A secondary power supply circuit for explosion-proof low-voltage equipment in underground mines

Abstract

This utility model provides a secondary power supply circuit for explosion-proof low-voltage equipment in underground mines, including a self-supply circuit I, a self-supply circuit II, an external supply circuit I, an external supply circuit II, and an inter-section switching circuit. The self-supply circuit I includes: a transformer T1, air switches ZK1, ZK2, and ZK3, intermediate relays KA1 and KA2, intermediate relay 1KA, a DC power supply KGDY1, an overvoltage relay GY1, and an undervoltage relay QY1. The external supply circuit I includes: an air switch ZK4 and a contactor KM1. One end of the first and second terminals of the air switch ZK4 are used to connect to the external power supply. This utility model can automatically switch the internal circuits of the self-supply circuit during primary high-voltage switching to ensure an output voltage of 220V, and also realizes the switching between the self-supply circuit and the external supply circuit.

Description

Technical Field

[0001] This utility model relates to a power supply circuit, and more particularly to a secondary power supply circuit for explosion-proof low-voltage equipment in underground mines. Background Technology

[0002] There are currently many 220V electrical devices in mines. To ensure electrical safety, two self-supply power sources are usually configured. When one self-supply power source needs maintenance, the system can switch to the other. If neither self-supply power source can provide power, it is necessary to switch to an external power source.

[0003] There are usually two voltages on the primary side of the mine. When different high voltages are used for the primary side, the voltage on the secondary side needs to be able to switch automatically to maintain a power supply of 220V. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this utility model provides a secondary power supply circuit for explosion-proof low-voltage equipment in underground mines, capable of automatically switching power supplies. To achieve the above technical objectives, the technical solution adopted in this utility model embodiment is as follows:

[0005] This utility model embodiment provides a secondary power supply circuit for explosion-proof low-voltage equipment in underground mines, including a self-supply circuit I, a self-supply circuit II, an external supply circuit I, an external supply circuit II, and an inter-section switching circuit;

[0006] The self-supply circuit of section I includes: transformer T1, air switch ZK1, ZK2, ZK3, intermediate relays KA1, KA2, intermediate relay 1KA, DC power supply KGDY1, overvoltage relay GY1, and undervoltage relay QY1.

[0007] The primary side of transformer T1 is used to connect to the primary high voltage. The secondary side of transformer T1 includes a main winding and an auxiliary winding; the main winding is equipped with an intermediate tap.

[0008] One end of the secondary main winding of transformer T1 is connected to one end of the first terminal of air switch ZK1. The other end of the first terminal of air switch ZK1 is connected to one end of the first terminal of the normally open contact KA2-1 of intermediate relay KA2. The other end of the first terminal of the normally open contact KA2-1 of intermediate relay KA2 is connected to one end of the first terminal of the normally closed contact KA1-1 of intermediate relay KA1. The other end of the first terminal of the normally closed contact KA1-1 of intermediate relay KA1 is connected to one end of the coil of intermediate relay 1KA and one end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA. The other end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA serves as the first output terminal of the I-section self-supply circuit.

[0009] One end of the intermediate tap on the secondary side of transformer T1 is connected to one end of the first terminal of air switch ZK2. The other end of the first terminal of air switch ZK2 is connected to one end of the first terminal of the normally closed contact KA2-2 of intermediate relay KA2. The other end of the first terminal of the normally closed contact KA2-2 of intermediate relay KA2 is connected to one end of the first terminal of the normally open contact KA1-2 of intermediate relay KA1. The other end of the first terminal of the normally open contact KA1-2 of intermediate relay KA1 is connected to one end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA.

[0010] The other end of the secondary main winding of transformer T1 is connected to one end of the second phase of air switch ZK1 and one end of the second phase of air switch ZK2; the other end of the second phase of air switch ZK1 is connected to one end of the second phase of the normally open contact KA2-1 of intermediate relay KA2; the other end of the second phase of the normally open contact KA2-1 of intermediate relay KA2 is connected to one end of the second phase of the normally closed contact KA1-1 of intermediate relay KA1; the other end of the second phase of the normally closed contact KA1-1 of intermediate relay KA1 is connected to the other end of the coil of intermediate relay 1KA and one end of the second phase of the normally open contact 1KA-1 of intermediate relay 1KA.

[0011] The other end of the second section of air switch ZK2 is connected to one end of the second section of intermediate relay KA2-2, which is normally closed. The other end of the second section of intermediate relay KA2-2 is connected to one end of the second section of intermediate relay KA1-2, which is normally open. The other end of the second section of intermediate relay KA1-2 is connected to one end of the second section of intermediate relay 1KA-1, which is normally open. The other end of the second section of intermediate relay 1KA-1 serves as the second output terminal of the I-stage self-supply circuit.

[0012] One end of the secondary auxiliary winding of transformer T1 is connected to one end of the first section of air switch ZK3. The other end of the first section of air switch ZK3 is connected to one detection terminal of overvoltage relay GY1 and one detection terminal of undervoltage relay QY1. The other end of the secondary auxiliary winding of transformer T1 is connected to one end of the second section of air switch ZK3. The other end of the second section of air switch ZK3 is connected to the other detection terminal of overvoltage relay GY1 and the other detection terminal of undervoltage relay QY1. The two power supply terminals of overvoltage relay GY1 and undervoltage relay QY1 are respectively connected to the other ends of the first and second sections of air switch ZK2.

[0013] The two power terminals of DC power supply KGDY1 are connected to the other ends of the first and second sections of air switch ZK2, respectively; the output terminal of DC power supply KGDY1 is connected to one end of the coil of intermediate relay KA1 and one end of the coil of intermediate relay KA2; the other end of the coil of intermediate relay KA1 is connected to one end of the normally closed contact QY1-1 of undervoltage relay QY1, and the other end of the normally closed contact QY1-1 of undervoltage relay QY1 is connected to one end of the normally open contact GY1-1 of overvoltage relay GY1; the other end of the coil of intermediate relay KA2 is connected to one end of the normally closed contact GY1-2 of overvoltage relay GY1, and the other end of the normally closed contact GY1-2 of overvoltage relay GY1 is connected to one end of the normally open contact QY1-2 of undervoltage relay QY1; the other end of the normally open contact GY1-1 of overvoltage relay GY1 and the other end of the normally open contact QY1-2 of undervoltage relay QY1 are connected to the common terminal of DC power supply KGDY1;

[0014] The external power supply circuit of section I includes: air switch ZK4 and contactor KM1; one end of the first and one end of the second section of air switch ZK4 are used to connect to the external power supply.

