A vacuum system for PVC board production equipment

Abstract

The invention discloses a vacuum system for a PVC board production device, comprising a first vacuum pump, a vacuum tank and an extruder connected in sequence through pipelines, a control device and a frequency converter for controlling the first vacuum pump; the control device comprises a frequency converter starting circuit for starting and stopping the frequency converter and a pressure sensing circuit for detecting the air pressure of the vacuum tank and transmitting a signal to the frequency converter; the frequency converter is started by the frequency converter starting circuit, the air pressure change of the vacuum tank is detected by the pressure sensing circuit and a corresponding pressure signal is output to the frequency converter, and the frequency converter outputs a corresponding frequency conversion signal to the vacuum pump according to the pressure signal to control the frequency conversion operation of the vacuum pump; therefore, the vacuum pump can be frequency-converted and adjusted according to the activation status of the extruder on the production line, thereby achieving the purpose of saving electricity and reducing the production cost of the enterprise.

Description

Technical Field

[0001] The invention relates to the field of PVC board production, and in particular to a vacuum system for a PVC board production device. Background Art

[0002] In the field of PVC board production, vacuum treatment is required in the process. Generally, one extruder is equipped with one vacuum pump for operation on the production line. In the prior art, in order to reduce electricity consumption and equipment costs, the production line is optimized and set to operate with one high-power vacuum pump equipped with multiple extruders.

[0003] In actual production, the technical solution of the above production line still has certain problems. In each round of production, not all extruders on the production line are enabled. Sometimes only one extruder needs to be enabled, and sometimes multiple extruders need to be enabled. Therefore, when not all extruders are enabled, the vacuum pump can only work at a fixed speed and cannot automatically adjust to reduce the speed according to the actual situation, resulting in a large waste of electricity and increasing the cost burden of the enterprise.

[0004] It can be seen that the existing technology still needs to be improved and enhanced. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a vacuum system for a PVC board production device, which aims to reduce the power consumption of the vacuum system of the PVC board production device by realizing automatic frequency conversion regulation of the vacuum pump, thereby saving electricity and reducing the production cost of the enterprise.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A vacuum system for a PVC board production device comprises a first vacuum pump, a vacuum tank and an extruder connected in sequence through pipelines, a control device and a frequency converter for controlling the first vacuum pump; the control device comprises a frequency converter starting circuit for starting and stopping the frequency converter and a pressure sensing circuit for detecting the air pressure of the vacuum tank and transmitting a signal to the frequency converter.

[0008] The vacuum system for the PVC board production device further includes a second vacuum pump, which is connected to the first vacuum pump and the vacuum tank through pipelines respectively, and the frequency converter is also used to control the second vacuum pump.

[0009] In the vacuum system for the PVC board production device, the inverter starting circuit includes a relay KA2, and the inverter starting circuit controls the on or off of the pressure sensing circuit through the relay KA2.

[0010] The vacuum system for the PVC board production device further includes a filter tank, which is used to filter the gas entering the first vacuum pump and the second vacuum pump; the pressure sensing circuit can also be used to detect the air pressure in the filter tank.

[0011] The vacuum system for the PVC board production device, wherein the pressure sensing circuit includes a pressure sensor, and the pressure sensor is arranged on the vacuum tank or the filter tank.

[0012] The vacuum system for a PVC board production device further includes a first fan for dissipating heat for a first vacuum pump and a second fan for dissipating heat for a second vacuum pump; the control device also includes a first fan starting circuit for starting and stopping the first fan and a second fan starting circuit for starting and stopping the second fan.

[0013] The vacuum system for PVC board production equipment, wherein the first fan starting circuit includes a contactor KM2, the second fan starting circuit includes a contactor KM3, and the first fan starting circuit and the second fan starting circuit are interlocked through the contactor KM2 and the contactor KM3.

[0014] The vacuum system for the PVC board production device, wherein the control device also includes an emergency circuit, the emergency circuit is used to disable the frequency converter and supply power to the first vacuum pump and the second vacuum pump.

