throw relay K1, and the other end of the fuse FU1 is connected to the AC input end of the rectifier bridge Z1, one end of the varistor RV1 is connected to the fuse FU1, and the other end of the varistor RV1 is connected to the normally open point 2 of the double-pole single-throw relay K2; the input and output of each phase power supply of the double-pole single-throw relay K1 and the double-pole single-throw relay K2 are selected at the diagonal position of the relay, and the same is true for the double-pole single-throw relay K3 and the double-pole single-throw relay K4. In this way, the electrical clearance and creepage distance between phases A and C are increased, avoiding conventional solutions such as Figure 4 The distance between phase A and phase C is limited by the distance between relay pins.

[0042] The backup circuit comprises a backup control circuit, a backup relay circuit, a backup protection circuit and a rectifier bridge Z2. One end of the backup control circuit receives a backup power selection signal from a processing module, and the other end is connected to a backup relay circuit. The backup relay circuit is connected to the A-phase and C-phase circuits of the backup power supply, and the backup relay circuit is connected to the AC input end of the rectifier bridge Z2 through the backup protection circuit. The positive pole of the rectifier bridge Z2 outputs a voltage VDC, and VDC supplies power to the current disconnecting module.

[0043] The standby control circuit includes a resistor R2, a resistor R4, a capacitor C2 and an NPN transistor Q2, one end of the resistor R2 is connected to a standby power selection signal, and the other end is connected to the base of the NPN transistor Q2, one end of the resistor R4 is connected to the other end of the resistor R2, and the other end of the resistor R4 is grounded, one end of the capacitor C2 is connected to the other end of the resistor R2, and the other end of the capacitor C2 is grounded, the emitter of the NPN transistor Q2 is grounded, and the collector of the NPN transistor Q2 is connected to the standby relay circuit.

[0044] The standby relay circuit includes a double-pole single-throw relay K3, a double-pole single-throw relay K4 and a diode D2, wherein the normally open point 1 of the double-pole single-throw relay K3 is connected to the A-phase circuit of the standby power supply, the normally open point 2 of the double-pole single-throw relay K3 is connected to the standby protection circuit, the power supply point of the double-pole single-throw relay K3 is respectively connected to the first power supply VCC1 and the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to the first power supply VCC1, the positive electrode of the diode D2 is also connected to the collector of the NPN transistor Q2 and the power supply point of the double-pole single-throw relay K4, the power supply point of the double-pole single-throw relay K4 is connected to the first power supply VCC1, the normally open point 1 of the double-pole single-throw relay K4 is connected to the C-phase circuit of the standby power supply, and the normally open point 2 of the double-pole single-throw relay K4 is connected to the standby protection circuit.

[0045] The backup protection circuit includes a fuse FU2 and a varistor RV2, one end of the fuse FU2 is connected to the normally open point 2 of the double-pole single-throw relay K4, and the other end of the fuse FU2 is connected to the AC input end of the rectifier bridge Z2, one end of the varistor RV2 is connected to the fuse FU2, and the other end of the varistor RV2 is connected to the normally open point 2 of the double-pole single-throw relay K3.

[0046] In this embodiment, the standby circuit includes a fuse FU2, a varistor RV2, a rectifier bridge Z2, a double-pole single-throw relay K3, a double-pole single-throw relay K4, a diode D2, an NPN transistor Q2, a resistor R2, a resistor R4 and a capacitor C2, one end of the resistor R2 is connected to the standby power selection signal, and the other end is connected to the base of the NPN transistor Q2, one end of the resistor R4 is connected to the other end of the resistor R2, and the other end of the resistor R4 is grounded, one end of the capacitor C2 is connected to the other end of the resistor R2, and the other end of the capacitor C2 is grounded, the emitter of the NPN transistor Q2 is grounded, the collector of the NPN transistor Q2, one end of the power supply point of the double-pole single-throw relay K3, and the double One end of the power supply point of the double-pole single-throw relay K4 is connected to the positive electrode of the diode D2, the negative electrode of the diode D2, the other end of the power supply point of the double-pole single-throw relay K1, and the other end of the power supply point of the double-pole single-throw relay K2 are all connected to the first power supply VCC1, the double-pole single-throw relay K3 is also connected to the A-phase circuit of the backup power supply, the double-pole single-throw relay K4 is also connected to the C-phase circuit of the backup power supply, the double-pole single-throw relay K4 is also connected to one end of the varistor RV2 through the fuse FU2, the double-pole single-throw relay K3 is connected to the other end of the varistor RV2, and the two ends of the varistor RV2 are respectively connected to the two AC voltage input ends of the rectifier bridge Z2, and the rectifier bridge Z2 outputs the voltage VDC.