[0015] The other end of the first unit of the air switch ZK4 is connected to one end of the first unit of the normally closed contact 1KA-2 of the intermediate relay 1KA. The other end of the first unit of the normally closed contact 1KA-2 of the intermediate relay 1KA is connected to one end of the first unit of the normally closed contact 2KA-2 of the intermediate relay 2KA. The other end of the first unit of the normally closed contact 2KA-2 of the intermediate relay 2KA is connected to one end of the coil of contactor KM1 and one end of the first unit of the normally open contact KM1-1 of contactor KM1. The other end of the first unit of the normally open contact KM1-1 of contactor KM1 serves as the first output terminal of the I-section external power supply circuit.

[0016] The other end of the second unit of air switch ZK4 is connected to one end of the second unit of the normally closed contact 1KA-2 of intermediate relay 1KA. The other end of the second unit of the normally closed contact 1KA-2 of intermediate relay 1KA is connected to one end of the second unit of the normally closed contact 2KA-2 of intermediate relay 2KA. The other end of the second unit of the normally closed contact 2KA-2 of intermediate relay 2KA is connected to the other end of the coil of contactor KM1 and one end of the second unit of the normally open contact KM1-1 of contactor KM1. The other end of the second unit of the normally open contact KM1-1 of contactor KM1 serves as the second output terminal of the I-section external power supply circuit.

[0017] The self-supply circuit of section II includes: transformer T2, air switch ZK5, ZK6, ZK7, intermediate relays KA3, KA4, intermediate relay 2KA, DC power supply KGDY2, overvoltage relay GY2, and undervoltage relay QY2.

[0018] The primary side of transformer T2 is used to connect to the primary high voltage. The secondary side of transformer T2 includes a main winding and an auxiliary winding; the main winding is equipped with an intermediate tap.

[0019] One end of the secondary main winding of transformer T2 is connected to one end of the first terminal of air switch ZK5. The other end of the first terminal of air switch ZK5 is connected to one end of the first terminal of the normally open contact KA4-1 of intermediate relay KA4. The other end of the first terminal of the normally open contact KA4-1 of intermediate relay KA4 is connected to one end of the first terminal of the normally closed contact KA3-1 of intermediate relay KA3. The other end of the first terminal of the normally closed contact KA3-1 of intermediate relay KA3 is connected to one end of the coil of intermediate relay 2KA and one end of the first terminal of the normally open contact 2KA-1 of intermediate relay 2KA. The other end of the first terminal of the normally open contact 2KA-1 of intermediate relay 2KA serves as the first output terminal of the II-stage self-supply circuit.

[0020] One end of the intermediate tap on the secondary side of transformer T2 is connected to one end of the first terminal of air switch ZK6. The other end of the first terminal of air switch ZK6 is connected to one end of the first terminal of intermediate relay KA4-2, which is normally closed. The other end of the first terminal of intermediate relay KA4-2 is connected to one end of the first terminal of intermediate relay KA3-2, which is normally open. The other end of the first terminal of intermediate relay KA3-2 is connected to one end of the first terminal of intermediate relay 2KA-1, which is normally open.

[0021] The other end of the secondary main winding of transformer T2 is connected to one end of the second section of air switch ZK5 and one end of the second section of air switch ZK6; the other end of the second section of air switch ZK5 is connected to one end of the second section of the normally open contact KA4-1 of intermediate relay KA4; the other end of the second section of the normally open contact KA4-1 of intermediate relay KA4 is connected to one end of the second section of the normally closed contact KA3-1 of intermediate relay KA3; the other end of the second section of the normally closed contact KA3-1 of intermediate relay KA3 is connected to the other end of the coil of intermediate relay 2KA and one end of the second section of the normally open contact 2KA-1 of intermediate relay 2KA.

[0022] The other end of the second unit of the air switch ZK6 is connected to one end of the second unit of the normally closed contact KA4-2 of the intermediate relay KA4. The other end of the second unit of the normally closed contact KA4-2 of the intermediate relay KA4 is connected to one end of the second unit of the normally open contact KA3-2 of the intermediate relay KA3. The other end of the second unit of the normally open contact KA3-2 of the intermediate relay KA3 is connected to one end of the second unit of the normally open contact 2KA-1 of the intermediate relay 2KA. The other end of the second unit of the normally open contact 2KA-1 of the intermediate relay 2KA serves as the second output terminal of the II-stage self-supply circuit.

[0023] One end of the secondary auxiliary winding of transformer T2 is connected to one end of the first section of air switch ZK7. The other end of the first section of air switch ZK7 is connected to one detection terminal of overvoltage relay GY2 and one detection terminal of undervoltage relay QY2. The other end of the secondary auxiliary winding of transformer T2 is connected to one end of the second section of air switch ZK7. The other end of the second section of air switch ZK7 is connected to the other detection terminal of overvoltage relay GY2 and the other detection terminal of undervoltage relay QY2. The two power supply terminals of overvoltage relay GY2 and undervoltage relay QY2 are respectively connected to the other ends of the first and second sections of air switch ZK6.

[0024] The two power terminals of DC power supply KGDY2 are connected to the other ends of the first and second sections of air switch ZK6, respectively; the output terminal of DC power supply KGDY2 is connected to one end of the coil of intermediate relay KA3 and one end of the coil of intermediate relay KA4; the other end of the coil of intermediate relay KA3 is connected to one end of the normally closed contact QY2-1 of undervoltage relay QY2, and the other end of the normally closed contact QY2-1 of undervoltage relay QY2 is connected to one end of the normally open contact GY2-1 of overvoltage relay GY2; the other end of the coil of intermediate relay KA4 is connected to one end of the normally closed contact GY2-2 of overvoltage relay GY2, and the other end of the normally closed contact GY2-2 of overvoltage relay GY2 is connected to one end of the normally open contact QY2-2 of undervoltage relay QY2; the other end of the normally open contact GY2-1 of overvoltage relay GY2 and the other end of the normally open contact QY2-2 of undervoltage relay QY2 are connected to the common terminal of DC power supply KGDY2;

[0025] The external power supply circuit in section II includes: air switch ZK8 and contactor KM2; one end of the first and one end of the second section of air switch ZK8 are used to connect to the external power supply.

[0026] The other end of the first section of the air switch ZK8 is connected to one end of the first section of the normally closed contact 2KA-3 of the intermediate relay 2KA. The other end of the first section of the intermediate relay 2KA-3 is connected to one end of the first section of the normally closed contact 1KA-3 of the intermediate relay 1KA. The other end of the first section of the intermediate relay 1KA-3 is connected to one end of the coil of contactor KM2 and one end of the first section of the normally open contact KM2-1 of contactor KM2. The other end of the first section of the normally open contact KM2-1 of contactor KM2 serves as the first output terminal of the II-stage external power supply circuit.

