Star-delta starting troubleshooting system

Abstract

The utility model relates to a star-delta start-up troubleshooting system, which belongs to the technical field of ship safety assessment and comprises a touch screen, a PLC (programmable logic controller), a master control circuit, an auxiliary control circuit, a first relay group, a second relay group and a motor M1. The motor M1 is connected with the main control circuit, and the auxiliary control circuit controls star-delta starting of the motor M1 through the main control circuit; the touch screen is connected with the input end of the PLC, the first relay set and the second relay set are both connected to the output end of the PLC, the first relay set is connected with the main control circuit, and the second relay set is connected with the auxiliary control circuit; when the troubleshooting system is used, the touch screen controls at least one electrical fault in the main control circuit and the auxiliary control circuit through the PLC, the first relay group and the second relay group, an examiner does not need to re-connect wires to set the fault, time is saved, convenience is achieved, the examination efficiency is improved, and due to the fact that an original control loop is not moved, the troubleshooting efficiency is improved. And the damage to various devices is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of ship safety assessment, and in particular relates to a star-delta starting fault troubleshooting system. Background Art

[0002] Marine motors are one of the important equipment of ships and are widely used in the power system, power generation system and auxiliary equipment of ships. The use scope of marine motors varies according to the different needs of ships. The use scope of marine motors involves all aspects of ships, such as main engine, auxiliary engine, auxiliary engine, anchor winch, etc.

[0003] Asynchronous motors are widely used due to their simple structure, low price, high reliability and other advantages. However, the starting current is relatively large during the starting process, so large-capacity motors must be started in a certain way. Star-delta switching starting is a simple and convenient step-down starting method. If the stator winding is connected in star shape during starting and then in delta shape after starting, the starting current can be reduced and its impact on the power grid can be reduced. This starting method is called star-delta step-down starting, or simply star-delta starting (Y-Δ starting).

[0004] The star-delta starting control circuit is composed of various devices and components. During operation, various faults may occur, such as short circuit, open circuit, overload, etc. These faults will affect the stable operation of the motor and may even cause damage to ship equipment or accidents. Therefore, the troubleshooting ability of ship personnel is required to be high. In order to improve the troubleshooting ability of ship personnel, some control circuits with faults are often set up to assess ship personnel. However, each time the assessment is conducted, the examiner needs to rearrange the lines and replace the faulty parts. It takes a lot of time to complete an assessment, and the wiring and removal back and forth are easy to damage the electrical components. This is the shortcoming of the existing technology. Summary of the invention

[0005] The purpose of the utility model is to address the problem in the prior art that in order to improve the troubleshooting ability of ship personnel, some control circuits with faults are often set to assess the ship personnel, but each time the assessment is performed, the examiner is required to rearrange the circuits and replace the faulty components, which not only wastes a lot of time, wiring and disconnecting wires back and forth, but also easily damages electrical components. A star-delta starting troubleshooting system is designed to solve the problems existing in the prior art.

[0006] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0007] A star-delta starting fault troubleshooting system comprises a touch screen, a PLC, a main control circuit, an auxiliary control circuit, a first relay group, a second relay group and a motor M1; the motor M1 is connected to the main control circuit, and the auxiliary control circuit controls the star-delta starting of the motor M1 through the main control circuit;

[0008] The touch screen is connected to the input end of the PLC, the first relay group and the second relay group are both connected to the output end of the PLC, the first relay group is connected to the main control circuit, and the second relay group is connected to the auxiliary control circuit;

[0009] When the fault detection system is in use, the touch screen controls at least one electrical fault in the main control circuit and the auxiliary control circuit through the PLC and the first relay group and the second relay group.

[0010] A further improvement of the technical solution is that the PLC adopts a PLC model of 6ES7 288-1SR30-OAAO.