[0047] In this embodiment, the present invention provides an electromagnet driving scheme for a three-position automatic transfer switch, such as Figure 1 . By optimizing the design of the power selection circuit, higher requirements for electrical clearance and creepage distance are met, and IGBT is used for current interruption, which has a stronger current interruption capability and is equipped with overcurrent protection and overcurrent alarm functions. Among them, the contents of the common power supply, backup power supply and processing module are not the focus of the present invention. The power selection and rectification module, current interruption module, overcurrent protection and alarm module, and conversion direction control module will be introduced in detail below.

[0048] 1. Select the power and rectifier module, the circuit is as follows Figure 2 .

[0049] Device Introduction:

[0050] FU1, FU2: fuse

[0051] RV1, RV2: Varistor

[0052] Z1, Z2: rectifier bridge

[0053] K1~K4: Double-pole single-throw relay

[0054] D1, D2: diodes

[0055] Q1, Q2: NPN transistor

[0056] R1~R4:resistance

[0057] C1, C2: capacitors

[0058] Module Introduction:

[0059] When the controller selects the common power supply, the processing module sets the "common power supply selection signal" high, then the transistor Q1 is turned on, the relays K1 and K2 are energized, and the A phase and C phase of the common power supply pass through a double-pole single-throw relay K1 and K2 respectively, and then pass through the fuse FU1 after coming out of the relay, and then connect to the two ends of the varistor RV1, and finally provide the DC power supply VDC for the subsequent circuit through the rectifier bridge Z1. The circuit for selecting the backup power supply is the same as the common power supply, and finally the output ends of the two rectifier bridges are combined.

[0060] Detailed analysis:

[0061] like Figure 3 The four pins of the double-pole single-throw relay are arranged in a rectangular shape. The input and output of each phase of the power supply select the two pins at the diagonal position of the relay. The design can ensure the distance between the input and output to the greatest extent. In addition, the A phase and C phase of each power supply pass through a relay respectively, and the distance between the two relays can be increased in the PCB design, thereby increasing the electrical clearance and creepage distance between phases A and C, avoiding the conventional solution such as Figure 4 The distance between phase A and phase C is limited by the distance between relay pins.

[0062] In addition, in the conventional solution, the output ends of the power selection relays of the common power supply and the backup power supply are first collected together and then pass through the disconnecting relay or the rectifier bridge of the subsequent stage. This may cause the power selection relays to be simultaneously attracted due to product vibration or single-chip microcomputer miscontrol, resulting in a short circuit. In the present invention, the common power supply and the backup power supply pass through the power selection relay and then pass through the rectifier bridge respectively before being collected together. In this way, even if the power selection relays are attracted at the same time, a short circuit will not be caused.

[0063] like Figure 5As shown, the first power supply VCC1 and the second power supply VCC2 of the current disconnection module and the overcurrent protection and alarm module 6 are connected to the isolation power supply module U4. The current disconnection module 4 includes a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R17, a capacitor C3, a capacitor C4, an NPN transistor Q4, an optical coupler U1, an IGBT and a diode D3. The IGBT is labeled Q3 in the figure. One end of the resistor R7 is connected to the current disconnection signal of the processing module, and the other end of the resistor R7 is respectively connected to the base of the NPN transistor Q4 and the output end of the overcurrent protection and alarm module. One end of the resistor R8 is connected to one end of the resistor R7, and the other end of the resistor R8 is grounded. One end of the capacitor C3 is connected to the resistor R7. At the other end, the other end of capacitor C3 is grounded, the emitter of NPN transistor Q4 is grounded, the collector of NPN transistor Q4 is connected to optocoupler U1, one end of optocoupler U1 is connected to the first power supply VCC1 through resistor R5, and the other end is respectively connected to the second power supply VCC2 and one end of resistor R6, the other end of resistor R6 is connected to the IGBT base, one end of resistor R9 is connected to one end of resistor R6, the other end of resistor R9 is grounded, one end of capacitor C4 is connected to the other end of resistor R6, the other end of capacitor C4 is grounded, the emitter of IGBT is respectively connected to resistor R17 and the input end of overcurrent protection and alarm module, resistor R17 is grounded, the collector of IGBT is divided into two paths, one path is connected to the conversion direction control module, and the other path is connected to VDC through diode D3.