[0027] The other end of the second unit of the air switch ZK8 is connected to one end of the second unit of the normally closed contact 2KA-3 of the intermediate relay 2KA. The other end of the second unit of the normally closed contact 2KA-3 of the intermediate relay 2KA is connected to one end of the second unit of the normally closed contact 1KA-3 of the intermediate relay 1KA. The other end of the second unit of the normally closed contact 1KA-3 of the intermediate relay 1KA is connected to the other end of the coil of contactor KM2 and one end of the second unit of the normally open contact KM2-1 of contactor KM2. The other end of the second unit of the normally open contact KM2-1 of contactor KM2 serves as the second output terminal of the II-stage external power supply circuit.

[0028] The inter-segment switching circuit includes normally closed contacts KM1-2 of contactor KM1, normally closed contacts KM2-2 of contactor KM2, normally closed contacts 2KA-4 of intermediate relay 2KA, normally closed contacts 1KA-4 of intermediate relay 1KA, normally closed contacts 2KA-5 of intermediate relay 2KA, and normally closed contacts 1KA-5 of intermediate relay 1KA.

[0029] The first output terminal of the self-supply circuit of section I is connected to the first output terminal of the external supply circuit of section I and connected to the first terminal of the normally closed contact KM1-2 of contactor KM1. The second output terminal of the self-supply circuit of section I is connected to the second output terminal of the external supply circuit of section I and connected to the second terminal of the normally closed contact KM1-2 of contactor KM1.

[0030] The other end of the first normally closed contact of contactor KM1-2 is connected to one end of the first normally closed contact of contactor KM2-2. The other end of the first normally closed contact of contactor KM2-2 is connected to one end of the normally closed contact 2KA-4 of intermediate relay 2KA and one end of the normally closed contact 1KA-4 of intermediate relay 1KA. The other end of the second normally closed contact of contactor KM1-2 is connected to one end of the second normally closed contact of contactor KM2-2. The other end of the second normally closed contact of contactor KM2-2 is connected to one end of the normally closed contact 2KA-5 of intermediate relay 2KA and one end of the normally closed contact 1KA-5 of intermediate relay 1KA.

[0031] The first output terminal of the self-supply circuit in section II is connected to the first output terminal of the external supply circuit in section II, and is connected to the other end of the normally closed contact 2KA-4 of intermediate relay 2KA and the other end of the normally closed contact 1KA-4 of intermediate relay 1KA; the second output terminal of the self-supply circuit in section II is connected to the second output terminal of the external supply circuit in section II, and is connected to the other end of the normally closed contact 2KA-5 of intermediate relay 2KA and the other end of the normally closed contact 1KA-5 of intermediate relay 1KA.

[0032] Furthermore, the DC power supply KGDY1 adopts a switching power supply.

[0033] Furthermore, the DC power supply KGDY2 adopts a switching power supply.

[0034] Furthermore, the overvoltage relay GY1 and undervoltage relay QY1 are configured such that when the primary side of transformer T1 is connected to the first high voltage, the overvoltage relay GY1 operates but the undervoltage relay QY1 does not operate; when the primary side of transformer T1 is connected to the second high voltage, the overvoltage relay GY1 does not operate but the undervoltage relay QY1 operates; the first high voltage is greater than the second voltage.

[0035] Furthermore, the overvoltage relay GY2 and the undervoltage relay QY2 are configured such that when the primary side of transformer T2 is connected to the first high voltage, the overvoltage relay GY2 operates but the undervoltage relay QY2 does not operate; when the primary side of transformer T2 is connected to the second high voltage, the overvoltage relay GY2 does not operate but the undervoltage relay QY2 operates; the first high voltage is greater than the second voltage.

[0036] The beneficial effects of the technical solution provided by this utility model embodiment are:

[0037] 1) When using the I-section self-supply circuit or the II-section self-supply circuit for power supply, the I-section external supply circuit or the II-section external supply circuit will be automatically disconnected.

[0038] 2) For the I-stage self-powered circuit or the II-stage self-powered circuit, when the primary side high voltage switches between the first high voltage and the second high voltage, the internal circuit will be automatically switched to ensure the output voltage of 220V.

[0039] 3) The I-section self-supply circuit and the II-section self-supply circuit can supply power to electrical equipment independently or simultaneously.

[0040] 4) When only the I-section external power supply circuit or the II-section external power supply circuit is used for power supply, the equipment will be automatically disconnected to prevent overload. Attached Figure Description

[0041] Figure 1 This is a circuit schematic diagram of an embodiment of the present utility model. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining this utility model and are not intended to limit this utility model.

[0043] like Figure 1 As shown in the figure, the present invention proposes a secondary power supply circuit for explosion-proof low-voltage equipment in underground mines, including a self-supply circuit I, a self-supply circuit II, an external supply circuit I, an external supply circuit II, and an inter-section switching circuit.

[0044] The self-supply circuit of section I includes: transformer T1, air switch ZK1, ZK2, ZK3, intermediate relays KA1, KA2, intermediate relay 1KA, DC power supply KGDY1, overvoltage relay GY1, and undervoltage relay QY1.

[0045] The primary side of transformer T1 is used to connect to the primary high voltage, which can be switched between 1140V and 660V. The secondary side of transformer T1 includes a main winding and an auxiliary winding. The main winding is equipped with a center tap. The main winding can output 220V when the primary high voltage is 660V, and the center tap can output 220V when the primary high voltage is 1140V.

[0046] One end of the secondary main winding of transformer T1 is connected to one end of the first terminal of air switch ZK1. The other end of the first terminal of air switch ZK1 is connected to one end of the first terminal of the normally open contact KA2-1 of intermediate relay KA2. The other end of the first terminal of the normally open contact KA2-1 of intermediate relay KA2 is connected to one end of the first terminal of the normally closed contact KA1-1 of intermediate relay KA1. The other end of the first terminal of the normally closed contact KA1-1 of intermediate relay KA1 is connected to one end of the coil of intermediate relay 1KA and one end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA. The other end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA serves as the first output terminal of the I-section self-supply circuit.

