Intelligent safety electric heating control circuit and control method thereof

Abstract

This invention relates to an intelligent safety electric heating control circuit and its control method. In the main circuit, multiple electric heaters are connected to a three-phase power supply via thyristors and electric heating contactor switches. In the secondary circuit, the normally open switch of the fault reset energized time-delay relay in the thyristor reset circuit is connected to the electric heating contactor. The electric heating start-up circuit includes a normally closed electric heating over-temperature protection switch, a start-up jog switch, and a start-up intermediate relay connected in series. A temperature controller is installed in the temperature controller circuit, and the adjustment control signal output of the temperature controller is connected to the thyristor. The electric heating over-temperature alarm circuit includes a normally open electric heating over-temperature protection switch and an over-temperature alarm relay connected in series. The electric heating fault alarm circuit includes a normally open thyristor alarm switch and a fault alarm relay connected in series. This circuit and its control method can simultaneously provide tiered alarms and precise fault location, significantly improving equipment operational reliability and ease of maintenance.

Description

Technical Field

[0001] This invention relates to an electric heating control technology, specifically an intelligent and safe electric heating control circuit and its control method. Background Technology

[0002] Electric heating technology is widely used in industrial production, building heating, and other fields due to its advantages such as high heating efficiency and convenient control. With the expansion of application scenarios and the improvement of intelligence levels, the market's requirements for its operational safety, temperature control accuracy, fault handling capabilities, and convenient remote operation and maintenance are increasing. Traditional technologies have many shortcomings: traditional on / off control leads to insufficient temperature control accuracy and large temperature fluctuations, and often only monitors the outlet temperature while neglecting the temperature monitoring of the electric heating element itself, easily causing overheating faults; fault protection mechanisms are simplistic and lack sufficient safety redundancy, relying on a single element or detection path for protection, and lacking effective monitoring and response to electrical faults such as overvoltage and overcurrent, easily leading to the escalation of faults; reporting... The alarm system is incomplete, with most alarms being single signals that cannot distinguish fault types, and some equipment lacks remote linkage capabilities, making fault location difficult and maintenance inefficient. Start-stop and reset controls have poor reliability, lacking effective self-locking anti-accidental touch design and reasonable delay mechanisms, making them prone to unexpected shutdowns or accidental starts, and difficult to balance flexible local and remote control. Power adjustment flexibility is insufficient, with most outputs being fixed or tiered, unable to achieve stepless adaptation, resulting in high energy consumption and impacting temperature control and equipment lifespan. Therefore, developing an intelligent and safe electric heating control technology with precise temperature control, tiered alarms, accurate fault location, high reliability, and convenient maintenance has become an urgent problem to be solved in the current electric heating field. Summary of the Invention

[0003] This invention provides an intelligent safety electric heating control circuit and its control method that can take into account graded alarms, accurate fault location, and significantly improve the reliability of equipment operation and the convenience of maintenance.

[0004] The technical solution adopted in this invention is: an intelligent and safe electric heating control circuit, including a main circuit and a secondary circuit. Multiple electric heaters on the main circuit are connected to a three-phase power supply via thyristors and electric heating contactor switches. The secondary circuit includes a thyristor reset circuit, an electric heating on / off circuit, an electric heating start circuit, a temperature controller circuit, an electric heating over-temperature alarm circuit, and an electric heating fault alarm circuit, all connected in parallel to the AC220 power supply. The thyristor reset circuit includes a local reset jog switch, a remote reset jog switch, and a fault reset energized time-delay relay connected in series. The electric heating on / off circuit includes a normally open switch of the fault reset energized time-delay relay and an electric heating contactor connected in series. The electric heating start circuit includes a normally closed switch for electric heating over-temperature protection, a local stop jog switch, a remote stop jog switch, a local start jog switch, and a starting intermediate relay connected in series. The local start jog switch is connected in parallel with the remote start jog switch and the first normally open switch of the starting intermediate relay. The temperature controller circuit is equipped with a temperature controller, and the temperature probe of the temperature controller is located at the air outlet. The adjustment control signal output of the temperature controller is connected to a thyristor. The electric heating over-temperature alarm circuit includes a normally open switch for electric heating over-temperature protection and an over-temperature alarm relay connected in series. The electric heating fault alarm circuit includes a normally open thyristor alarm switch and a fault alarm relay connected in series.

[0005] The normally open switch of the over-temperature alarm relay and the normally open switch of the fault alarm relay are connected to the remote integrated monitoring circuit.

