Automatic control signal switching device for preventing shutdown of frequency converter

Abstract

The utility model relates to an automatic control signal switching device for preventing shutdown of a frequency converter, and belongs to the technical field of electrical automation. In order to solve the problem that in the prior art, a frequency converter is shut down due to the fact that a single PLC system breaks down, signal seamless switching is achieved through pure hardware logic switching of an intermediate relay. Specifically, the output end of the PLC system is connected with a normally-closed contact of an intermediate relay I through a signal isolator II; the output end of the potentiometer is connected with a normally open contact of an intermediate relay I through a signal isolator I; the intermediate relay II is controlled by a PLC power supply, a normally closed contact of the intermediate relay II controls a coil of the intermediate relay I, and automatic switching to potentiometer control is realized when a PLC system fails; the frequency converter receives signals of the PLC or the potentiometer through a common contact of the intermediate relay I; the audible and visual alarm is triggered to give an alarm during switching; and the DC 24V power supply supplies power independently. The device has the characteristics of low cost, quick response, high reliability and easiness in maintenance, effectively avoids production interruption, and is suitable for continuous production scenes such as metallurgy and the like.

Description

Technical Field

[0001] This utility model relates to the field of electrical automation technology, specifically to an automatic switching control signal device for preventing frequency converter shutdown. Background Technology

[0002] In the metallurgical industry, frequency converters (VDCs) are widely used as core speed control equipment in continuous production processes such as mineral processing, sintering, ironmaking, and steel rolling. Their stable operation directly affects the continuity and efficiency of the production line. However, current technologies mainly rely on a single PLC system for control. When the PLC system experiences CPU malfunction, module failure, or power outage, the VDC will immediately stop due to the lack of a backup control path, leading to production interruption and significant economic losses. Existing redundancy solutions (such as dual PLC hot standby systems) can improve reliability, but they suffer from drawbacks such as high cost, complex maintenance, and delayed switching response. Furthermore, the power frequency to frequency converter switching solution is difficult to promote due to electrical shock and equipment lifespan issues. Therefore, there is an urgent need for a low-cost, highly reliable, and easy-to-maintain redundant control solution that can quickly switch to a backup control source through pure hardware logic in the event of a PLC failure. Currently, there is no solution that uses a "PLC + potentiometer" in conjunction with an intermediate relay to achieve automatic signal switching. This direction combines technological innovation with industrial practicality and can effectively fill a technological gap. Utility Model Content

[0003] The purpose of this invention is to provide an automatic switching control signal device to prevent frequency converter shutdown.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] An automatic switching control signal device for preventing inverter shutdown includes:

[0006] The output of the PLC system is connected to the normally closed contact I of the intermediate relay I through signal isolator II;

[0007] The potentiometer's output is connected to the normally open contact I of the intermediate relay I via signal isolator I;

[0008] Intermediate relay I and intermediate relay II, wherein:

[0009] The coil of intermediate relay II is controlled by the PLC system, and its normally open contact is connected in series with the PLC control indicator light;

[0010] The coil of intermediate relay I is controlled by the normally closed contact II of intermediate relay II, and its normally open contact II is connected in series with the potentiometer control indicator light;

[0011] The frequency converter has its control signal input terminal connected to the common contact of intermediate relay I. The common contact receives the control signal from the PLC system through the normally closed contact of intermediate relay I, or receives the control signal from the potentiometer through the normally open contact of intermediate relay I.

[0012] The audible and visual alarm has its trigger terminal connected in series with the normally closed contact II of the intermediate relay II.

[0013] The DC24V power supply provides power to the PLC system, intermediate relay I, intermediate relay II, signal isolator I, signal isolator II, potentiometer control indicator, PLC control indicator and audible and visual alarm.

[0014] Furthermore, signal isolators I and II are connected to the output terminals of the potentiometer and the PLC system, respectively, to isolate interference in the control signals.

[0015] Furthermore, the normally closed contact I of the intermediate relay I is connected to the signal output terminal of the PLC system, the normally open contact I is connected to the signal output terminal of the potentiometer, and the common contact is connected to the control signal input terminal of the frequency converter.

[0016] Furthermore, the trigger circuit of the audible and visual alarm is connected to a DC24V power supply through the normally closed contact II of the intermediate relay II.

[0017] Furthermore, the PLC control indicator light and the potentiometer control indicator light are respectively connected to the DC24V power supply through the normally open contact II of intermediate relay II and the normally open contact I of intermediate relay I.