[0047] One end of the intermediate tap on the secondary side of transformer T1 is connected to one end of the first terminal of air switch ZK2. The other end of the first terminal of air switch ZK2 is connected to one end of the first terminal of the normally closed contact KA2-2 of intermediate relay KA2. The other end of the first terminal of the normally closed contact KA2-2 of intermediate relay KA2 is connected to one end of the first terminal of the normally open contact KA1-2 of intermediate relay KA1. The other end of the first terminal of the normally open contact KA1-2 of intermediate relay KA1 is connected to one end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA.

[0048] The other end of the secondary main winding of transformer T1 is connected to one end of the second phase of air switch ZK1 and one end of the second phase of air switch ZK2; the other end of the second phase of air switch ZK1 is connected to one end of the second phase of the normally open contact KA2-1 of intermediate relay KA2; the other end of the second phase of the normally open contact KA2-1 of intermediate relay KA2 is connected to one end of the second phase of the normally closed contact KA1-1 of intermediate relay KA1; the other end of the second phase of the normally closed contact KA1-1 of intermediate relay KA1 is connected to the other end of the coil of intermediate relay 1KA and one end of the second phase of the normally open contact 1KA-1 of intermediate relay 1KA.

[0049] The other end of the second section of air switch ZK2 is connected to one end of the second section of intermediate relay KA2-2, which is normally closed. The other end of the second section of intermediate relay KA2-2 is connected to one end of the second section of intermediate relay KA1-2, which is normally open. The other end of the second section of intermediate relay KA1-2 is connected to one end of the second section of intermediate relay 1KA-1, which is normally open. The other end of the second section of intermediate relay 1KA-1 serves as the second output terminal of the I-stage self-supply circuit.

[0050] One end of the secondary auxiliary winding of transformer T1 is connected to one end of the first section of air switch ZK3. The other end of the first section of air switch ZK3 is connected to one detection terminal of overvoltage relay GY1 and one detection terminal of undervoltage relay QY1. The other end of the secondary auxiliary winding of transformer T1 is connected to one end of the second section of air switch ZK3. The other end of the second section of air switch ZK3 is connected to the other detection terminal of overvoltage relay GY1 and the other detection terminal of undervoltage relay QY1. The two power supply terminals of overvoltage relay GY1 and undervoltage relay QY1 are respectively connected to the other ends of the first and second sections of air switch ZK2.

[0051] The overvoltage relay GY1 and undervoltage relay QY1 are configured such that when the primary side of transformer T1 is connected to the first high voltage, the overvoltage relay GY1 operates but the undervoltage relay QY1 does not operate; when the primary side of transformer T1 is connected to the second high voltage, the overvoltage relay GY1 does not operate but the undervoltage relay QY1 operates; the first high voltage is greater than the second voltage; in this embodiment, the first high voltage is 1140V and the second high voltage is 660V.

[0052] The two power terminals of DC power supply KGDY1 are connected to the other ends of the first and second sections of air switch ZK2, respectively; the output terminal of DC power supply KGDY1 is connected to one end of the coil of intermediate relay KA1 and one end of the coil of intermediate relay KA2; the other end of the coil of intermediate relay KA1 is connected to one end of the normally closed contact QY1-1 of undervoltage relay QY1, and the other end of the normally closed contact QY1-1 of undervoltage relay QY1 is connected to one end of the normally open contact GY1-1 of overvoltage relay GY1; the other end of the coil of intermediate relay KA2 is connected to one end of the normally closed contact GY1-2 of overvoltage relay GY1, and the other end of the normally closed contact GY1-2 of overvoltage relay GY1 is connected to one end of the normally open contact QY1-2 of undervoltage relay QY1; the other end of the normally open contact GY1-1 of overvoltage relay GY1 and the other end of the normally open contact QY1-2 of undervoltage relay QY1 are connected to the common terminal of DC power supply KGDY1;

[0053] The external power supply circuit of section I includes: air switch ZK4 and contactor KM1; one end of the first and one end of the second section of air switch ZK4 are used to connect to the external power supply.

[0054] The other end of the first unit of the air switch ZK4 is connected to one end of the first unit of the normally closed contact 1KA-2 of the intermediate relay 1KA. The other end of the first unit of the normally closed contact 1KA-2 of the intermediate relay 1KA is connected to one end of the first unit of the normally closed contact 2KA-2 of the intermediate relay 2KA. The other end of the first unit of the normally closed contact 2KA-2 of the intermediate relay 2KA is connected to one end of the coil of contactor KM1 and one end of the first unit of the normally open contact KM1-1 of contactor KM1. The other end of the first unit of the normally open contact KM1-1 of contactor KM1 serves as the first output terminal of the I-section external power supply circuit.

[0055] The other end of the second unit of air switch ZK4 is connected to one end of the second unit of the normally closed contact 1KA-2 of intermediate relay 1KA. The other end of the second unit of the normally closed contact 1KA-2 of intermediate relay 1KA is connected to one end of the second unit of the normally closed contact 2KA-2 of intermediate relay 2KA. The other end of the second unit of the normally closed contact 2KA-2 of intermediate relay 2KA is connected to the other end of the coil of contactor KM1 and one end of the second unit of the normally open contact KM1-1 of contactor KM1. The other end of the second unit of the normally open contact KM1-1 of contactor KM1 serves as the second output terminal of the I-section external power supply circuit.

[0056] The self-supply circuit of section II includes: transformer T2, air switch ZK5, ZK6, ZK7, intermediate relays KA3, KA4, intermediate relay 2KA, DC power supply KGDY2, overvoltage relay GY2, and undervoltage relay QY2.

[0057] The primary side of transformer T2 is used to connect to the primary high voltage, which can be switched between 1140V and 660V. The secondary side of transformer T2 includes a main winding and an auxiliary winding. The main winding is equipped with a center tap. The main winding can output 220V when the primary high voltage is 660V, and the center tap can output 220V when the primary high voltage is 1140V.

[0058] One end of the secondary main winding of transformer T2 is connected to one end of the first terminal of air switch ZK5. The other end of the first terminal of air switch ZK5 is connected to one end of the first terminal of the normally open contact KA4-1 of intermediate relay KA4. The other end of the first terminal of the normally open contact KA4-1 of intermediate relay KA4 is connected to one end of the first terminal of the normally closed contact KA3-1 of intermediate relay KA3. The other end of the first terminal of the normally closed contact KA3-1 of intermediate relay KA3 is connected to one end of the coil of intermediate relay 2KA and one end of the first terminal of the normally open contact 2KA-1 of intermediate relay 2KA. The other end of the first terminal of the normally open contact 2KA-1 of intermediate relay 2KA serves as the first output terminal of the II-stage self-supply circuit.