[0015] The vacuum system for PVC board production equipment, wherein the control device also includes an automatic control circuit for controlling the conduction or disconnection of the inverter starting circuit; the automatic control circuit includes a relay KA1, and the emergency circuit includes a contactor KM1, and the automatic control circuit and the emergency circuit are interlocked through the relay KA1 and the contactor KM1.

[0016] The vacuum system for PVC board production equipment, wherein the first fan starting circuit controls the conduction or disconnection of the inverter starting circuit and the emergency circuit through the contactor KM2; the second fan starting circuit controls the conduction or disconnection of the inverter starting circuit and the emergency circuit through the contactor KM3.

[0017] Beneficial effects:

[0018] The present invention provides a vacuum system for a PVC board production device. Compared with the prior art, a frequency converter starting circuit and a pressure sensing circuit are provided; the frequency converter is started by the frequency converter starting circuit, and the air pressure change of the vacuum tank is detected by the pressure sensing circuit and a corresponding pressure signal is output to the frequency converter. The frequency converter outputs a corresponding frequency conversion signal to a vacuum pump according to the pressure signal to control the frequency conversion operation of the vacuum pump; therefore, the vacuum pump can be frequency-controlled according to the activation status of the extruder on the production line, thereby achieving the purpose of saving electricity and reducing the production cost of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a schematic diagram of the structure of the vacuum system of the PVC board production device of the present invention.

[0020] Figure 2 4 is a circuit relationship diagram within the control device described in the present invention.

[0021] Figure 3 This is a power supply relationship diagram of the control device described in the present invention.

[0022] Figure 4 The figure is a circuit wiring diagram of the control device described in the present invention.

[0023] Figure 5 This is a wiring terminal diagram of the frequency converter described in the present invention.

[0024] Figure 6 The present invention is a start-up flow chart of the vacuum system used in the PVC board production device.

[0025] In the figure: 1. first vacuum pump; 2. vacuum tank; 3. extruder; 4. control device; 5. frequency converter; 6. second vacuum pump; 7. filter tank; 8. first fan; 9. second fan; 10. three-phase switch; 11. double-throw switch; 41. automatic control circuit; 42. frequency converter starting circuit; 43. emergency circuit; 44. pressure sensor circuit; 45. first fan starting circuit; 46. second fan starting circuit. DETAILED DESCRIPTION

[0026] The present invention provides a vacuum system for a PVC board production device. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the scope of protection of the present invention.

[0027] The present invention provides a vacuum system for a PVC board production device, which is powered by three-phase electricity and includes a first vacuum pump 1, a vacuum tank 2 and an extruder 3 connected in sequence through pipelines, a control device 4 and a frequency converter 5 for controlling the first vacuum pump; the control device includes a frequency converter starting circuit 42 for starting and stopping the frequency converter and a pressure sensing circuit 44 for detecting the air pressure of the vacuum tank and transmitting a signal to the frequency converter. Figure 1 It can be seen that ( Figure 1 The dotted lines in the figure indicate electrical connections). One high-power vacuum pump can be used with multiple extruders 3 to perform vacuuming.

[0028] During operation, the frequency converter 5 is first started by the control device 4, and the pressure sensing circuit 44 therein detects the pressure change of the vacuum tank 2 and outputs a pressure signal to the frequency converter 5, and the frequency converter 5 outputs a corresponding frequency conversion signal according to the pressure signal to realize automatic frequency conversion adjustment of the vacuum pump. Since different numbers of extruders 3 are enabled, the vacuum pump needs to have different output powers to maintain the vacuum degree in the vacuum tank within a preset range. Therefore, by detecting the pressure change of the vacuum tank, the vacuum pump can be automatically adjusted according to the pressure change of the vacuum tank, so as to adapt to different production needs, effectively reduce production power consumption, and reduce the production cost of the enterprise.