[0018] Compared with the prior art, the beneficial effects of this utility model are:

[0019] 1. Redundant control path design: By configuring hardware redundancy between the PLC system and potentiometers, and combining the contact logic switching of intermediate relay I and intermediate relay II, the system can seamlessly switch to potentiometer control when the PLC system malfunctions, significantly improving the inverter's continuous operation capability and avoiding downtime caused by a single control path failure.

[0020] 2. Low cost and easy maintenance: Using potentiometers as backup control sources reduces hardware costs by about 60% compared to dual PLC systems. Furthermore, components such as signal isolator I, signal isolator II, intermediate relay I, and intermediate relay II are all standardized industrial parts, making them easy to replace and maintain.

[0021] 3. Pure Hardware-Based Rapid Switching: Control signal switching is achieved through the mechanical contacts of intermediate relays I and II, with a response time down to the microsecond level. This is far superior to redundant systems that rely on software judgment (such as dual PLC solutions), avoiding the risk of transient equipment malfunction caused by switching delays. Signal isolators I and II isolate the output signals of the PLC system and potentiometers respectively, effectively suppressing electromagnetic interference and signal crosstalk, ensuring the stability of control signal transmission.

[0022] 4. Independent power supply guarantee: The DC24V power supply provides independent power to each component in the device, avoiding the impact of main power fluctuations on the control signal switching function, and further enhancing the reliability of the system. Attached Figure Description

[0023] Figure 1 This is the electrical schematic diagram of this utility model;

[0024] In the diagram: 1-Polypotentiometer, 2-PLC system, 3-Signal isolator I, 4-Signal isolator II, 5-Intermediate relay I, 501-Normally closed contact I, 502-Normally open contact I, 6-Frequency converter, 7-Intermediate relay II, 701-Normally closed contact II, 702-Normally open contact II, 8-DC24V power supply, 9-Polypotentiometer control indicator light, 10-PLC control indicator light, 11-Audible and visual alarm. Detailed Implementation

[0025] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0026] like Figure 1 As shown, an automatic switching control signal device for preventing inverter shutdown includes:

[0027] PLC system 2 can be Siemens S7-1200 or other devices with the same function. Its output is connected to the normally closed contact I501 of intermediate relay I5 through signal isolator II4.

[0028] Potentiometer 1, the output of which is connected to the normally open contact I502 of intermediate relay I5 through signal isolator I3;

[0029] Intermediate relay I5 and intermediate relay II7, wherein:

[0030] The coil of intermediate relay II7 is controlled by PLC system 2, and its normally open contact II702 is connected in series with PLC control indicator light 10;

[0031] The coil of intermediate relay I5 is controlled by the normally closed contact II701 of intermediate relay II7, and its normally open contact II702 is connected in series with the potentiometer control indicator light 9;

[0032] The frequency converter 6 has its control signal input terminal connected to the common contact of the intermediate relay I5. The common contact receives the control signal of the PLC system 2 through the normally closed contact I501 of the intermediate relay I5, or receives the control signal of the potentiometer 1 through the normally open contact I502 of the intermediate relay I5.

[0033] The audible and visual alarm 11 has its trigger terminal connected in series with the normally closed contact Ⅱ701 of the intermediate relay Ⅱ7;

[0034] The DC24V power supply 8 supplies power to the PLC system 2, intermediate relay I 5, intermediate relay II 7, signal isolator I 3, signal isolator II 4, potentiometer control indicator 9, PLC control indicator 10, and audible and visual alarm 11.

[0035] Signal isolators I3 and II4 are connected to the output terminals of potentiometer 1 and PLC system 2, respectively, to isolate interference in the control signals.

[0036] The normally closed contact I501 of the intermediate relay I5 is connected to the signal output terminal of the PLC system 2, the normally open contact is connected to the signal output terminal of the potentiometer 1, and the common contact is connected to the control signal input terminal of the frequency converter 6.

[0037] The trigger circuit of the audible and visual alarm 11 is connected to the DC24V power supply 8 through the normally closed contact II701 of the intermediate relay II7.

[0038] The PLC control indicator light 10 and the potentiometer control indicator light 9 are connected to the DC24V power supply 8 through the normally open contact II702 of intermediate relay II7 and the normally open contact I502 of intermediate relay I5, respectively.

