Remote safe parking system of frequency converter

Abstract

A frequency converter remote safety parking system belongs to the field of electrical control technology and comprises a safety relay A1, three intermediate relays KA1, KA2 and KA3, a key switch-Sx and a PLC (programmable logic controller) control system. Wherein the-KA1 controls a monitoring channel of a frequency converter control unit, the-KA2 controls a monitoring channel of a frequency converter motor module, and the PLC control system is used for sending a frequency converter safe stopping instruction and monitoring whether the STO function of the frequency converter is effective or not through the-KA3; the PLC control system comprises two PLC digital quantity input channels, a PLC digital quantity output channel and a man-machine interface picture; and the normally open contact of the key switch-Sx is connected with the digital quantity input of the PLC. According to the utility model, a method for realizing remote safe stopping of the frequency converter by utilizing the safe torque function STO can be widely applied to industries such as chemical engineering, metallurgy and mechanical manufacturing.

Description

Technical Field

[0001] The utility model belongs to the field of electric control technology, and is a system for realizing remote safe parking of a frequency converter by using the safe torque function (STO) of the frequency converter, PLC technology and network technology. Background Technique

[0002] In the production of iron and steel enterprises, various models of frequency converters are widely used. If equipment needs to be repaired, it is necessary to go to the central control room to put forward a repair request, and then go to the electrical room to cut off the main power supply of the frequency converter; after the repair is completed, it is necessary to go to the central control room to put forward a resumption of production request, and then go to the electrical room to supply power to the frequency converter. The whole process is cumbersome and time-consuming, but it is essential for safe repair. On the premise of ensuring safe repair, how to shorten the power-on and power-off time of the frequency converter can greatly improve the production efficiency of iron and steel enterprises, so it has high economic benefits.

[0003] The safe torque function (STO) is a basic safety function integrated in the frequency converter. It meets the relevant requirements of IEC 60204-1 stop category 0 uncontrolled parking, aiming to protect operators and equipment from electrical hazards and ensure the safety of equipment during normal operation and maintenance. Taking the Siemens S120 frequency converter as an example, after activating the STO, the S120 will immediately block the pulses and the output torque will be 0. If the motor is stationary when the STO is activated, it can prevent the stationary motor from starting accidentally; if the motor is rotating when the STO is activated, the motor will continue to rotate by inertia until it stops. If the motor is equipped with a brake, the brake will close immediately.

[0004] Using the STO function of the frequency converter makes it possible to achieve remote safe parking of the frequency converter. Content of the Utility Model

[0005] The utility model aims to provide a method for realizing remote safe parking of a frequency converter by using the safe torque function (STO) of the frequency converter, which can be widely applied in industries such as chemical industry, metallurgy, and machinery manufacturing.

[0006] Technical Solution of the Utility Model:

[0007] A remote safety stop system for a frequency converter includes a safety relay - A1, three intermediate relays - KA1, - KA2, and - KA3, a key switch - Sx, and a set of PLC control systems. Among them, - KA1 controls the monitoring channel of the frequency converter control unit, - KA2 controls the monitoring channel of the frequency converter motor module, and the PLC control system is used to issue a safety stop command for the frequency converter and monitor whether the STO function of the frequency converter is effective through - KA3. The PLC control system includes two digital input channels of the PLC, a digital output channel of the PLC, and a human - machine interface screen. The normally open contact of the key switch - Sx is connected to the digital input of the PLC.

[0008] The connection method between the digital output channel of the PLC and the safety relay: The digital output channel - PLC_DOx.x of the PLC directly controls the power supply - A1:A1 of the safety relay. The first input channel S12 of the safety relay is directly connected to its internal power supply S11, the second input channel S22 of the safety relay is directly connected to its internal power supply S21, the reset terminal S34 of the safety relay is also directly connected to its internal power supply S33. Two safety contacts of the safety relay control one relay - KA1, and the other two safety contacts of the safety relay control another relay - KA2.

[0009] The connection method between - KA1 and - KA2 and the frequency converter: The DC power supply + 24V passes through the normally closed contact of - KA1 and is connected between the fail - safe digital input interface F - DI and M of the frequency converter control unit to form a control unit monitoring channel; The DC power supply + 24V passes through the normally closed contact of - KA2 and is connected between EP + 24V and EP M of the frequency converter motor module to form a motor module monitoring channel.

[0010] For - KA3, its normally open contact is connected to the digital input of the PLC.