[0064] The overcurrent protection and alarm module includes a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, an operational amplifier U3, a diode D4, a capacitor C5, an NPN transistor Q5, a MOS transistor Q6 and an optocoupler U2. The operational amplifier U3 in-phase input end is connected to the emitter of the IGBT, the operational amplifier U3 inverting input end is respectively connected to the resistor R11 and the resistor R16, the other end of the resistor R11 is connected to the second power supply VCC2, the other end of the resistor R16 is grounded, the output end of the operational amplifier U3 is connected to one end of the resistor R13 through a diode D4, the other end of the resistor R13 is connected to the MOS transistor Q6, the resistor R15 One end is connected to one end of resistor R13, and the other end of resistor R15 is grounded. One end of capacitor C5 is connected to the other end of resistor R13, and the other end of capacitor C5 is grounded. One end of MOS tube Q6 is grounded, and the other end is connected to optocoupler U2. One end of optocoupler U2 is connected to the second power supply VCC2 through resistor R10, and the other end is respectively connected to the first power supply VCC1 and one end of resistor R12. When optocoupler U2 is connected to resistor R12, it sends an overcurrent alarm signal to the input end of the processing module. The other end of resistor R12 is connected to the base of NPN transistor Q5. One end of resistor R14 is connected to one end of resistor R12, and the other end of resistor R14 is grounded. The emitter of NPN transistor Q5 is grounded, and the collector of NPN transistor Q5 is connected to resistor R7.

[0065] In this embodiment, the current breaking module, the overcurrent protection and alarm module, the circuit is as follows Figure 5 .

[0066] Device Introduction:

[0067] R5~R16:resistance

[0068] R17: sampling resistor

[0069] C3~C7:Capacitor

[0070] D3, D4: diodes

[0071] U1, U2: Optocoupler

[0072] U3: Operational Amplifier

[0073] U4: Isolated power module

[0074] Q3: IGBT

[0075] Q4, Q5: NPN transistors

[0076] Q6: N-channel MOS tube

[0077] Module Introduction:

[0078] When the electromagnet needs to be energized, the corresponding relay is first energized, and then the processing module sets the "current disconnect signal" to high, then the transistor Q4 is turned on in sequence, the optocoupler U1 is turned on, and the IGBT Q3 is turned on. It will be mentioned later that one end of the electromagnet is connected to VDC and the other end is connected to the signal "IGBT_C", so the electromagnet is energized at this time; similarly, when the "current disconnect signal" is set to low, the transistor Q4 is turned off, the optocoupler U1 is turned off, the IGBT Q3 is turned off, and the electromagnet loses power.

[0079] In addition, a comparator is designed using the operational amplifier U3. When the electromagnet is energized, the current will pass through the sampling resistor R17. The "+" input of U3 collects the voltage of the sampling resistor R17, and the "-" input collects the voltage of R11 and R16. The values ​​of resistors R11 and R16 are calculated according to the overcurrent threshold of the electromagnet and the value of R17 to form a voltage threshold. For example: the VCC2 voltage is 3.3V, the overcurrent protection threshold of the electromagnet is 10A, and the resistance of R17 is 0.05Ω. Then, the voltage threshold of the "-" input of the comparator needs to be set to 10A*0.05Ω=0.5V, then the resistance of R11 can be set to 5.6k, and the resistance of R16 can be set to 1k, forming a voltage threshold of 0.5V. When overcurrent occurs, the voltage at the "+" input terminal of the operational amplifier U3 is higher than the voltage at the "-" input terminal, and the output of the operational amplifier U3 changes from a low level to a high level. The MOS tube Q6 is turned on in turn, the optocoupler U2 is turned on, and the "overcurrent alarm signal" changes from a low level to a high level, the transistor Q5 is turned on, the transistor Q4 is turned off, the optocoupler U1 is turned off, the IGBT Q3 is turned off, and the electromagnet loses power. The entire process from overcurrent to automatic power-off is completed within microseconds, and an alarm signal is sent to the processing module at the same time, notifying the processing module to set the "current disconnection signal" low to cut off the power to the electromagnet.