[0059] One end of the intermediate tap on the secondary side of transformer T2 is connected to one end of the first terminal of air switch ZK6. The other end of the first terminal of air switch ZK6 is connected to one end of the first terminal of intermediate relay KA4-2, which is normally closed. The other end of the first terminal of intermediate relay KA4-2 is connected to one end of the first terminal of intermediate relay KA3-2, which is normally open. The other end of the first terminal of intermediate relay KA3-2 is connected to one end of the first terminal of intermediate relay 2KA-1, which is normally open.

[0060] The other end of the secondary main winding of transformer T2 is connected to one end of the second section of air switch ZK5 and one end of the second section of air switch ZK6; the other end of the second section of air switch ZK5 is connected to one end of the second section of the normally open contact KA4-1 of intermediate relay KA4; the other end of the second section of the normally open contact KA4-1 of intermediate relay KA4 is connected to one end of the second section of the normally closed contact KA3-1 of intermediate relay KA3; the other end of the second section of the normally closed contact KA3-1 of intermediate relay KA3 is connected to the other end of the coil of intermediate relay 2KA and one end of the second section of the normally open contact 2KA-1 of intermediate relay 2KA.

[0061] The other end of the second unit of the air switch ZK6 is connected to one end of the second unit of the normally closed contact KA4-2 of the intermediate relay KA4. The other end of the second unit of the normally closed contact KA4-2 of the intermediate relay KA4 is connected to one end of the second unit of the normally open contact KA3-2 of the intermediate relay KA3. The other end of the second unit of the normally open contact KA3-2 of the intermediate relay KA3 is connected to one end of the second unit of the normally open contact 2KA-1 of the intermediate relay 2KA. The other end of the second unit of the normally open contact 2KA-1 of the intermediate relay 2KA serves as the second output terminal of the II-stage self-supply circuit.

[0062] One end of the secondary auxiliary winding of transformer T2 is connected to one end of the first section of air switch ZK7. The other end of the first section of air switch ZK7 is connected to one detection terminal of overvoltage relay GY2 and one detection terminal of undervoltage relay QY2. The other end of the secondary auxiliary winding of transformer T2 is connected to one end of the second section of air switch ZK7. The other end of the second section of air switch ZK7 is connected to the other detection terminal of overvoltage relay GY2 and the other detection terminal of undervoltage relay QY2. The two power supply terminals of overvoltage relay GY2 and undervoltage relay QY2 are respectively connected to the other ends of the first and second sections of air switch ZK6.

[0063] The overvoltage relay GY2 and undervoltage relay QY2 are configured such that when the primary side of transformer T2 is connected to the first high voltage, the overvoltage relay GY2 operates but the undervoltage relay QY2 does not operate; when the primary side of transformer T2 is connected to the second high voltage, the overvoltage relay GY2 does not operate but the undervoltage relay QY2 operates; the first high voltage is greater than the second voltage; in this embodiment, the first high voltage is 1140V and the second high voltage is 660V;

[0064] The two power terminals of DC power supply KGDY2 are connected to the other ends of the first and second sections of air switch ZK6, respectively; the output terminal of DC power supply KGDY2 is connected to one end of the coil of intermediate relay KA3 and one end of the coil of intermediate relay KA4; the other end of the coil of intermediate relay KA3 is connected to one end of the normally closed contact QY2-1 of undervoltage relay QY2, and the other end of the normally closed contact QY2-1 of undervoltage relay QY2 is connected to one end of the normally open contact GY2-1 of overvoltage relay GY2; the other end of the coil of intermediate relay KA4 is connected to one end of the normally closed contact GY2-2 of overvoltage relay GY2, and the other end of the normally closed contact GY2-2 of overvoltage relay GY2 is connected to one end of the normally open contact QY2-2 of undervoltage relay QY2; the other end of the normally open contact GY2-1 of overvoltage relay GY2 and the other end of the normally open contact QY2-2 of undervoltage relay QY2 are connected to the common terminal of DC power supply KGDY2;

[0065] The external power supply circuit in section II includes: air switch ZK8 and contactor KM2; one end of the first and one end of the second section of air switch ZK8 are used to connect to the external power supply.

[0066] The other end of the first section of the air switch ZK8 is connected to one end of the first section of the normally closed contact 2KA-3 of the intermediate relay 2KA. The other end of the first section of the intermediate relay 2KA-3 is connected to one end of the first section of the normally closed contact 1KA-3 of the intermediate relay 1KA. The other end of the first section of the intermediate relay 1KA-3 is connected to one end of the coil of contactor KM2 and one end of the first section of the normally open contact KM2-1 of contactor KM2. The other end of the first section of the normally open contact KM2-1 of contactor KM2 serves as the first output terminal of the II-stage external power supply circuit.

[0067] The other end of the second unit of the air switch ZK8 is connected to one end of the second unit of the normally closed contact 2KA-3 of the intermediate relay 2KA. The other end of the second unit of the normally closed contact 2KA-3 of the intermediate relay 2KA is connected to one end of the second unit of the normally closed contact 1KA-3 of the intermediate relay 1KA. The other end of the second unit of the normally closed contact 1KA-3 of the intermediate relay 1KA is connected to the other end of the coil of contactor KM2 and one end of the second unit of the normally open contact KM2-1 of contactor KM2. The other end of the second unit of the normally open contact KM2-1 of contactor KM2 serves as the second output terminal of the II-stage external power supply circuit.

[0068] The inter-segment switching circuit includes normally closed contacts KM1-2 of contactor KM1, normally closed contacts KM2-2 of contactor KM2, normally closed contacts 2KA-4 of intermediate relay 2KA, normally closed contacts 1KA-4 of intermediate relay 1KA, normally closed contacts 2KA-5 of intermediate relay 2KA, and normally closed contacts 1KA-5 of intermediate relay 1KA.

[0069] The first output terminal of the self-supply circuit of section I is connected to the first output terminal of the external supply circuit of section I and connected to the first terminal of the normally closed contact KM1-2 of contactor KM1. The second output terminal of the self-supply circuit of section I is connected to the second output terminal of the external supply circuit of section I and connected to the second terminal of the normally closed contact KM1-2 of contactor KM1.

[0070] The other end of the first normally closed contact of contactor KM1-2 is connected to one end of the first normally closed contact of contactor KM2-2. The other end of the first normally closed contact of contactor KM2-2 is connected to one end of the normally closed contact 2KA-4 of intermediate relay 2KA and one end of the normally closed contact 1KA-4 of intermediate relay 1KA. The other end of the second normally closed contact of contactor KM1-2 is connected to one end of the second normally closed contact of contactor KM2-2. The other end of the second normally closed contact of contactor KM2-2 is connected to one end of the normally closed contact 2KA-5 of intermediate relay 2KA and one end of the normally closed contact 1KA-5 of intermediate relay 1KA.