[0011] A further improvement of the present technical solution is that the first relay group includes relay KA1, relay KA2, relay KA3, relay KA4, relay KA5, relay KA6, relay KA7, relay KA8 and relay KA9, and the first end of the coil of relay KA1, the first end of the coil of relay KA2, the first end of the coil of relay KA3, the first end of the coil of relay KA4, the first end of the coil of relay KA5, the first end of the coil of relay KA6, the first end of the coil of relay KA7, the first end of the coil of relay KA8 and the first end of the coil of relay KA9 are all connected to the output end of the PLC, and the second end of the coil of relay KA1, the second end of the coil of relay KA2, the second end of the coil of relay KA3, the second end of the coil of relay KA4, the second end of the coil of relay KA5, the second end of the coil of relay KA6, the second end of the coil of relay KA7, the second end of the coil of relay KA8 and the second end of the coil of relay KA9 are all connected to the neutral line of the AC power supply connected to the PLC, and the PLC is connected to the live line of the AC power supply.

[0012] A further improvement of the present technical solution is that the second relay group includes relays KA10 to KA21, the first ends of the coils of relays KA10 to KA21 are connected to the output end of the PLC, and the second ends of the coils of relays KA10 to KA21 are connected to the neutral line of the AC power supply connected to the PLC.

[0013] A further improvement of the technical solution is that the auxiliary control circuit includes fuse FU2, fuse FU3, start indicator LED1, start switch SB1, emergency stop switch SB2, contactor KM1, contactor KM2, contactor KM3, time relay KT1 and conversion indicator LED2;

[0014] A first end of fuse FU2 is connected to any live wire of an external three-phase four-wire alternating current, a second end of fuse FU2 is connected to a first end of a start indicator light LED1 and a first end of an emergency stop switch SB2, a first end of fuse FU3 is connected to a neutral wire of an external three-phase four-wire alternating current, a second end of fuse FU3 is connected to a second end of the start indicator light LED1, a second end of the emergency stop switch SB2 is connected to a first end of the start switch SB1 and a first end of a normally closed switch of relay KA14, a second end of the start switch SB1 is connected to a first end of a coil of contactor KM1 through a normally closed switch of relay KA15, and a second end of the coil of contactor KM1 is connected to a second end of fuse FU3;

[0015] The second end of the normally closed switch of relay KA14 is connected to the first end of the normally open switch of contactor KM1 and the first end of the normally open switch of relay KA10, the second end of the normally open switch of contactor KM1 is connected to the second end of the starting switch SB1 and the second end of the normally open switch of relay KA10, the second end of the normally open switch of relay KA10 is also connected to the first end of the normally closed switch of contactor KM3, the first end of the normally closed switch of relay KA13 and the first end of the normally closed switch of relay KA19, the second end of the normally closed switch of contactor KM3 and the first end of the normally closed switch of relay KA13 The second ends of the normally closed switches are connected to the first ends of the normally closed switches of relay KA16 and relay KA17, the second end of the normally closed switch of relay KA16 is connected to the first end of the coil of time relay KT1, the second end of time relay KT1 is connected to the second end of fuse FU3, the second end of the normally closed switch of relay KA17 is connected to the first end of the coil of contactor KM2 via the normally closed switch of time relay KT1 and the normally closed switch of relay KA18 in sequence, and the second end of the coil of contactor KM2 is connected to the second end of fuse FU3;

[0016] The second end of the normally closed switch of relay KA19 is connected to the first end of the normally closed switch of contactor KM2 and the first end of the normally closed switch of relay KA11, the second end of the normally closed switch of contactor KM2 is connected to the second end of the normally closed switch of relay KA11, the first end of the normally open switch of time relay KT1 and the first end of the normally closed switch of relay KA20, the second end of the normally open switch of time relay KT1 is connected to the first end of the coil of contactor KM3 through the normally closed switch of relay KA21, and the second end of the coil of contactor KM3 is connected to the second end of fuse FU3; the second end of the normally closed switch of relay KA20 is connected to the first end of the normally open switch of contactor KM3 and the first end of the normally open switch of relay KA12, the second end of the normally open switch of contactor KM3 and the second end of the normally open switch of relay KA12 are both connected to the second end of the normally open switch of time relay KT1 and the first end of the conversion indicator light LED2, and the second end of the conversion indicator light LED2 is connected to the second end of fuse FU3.