[0006] The thyristor is equipped with a control power connector, an adjustment control signal connector, a start signal connector, an alarm signal connector, and a communication connector. The control power connector is connected to an AC220 power supply, the adjustment control signal connector is connected to a temperature controller, the start signal connector is connected to the second normally open switch of the start intermediate relay, the alarm signal connector has a built-in normally open alarm switch of the thyristor, and the communication connector is connected to a remote integrated monitoring circuit.

[0007] Both the over-temperature alarm relay and the fault alarm relay are equipped with alarm lights connected in parallel.

[0008] The temperature controller is equipped with a PT100 temperature sensor, which is located at the rear end of the electric heater.

[0009] A smart and safe electric heating control method, characterized by the following steps: Before startup, the AC220 power supply is turned on, connecting the SCR control power connector. The fault reset delay relay on the SCR reset circuit is energized, and the normally open switch of the fault reset delay relay on the electric heating on / off circuit closes after a delay, energizing the electric heating contactor. The normally open switch of the electric heating contactor in the main circuit closes. When electric heating needs to be started, press the local start jog switch or the remote local start jog switch. The starting intermediate relay is energized, and the first normally open switch of the starting intermediate relay closes, locking the local start jog switch and the remote local start jog switch so that the electric heating start circuit remains energized. The second normally open switch of the starting intermediate relay closes, keeping the SCR connected, and the main circuit is turned on, allowing the electric heating to operate. When the temperature probe of the temperature controller detects the temperature of the air outlet in real time, the electric heating power is adjusted in real time through the control signal connector of the thyristor connected to the temperature controller. When the PT100 temperature sensor sends a temperature signal back from the temperature controller indicating an overheating abnormality in the electric heating, the normally closed switch of the electric heating overheat protection circuit in the electric heating start-up circuit opens, the starting intermediate relay is de-energized, the first and second normally open switches of the starting intermediate relay open, the thyristor disconnects the main circuit power connection of the electric heating, and the electric heating stops. At this time, the normally open switch of the electric heating overheat protection circuit closes, the normally open switch of the thyristor alarm circuit closes, the overheat alarm relay and the fault alarm relay are energized, and the indicator lights illuminate. The normally open switches of the overheat alarm relay and the normally open switch of the fault alarm relay connected to the remote integrated monitoring circuit close and connect, triggering an overheating and / or electric heating alarm in the remote integrated monitoring circuit. When the thyristor monitors the electric heating overvoltage or overcurrent, the normally open switch of the thyristor alarm closes, connecting the electric heating fault alarm circuit. The fault alarm relay is energized, and the normally open switch of the fault alarm relay closes, triggering the electric heating alarm in the remote integrated monitoring circuit. When the temperature sensor of PT100 temperature sensor receives a temperature signal from temperature controller and the electric heating temperature remains too low, or when the thyristor detects undervoltage, phase error, or phase loss in electric heating, the normally open switch of thyristor alarm closes, connecting the electric heating fault alarm circuit, the fault alarm relay is energized, the normally open switch of the fault alarm relay closes, and the electric heating alarm is triggered by the remote integrated monitoring circuit. When the temperature monitoring or switch closure of the electric heating over-temperature protection fails, the temperature controller inputs an adjustment control signal connector, which, combined with the closed normally open switch of the built-in thyristor alarm, ensures that the electric heating fault alarm circuit is energized, the fault alarm relay is energized, the normally open switch of the fault alarm relay is closed, and the remote integrated monitoring circuit alarms the electric heating. Before troubleshooting, press the local stop jog switch or the remote stop jog switch to momentarily de-energize the intermediate relay and disconnect the first normally open switch of the intermediate relay to ensure stable power de-energization of the electric heating starting circuit. After the fault is cleared, first press the local reset jog switch or remote reset jog switch on the thyristor reset circuit. The fault reset power-delay relay will be de-energized momentarily. After the normally open switch of the fault reset power-delay relay is opened, it needs to close after a delay to connect the electric heating contactor, ensuring that the electric heating contactor switch is closed. After the delay ends, press the local start jog switch to connect the electric heating start circuit, start the intermediate relay to be energized, connect the start signal connector of the thyristor, and the electric heating will be energized and reset.