[0080] Since the output end of the optocoupler U1, the input end of the optocoupler U2, the operational amplifier U3, the IGBT Q3 and other devices are connected to the electromagnet drive power supply, an isolated power supply module U4 is used to convert VCC1 into VCC2 to power this part of the circuit to ensure the isolation characteristics between the strong and weak currents of the controller.

[0081] Detailed analysis:

[0082] When the overcurrent is eliminated, the output of the operational amplifier U3 will change from a high level to a low level. Due to the reverse cutoff characteristics of the diode D4, the charge of the capacitor C5 will be slowly discharged through the resistors R13 and R15, that is, the gate voltage of the MOS tube Q6 will slowly decrease. When it is lower than the conduction threshold, the MOS tube Q6 will be turned off, which plays a role of delayed shutdown. During this delay, the "overcurrent alarm signal" presents a stable high level, and the delay can be set to a longer time by adjusting the value of the resistor and capacitor, so that the processing module has enough time to identify the "overcurrent alarm signal" and set the "current disconnection signal" to a low level to cut off the power to the electromagnet. If there is no diode D4, when the overcurrent is eliminated, the voltage on R17 is 0V, the operational amplifier U3 outputs a low level, the MOS tube Q6 will be quickly turned off, and the overcurrent protection will be eliminated. The IGBT Q3 will be turned on again, and then the overcurrent protection will be performed again. The whole process time is extremely short. In this way, the electromagnet will be repeatedly powered. Moreover, at this time, the "overcurrent alarm signal" is not a stable high level, but a high-frequency fluctuating signal with an interval of microseconds, which will be difficult for the processing module to effectively identify.

[0083] The switching direction control module comprises a first control signal circuit, a second control signal circuit and a load circuit, wherein the input end of the first control signal circuit is respectively connected to the processing module and the IGBT collector, the output end of the first control signal circuit is respectively connected to the second control signal circuit and the load circuit, the input end of the second control signal circuit is connected to the processing module, and the output end of the second control signal circuit is connected to the load circuit;

[0084] The load circuit includes electromagnet No. 1, electromagnet No. 2 and electromagnet No. 3, one end of electromagnet No. 1 is connected to VDC, and the other end is connected to the first control signal circuit, one end of electromagnet No. 2 and one end of electromagnet No. 3 are both connected to VDC, and the other ends of electromagnet No. 2 and No. 3 are both connected to the second control signal circuit.

[0085] The first control signal circuit includes a resistor R18, a resistor R19, a capacitor C8, an NPN transistor Q7, a diode D5 and a single-pole double-throw relay K5, one end of the resistor R18 receives a No. 1 conversion direction control signal of the processing module, the other end of the resistor R18 is connected to the base of the NPN transistor Q7, one end of the resistor R19 is connected to the other end of the resistor R18, the other end of the resistor R19 is grounded, one end of the capacitor C8 is connected to the other end of the resistor R18, the other end of the capacitor C8 is grounded, the emitter of the NPN transistor Q7 is grounded, the collector of the NPN transistor Q7 is divided into two paths, one path is connected to the first power supply VCC1 through the diode D5, and the other path is connected to the power supply point of the single-pole double-throw relay K5, the power supply point of the single-pole double-throw relay K5 is connected to the first power supply VCC1, the normally closed point of the single-pole double-throw relay K5 is respectively connected to the collector of the IGBT and the No. 1 electromagnet, and the normally open point of the single-pole double-throw relay K5 is connected to the second control signal circuit.