[0071] The first output terminal of the self-powered circuit in section II is connected to the first output terminal of the external power supply circuit in section II, and is connected to the other end of the normally closed contact 2KA-4 of intermediate relay 2KA and the other end of the normally closed contact 1KA-4 of intermediate relay 1KA; the second output terminal of the self-powered circuit in section II is connected to the second output terminal of the external power supply circuit in section II, and is connected to the other end of the normally closed contact 2KA-5 of intermediate relay 2KA and the other end of the normally closed contact 1KA-5 of intermediate relay 1KA.

[0072] The working principle of this utility model is as follows:

[0073] For the I-section self-supply circuit, if the primary side high voltage is 10kV, the overvoltage relay GY1 will operate, while the undervoltage relay QY1 will not operate. At this time, the normally open contact GY1-1 of the overvoltage relay GY1 will close, the coil of the intermediate relay KA1 will be energized, the normally closed contact KA1-1 of the intermediate relay KA1 will open, and the normally open contact KA1-2 of the intermediate relay KA1 will close. The intermediate tap on the secondary side of the transformer T1 will output 220V voltage to the electrical equipment. When the primary side high voltage is 6kV, the undervoltage relay QY1 will operate, the overvoltage relay GY1 will not operate, the normally open contact QY1-2 of the undervoltage relay QY1 will close, the coil of the intermediate relay KA2 will be energized, the normally open contact KA2-1 of the intermediate relay KA2 will close, and the normally closed contact KA2-2 of the intermediate relay KA2 will open. The main winding on the secondary side of the transformer T2 will output 220V voltage to the electrical equipment.

[0074] For the self-powered circuit of section II, the working principle is the same as that of the self-powered circuit of section I. When the self-powered circuit of section I or section II is powered, the normally closed contact 1KA-2 of intermediate relay 1KA or the normally closed contact 2KA-2 of intermediate relay 2KA is opened, and the normally closed contact 2KA-3 of intermediate relay 2KA or the normally closed contact 1KA-3 of intermediate relay 1KA is opened to prevent simultaneous connection to the self-powered circuit and the external power supply circuit.

[0075] If the self-supply circuit of section I needs to be de-energized for maintenance, the external supply circuit of section I can be energized by the external power supply. At this time, the coil of contactor KM1 is energized, the normally open contact KM1-1 of contactor KM1 closes, and the external supply circuit of section I supplies power to the electrical equipment.

[0076] If the self-supply circuit of section II needs to be de-energized for maintenance, the external supply circuit of section II can be energized by the external power supply. At this time, the coil of contactor KM2 is energized, the normally open contact KM2-1 of contactor KM2 closes, and the external supply circuit of section II supplies power to the electrical equipment.

[0077] When the external power supply circuit I or the external power supply circuit II is powered, the normally closed contact KM1-2 of contactor KM1 or the normally closed contact KM2-2 of contactor KM2 will be opened; this prevents overload when powering all electrical equipment due to insufficient power supply from one external power supply circuit.

[0078] When the I-section self-supply circuit and the II-section self-supply circuit are powered simultaneously, the normally closed contacts 2KA-4, 1KA-4, 2KA-5, and 1KA-5 of the intermediate relays 2KA, 1KA-5, 2KA-5, 2KA-5, 1KA-5 of the intermediate relays 1KA and 2KA-5 are all open. At this time, the I-section self-supply circuit and the II-section self-supply circuit can supply power to their respective electrical equipment.

[0079] The DC power supply KGDY1 is a switching power supply, which can operate with an input voltage between 120V and 220V.

[0080] The DC power supply KGDY2 is a switching power supply, which can operate with an input voltage between 120V and 220V.

[0081] Therefore, regardless of whether the primary side high voltage is 1140V or 660V, the voltage of the intermediate tap on the secondary side of transformer T1 or T2 is between 127V and 220V, which can ensure the normal operation of DC power supply KGDY1 and DC power supply KGDY2.