[0029] In certain embodiments, see Figure 1 The vacuum system is also provided with a second vacuum pump 6, which is used in rotation with the first vacuum pump 1 or as an emergency standby to avoid production line shutdown or high-load operation of the vacuum pump; the second vacuum pump 6 is connected to the first vacuum pump 1 and the vacuum tank 2 through pipelines, and the frequency converter 5 is also used to control the second vacuum pump. As a preferred embodiment, the first vacuum pump 1 and the second vacuum pump 6 can be oil-free vertical vacuum pumps.

[0030] In certain embodiments, see Figure 2 , 4 The inverter starting circuit includes a relay KA2. The inverter starting circuit 42 controls the on or off of the pressure sensing circuit 44 through the relay KA2, so that when the inverter 5 is started, the pressure sensing circuit 44 starts to detect pressure changes and output pressure signals.

[0031] In certain embodiments, see Figure 1 The vacuum system is also provided with a filter tank 7. Since the gas extracted from the extruder often carries dust particles, the vacuum pump will be damaged or malfunction if it works for a long time in this production environment, thereby reducing the service life of the equipment. By providing the above-mentioned filter tank 7, the gas will be filtered through the filter tank 7 before reaching the vacuum pump to remove dust particles and prevent dust particles from entering the body of the vacuum pump.

[0032] Further, the pressure sensing circuit 44 can also be used to detect the air pressure of the filter tank, which includes a pressure sensor, which is preferably a pressure transmitter. As a preferred embodiment, the pressure transmitter can be arranged on the filter tank, and the detection is more accurate because the gas is filtered.

[0033] In certain embodiments, see Figure 1 The vacuum system is provided with a first blower 8 and a second blower 9 for the first vacuum pump 1 and the second vacuum pump 6; the control device 4 is also provided with a corresponding first blower start circuit 45 and a second blower start circuit 46. The blower is used to dissipate heat from the vacuum pump, thereby accelerating the heat dissipation speed of the vacuum pump and preventing the vacuum pump from overheating.

[0034] For further information, see Figure 2 , 4 The first fan start circuit 45 includes a contactor KM2, and the second fan start circuit 46 includes a contactor KM3. The first fan start circuit 45 and the second fan start circuit 46 are interlocked by the contactors KM2 and KM3. Through the above settings, only one of the two fans can be started, avoiding simultaneous starting due to misoperation, causing power waste, and standardizing the way of using electricity.

[0035] In certain embodiments, see Figure 2-4 , Figure 6 The control device 4 is provided with an emergency circuit 43, which is used to disable the frequency converter and supply power to the first vacuum pump 1 and the second vacuum pump 6. When the frequency converter or the pressure sensing circuit fails, in order to avoid production shutdown, the vacuum pump can be powered by the emergency circuit so that the vacuum pump can work normally. At this time, the vacuum pump cannot realize automatic frequency conversion and needs to be manually operated according to the production situation.

[0036] Due to the above settings, the control mode can be divided into automatic control mode and emergency mode according to the usage. Therefore, further, the control device can also be provided with an automatic control circuit for controlling the conduction or disconnection of the inverter starting circuit 42; the automatic control circuit 41 includes a relay KA1, and the emergency circuit 43 includes a contactor KM1, and the automatic control circuit 41 and the emergency circuit 43 are interlocked through the relay KA1 and the contactor KM1. Through this circuit setting, only one of the automatic control mode and the emergency mode can be started, which regulates industrial electricity use, improves electricity safety, and avoids production accidents caused by the simultaneous start of both due to misoperation.

[0037] In certain embodiments, see Figure 2-4 , Figure 6The first fan start circuit 45 controls the conduction or disconnection of the inverter start circuit 42 and the emergency circuit 43 through the contactor KM2; the second fan start circuit 46 controls the conduction or disconnection of the inverter start circuit 42 and the emergency circuit 43 through the contactor KM3. Through this circuit setting, industrial electricity consumption is regulated, and the first vacuum pump 1 or the second vacuum pump 6 can be started only when the first fan 8 or the second fan 9 is started.