[0017] A further improvement of the technical solution is that the main control circuit includes an air switch SQ1, a fuse FU1 and a thermal relay FR1;

[0018] The first end of the air switch SQ1 is connected to the three-phase live wire of the external three-phase four-wire alternating current, the second end of the air switch SQ1 is connected to the first end of the main contact of the contactor KM1 and the first end of the main contact of the contactor KM3 through the fuse FU1 and the thermal relay FR1 in sequence, the second end of the main contact of the contactor KM1 is connected to the U1, V1, W1 ends of the stator winding of the motor M1, the second end of the main contact of the contactor KM3 is connected to the U2, V2, W2 ends of the stator winding of the motor M1, the first end of the main contact of the contactor KM2 is star-connected, and the second end of the main contact of the contactor KM2 is connected to the U2, V2, W2 ends of the stator winding of the motor M1; relay KA1, relay KA2 and relay KA3 are respectively connected in parallel at the two ends of the corresponding main contacts of the contactor KM1, relay KA4, relay KA5 and relay KA6 are respectively connected in parallel at the two ends of the corresponding main contacts of the contactor KM2, and relay KA7, relay KA8 and relay KA9 are respectively connected in parallel at the two ends of the corresponding main contacts of the contactor KM3.

[0019] The beneficial effect of the utility model is that the utility model can set various electrical faults through the touch screen, and then control at least one electrical fault in the main control circuit and the auxiliary control circuit through the PLC and the first relay group and the second relay group. There is no need for the examiner to rewire to set the fault, which saves time and is convenient, improves the examination efficiency, and because the original control circuit is not changed, the damage to various devices is reduced.

[0020] In addition, the utility model has a reliable design principle, a simple structure and a very broad application prospect.

[0021] It can be seen that compared with the prior art, the present invention has outstanding substantive features and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The following is a relationship diagram of the troubleshooting system.

[0023] Figure 2 This is the circuit schematic of PLC.

[0024] Figure 3 This is the schematic diagram of the main control circuit.

[0025] Figure 4 This is the schematic diagram of the auxiliary control circuit. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] The key terms appearing in the present invention are explained below.

[0029] PLC, Programmable Logic Controller, uses a type of programmable memory to store programs internally, executes user-oriented instructions such as logic operations, sequential control, timing, counting and arithmetic operations, and controls various types of machinery or production processes through digital or analog input / output. It has powerful functions and high performance-price ratio. A small PLC has hundreds of programming elements available for users to use. It has powerful functions and can realize very complex control functions. Compared with the relay system with the same function, it has a very high performance-price ratio. PLC can realize decentralized control and centralized management through communication networking.

[0030] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the utility model provides a star-delta startup fault troubleshooting system, including a touch screen, a PLC, a main control circuit, an auxiliary control circuit, a first relay group, a second relay group and a motor M1; the motor M1 is connected to the main control circuit, and the auxiliary control circuit controls the star-delta startup of the motor M1 through the main control circuit; the touch screen is connected to the input end of the PLC, the first relay group and the second relay group are both connected to the output end of the PLC, the first relay group is connected to the main control circuit, and the second relay group is connected to the auxiliary control circuit; when the fault troubleshooting system is in use, the touch screen controls the main control circuit and the auxiliary control circuit through the PLC and the first relay group and the second relay group to prevent at least one electrical fault from occurring. Among them, the PLC adopts a PLC model of 6ES7288-1SR30-OAAO, which supports SIMATIC S7-1500, SIMATIC S7-1200, SIMATIC S7-300 and SIMATIC S7-400 PLC controllers.

[0031] Among them, the communication connection between PLC and touch screen can be realized in the following ways:

[0032] 1. Serial port connection: PLC and touch screen communicate through serial port. PLC and touch screen have their own serial port interfaces respectively, which are connected together through serial port lines.

[0033] 2. Ethernet connection: PLC and touch screen communicate via Ethernet. PLC and touch screen each have their own Ethernet interface, connected together via Ethernet cable.

[0034] 3. Wireless connection: PLC and touch screen are connected through wireless communication. A wireless module can be used to connect PLC and touch screen together and communicate through wireless signals. Wireless communication can be achieved using technologies such as Bluetooth and Wi-Fi. The above are common communication connection methods between PLC and touch screen.