[0082] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although this utility model has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications and substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A secondary power supply circuit for an intrinsically safe low voltage device downhole, characterized in that, Includes a self-supply circuit for section I, a self-supply circuit for section II, an external supply circuit for section I, an external supply circuit for section II, and an inter-section switching circuit; The self-supply circuit of section I includes: transformer T1, air switch ZK1, ZK2, ZK3, intermediate relays KA1, KA2, intermediate relay 1KA, DC power supply KGDY1, overvoltage relay GY1, and undervoltage relay QY1. The primary side of transformer T1 is used to connect to the primary high voltage. The secondary side of transformer T1 includes a main winding and an auxiliary winding; the main winding is equipped with an intermediate tap. One end of the secondary main winding of transformer T1 is connected to one end of the first terminal of air switch ZK1. The other end of the first terminal of air switch ZK1 is connected to one end of the first terminal of the normally open contact KA2-1 of intermediate relay KA2. The other end of the first terminal of the normally open contact KA2-1 of intermediate relay KA2 is connected to one end of the first terminal of the normally closed contact KA1-1 of intermediate relay KA1. The other end of the first terminal of the normally closed contact KA1-1 of intermediate relay KA1 is connected to one end of the coil of intermediate relay 1KA and one end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA. The other end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA serves as the first output terminal of the I-section self-supply circuit. One end of the intermediate tap on the secondary side of transformer T1 is connected to one end of the first terminal of air switch ZK2. The other end of the first terminal of air switch ZK2 is connected to one end of the first terminal of the normally closed contact KA2-2 of intermediate relay KA2. The other end of the first terminal of the normally closed contact KA2-2 of intermediate relay KA2 is connected to one end of the first terminal of the normally open contact KA1-2 of intermediate relay KA1. The other end of the first terminal of the normally open contact KA1-2 of intermediate relay KA1 is connected to one end of the first terminal of the normally open contact 1KA-1 of intermediate relay 1KA. The other end of the secondary main winding of transformer T1 is connected to one end of the second phase of air switch ZK1 and one end of the second phase of air switch ZK2; the other end of the second phase of air switch ZK1 is connected to one end of the second phase of the normally open contact KA2-1 of intermediate relay KA2; the other end of the second phase of the normally open contact KA2-1 of intermediate relay KA2 is connected to one end of the second phase of the normally closed contact KA1-1 of intermediate relay KA1; the other end of the second phase of the normally closed contact KA1-1 of intermediate relay KA1 is connected to the other end of the coil of intermediate relay 1KA and one end of the second phase of the normally open contact 1KA-1 of intermediate relay 1KA. The other end of the second section of air switch ZK2 is connected to one end of the second section of intermediate relay KA2-2, which is normally closed. The other end of the second section of intermediate relay KA2-2 is connected to one end of the second section of intermediate relay KA1-2, which is normally open. The other end of the second section of intermediate relay KA1-2 is connected to one end of the second section of intermediate relay 1KA-1, which is normally open. The other end of the second section of intermediate relay 1KA-1 serves as the second output terminal of the I-stage self-supply circuit. One end of the secondary auxiliary winding of transformer T1 is connected to one end of the first section of air switch ZK3. The other end of the first section of air switch ZK3 is connected to one detection terminal of overvoltage relay GY1 and one detection terminal of undervoltage relay QY1. The other end of the secondary auxiliary winding of transformer T1 is connected to one end of the second section of air switch ZK3. The other end of the second section of air switch ZK3 is connected to the other detection terminal of overvoltage relay GY1 and the other detection terminal of undervoltage relay QY1. The two power supply terminals of overvoltage relay GY1 and undervoltage relay QY1 are respectively connected to the other ends of the first and second sections of air switch ZK2. The two power terminals of DC power supply KGDY1 are connected to the other ends of the first and second sections of air switch ZK2, respectively; the output terminal of DC power supply KGDY1 is connected to one end of the coil of intermediate relay KA1 and one end of the coil of intermediate relay KA2; the other end of the coil of intermediate relay KA1 is connected to one end of the normally closed contact QY1-1 of undervoltage relay QY1, and the other end of the normally closed contact QY1-1 of undervoltage relay QY1 is connected to one end of the normally open contact GY1-1 of overvoltage relay GY1; the other end of the coil of intermediate relay KA2 is connected to one end of the normally closed contact GY1-2 of overvoltage relay GY1, and the other end of the normally closed contact GY1-2 of overvoltage relay GY1 is connected to one end of the normally open contact QY1-2 of undervoltage relay QY1; the other end of the normally open contact GY1-1 of overvoltage relay GY1 and the other end of the normally open contact QY1-2 of undervoltage relay QY1 are connected to the common terminal of DC power supply KGDY1; The external power supply circuit of section I includes: air switch ZK4 and contactor KM1; one end of the first and one end of the second section of air switch ZK4 are used to connect to the external power supply. The other end of the first unit of the air switch ZK4 is connected to one end of the first unit of the normally closed contact 1KA-2 of the intermediate relay 1KA. The other end of the first unit of the normally closed contact 1KA-2 of the intermediate relay 1KA is connected to one end of the first unit of the normally closed contact 2KA-2 of the intermediate relay 2KA. The other end of the first unit of the normally closed contact 2KA-2 of the intermediate relay 2KA is connected to one end of the coil of contactor KM1 and one end of the first unit of the normally open contact KM1-1 of contactor KM1. The other end of the first unit of the normally open contact KM1-1 of contactor KM1 serves as the first output terminal of the I-section external power supply circuit. The other end of the second unit of air switch ZK4 is connected to one end of the second unit of the normally closed contact 1KA-2 of intermediate relay 1KA. The other end of the second unit of the normally closed contact 1KA-2 of intermediate relay 1KA is connected to one end of the second unit of the normally closed contact 2KA-2 of intermediate relay 2KA. The other end of the second unit of the normally closed contact 2KA-2 of intermediate relay 2KA is connected to the other end of the coil of contactor KM1 and one end of the second unit of the normally open contact KM1-1 of contactor KM1. The other end of the second unit of the normally open contact KM1-1 of contactor KM1 serves as the second output terminal of the I-section external power supply circuit. The self-supply circuit of section II includes: transformer T2, air switch ZK5, ZK6, ZK7, intermediate relays KA3, KA4, intermediate relay 2KA, DC power supply KGDY2, overvoltage relay GY2, and undervoltage relay QY2. The primary side of transformer T2 is used to connect to the primary high voltage. The secondary side of transformer T2 includes a main winding and an auxiliary winding; the main winding is equipped with an intermediate tap. One end of the secondary main winding of transformer T2 is connected to one end of the first terminal of air switch ZK5. The other end of the first terminal of air switch ZK5 is connected to one end of the first terminal of the normally open contact KA4-1 of intermediate relay KA4. The other end of the first terminal of the normally open contact KA4-1 of intermediate relay KA4 is connected to one end of the first terminal of the normally closed contact KA3-1 of intermediate relay KA3. The other end of the first terminal of the normally closed contact KA3-1 of intermediate relay KA3 is connected to one end of the coil of intermediate relay 2KA and one end of the first terminal of the normally open contact 2KA-1 of intermediate relay 2KA. The other end of the first terminal of the normally open contact 2KA-1 of intermediate relay 2KA serves as the first output terminal of the II-stage self-supply circuit. One end of the intermediate tap on the secondary side of transformer T2 is connected to one end of the first terminal of air switch ZK6. The other end of the first terminal of air switch ZK6 is connected to one end of the first terminal of intermediate relay KA4-2, which is normally closed. The other end of the first terminal of intermediate relay KA4-2 is connected to one end of the first terminal of intermediate relay KA3-2, which is normally open. The other end of the first terminal of intermediate relay KA3-2 is connected to one end of the first terminal of intermediate relay 2KA-1, which is normally open. The other end of the secondary main winding of transformer T2 is connected to one end of the second section of air switch ZK5 and one end of the second section of air switch ZK6; the other end of the second section of air switch ZK5 is connected to one end of the second section of the normally open contact KA4-1 of intermediate relay KA4; the other end of the second section of the normally open contact KA4-1 of intermediate relay KA4 is connected to one end of the second section of the normally closed contact KA3-1 of intermediate relay KA3; the other end of the second section of the normally closed contact KA3-1 of intermediate relay KA3 is connected to the other end of the coil of intermediate relay 2KA and one end of the second section of the normally open contact 2KA-1 of intermediate relay 2KA. The other end of the second unit of the air switch ZK6 is connected to one end of the second unit of the normally closed contact KA4-2 of the intermediate relay KA4. The other end of the second unit of the normally closed contact KA4-2 of the intermediate relay KA4 is connected to one end of the second unit of the normally open contact KA3-2 of the intermediate relay KA3. The other end of the second unit of the normally open contact KA3-2 of the intermediate relay KA3 is connected to one end of the second unit of the normally open contact 2KA-1 of the intermediate relay 2KA. The other end of the second unit of the normally open contact 2KA-1 of the intermediate relay 2KA serves as the second output terminal of the II-stage self-supply circuit. One end of the secondary auxiliary winding of transformer T2 is connected to one end of the first section of air switch ZK7. The other end of the first section of air switch ZK7 is connected to one detection terminal of overvoltage relay GY2 and one detection terminal of undervoltage relay QY2. The other end of the secondary auxiliary winding of transformer T2 is connected to one end of the second section of air switch ZK7. The other end of the second section of air switch ZK7 is connected to the other detection terminal of overvoltage relay GY2 and the other detection terminal of undervoltage relay QY2. The two power supply terminals of overvoltage relay GY2 and undervoltage relay QY2 are respectively connected to the other ends of the first and second sections of air switch ZK6. The two power terminals of DC power supply KGDY2 are connected to the other ends of the first and second sections of air switch ZK6, respectively; the output terminal of DC power supply KGDY2 is connected to one end of the coil of intermediate relay KA3 and one end of the coil of intermediate relay KA4; the other end of the coil of intermediate relay KA3 is connected to one end of the normally closed contact QY2-1 of undervoltage relay QY2, and the other end of the normally closed contact QY2-1 of undervoltage relay QY2 is connected to one end of the normally open contact GY2-1 of overvoltage relay GY2; the other end of the coil of intermediate relay KA4 is connected to one end of the normally closed contact GY2-2 of overvoltage relay GY2, and the other end of the normally closed contact GY2-2 of overvoltage relay GY2 is connected to one end of the normally open contact QY2-2 of undervoltage relay QY2; the other end of the normally open contact GY2-1 of overvoltage relay GY2 and the other end of the normally open contact QY2-2 of undervoltage relay QY2 are connected to the common terminal of DC power supply KGDY2; The external power supply circuit in section II includes: air switch ZK8 and contactor KM2; one end of the first and one end of the second section of air switch ZK8 are used to connect to the external power supply. The other end of the first section of the air switch ZK8 is connected to one end of the first section of the normally closed contact 2KA-3 of the intermediate relay 2KA. The other end of the first section of the intermediate relay 2KA-3 is connected to one end of the first section of the normally closed contact 1KA-3 of the intermediate relay 1KA. The other end of the first section of the intermediate relay 1KA-3 is connected to one end of the coil of contactor KM2 and one end of the first section of the normally open contact KM2-1 of contactor KM2. The other end of the first section of the normally open contact KM2-1 of contactor KM2 serves as the first output terminal of the II-stage external power supply circuit. The other end of the second unit of the air switch ZK8 is connected to one end of the second unit of the normally closed contact 2KA-3 of the intermediate relay 2KA. The other end of the second unit of the normally closed contact 2KA-3 of the intermediate relay 2KA is connected to one end of the second unit of the normally closed contact 1KA-3 of the intermediate relay 1KA. The other end of the second unit of the normally closed contact 1KA-3 of the intermediate relay 1KA is connected to the other end of the coil of contactor KM2 and one end of the second unit of the normally open contact KM2-1 of contactor KM2. The other end of the second unit of the normally open contact KM2-1 of contactor KM2 serves as the second output terminal of the II-stage external power supply circuit. The inter-segment switching circuit includes normally closed contacts KM1-2 of contactor KM1, normally closed contacts KM2-2 of contactor KM2, normally closed contacts 2KA-4 of intermediate relay 2KA, normally closed contacts 1KA-4 of intermediate relay 1KA, normally closed contacts 2KA-5 of intermediate relay 2KA, and normally closed contacts 1KA-5 of intermediate relay 1KA. The first output terminal of the self-supply circuit of section I is connected to the first output terminal of the external supply circuit of section I and connected to the first terminal of the normally closed contact KM1-2 of contactor KM1. The second output terminal of the self-supply circuit of section I is connected to the second output terminal of the external supply circuit of section I and connected to the second terminal of the normally closed contact KM1-2 of contactor KM1. The other end of the first normally closed contact of contactor KM1-2 is connected to one end of the first normally closed contact of contactor KM2-2. The other end of the first normally closed contact of contactor KM2-2 is connected to one end of the normally closed contact 2KA-4 of intermediate relay 2KA and one end of the normally closed contact 1KA-4 of intermediate relay 1KA. The other end of the second normally closed contact of contactor KM1-2 is connected to one end of the second normally closed contact of contactor KM2-2. The other end of the second normally closed contact of contactor KM2-2 is connected to one end of the normally closed contact 2KA-5 of intermediate relay 2KA and one end of the normally closed contact 1KA-5 of intermediate relay 1KA. The first output terminal of the self-supply circuit in section II is connected to the first output terminal of the external supply circuit in section II, and is connected to the other end of the normally closed contact 2KA-4 of intermediate relay 2KA and the other end of the normally closed contact 1KA-4 of intermediate relay 1KA; the second output terminal of the self-supply circuit in section II is connected to the second output terminal of the external supply circuit in section II, and is connected to the other end of the normally closed contact 2KA-5 of intermediate relay 2KA and the other end of the normally closed contact 1KA-5 of intermediate relay 1KA.