[0010] The beneficial effects of this invention are: 1. The temperature controller sensor monitors the temperature in real time. Once an over-temperature anomaly is detected, dual protection is triggered: First, the normally closed over-temperature protection switch of the electric heating start-up circuit opens, de-energizing the intermediate relay and cutting off the main circuit power supply to the thyristor, achieving instantaneous shutdown of the electric heating; Second, the normally open over-temperature protection switch closes, linking the over-temperature alarm relay and the fault alarm relay, illuminating the local alarm light, and reporting to the remote monitoring circuit, forming an over-temperature protection closed loop. Simultaneously, the dual redundancy protection of the controller signal and the thyristor alarm switch ensures that even if a single temperature monitoring or switching element fails, the fault alarm circuit remains operational, preventing over-temperature protection failure and fundamentally eliminating safety accidents such as heating element burnout and fires.

[0011] 2. Real-time detection of core electrical faults such as overvoltage, overcurrent, undervoltage, phase reversal, and phase loss is achieved through the built-in monitoring of the thyristor: When any fault occurs, the normally open alarm switch of the thyristor immediately closes, triggering the fault alarm relay to act, with local indicator lights indicating the fault and remote monitoring reporting, facilitating rapid response by maintenance personnel; For faults such as overvoltage and overcurrent that directly cause overheating, while the thyristor synchronously cuts off the main circuit power supply, an overheat protection switch also cuts off the electric heater start-up circuit and connects the electric heater overheating alarm circuit. Multiple alarms and fault protection methods effectively prevent continuous damage to heating elements caused by the inability to alarm due to faults; For indirect overheating faults such as undervoltage, phase reversal, and phase loss, timely investigation is conducted through alarm reminders to prevent secondary risks such as circuit aging and local overheating caused by long-term abnormal operation, achieving full coverage of fault types and hierarchical protection response.

[0012] 3. When the outlet temperature fluctuation is minimal, the temperature controller collects the actual outlet temperature in real time and dynamically adjusts the thyristor conduction state by regulating the control signal, achieving stepless adaptation of heating power: when the temperature is below the set value, the thyristor conduction angle is increased to boost power; when the temperature approaches the set value, the conduction angle is decreased or intermittent operation is used, avoiding the temperature overshoot problem of traditional on / off control and ensuring that the outlet temperature remains stable within the set range. The temperature control accuracy is significantly better than traditional control methods. Simultaneously, the PT100 sensor is installed at the rear end of the electric heater to directly monitor the electric heater temperature and directly monitor and protect against over-temperature alarms.

[0013] 4. To ensure reliable operation during the startup phase, a local / remote start-up jog switch and a self-locking design for the intermediate relay are adopted. After pressing the start button, the first normally open switch of the intermediate relay closes and locks the circuit, ensuring continuous and stable operation of the electric heating and preventing unexpected shutdowns caused by accidental touch of the stop button or momentary power outages. During the stop phase, the local / remote stop jog switch triggers the intermediate relay to momentarily de-energize, ensuring stable circuit disconnection. During the reset phase, a reset operation and a fault reset power-on delay relay closure process are set up. After the fault is cleared, the reset operation must be performed first, and restarting can only be performed after the delay ends. This completely avoids accidental startup when the fault is not completely cleared. At the same time, the delay closure design provides sufficient reset time for circuit components, preventing short circuits or damage caused by asynchronous component actions, and significantly improving the stability of circuit operation.

[0014] 5. Tiered alarm for over-temperature faults and electrical faults in electric heating: When the temperature exceeds the limit, the over-temperature alarm relay and the fault alarm relay will activate simultaneously. When there is an electrical fault, only the fault alarm relay will activate. Combined with the linkage between the local alarm light and the remote integrated monitoring circuit, maintenance personnel can quickly distinguish the nature of the fault by the alarm type. In addition, by combining the fault data transmitted by the thyristor communication connector, the fault location can be accurately located without having to check the line point by point, which greatly shortens the fault diagnosis time. Attached Figure Description

[0015] Figure 1 This is the electrical schematic diagram of the present invention.