[0011] The design of energizing the safety relay to activate the STO is adopted. The normally closed contact of the relay monitors the STO of the frequency converter. In this way, even if the PLC control system fails, it does not affect the normal operation of the frequency converter, and the impact of the remote power - on / off system on the operation of production equipment is avoided to the greatest extent. After the STO of the frequency converter is enabled, the "STO is effective during driving" signal it sends is fed back to the PLC control system and indicated on the human - machine interface screen.

[0012] Advantages of the present utility model: The present utility model provides a system for remote safe parking of a frequency converter, which has three main advantages: First, by using the safe torque-off (STO) function of the frequency converter and realizing remote safe parking of the frequency converter through a control signal, compared with cutting off the main circuit power supply of the frequency converter, the overhaul power-on and power-off time can be greatly shortened, and the production efficiency can be improved; Second, a safety relay is used to control the dual-channel signals of the STO of the frequency converter, which is safer and more reliable; Third, even if the PLC control system fails, it will not affect the normal operation of the frequency converter, and the influence of the remote power-on and power-off system on the operation of production equipment is avoided to the greatest extent. Description of the Drawings

[0013] Figure 1 is the electrical schematic diagram of the safety relay.

[0014] Figure 2 is the electrical schematic diagram for the frequency converter to achieve STO (taking the motor module and control unit CU320-2 of the Siemens S120 book-type frequency converter as an example).

[0015] Figure 3 is the electrical schematic diagram of the PLC digital input.

[0016] In the figure: -A1: Safety relay; -PLC_DOx.x: Digital output channel of the PLC; -KA1, -KA2: Intermediate relays; -A2: Siemens S120 control unit CU320-2; -A3: Siemens S120 book-type frequency converter motor module; -KA3: Intermediate relay; -A4: PLC digital input module; -Sx: Key switch. Detailed Embodiment

[0017] The following is further described in conjunction with the embodiments of the drawings.

[0018] A system for remote safe parking of a frequency converter includes a safety relay -A1, three intermediate relays -KA1, -KA2, and -KA3, a key switch -Sx, and a set of PLC control systems. The PLC control system includes two digital input channels and one digital output channel of the PLC and a human-machine interface. In the embodiment, through the safety relay, a design scheme of dual-channel STO monitoring is adopted, that is, the control unit STO monitoring channel and the motor module STO monitoring channel. The integrated safety function structure type of the Siemens S120 frequency converter conforms to the Category 3 type defined in ISO13849-1, and this type adopts a dual-channel with cross-monitoring function. Inside the S120, both the input channel, the logic processing channel, and the output channel adopt a dual-channel structure, and continuous cross-comparisons are made on the safety-related data and processing results in the two channels. When data inconsistencies are found, the safety function will trigger a safety stop response.

[0019] Figure 1 As shown in the figure, the wiring method of the safety relay: The power supply of the safety relay - A1:A1 is directly controlled by a digital output channel - PLC_DOx.x of a PLC. The first input channel S12 of the safety relay is directly connected to its internal power supply S11. The second input channel S22 of the safety relay is directly connected to its internal power supply S21. The reset terminal S34 of the safety relay is also directly connected to its internal power supply S33. The safety contacts 13 and 14 of the safety relay control a relay - KA1, and the safety contacts 23 and 24 of the safety relay control another relay - KA2.

[0020] Figure 2 As shown in the figure, the wiring method of the dual - channel STO monitoring and the "STO in drive is effective" feedback: The DC power supply +24V is connected between the fault - safe digital input interface F - DI and M of the frequency converter control unit through the normally - closed contact of - KA1, and the DC power supply +24V is connected between the EP +24V and EP M of the frequency converter motor module through the normally - closed contact of - KA2. The output signal parameter of a certain digital output terminal DOx of the frequency converter control unit is set to "STO in drive is effective". After the STO of the frequency converter is activated, DOx outputs a high level and the intermediate relay - KA3 is energized, otherwise - KA3 loses power.

[0021] Figure 3 As shown in the figure, the wiring of the PLC digital input module: The contact of the key switch - Sx is connected to the channel DIx.a of the digital input module of the PLC, and the normally - open contact of - KA3 is connected to the digital input terminal DIxb of the PLC. The key switch - Sx is installed on the console in the central control room, and the human - machine interface screen of the PLC control system is also installed on the console.