2. The secondary power supply circuit for explosion-proof low-voltage equipment in underground mines as described in claim 1, characterized in that, The DC power supply KGDY1 uses a switching power supply.

3. The secondary power supply circuit for explosion-proof low-voltage equipment in underground mines as described in claim 1, characterized in that, The DC power supply KGDY2 uses a switching power supply.

4. The secondary power supply circuit for explosion-proof low-voltage equipment in underground mines as described in claim 1, characterized in that, The overvoltage relay GY1 and undervoltage relay QY1 are configured such that when the primary side of transformer T1 is connected to the first high voltage, the overvoltage relay GY1 operates but the undervoltage relay QY1 does not operate; when the primary side of transformer T1 is connected to the second high voltage, the overvoltage relay GY1 does not operate but the undervoltage relay QY1 operates; the first high voltage is greater than the second voltage.

5. The secondary power supply circuit for explosion-proof low-voltage equipment in underground mines as described in claim 1, characterized in that, The overvoltage relay GY2 and undervoltage relay QY2 are configured such that when the primary side of transformer T2 is connected to the first high voltage, the overvoltage relay GY2 operates but the undervoltage relay QY2 does not operate; when the primary side of transformer T2 is connected to the second high voltage, the overvoltage relay GY2 does not operate but the undervoltage relay QY2 operates; the first high voltage is greater than the second voltage.

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