[0086] The second control signal circuit includes a resistor R20, a resistor R21, a capacitor C9, an NPN transistor Q8, a diode D6 and a single-pole double-throw relay K6, one end of the resistor R20 receives the second conversion direction control signal of the processing module, the other end of the resistor R20 is connected to the base of the NPN transistor Q8, one end of the resistor R21 is connected to the other end of the resistor R20, the other end of the resistor R21 is grounded, one end of the capacitor C9 is connected to the other end of the resistor R20, the other end of the capacitor C9 is grounded, the emitter of the NPN transistor Q8 is grounded, and the collector of the NPN transistor Q8 is divided into two paths, one path is connected to the first power supply VCC1 through the diode D6, and the other path is connected to the power supply point of the single-pole double-throw relay K6, the power supply point of the single-pole double-throw relay K6 is connected to the first power supply VCC1, the normally closed point of the single-pole double-throw relay K6 is respectively connected to the normally open point of the single-pole double-throw relay K5 and the second electromagnet, and the normally open point of the single-pole double-throw relay K6 is connected to the third electromagnet.

[0087] In this embodiment, the switching direction control module, the circuit is as follows Figure 6 .

[0088] Device Introduction:

[0089] R18~R21:Resistance

[0090] C8, C9: capacitors

[0091] D5, D6: diodes

[0092] Q7, Q8: NPN transistors

[0093] K5, K6: single-pole double-throw relay

[0094] Solenoid 1: The electromagnet that drives the switch to the common position

[0095] Solenoid 2: The electromagnet that drives the switch to the standby position

[0096] Electromagnet 3: The electromagnet that drives the switch to the double position

[0097] Module Introduction:

[0098] One end of the electromagnet is connected to VDC, and the other end is connected to the signal "IGBT_C" through relays K5 and K6. The switching direction control signal 1 and the switching direction control signal 2 control the contact of relays K5 and K6 by controlling transistors Q7 and Q8 respectively. The control relationship is shown in Table 1.

[0099] Table 1

[0100] Switch direction control signal 1 Switch direction control signal 2 Corresponding electromagnet Low level Low level Electromagnet 1 High level Low level Electromagnet 2 High level High level Electromagnet 3

[0101] Detailed analysis:

[0102] This solution only needs two control signals to control the three electromagnets to be energized, and no interlocking circuit is required. Only one electromagnet will be energized for any level combination of the two control signals. The conventional solution uses three control signals to control the three electromagnets to be energized, which not only wastes IO, but also burns out the fuse or damages the mechanical structure if two or three electromagnets are energized at the same time due to miscontrol by the processing module.

[0103] Example 1

[0104] Next, the present invention will be introduced with a single conversion action. The conversion process is as follows: Figure 7 . Since this patent focuses on the electromagnet drive part, the situation where the position feedback signal is abnormal or the conversion fails due to mechanical structure failure is not discussed here. Assume a scenario: the normal power supply and the backup power supply are normal, and the automatic transfer switch is currently in the normal position. At this time, the normal power supply is lost and the switch needs to be switched to the backup position. The first step is to switch to the double-open position. The conversion process is as follows:

[0105] 1. Select power supply: In this scenario, the backup power supply should be selected, and the processing module sets the "backup power supply selection signal" to high.

[0106] 2. Select electromagnet: Electromagnet 3 should be selected for the double-open position. According to Table 1, the processing module sets the "conversion direction control signal 1" and "conversion direction control signal 2" to high.

[0107] 3. Delay T1: The relays in steps 1 and 2 need to be fully energized to pass currents greater than their breaking capacity, so a delay of T1 is required and T1 must be greater than the longest operating time of the relay.

[0108] 4. Current breaking module is turned on: The processing module sets the "current breaking signal" high, the IGBT is turned on, the electromagnet is energized, and the switch starts to switch. At the same time, the hardware starts to monitor whether overcurrent occurs. It is assumed here that no overcurrent occurs.

[0109] 5. Delay T2: The time required for switch conversion.

[0110] 6. Detect position feedback signal: When the switch is in place, the controller receives the position feedback signal.

[0111] 7. Current disconnect module shuts down: The processing module sets the "current disconnect signal" to low, the IGBT is shut down, and the electromagnet loses power.

[0112] 8. Delay T3: It takes some time from the IGBT turning off to the electromagnet current completely disappearing, so the delay T3 is to wait until the electromagnet completely loses power before taking the next step to avoid damaging the relay contacts.