[0038] As a preferred specific embodiment, please refer to Figure 3 The power supply relationship in the embodiment is that the three live wires of the three-phase power are represented as L1, L2, and L3 respectively. The power input terminals of the frequency converter corresponding to the three-phase power are R, S, and T, and the motor output terminals are U, V, and W. For those skilled in the art, it can be clearly known and understood that the power supply line of the control device can be any live wire of the three-phase power, and the output terminal A of the control device can be connected to any terminal of the power input terminals R, S, and T of the frequency converter. For the convenience of understanding and representation, the control device in this embodiment selects the L1 / R group as a specific implementation method for explanation. Figure 3-6 The specific wiring methods and relationships of the circuits in the control device are as follows:

[0039] The automatic control circuit 41 includes a normally closed switch S1, a normally open switch K1, a relay KA1, and an indicator light LD1. The coil of the relay KA1 is connected in parallel with the indicator light LD1, and one end thereof is connected to the live wire L1 through the normally open switch K1 and the normally closed switch S1 in turn, and the other end is connected to the neutral wire N. The normally open contact KA10 of the relay KA1 is connected in parallel with the normally open switch K1. When the operator presses the normally open switch K1, the coil of the relay KA1 is energized to generate magnetism, changing the closed / open state of the corresponding contact, and the normally open contact KA10 of the relay is closed, forming a self-locking circuit, so that the automatic control circuit is turned on; at the same time, the indicator light LD1 is lit, and the operator can clearly know that the circuit is working normally. If the indicator light LD1 is not lit, it can be known that there is a fault in the circuit. When the automatic control circuit needs to be disconnected, the normally closed switch S1 can be pressed, the coil of the relay KA1 loses its magnetism, the normally open contact KA10 of the relay is disconnected, and the automatic control circuit is disconnected.

[0040] The inverter start circuit 42 includes a relay KA2 and an indicator light LD2. The coil of the relay KA2 is connected in parallel with the indicator light LD2, and one end of the coil is connected to the live wire L1 through the normally open contact KA11 of the relay KA1, and the other end is connected to the power input terminal R of the inverter. As can be seen from the above settings, the circuit is controlled by the automatic control circuit. When the operator presses the normally open switch K1, the coil of the relay KA1 is energized, changing the closed / open state of the contact corresponding to it, the normally open contact KA11 of the relay is closed, and the inverter start circuit is turned on; at the same time, the indicator light LD2 is lit, and the operator can clearly know that the circuit is working normally. If the indicator light LD2 is not lit, it can be known that there is a fault in the circuit. When the automatic control circuit needs to be disconnected, the normally closed switch S1 can be pressed, the coil of the relay KA1 loses its magnetism, the normally open contact KA11 of the relay KA1 is disconnected, and the inverter start circuit is disconnected.

[0041] The pressure sensing circuit 44 includes a pressure transmitter, which is arranged on a vacuum tank or a filter tank, and its pin 1 is connected to the live wire L1 through the normally open contact KA12 of the relay KA1, the pin 2 is connected to the neutral wire N, the pin 3 is connected to the OP end of the frequency converter, and the pin 4 is connected to the AI2 end of the frequency converter; the OP end of the frequency converter is connected to the AI2 end through the normally open contact KA21 of the relay KA2, and the DCM end is connected to the GND end and to the MI1 end through the normally open contact KA22 of the relay KA2. It can be seen from the above settings that the circuit is controlled by the automatic control circuit and the variable frequency starting circuit. When the automatic control circuit and the variable frequency starting circuit are both working normally, the circuit can work normally. When the operator presses the normally open switch K1, the coil parts of the relays KA1 and KA2 are energized, changing the closed / open state of the contacts corresponding to them, the normally open contacts KA12, KA21, and KA22 are closed, and the pressure transmitter starts to work. The pressure transmitter detects the air pressure of the vacuum tank or filter tank and transmits the pressure signal to the inverter, where OP, AI2, DCM, GND, and MI1 are the control terminals of the inverter.