[0016] In the diagram: Main circuit A, Secondary circuit B, Remote integrated monitoring circuit C, Three-phase power supply LNP, SCR KKG, Control power connector KKG-LN, Regulating control signal connector KKG-IM, Start signal connector KKG-KA, Alarm signal connector KKG-LX, SCR alarm normally open switch KKG-1, Electric heater EE, AC220 power supply LN, Fault reset energized delay relay KT, Fault reset energized delay relay normally open switch KT-1, Electric heater contactor KM, Electric heater contactor switch KM-1, Local start jog switch SB1, Local stop jog switch SB2, Local reset jog switch SB3, Remote reset point SB4, remote start jog switch SB5, remote stop jog switch SB6, starting intermediate relay KA1, starting intermediate relay first normally open switch KA1-1, starting intermediate relay second normally open switch KA1-2, temperature controller MK, controller signal connector MK-IM, temperature sensor PT100, electric heating over-temperature protection normally closed switch CW-1, electric heating over-temperature protection normally open switch CW-2, over-temperature alarm relay KA2, over-temperature alarm relay normally open switch KA2-2, over-temperature alarm indicator HL1, fault alarm relay KA3, fault alarm relay normally open switch KA3-1, fault alarm indicator HL2. Detailed Implementation

[0017] The following explanation, in conjunction with the accompanying drawings, will provide further details.

[0018] Figure 1 As shown: An intelligent safety electric heating control circuit includes a main circuit A, a secondary circuit B, and a remote integrated monitoring circuit C. Multiple electric heaters EE on the main circuit A are connected to a three-phase power supply LNP via a thyristor KKG and an electric heating contactor switch KM-1. The secondary circuit B includes a thyristor reset circuit, an electric heating on / off circuit, an electric heating start circuit, a temperature controller circuit, an electric heating over-temperature alarm circuit, and an electric heating fault alarm circuit, all connected in parallel to the AC220 power supply LN.

[0019] The thyristor reset circuit includes a local reset jog switch SB3, a remote reset jog switch SB4, and a fault reset power-on delay relay KT connected in series. The electric heating on / off circuit includes a fault reset energized delay relay normally open switch KT-1 and an electric heating contactor KM connected in series. The electric heating start circuit includes an electric heating over-temperature protection normally closed switch CW-1, a local stop jog switch SB2, a remote stop jog switch SB6, a local start jog switch SB1, and a start intermediate relay KA1 connected in series. The local start jog switch SB1 is connected in parallel with a remote start jog switch SB5 and the first normally open switch KA1-1 of the start intermediate relay. The temperature controller circuit is equipped with a temperature controller MK, the temperature probe of which is located at the air outlet. The controller signal connector MK-IM of the temperature controller is connected to the adjustment control signal connector KKG-IM of the thyristor KKG. The temperature controller MK is also connected to a temperature sensor PT100, which is located near the electric heater EE.

[0020] The electric heating over-temperature alarm circuit includes an electric heating over-temperature protection normally open switch CW-2 and an over-temperature alarm relay KA2 connected in series, with an over-temperature alarm indicator HL1 connected in parallel on the over-temperature alarm relay KA2; The electric heating fault alarm circuit includes a normally open thyristor alarm switch KKG-1 and a fault alarm relay KA3 connected in series, with a fault alarm indicator HL2 connected in parallel to the fault alarm relay KA3.

[0021] The normally open switch KA2-1 of the over-temperature alarm relay KA2 and the normally open switch KA3-1 of the fault alarm relay KA3 are connected to the remote integrated monitoring circuit C.

[0022] In this embodiment, the thyristor KKG has a control power connector KKG-LN, an adjustment control signal connector KKG-IM, a start signal connector KKG-KA, and an alarm signal connector KKG-LX. The control power connector KKG-LN is connected to the AC220 power supply LN, the adjustment control signal connector KKG-IM is connected to the temperature controller MK, the start signal connector KKG-KA is connected to the second normally open switch KA1-2 of the start intermediate relay, the alarm signal connector KKG-LX has a built-in thyristor alarm normally open switch KKG-1, and the communication connector is connected to the remote integrated monitoring circuit.