[0113] 9. The power selection relay is disconnected: the processing module sets the "backup power selection signal" to a low level.

[0114] 10. Electromagnet selection relay release: The processing module sets "conversion direction control signal 1" and "conversion direction control signal 2" to low.

[0115] 11. At this point, a single conversion action is completed.

[0116] 12. If an overcurrent occurs during the process from step 4 to step 7, the hardware disconnection current disconnection module is executed: the voltage at the "+" input terminal of the operational amplifier U3 is higher than the voltage at the "-" input terminal, and the output of the operational amplifier U3 changes from a low level to a high level. The MOS tube Q6 is turned on, the optocoupler U2 is turned on, and the "overcurrent alarm signal" changes from a low level to a high level. The transistor Q5 is turned on, the transistor Q4 is turned off, the optocoupler U1 is turned off, the IGBT Q3 is turned off, and the electromagnet loses power. However, after the overcurrent state is eliminated, the output of U3 will also change from a high level to a low level. Due to the reverse cutoff characteristic of the diode D4, the charge of the capacitor C5 will be slowly discharged through the resistors R13 and R15, that is, the gate voltage of the MOS tube Q6 will slowly decrease. When it is lower than the conduction threshold, the MOS tube Q6 will be turned off, which plays a role of delayed shutdown, that is, the overcurrent protection state continues for a period of time, waiting for the processor to disconnect the current disconnection module from the program.

[0117] 13. Send an alarm signal: The hardware will send an "overcurrent alarm signal" to the processing module.

[0118] 14. Program disconnection current disconnection module: After receiving the "overcurrent alarm signal", the processing module will set the "current disconnection signal" to low, and then the electromagnet will remain in the power-off state.

[0119] 15. Delay T3: Although the current disconnect module has been turned off in step 12, in order to ensure the design margin, it is still necessary to delay T3 and wait until the electromagnet is completely de-energized before proceeding to the next step to avoid damaging the relay contacts.

[0120] 16. The power selection relay is disconnected: the processing module sets the "backup power selection signal" to a low level.

[0121] 17. Electromagnet selection relay release: The processing module sets "conversion direction control signal 1" and "conversion direction control signal 2" to low.

[0122] 18. At this point, the conversion stops.

[0123] The above describes the process of the switch turning from the normal position to the double-off position. Other actions such as turning from the double-off position to the standby position, from the standby position to the double-off position, and from the double-off position to the normal position are the same as the above process except that the selected power supply and electromagnet are different.