[0022] Figure 3 As shown in the figure: When the contact of the key switch - Sx is in the open state, the PLC control system controls the digital output channel - PLC_DOx.x of the PLC to output a low level through the program, such as Figure 1 As shown in the figure, the power supply of the safety relay - A1 is disconnected, and the internal relays - K1 and - K2 are not energized, and the coils of the relays - KA1 and - KA2 controlled by the safety contacts are not energized. In Figure 2Among them, the normally closed contact of -KA1 closes, and the monitoring channel circuit of the frequency converter control unit closes; the normally closed contact of -KA2 closes, and the monitoring channel circuit of the frequency converter motor module closes, and the frequency converter is in the normal working state, that is, STO is not activated. Since the intermediate relay -KA3 does not pull in, an indication signal is obtained on the human-machine interface screen: the frequency converter is in the normal working state. At this time, even if the PLC system fails, such as a power outage, it will not affect the operation of the frequency converter, because the coils of -KA1 and -KA2 are not powered, and no monitoring channel will be disconnected.

[0023] When maintenance is required for the equipment, the operator in the central control room switches the contact of the key switch -Sx to the closed state, and the key is taken away by the maintenance personnel to prevent accidental startup. After the key switch -Sx is closed, the PLC control system controls the digital output channel -PLC_DOx.x to output a high level through the program, as Figure 1 shown, to connect the power supply of the safety relay -A1. The coil of the power-off delay relay -K3 inside the safety relay -A1 is energized, and then the coils of the relays -K1 and -K2 are energized and pulled in, and their normally open contacts close, and the coils of -KA1 and -KA2 are energized.

[0024] Figure 2 shown: the normally closed contact of -KA1 opens, disconnecting the circuit between the frequency converter control unit F-DI and M, and the STO monitoring channel of the control unit is activated; the normally closed contact of -KA2 opens, disconnecting the circuit between the EP +24V and EP M of the frequency converter motor module, and the STO monitoring channel of the motor is activated. After the STO of the frequency converter is activated, its digital output terminal DOx outputs a high level, and the intermediate relay -KA3 pulls in, and this signal is sent to the digital input terminal DIxb of the PLC, so that an indication signal --- the STO of the frequency converter is activated is obtained on the human-machine interface screen, informing the maintenance personnel that they can perform maintenance safely. After the maintenance is completed, the key is returned to the operator in the central control room, and the operator in the central control room switches the contact of the key switch -Sx to the open state, the power supply of the safety relay -A1 is disconnected, and the frequency converter returns to the normal working state.

Claims

1. A remote safety stop system for a frequency converter, characterized in that: It includes a safety relay - A1, three intermediate relays - KA1, - KA2, and - KA3, a key switch - Sx, and a set of PLC control systems. Among them, - KA1 controls the monitoring channel of the frequency converter control unit, - KA2 controls the monitoring channel of the frequency converter motor module, and the PLC control system is used to issue a safety stop instruction for the frequency converter and monitor whether the STO function of the frequency converter is effective through - KA3. The said PLC control system includes two digital input channels of the PLC and one digital output channel of the PLC, as well as a human-machine interface screen. The normally open contact of the key switch - Sx is connected to the digital input of the PLC.

2. The remote safety parking system for a frequency converter according to claim 1, wherein: The connection method between the digital output channel of the PLC and the safety relay: The digital output channel - PLC_DOx.x of the PLC directly controls the power supply of the safety relay - A1:A1. The first input channel S12 of the safety relay is directly connected to its internal power supply S11. The second input channel S22 of the safety relay is directly connected to its internal power supply S21. The reset terminal S34 of the safety relay is also directly connected to its internal power supply S33. Two safety contacts of the safety relay control one relay - KA1, and the other two safety contacts of the safety relay control another relay - KA2.

3. The remote safety parking system for a frequency converter according to claim 1, wherein: The connection method between - KA1 and - KA2 and the frequency converter: The DC power supply +24V passes through the normally closed contact of - KA1 and is connected between the fail-safe digital input interface F - DI and M of the frequency converter control unit to form a control unit monitoring channel. The DC power supply +24V passes through the normally closed contact of - KA2 and is connected between the EP +24V and EP M of the frequency converter motor module to form a motor module monitoring channel.

4. A remote safety stop system for a frequency converter according to claim 1, characterized in that: For the said - KA3, its normally open contact is connected to the digital input of the PLC.

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