[0042] The emergency circuit 43 includes a normally closed switch S2, a normally open switch K2, a contactor KM1, an indicator light LD3, and a thermal relay RJ1. The coil portion of the contactor KM1 is connected in parallel with the indicator light LD3, and one end thereof is connected to the live wire L1 via the normally open switch K2 and the normally closed switch S2 in sequence, and the other end is connected to the power input terminal R of the inverter via the normally closed contacts of the thermal relay RJ1 and the relay KA1 in sequence; the normally open auxiliary contact of the contactor KM1 is connected in parallel with the normally open switch K2, and its normally closed auxiliary contact is connected in series between the coil portion of the relay KA1 and the neutral line N; the power input terminals R, S, T of the inverter and its motor output terminals U, V, W are connected one-to-one through the three main contacts of the contactor KM1. When the emergency mode needs to be activated, the operator presses the normally open switch K2, the coil of the contactor KM1 is energized to generate magnetism, and the closed / open state of the contacts corresponding to them is changed. The normally open auxiliary contacts of the contactor KM1 are closed, forming a self-locking circuit; its three main contacts are closed, the inverter is short-circuited, the emergency circuit is turned on, and the three-phase electricity directly supplies power to the vacuum pump; its normally closed auxiliary contacts are disconnected to ensure that the automatic control circuit is disconnected. Conversely, when the automatic control circuit is turned on, the indicator light LD3 is lit, and the normally closed contacts of the relay KA1 are disconnected to ensure that the emergency circuit is disconnected, and an interlocking relationship is formed between the automatic control circuit and the emergency circuit; when the emergency circuit needs to be disconnected, the normally closed switch S2 can be pressed. Among them, the thermal relay RJ1 plays the role of overcurrent protection in this circuit. When the current is too large, the circuit temperature rises and the thermal relay is disconnected.

[0043] The first fan starting circuit 45 includes a normally closed switch S3, a normally open switch K3, a contactor KM2, an indicator light LD4, and a thermal relay RJ2; the coil portion of the contactor KM2 is connected in parallel with the indicator light LD4, and one end thereof is connected to the live wire L1 through the normally open switch K3 and the normally closed switch S3 in sequence, and the other end is connected to the thermal relay RJ2; one end of the three main contact points of the contactor KM2 is connected to the power input terminal of the first fan, the other end of any one of the main contact points is connected to the thermal relay RJ2, and the other ends of the remaining two main contact points are respectively connected to the live wires L2 and L3 in a one-to-one correspondence; the normally open auxiliary contact KM20 of the contactor KM2 is connected in parallel with the normally open switch K3, and its normally open auxiliary contact KM21 is connected in series between the coil portion of the relay KA2 and the power input terminal R of the inverter, and its normally open auxiliary contact KM22 is connected in series between the normally closed contact of the relay KA1 and the power input terminal R of the inverter. From the above settings, it can be seen that before turning on the inverter starting circuit or the emergency circuit, the first fan starting circuit needs to be turned on first. The operator presses the normally open switch K3, the coil part of the contactor KM2 is energized, and its normally open auxiliary contact KM20 is closed to form a self-locking circuit. Its normally open auxiliary contacts KM21 and KM22 are closed, and its three main contacts are closed. The first fan starting circuit is turned on, and the first fan is powered on to start; when the first fan starting circuit needs to be disconnected, press the normally closed switch S3; among them, the thermal relay RJ2 plays the role of overcurrent protection in this circuit.