[0023] The steps of the electric heating control method in this embodiment are as follows: 1. Before starting, power on the AC220 power supply and connect the SCR control power connector. The fault reset delay relay on the SCR reset circuit is energized, and the normally open switch of the fault reset delay relay on the electric heating on / off circuit closes after a delay, energizing the electric heating contactor. The normally open switch of the electric heating contactor in the main circuit closes. When it is necessary to start the electric heating, press the local start jog switch or the remote local start jog switch. The starting intermediate relay is energized, and the first normally open switch of the starting intermediate relay closes, locking the local start jog switch and the remote local start jog switch so that the electric heating start circuit remains energized. The second normally open switch of the starting intermediate relay closes, keeping the SCR connected, and the main circuit is turned on, allowing the electric heating to operate. 2. When the temperature probe of the temperature controller detects the temperature of the air outlet in real time, the electric heating power is adjusted in real time through the control signal connector of the thyristor connected to the temperature controller. 3. When the PT100 temperature sensor sends a temperature signal back from the temperature controller indicating an abnormal overheating of the electric heater, the normally closed switch of the overheating protection in the electric heater start-up circuit opens, the intermediate relay is de-energized, the first and second normally open switches of the intermediate relay open, the thyristor disconnects the main power supply connection of the electric heater, and the electric heater stops. At this time, the normally open switch of the overheating protection closes, the normally open switch of the thyristor alarm closes, the overheating alarm relay and the fault alarm relay are energized, and the indicator lights up. The normally open switches of the overheating alarm relay and the normally open switch of the fault alarm relay connected to the remote integrated monitoring circuit close and connect, and the remote integrated monitoring circuit alarms for overheating and / or electric heating. 4. When the thyristor monitors the electric heating overvoltage or overcurrent, the normally open switch of the thyristor alarm closes, connecting the electric heating fault alarm circuit. The fault alarm relay is energized, and the normally open switch of the fault alarm relay closes, triggering the electric heating alarm in the remote integrated monitoring circuit. 5. When the temperature sensor of PT100 provides feedback from the temperature controller that the electric heating temperature remains too low, or when the thyristor detects undervoltage, phase reversal, or phase loss in the electric heating, the normally open switch of the thyristor alarm closes, connecting the electric heating fault alarm circuit. The fault alarm relay is energized, and the normally open switch of the fault alarm relay closes, triggering the electric heating alarm in the remote integrated monitoring circuit. 6. When the temperature monitoring or switch closure of the electric heating over-temperature protection fails, the temperature controller inputs the adjustment control signal connector, and the built-in thyristor alarm normally open switch closes to ensure that the electric heating fault alarm circuit is energized, the fault alarm relay is energized, the normally open switch of the fault alarm relay closes, and the remote integrated monitoring circuit alarms the electric heating. Before troubleshooting, press the local stop jog switch or the remote stop jog switch to momentarily de-energize the intermediate relay and disconnect the first normally open switch of the intermediate relay to ensure stable power de-energization of the electric heating starting circuit. 7. After the fault is cleared, first press the local reset jog switch or remote reset jog switch on the thyristor reset circuit. The fault reset power-delay relay will be de-energized momentarily. After the normally open switch of the fault reset power-delay relay is opened, it needs to close after a delay to connect the electric heating contactor, ensuring that the electric heating contactor switch is closed. After the delay ends, press the local start jog switch to connect the electric heating start circuit, energize the start relay, connect the start signal connector of the thyristor, and the electric heating will be energized and reset.

Claims

1. An intelligent safety electric heating control circuit, comprising a main circuit and a secondary circuit. Multiple electric heaters on the main circuit are connected to a three-phase power supply via thyristors and electric heating contactor switches. The secondary circuit includes a thyristor reset circuit, an electric heating on / off circuit, an electric heating start-up circuit, a temperature controller circuit, an electric heating over-temperature alarm circuit, and an electric heating fault alarm circuit, all connected in parallel to the AC220V power supply. The thyristor reset circuit includes a local reset jog switch, a remote reset jog switch, and a fault reset energized time-delay relay connected in series. The electric heating on / off circuit includes a normally open switch of the fault reset energized time-delay relay and an electric heating contactor connected in series. The electric heating start-up circuit... The circuit includes a normally closed switch for electric heating over-temperature protection, a local stop jog switch, a remote stop jog switch, a local start jog switch, and a starting intermediate relay connected in series. The local start jog switch is connected in parallel with the remote start jog switch and the first normally open switch of the starting intermediate relay. The temperature controller circuit is equipped with a temperature controller, and the temperature probe of the temperature controller is located at the air outlet. The adjustment control signal output of the temperature controller is connected to a thyristor. The electric heating over-temperature alarm circuit includes a normally open switch for electric heating over-temperature protection and an over-temperature alarm relay connected in series. The electric heating fault alarm circuit includes a normally open thyristor alarm switch and a fault alarm relay connected in series.

2. The intelligent safety electric heating control circuit according to claim 1, characterized in that: The normally open switch of the over-temperature alarm relay and the normally open switch of the fault alarm relay are connected to the remote integrated monitoring circuit.