[0124] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An automatic transfer switch electromagnet drive circuit, characterized in that: It includes a common power supply, a backup power supply, a power selection and rectification module, a current disconnecting module, a switching direction control module, an overcurrent protection and alarm module and a processing module, wherein the output signal of the processing module is respectively connected to the control end of the power selection and rectification module, the control end of the current disconnecting module and the control end of the switching direction control module, the input end of the power selection and rectification module is respectively connected to the common power supply and the backup power supply, the output end of the power selection and rectification module is connected to the input end of the current disconnecting module, the output end of the current disconnecting module is connected to the switching direction control module, the output signal of the current disconnecting module is connected to the control end of the overcurrent protection and alarm module, and the output signal of the overcurrent protection and alarm module is respectively connected to the control end of the current disconnecting module and the processing module; The power selection and rectification module includes a common circuit for receiving a common power supply and a standby circuit for receiving a standby power supply. The common circuit includes a power selection circuit and a rectification circuit, so the power selection circuit includes a common control circuit and a common relay circuit. The rectification circuit includes a common protection circuit and a rectifier bridge Z1. One end of the common control circuit receives a common power selection signal from the processing module, and the other end is connected to a common relay circuit. The common relay circuit is connected to the A-phase and C-phase circuits of the common power supply, and the common relay circuit is connected to the AC input end of the rectifier bridge Z1 through the common protection circuit. The rectifier bridge Z1 outputs a voltage VDC. The principle of the standby circuit is the same as that of the common circuit; The common control circuit comprises a resistor R1, a resistor R3, a capacitor C1 and an NPN transistor Q1, wherein one end of the resistor R1 is connected to a common power selection signal of a processing module, and the other end is connected to a base of the NPN transistor Q1, one end of the resistor R3 is connected to the other end of the resistor R1, and the other end of the resistor R3 is grounded, one end of the capacitor C1 is connected to the other end of the resistor R1, and the other end of the capacitor C1 is grounded, the emitter of the NPN transistor Q1 is grounded, and the collector of the NPN transistor Q1 is connected to a common relay circuit; The common relay circuit comprises a double-pole single-throw relay K1, a double-pole single-throw relay K2 and a diode D1, wherein a normally open point 1 of the double-pole single-throw relay K1 is connected to a phase A circuit of a common power supply, a normally open point 2 of the double-pole single-throw relay K1 is connected to a common protection circuit, a power supply point of the double-pole single-throw relay K1 is respectively connected to a first power supply VCC1 and a positive electrode of a diode D1, a negative electrode of the diode D1 is connected to the first power supply VCC1, a positive electrode of the diode D1 is also connected to a collector of an NPN transistor Q1 and a power supply point of the double-pole single-throw relay K2, a power supply point of the double-pole single-throw relay K2 is connected to the first power supply VCC1, a normally open point 1 of the double-pole single-throw relay K2 is connected to a phase C circuit of a common power supply, and a normally open point 2 of the double-pole single-throw relay K2 is connected to a common protection circuit; The commonly used protection circuit includes a fuse FU1 and a varistor RV1, one end of the fuse FU1 is connected to the normally open point 2 of the double-pole single-throw relay K1, the other end of the fuse FU1 is connected to the AC input end of the rectifier bridge Z1, one end of the varistor RV1 is connected to the fuse FU1, and the other end of the varistor RV1 is connected to the normally open point 2 of the double-pole single-throw relay K2; The input and output of each phase power supply of the double-pole single-throw relay K1 and the double-pole single-throw relay K2 are both selected at the diagonal position of the relay; The four pins of the four double-pole single-throw relays are arranged in a rectangular shape. The input and output of each phase of power select the two pins at the diagonal position of the relay, and the A phase and C phase of each power supply pass through a relay respectively.

2. The automatic transfer switch electromagnet drive circuit according to claim 1, characterized in that: The first power supply VCC1 and the second power supply VCC2 of the current disconnection module and the overcurrent protection and alarm module 6 are all connected to the isolation power supply module U4. The current disconnection module 4 includes a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor 9, a resistor R17, a capacitor C3, a capacitor C4, an NPN transistor Q4, an optical coupler U1, an IGBT and a diode D3. One end of the resistor R7 is connected to the current disconnection signal of the processing module, and the other end of the resistor R7 is respectively connected to the base of the NPN transistor Q4 and the output end of the overcurrent protection and alarm module. One end of the resistor R8 is connected to one end of the resistor R7, and the other end of the resistor R8 is grounded. One end of the capacitor C3 is connected to the other end of the resistor R7, and the other end of the capacitor C3 is connected to the base of the NPN transistor Q4 and the output end of the overcurrent protection and alarm module. One end is grounded, the emitter of NPN transistor Q4 is grounded, the collector of NPN transistor Q4 is connected to optocoupler U1, one end of optocoupler U1 is connected to the first power supply VCC1 through resistor R5, and the other end is respectively connected to the second power supply VCC2 and one end of resistor R6, the other end of resistor R6 is connected to the IGBT base, one end of resistor R9 is connected to one end of resistor R6, the other end of resistor R9 is grounded, one end of capacitor C4 is connected to the other end of resistor R6, the other end of capacitor C4 is grounded, the emitter of IGBT is respectively connected to resistor R17 and the input end of overcurrent protection and alarm module, resistor R17 is grounded, the collector of IGBT is divided into two paths, one path is connected to the conversion direction control module, and the other path is connected to VDC through diode D3.