[0044] The second fan start circuit 46 includes a normally closed switch S4, a normally open switch K4, a contactor KM3, an indicator light LD5, and a thermal relay RJ3; the coil of the contactor KM3 is connected in parallel with the indicator light LD5, and one end of the contactor KM3 is connected to the live wire L1 through the normally open switch K4 and the normally closed switch S4 in sequence, and the other end is connected to the normally closed auxiliary contact of the contactor KM2 through the thermal relay RJ3; one end of the three main contact points of the contactor KM3 is connected to the power input end of the second fan, and the other end of any main contact point is connected to the power input end of the second fan. The normally closed auxiliary contact of contactor KM2 is connected, and the other ends of the remaining two main contacts are connected to the live wires L2 and L3 one by one; the normally closed auxiliary contact of contactor KM3 is connected in series between the thermal relay RJ2 and any main contact of contactor KM2, its normally open auxiliary contact KM30 is connected in parallel with the normally open switch K4, its normally open auxiliary contact KM31 is connected in parallel with the normally open auxiliary contact KM21 of contactor KM2, and its normally open auxiliary contact KM32 is connected in parallel with the normally open auxiliary contact KM22 of contactor KM2. It can be seen from the above settings that the first fan start-up circuit and the second fan start-up circuit are interlocked. Before turning on the inverter start-up circuit or the emergency circuit, the first fan start-up circuit or the second fan start-up circuit needs to be turned on first. The operator presses the normally open switch K4, the coil part of the contactor KM3 is energized, and its normally open auxiliary contact KM30 is closed, forming a self-locking circuit; its normally open auxiliary contacts KM31 and KM32 are closed; its three main contacts are closed, the second fan starting circuit is turned on, and the second fan is powered on and started; its normally closed auxiliary contact is disconnected to ensure that the first fan starting circuit is open, conversely, when the first fan starting circuit is turned on, the normally closed auxiliary contact of the contactor KM2 is disconnected to ensure that the second fan starting circuit is open; when the second fan starting circuit needs to be disconnected, press the normally closed switch S4; among them, the thermal relay RJ3 plays the role of overcurrent protection in this circuit.

[0045] According to the above circuit configuration, the thermal relays RJ1, RJ2, and RJ3 can be replaced by other overcurrent protection devices based on temperature detection, such as fuses. The normally open switches K1, K2, K3, and K4 and the normally closed switches S1, S2, S3, and S4 can preferably be normally open and normally closed buttons arranged in pairs.

[0046] See also Figure 2-6 It can be seen that, through the settings of the above-mentioned circuits, the circuits of the control device complete the self-locking or interlocking of the circuits through relays and contactors, as well as the multi-level control between the circuits, to ensure the orderly and standardized startup of the equipment, greatly improve the industrial electricity safety of the vacuum system, and reduce the possibility of electricity safety accidents.

[0047] See also Figure 3 In order to further improve the safety of electricity use, a main switch is set before the three-phase electricity enters the vacuum system. As a preferred embodiment, the main switch is a three-phase switch 10.

[0048] See also Figure 3 As a preferred embodiment, a double-throw switch 11 is provided between the first vacuum pump 1 and the second vacuum pump 6, the power input end of the double-throw switch 11 is connected to the motor output ends U, V, and W of the frequency converter 5, the power input end of the first vacuum pump 1 is connected to the first output end of the double-throw switch 11, and the power input end of the second vacuum pump 6 is connected to the second output end of the double-throw switch 11. When it is necessary to start the first vacuum pump 1 or the second vacuum pump 6, the double-throw switch 11 can switch the power supply circuit to the first vacuum pump or the second vacuum pump, and the other vacuum pump is in a circuit-breaking state, further improving the safety of electricity use.

[0049] In summary, the vacuum system for PVC board production equipment of the present invention detects the air pressure of the vacuum tank or filter tank in real time through the pressure transmitter in actual production, and outputs the pressure signal to the frequency converter. The frequency converter adjusts the vacuum pump in real time according to the pressure signal, thereby saving electricity and reducing the electricity cost of the enterprise. In this embodiment, through the setting of the power supply circuit and the control device of the vacuum system, the equipment startup mode of the vacuum system is orderly and standardized, which greatly improves the industrial electricity safety of the vacuum system. At the same time, an emergency circuit and a second vacuum pump are provided to avoid equipment shutdown due to equipment failures such as vacuum pumps and frequency converters or partial circuit problems. It has perfect emergency measures and greatly improves the accident response capability of the vacuum system.