3. The intelligent safety electric heating control circuit according to claim 1, characterized in that: The thyristor is equipped with a control power connector, an adjustment control signal connector, a start signal connector, an alarm signal connector, and a communication connector. The control power connector is connected to an AC220 power supply, the adjustment control signal connector is connected to a temperature controller, the start signal connector is connected to the second normally open switch of the start intermediate relay, the alarm signal connector has a built-in normally open alarm switch of the thyristor, and the communication connector is connected to a remote integrated monitoring circuit.

4. The intelligent safety electric heating control circuit according to claim 1, characterized in that: Both the over-temperature alarm relay and the fault alarm relay are equipped with alarm lights connected in parallel.

5. The intelligent safety electric heating control circuit according to claim 1, characterized in that: The temperature controller is also connected to a PT100 temperature sensor, which is located at the rear end of the electric heater.

6. An intelligent and safe electric heating control method, characterized in that: The steps are as follows: (1) Before starting, the AC220 power supply is turned on, the thyristor control power connector is connected, the fault reset delay relay on the thyristor reset circuit is energized, the normally open switch of the fault reset delay relay on the electric heating on / off circuit is closed after a delay, the electric heating contactor is energized, and the normally open switch of the electric heating contactor in the main circuit is closed. When it is necessary to start the electric heating, press the local start jog switch or start the remote local start jog switch, the start intermediate relay is energized, the first normally open switch of the start intermediate relay is closed, the local start jog switch and the remote local start jog switch are locked so that the electric heating start circuit is kept energized; the second normally open switch of the start intermediate relay is closed, the thyristor is kept connected, the main circuit is turned on, and the electric heating is energized and works. (2) When the temperature probe of the temperature controller detects the temperature of the air outlet in real time, the electric heating power is adjusted in real time through the control signal connector of the thyristor connected to the temperature controller. (3) When the PT100 temperature sensor feeds back the temperature signal from the temperature controller and the electric heating is abnormally overheated, the normally closed switch of the electric heating overheat protection circuit of the electric heating start-up circuit is opened, the start-up intermediate relay is de-energized, the first and second normally open switches of the start-up intermediate relay are opened, the thyristor disconnects the main circuit power supply connection of the electric heating, and the electric heating stops. At this time, the normally open switch for electric heating over-temperature protection is closed, the normally open switch for thyristor alarm is closed, the over-temperature alarm relay and the fault alarm relay are energized, and the indicator light illuminates. The normally open switches for the over-temperature alarm relay and the normally open switches for the fault alarm relay connected to the remote integrated monitoring circuit are closed and connected, and the remote integrated monitoring circuit triggers an over-temperature and / or electric heating alarm. (4) When the thyristor monitors the electric heating overvoltage or overcurrent, the normally open switch of the thyristor alarm closes, the electric heating fault alarm circuit is connected, the fault alarm relay is energized, the normally open switch of the fault alarm relay closes, and the remote integrated monitoring circuit alarms the electric heating. (5) When the temperature sensor of PT100 is fed back by the temperature controller and the electric heating temperature is kept too low, or when the thyristor detects undervoltage, phase error, or phase loss of the electric heating, the normally open switch of the thyristor alarm is closed, the electric heating fault alarm circuit is connected, the fault alarm relay is energized, the normally open switch of the fault alarm relay is closed, and the electric heating alarm of the remote integrated monitoring circuit is activated. (6) When the temperature monitoring or switch closure of the electric heating over-temperature protection fails, the temperature controller inputs the adjustment control signal connector, and the built-in thyristor alarm normally open switch closes to ensure that the electric heating fault alarm circuit is energized, the fault alarm relay is energized, the normally open switch of the fault alarm relay closes, and the remote integrated monitoring circuit alarms the electric heating. (7) Before the fault is repaired, press the local stop jog switch or the remote stop jog switch to start the intermediate relay to lose power momentarily, and the first normally open switch of the intermediate relay to open, so as to ensure that the electric heating start circuit loses power stably. After the fault is cleared, first press the local reset jog switch or remote reset jog switch on the thyristor reset circuit. The fault reset power-delay relay will be de-energized momentarily. After the normally open switch of the fault reset power-delay relay is opened, it needs to close after a delay to connect the electric heating contactor, ensuring that the electric heating contactor switch is closed. After the delay ends, press the local start jog switch to connect the electric heating start circuit, start the intermediate relay to be energized, connect the start signal connector of the thyristor, and the electric heating will be energized and reset.

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