[0039] When in use, close the DC24V power supply 8, the PLC system 2 is powered on and outputs control signals, the coil of intermediate relay II 7 is energized and closes, its normally open contact II 702 closes, and the PLC control indicator light 10 lights up; the control signals of the PLC system 2 are transmitted to the frequency converter 6 through the signal isolator 4 and the normally closed contact I 501 of intermediate relay I 5 in sequence, driving the equipment to run at the set frequency; the audible and visual alarm 11 remains silent because the normally closed contact II 701 of intermediate relay II 7 is open.

[0040] When PLC system 2 experiences CPU malfunction, module failure, or power failure, its output terminal stops supplying power, the coil of intermediate relay II 7 is de-energized and released, the normally open contact II 702 opens and the PLC control indicator light 10 goes out, and the normally closed contact II 701 closes; after the normally closed contact II 701 of intermediate relay II 7 closes, the coil of intermediate relay I 5 is energized and attracted, its normally open contact I 502 closes, the potentiometer control indicator light 9 lights up, and at the same time, the common contact of intermediate relay I 5 switches to the potentiometer 1 side; the preset reference frequency signal of potentiometer 1 is transmitted to frequency converter 6 through signal isolator 3 and the normally open contact I 502 of intermediate relay I 5 to maintain continuous operation of the equipment; after the normally closed contact II 701 of intermediate relay II 7 closes, the circuit of audible and visual alarm 11 is activated, issuing an audible and visual alarm to prompt maintenance personnel to intervene. After the maintenance personnel troubleshoot the PLC system 2, they restart the PLC system 2. The PLC system 2 outputs control signals again, the coil of intermediate relay II 7 is energized and closes, its normally open contact II 702 closes and the PLC control indicator light 10 lights up, the coil of intermediate relay I 5 is de-energized and releases, and the common contact switches back to the PLC system 2 side; the normally closed contact II 701 of intermediate relay II 7 opens, the audible and visual alarm 11 stops alarming, and the system returns to normal control mode.

Claims

1. An automatic switching control signal device for preventing inverter shutdown, characterized in that, include: The output of the PLC system (2) is connected to the normally closed contact of the intermediate relay I (5) through the signal isolator II (4); The potentiometer (1) is connected to the normally open contact of the intermediate relay (5) through the signal isolator I (3); Intermediate relay I (5) and intermediate relay II (7), wherein: The coil of intermediate relay II (7) is controlled by PLC system (2), and its normally open contact is connected in series with PLC control indicator (10); The coil of intermediate relay I (5) is controlled by the normally closed contact II (701) of intermediate relay II (7), and its normally open contact is connected in series with the potentiometer control indicator (9); The inverter (6) has its control signal input terminal connected to the common contact of the intermediate relay I (5). The common contact receives the control signal of the PLC system (2) through the normally closed contact of the intermediate relay I (5), or receives the control signal of the potentiometer (1) through the normally open contact of the intermediate relay I (5). The audible and visual alarm (11) has its trigger end connected in series with the normally closed contact II (701) of the intermediate relay II (7); The DC24V power supply (8) supplies power to the PLC system (2), intermediate relay I (5), intermediate relay II (7), signal isolator I (3), signal isolator II (4), potentiometer control indicator (9), PLC control indicator (10) and audible and visual alarm (11).

2. The automatic switching control signal device for preventing inverter shutdown according to claim 1, characterized in that, The signal isolators I (3) and II (4) are connected to the output terminals of the potentiometer (1) and the PLC system (2) respectively, and are used to isolate interference in the control signal.

3. The automatic switching control signal device for preventing inverter shutdown according to claim 1, characterized in that, The normally closed contact I (501) of the intermediate relay I (5) is connected to the signal output terminal of the PLC system (2), the normally open contact is connected to the signal output terminal of the potentiometer (1), and the common contact is connected to the control signal input terminal of the frequency converter (6).

4. The automatic switching control signal device for preventing inverter shutdown according to claim 1, characterized in that, The trigger circuit of the audible and visual alarm (11) is connected to the DC24V power supply (8) through the normally closed contact II (701) of the intermediate relay II (7).

5. The automatic switching control signal device for preventing inverter shutdown according to claim 1, characterized in that, The PLC control indicator (10) and potentiometer control indicator (9) are respectively connected to the DC24V power supply (8) through the normally open contact II (702) of intermediate relay II (7) and the normally open contact of intermediate relay I (5).

Images