[0035] Specifically, the first relay group includes relay KA1, relay KA2, relay KA3, relay KA4, relay KA5, relay KA6, relay KA7, relay KA8 and relay KA9, and the first end of the coil of relay KA1, the first end of the coil of relay KA2, the first end of the coil of relay KA3, the first end of the coil of relay KA4, the first end of the coil of relay KA5, the first end of the coil of relay KA6, the first end of the coil of relay KA7, the first end of the coil of relay KA8 and the first end of the coil of relay KA9 are all connected to the output end of the PLC, and the second end of the coil of relay KA1, the second end of the coil of relay KA2, the second end of the coil of relay KA3, the second end of the coil of relay KA4, the second end of the coil of relay KA5, the second end of the coil of relay KA6, the second end of the coil of relay KA7, the second end of the coil of relay KA8 and the second end of the coil of relay KA9 are all connected to the neutral line of the AC power supply connected to the PLC, and the PLC is connected to the live line of the AC power supply.

[0036] The second relay group includes relays KA10 to KA21, the first ends of the coils of relays KA10 to KA21 are connected to the output end of the PLC, and the second ends of the coils of relays KA10 to KA21 are connected to the neutral line of the AC power supply connected to the PLC.

[0037] In addition, the auxiliary control circuit includes fuse FU2, fuse FU3, start indicator light LED1, start switch SB1, emergency stop switch SB2, contactor KM1, contactor KM2, contactor KM3, time relay KT1 and conversion indicator light LED2.

[0038] Specifically, the first end of fuse FU2 is connected to any live wire of the external three-phase four-wire alternating current, the second end of fuse FU2 is connected to the first end of the start indicator light LED1 and the first end of the emergency stop switch SB2, the first end of fuse FU3 is connected to the neutral wire of the external three-phase four-wire alternating current, the second end of fuse FU3 is connected to the second end of the start indicator light LED1, the second end of the emergency stop switch SB2 is connected to the first end of the start switch SB1 and the first end of the normally closed switch of relay KA14, the second end of the start switch SB1 is connected to the first end of the coil of contactor KM1 through the normally closed switch of relay KA15, and the second end of the coil of contactor KM1 is connected to the second end of fuse FU3; relay KA15 The second end of the normally closed switch of contactor KM1 is connected to the first end of the normally open switch of contactor KM1 and the first end of the normally open switch of relay KA10, the second end of the normally open switch of contactor KM1 is connected to the second end of the starting switch SB1 and the second end of the normally open switch of relay KA10, the second end of the normally open switch of relay KA10 is also connected to the first end of the normally closed switch of contactor KM3, the first end of the normally closed switch of relay KA13 and the first end of the normally closed switch of relay KA19, the second end of the normally closed switch of contactor KM3 and the second end of the normally closed switch of relay KA13 are both connected to the first end of the normally closed switch of relay KA16 and the first end of the normally closed switch of relay KA17, relay KA16 The second end of the normally closed switch of relay KA19 is connected to the first end of the coil of contactor KM2 and the first end of the normally closed switch of relay KA11, and the second end of the normally closed switch of contactor KM2 is connected to the second end of fuse FU3. The second end of the normally closed switch of relay KA19 is connected to the first end of the normally closed switch of contactor KM2 and the first end of the normally closed switch of relay KA11, and the second end of the normally closed switch of contactor KM2 is connected to the second end of the normally closed switch of relay KA11 and the normally open switch of time relay KT1. and the first end of the normally closed switch of relay KA20, the second end of the normally open switch of time relay KT1 is connected to the first end of the coil of contactor KM3 through the normally closed switch of relay KA21, and the second end of the coil of contactor KM3 is connected to the second end of fuse FU3; the second end of the normally closed switch of relay KA20 is connected to the first end of the normally open switch of contactor KM3 and the first end of the normally open switch of relay KA12, the second end of the normally open switch of contactor KM3 and the second end of the normally open switch of relay KA12 are both connected to the second end of the normally open switch of time relay KT1 and the first end of the switching indicator light LED2, and the second end of the switching indicator light LED2 is connected to the second end of fuse FU3.