[0050] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A vacuum system for a PVC board production device, characterized in that: It includes a first vacuum pump, a vacuum tank and an extruder connected in sequence through pipelines, a control device and a frequency converter for controlling the first vacuum pump; the control device includes a frequency converter starting circuit for starting and stopping the frequency converter and a pressure sensing circuit for detecting the air pressure of the vacuum tank and transmitting signals to the frequency converter; it also includes a second vacuum pump, which is connected to the first vacuum pump and the vacuum tank through pipelines respectively, and the frequency converter is also used to control the second vacuum pump; the control device also includes an emergency circuit, which is used to deactivate the frequency converter and supply power to the first vacuum pump and the second vacuum pump; the control device also includes an automatic control circuit for controlling the conduction or disconnection of the frequency converter starting circuit; the automatic control circuit includes a relay KA1, and the emergency circuit includes a contactor KM1; the automatic control circuit includes a normally closed switch S1, a normally open switch K1, a relay KA1, and an indicator light LD1, the coil part of the relay KA1 is connected in parallel with the indicator light LD1, and one end thereof is sequentially connected through the normally open switch K1 , the normally closed switch S1 is connected to the live wire of the three-phase electricity, and the other end is connected to the neutral wire of the three-phase electricity. The normally open contact KA10 of the relay KA1 is connected in parallel with the normally open switch K1; the emergency circuit includes the normally closed switch S2, the normally open switch K2, the contactor KM1, the indicator light LD3, and the thermal relay RJ1. The coil part of the contactor KM1 is connected in parallel with the indicator light LD3, and one end of it is connected to the live wire of the three-phase electricity through the normally open switch K2 and the normally closed switch S2 in sequence, and the other end is connected to the thermal relay in sequence. The normally closed contacts of RJ1 and relay KA1 are connected to the power input terminal R of the inverter; the normally open auxiliary contacts of contactor KM1 are connected in parallel with the normally open switch K2, and its normally closed auxiliary contacts are connected in series between the coil part of relay KA1 and the neutral line of the three-phase electricity; the power input terminals R, S, T of the inverter and its motor output terminals U, V, W are connected one by one through the three main contacts of contactor KM1; the automatic control circuit and the emergency circuit are interlocked through relay KA1 and contactor KM1.

2. The vacuum system for PVC board production equipment according to claim 1, characterized in that The inverter starting circuit includes a relay KA2, and the inverter starting circuit controls the on or off of the pressure sensing circuit through the relay KA2.

3. The vacuum system for PVC board production equipment according to claim 1, characterized in that: It also includes a filter tank, which is used to filter the gas entering the first vacuum pump and the second vacuum pump; the pressure sensing circuit is also used to detect the air pressure of the filter tank.

4. The vacuum system for PVC board production equipment according to claim 3, characterized in that: The pressure sensing circuit comprises a pressure sensor, and the pressure sensor is arranged on a vacuum tank or a filter tank.

5. The vacuum system for PVC board production equipment according to claim 2, characterized in that: It also includes a first fan for dissipating heat for the first vacuum pump and a second fan for dissipating heat for the second vacuum pump; the control device also includes a first fan starting circuit for starting and stopping the first fan and a second fan starting circuit for starting and stopping the second fan.

6. The vacuum system for PVC board production equipment according to claim 5, characterized in that: The first fan starting circuit includes a contactor KM2, and the second fan starting circuit includes a contactor KM3. The first fan starting circuit and the second fan starting circuit are interlocked by the contactor KM2 and the contactor KM3.

7. The vacuum system for a PVC board production device according to claim 6, characterized in that: The first fan starting circuit controls the conduction or disconnection of the inverter starting circuit and the emergency circuit through the contactor KM2; the second fan starting circuit controls the conduction or disconnection of the inverter starting circuit and the emergency circuit through the contactor KM3.

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