3. The automatic transfer switch electromagnet drive circuit according to claim 2, characterized in that: The overcurrent protection and alarm module includes a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, an operational amplifier U3, a diode D4, a capacitor C5, an NPN transistor Q5, a MOS transistor Q6 and an optocoupler U2. The operational amplifier U3 in-phase input end is connected to the emitter of the IGBT, the operational amplifier U3 inverting input end is respectively connected to the resistor R11 and the resistor R16, the other end of the resistor R11 is connected to the second power supply VCC2, the other end of the resistor R16 is grounded, the output end of the operational amplifier U3 is connected to one end of the resistor R13 through a diode D4, the other end of the resistor R13 is connected to the MOS transistor Q6, the resistor R15 One end is connected to one end of resistor R13, and the other end of resistor R15 is grounded. One end of capacitor C5 is connected to the other end of resistor R13, and the other end of capacitor C5 is grounded. One end of MOS tube Q6 is grounded, and the other end is connected to optocoupler U2. One end of optocoupler U2 is connected to the second power supply VCC2 through resistor R10, and the other end is respectively connected to the first power supply VCC1 and one end of resistor R12. When optocoupler U2 is connected to resistor R12, it sends an overcurrent alarm signal to the input end of the processing module. The other end of resistor R12 is connected to the base of NPN transistor Q5. One end of resistor R14 is connected to one end of resistor R12, and the other end of resistor R14 is grounded. The emitter of NPN transistor Q5 is grounded, and the collector of NPN transistor Q5 is connected to resistor R7.

4. The automatic transfer switch electromagnet drive circuit according to claim 1, characterized in that: The switching direction control module comprises a first control signal circuit, a second control signal circuit and a load circuit, wherein the input end of the first control signal circuit is respectively connected to the processing module and the IGBT collector, the output end of the first control signal circuit is respectively connected to the second control signal circuit and the load circuit, the input end of the second control signal circuit is connected to the processing module, and the output end of the second control signal circuit is connected to the load circuit; The load circuit includes electromagnet No. 1, electromagnet No. 2 and electromagnet No. 3, one end of electromagnet No. 1 is connected to VDC, and the other end is connected to the first control signal circuit, one end of electromagnet No. 2 and one end of electromagnet No. 3 are both connected to VDC, and the other ends of electromagnet No. 2 and No. 3 are both connected to the second control signal circuit.

5. The automatic transfer switch electromagnet drive circuit according to claim 4, characterized in that: The first control signal circuit includes a resistor R18, a resistor R19, a capacitor C8, an NPN transistor Q7, a diode D5 and a single-pole double-throw relay K5, one end of the resistor R18 receives a No. 1 conversion direction control signal of the processing module, the other end of the resistor R18 is connected to the base of the NPN transistor Q7, one end of the resistor R19 is connected to the other end of the resistor R18, the other end of the resistor R19 is grounded, one end of the capacitor C8 is connected to the other end of the resistor R18, the other end of the capacitor C8 is grounded, the emitter of the NPN transistor Q7 is grounded, the collector of the NPN transistor Q7 is divided into two paths, one path is connected to the first power supply VCC1 through the diode D5, and the other path is connected to the power supply point of the single-pole double-throw relay K5, the power supply point of the single-pole double-throw relay K5 is connected to the first power supply VCC1, the normally closed point of the single-pole double-throw relay K5 is respectively connected to the collector of the IGBT and the No. 1 electromagnet, and the normally open point of the single-pole double-throw relay K5 is connected to the second control signal circuit.

6. The automatic transfer switch electromagnet drive circuit according to claim 5, characterized in that: The second control signal circuit includes a resistor R20, a resistor R21, a capacitor C9, an NPN transistor Q8, a diode D6 and a single-pole double-throw relay K6, one end of the resistor R20 receives the second conversion direction control signal of the processing module, the other end of the resistor R20 is connected to the base of the NPN transistor Q8, one end of the resistor R21 is connected to the other end of the resistor R20, the other end of the resistor R21 is grounded, one end of the capacitor C9 is connected to the other end of the resistor R20, the other end of the capacitor C9 is grounded, the emitter of the NPN transistor Q8 is grounded, and the collector of the NPN transistor Q8 is divided into two paths, one path is connected to the first power supply VCC1 through the diode D6, and the other path is connected to the power supply point of the single-pole double-throw relay K6, the power supply point of the single-pole double-throw relay K6 is connected to the first power supply VCC1, the normally closed point of the single-pole double-throw relay K6 is respectively connected to the normally open point of the single-pole double-throw relay K5 and the second electromagnet, and the normally open point of the single-pole double-throw relay K6 is connected to the third electromagnet.

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