[0039] The main control circuit includes an air switch SQ1, a fuse FU1 and a thermal relay FR1; the first end of the air switch SQ1 is connected to the three-phase live wire of the external three-phase four-wire AC power, the second end of the air switch SQ1 is connected to the first end of the main contact of the contactor KM1 and the first end of the main contact of the contactor KM3 through the fuse FU1 and the thermal relay FR1 in sequence, the second end of the main contact of the contactor KM1 is connected to the U1, V1, W1 ends of the stator winding of the motor M1, and the second end of the main contact of the contactor KM3 is connected to the U1 of the stator winding of the motor M1. 2, V2, W2 terminals, the first end of the main contact of contactor KM2 is star-connected, and the second end of the main contact of contactor KM2 is connected to the U2, V2, W2 terminals of the stator winding of motor M1; relay KA1, relay KA2 and relay KA3 are respectively connected in parallel at the two ends of the corresponding main contacts of contactor KM1, relay KA4, relay KA5 and relay KA6 are respectively connected in parallel at the two ends of the corresponding main contacts of contactor KM2, relay KA7, relay KA8 and relay KA9 are respectively connected in parallel at the two ends of the corresponding main contacts of contactor KM3.

[0040] When the troubleshooting system is in use, various electrical faults can be set through the touch screen, and then at least one electrical fault can be controlled in the main control circuit and the auxiliary control circuit through the PLC and the first relay group and the second relay group. The examiner does not need to rewire to set the fault, which saves time and is convenient, improves the examination efficiency, and because the original control circuit is not changed, the damage to various components is reduced.

[0041] The above disclosure is only the preferred implementation mode of the utility model, but the utility model is not limited thereto. Any non-creative changes that can be thought of by technicians in this field, as well as several improvements and modifications made without departing from the principle of the utility model, should fall within the scope of protection of the utility model.

Claims

1. A star-delta starting fault troubleshooting system, characterized in that: It includes a touch screen, a PLC, a main control circuit, an auxiliary control circuit, a first relay group, a second relay group and a motor M1; the motor M1 is connected to the main control circuit, and the auxiliary control circuit controls the star-delta starting of the motor M1 through the main control circuit; The touch screen is connected to the input end of the PLC, the first relay group and the second relay group are both connected to the output end of the PLC, the first relay group is connected to the main control circuit, and the second relay group is connected to the auxiliary control circuit; When the fault detection system is in use, the touch screen controls at least one electrical fault in the main control circuit and the auxiliary control circuit through the PLC and the first relay group and the second relay group.

2. The star-delta starting fault troubleshooting system according to claim 1, characterized in that: The PLC used is 6ES7288-1SR30-OAAO.

3. The star-delta startup troubleshooting system according to claim 1, characterized in that: The first relay group includes relay KA1, relay KA2, relay KA3, relay KA4, relay KA5, relay KA6, relay KA7, relay KA8 and relay KA9. The first end of the coil of relay KA1, the first end of the coil of relay KA2, the first end of the coil of relay KA3, the first end of the coil of relay KA4, the first end of the coil of relay KA5, the first end of the coil of relay KA6, the first end of the coil of relay KA7, the first end of the coil of relay KA8 and the first end of the coil of relay KA9 are all connected to the output end of the PLC, and the second end of the coil of relay KA1, the second end of the coil of relay KA2, the second end of the coil of relay KA3, the second end of the coil of relay KA4, the second end of the coil of relay KA5, the second end of the coil of relay KA6, the second end of the coil of relay KA7, the second end of the coil of relay KA8 and the second end of the coil of relay KA9 are all connected to the neutral line of the AC power supply connected to the PLC, and the PLC is connected to the live line of the AC power supply.

4. The star-delta startup troubleshooting system according to claim 3, characterized in that: The second relay group includes relays KA10 to KA21, the first ends of the coils of relays KA10 to KA21 are connected to the output end of the PLC, and the second ends of the coils of relays KA10 to KA21 are connected to the neutral line of the AC power supply connected to the PLC.

5. The star-delta startup troubleshooting system according to claim 4, characterized in that: The auxiliary control circuit includes fuse FU2, fuse FU3, start indicator LED1, start switch SB1, emergency stop switch SB2, contactor KM1, contactor KM2, contactor KM3, time relay KT1 and conversion indicator LED2; A first end of fuse FU2 is connected to any live wire of an external three-phase four-wire alternating current, a second end of fuse FU2 is connected to a first end of a start indicator light LED1 and a first end of an emergency stop switch SB2, a first end of fuse FU3 is connected to a neutral wire of an external three-phase four-wire alternating current, a second end of fuse FU3 is connected to a second end of the start indicator light LED1, a second end of the emergency stop switch SB2 is connected to a first end of the start switch SB1 and a first end of a normally closed switch of relay KA14, a second end of the start switch SB1 is connected to a first end of a coil of contactor KM1 through a normally closed switch of relay KA15, and a second end of the coil of contactor KM1 is connected to a second end of fuse FU3; The second end of the normally closed switch of relay KA14 is connected to the first end of the normally open switch of contactor KM1 and the first end of the normally open switch of relay KA10, the second end of the normally open switch of contactor KM1 is connected to the second end of the starting switch SB1 and the second end of the normally open switch of relay KA10, the second end of the normally open switch of relay KA10 is also connected to the first end of the normally closed switch of contactor KM3, the first end of the normally closed switch of relay KA13 and the first end of the normally closed switch of relay KA19, the second end of the normally closed switch of contactor KM3 and the first end of the normally closed switch of relay KA13 The second ends of the normally closed switches are connected to the first ends of the normally closed switches of relay KA16 and relay KA17, the second end of the normally closed switch of relay KA16 is connected to the first end of the coil of time relay KT1, the second end of time relay KT1 is connected to the second end of fuse FU3, the second end of the normally closed switch of relay KA17 is connected to the first end of the coil of contactor KM2 via the normally closed switch of time relay KT1 and the normally closed switch of relay KA18 in sequence, and the second end of the coil of contactor KM2 is connected to the second end of fuse FU3; The second end of the normally closed switch of relay KA19 is connected to the first end of the normally closed switch of contactor KM2 and the first end of the normally closed switch of relay KA11, the second end of the normally closed switch of contactor KM2 is connected to the second end of the normally closed switch of relay KA11, the first end of the normally open switch of time relay KT1 and the first end of the normally closed switch of relay KA20, the second end of the normally open switch of time relay KT1 is connected to the first end of the coil of contactor KM3 through the normally closed switch of relay KA21, and the second end of the coil of contactor KM3 is connected to the second end of fuse FU3; the second end of the normally closed switch of relay KA20 is connected to the first end of the normally open switch of contactor KM3 and the first end of the normally open switch of relay KA12, the second end of the normally open switch of contactor KM3 and the second end of the normally open switch of relay KA12 are both connected to the second end of the normally open switch of time relay KT1 and the first end of the conversion indicator light LED2, and the second end of the conversion indicator light LED2 is connected to the second end of fuse FU3.

6. The star-delta startup troubleshooting system according to claim 5, characterized in that: The main control circuit includes air switch SQ1, fuse FU1 and thermal relay FR1; The first end of the air switch SQ1 is connected to the three-phase live wire of the external three-phase four-wire alternating current, the second end of the air switch SQ1 is connected to the first end of the main contact of the contactor KM1 and the first end of the main contact of the contactor KM3 through the fuse FU1 and the thermal relay FR1 in sequence, the second end of the main contact of the contactor KM1 is connected to the U1, V1, W1 ends of the stator winding of the motor M1, the second end of the main contact of the contactor KM3 is connected to the U2, V2, W2 ends of the stator winding of the motor M1, the first end of the main contact of the contactor KM2 is star-connected, and the second end of the main contact of the contactor KM2 is connected to the U2, V2, W2 ends of the stator winding of the motor M1; relay KA1, relay KA2 and relay KA3 are respectively connected in parallel at the two ends of the corresponding main contacts of the contactor KM1, relay KA4, relay KA5 and relay KA6 are respectively connected in parallel at the two ends of the corresponding main contacts of the contactor KM2, and relay KA7, relay KA8 and relay KA9 are respectively connected in parallel at the two ends of the corresponding main contacts of the contactor KM3.

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