Abstract: This paper focuses on the application of the new temperature control device in the temperature control system of Tianjin furnace. The principle, performance and function of the composition of the temperature control system are explained in detail. In this paper, the operating principle of the system and the effect of the system are analyzed and explained. Finally, it is pointed out that the temperature control system is a new type of temperature control device that is widely used, economical, and has significant control effects and is widely recommended.
Keywords: temperature control heating furnace intelligent control furnace temperature AI-808P
1 Introduction
The Tianjin furnace is mainly composed of a roller drive system and a temperature-controlled heating system. The original Tianjin furnace temperature control heating system is mainly composed of contactors and temperature control instruments. The total power of the Tianjin furnace heating system is 546KW, divided into 5 heating zones. The heating body is made of iron-chromium-aluminum material, the temperature is 0～1100°C, the nickel-chromium-nickel-silicon thermocouple is used as the temperature measurement, and the temperature display instrument is a circular-type temperature recorder. At the same time, the circular pattern temperature recorder is used to control the relay heating, and the relay controls the contactor to open and close, so that the heating temperature is substantially consistent with the given temperature. The heating power source is a low voltage 380V three-phase power source. The heating bodies are connected in a star shape and they are arranged on the top of the furnace and on the bottom of the furnace. There are many disadvantages in applying this temperature-controlled heating system, mainly in the following aspects:
(1) Since the control mode is three-position control (heating, holding, stopping), this control mode has large temperature control fluctuations, poor temperature control accuracy (±10 degrees), and the heating power is not adjustable, so the energy is wasted. , heating efficiency is low. Other relay contacts operate frequently, resulting in severe contact wear. The failure rate has risen year by year and has already pose a serious threat to production.
(2) The temperature control instrument is seriously aging, there are faults such as control failure, and the accuracy of instrument control is also difficult to meet the accuracy requirements of modern production processes. Moreover, this instrument requires frequent daily maintenance.
(3) When the system is running, the noise is large and the vibration is large (the contactor is poorly formed). In this way, the components of the contactor are easily loosened, causing serious heat generation at the joint, and it is easy to form a fire accident and other electrical faults.
2. New temperature control system
2.1 The composition of the temperature control system
The new temperature-controlled heating system consists of low-voltage control components such as temperature control instruments, thyristor trigger circuits and paperless recorders. The system consists of one incoming line Cabinet and three control cabinets, respectively controlling the main power system of the Tianjin furnace and the five-zone heating system and the door drive control system (the jog lifting control of the front and rear furnace doors). The specific instructions are as follows:
2.1.1 Incoming cabinet operation
Incoming cabinet operations include closing and opening operations. The panel indicates voltage indication, normal power supply indication, open separation indication, and active power metering.
2.1.2 furnace door drive control system
The furnace door drive control system performs the lifting operation of the front and rear furnace doors, and the furnace door control system is controlled by jog operation. The electric control has upper and lower limits and lifting interlock control.
2.1.3 Control Power System
The control power supply mainly provides the control power of the five-zone heating circuit and the control power of the instrument and the furnace door. Among them, the instrument power supply is used to ensure the safety and reliability of the instrument, and the 380V/220V isolation transformer is used for power supply. The operation of the control power supply is achieved by splitting the relevant air circuit breaker and engaging the relevant buttons.
2.1.4 Five-zone heating circuit operation
The five-zone heating circuit operation is divided into single-action and linkage operation. When single-action, the single-action/linkage button is selected as the single-action position. At this time, the stop-and-go operation of each zone is realized by operating the start-stop button of each zone, and the corresponding indicator light is illuminated when the power is stopped. When linkage, select the linkage position, press the start button, the contactors of each zone are closed, and the corresponding running indicator lights; when the corresponding linkage stop button is pressed, the contactors of each zone are disconnected, and the corresponding stop indicator lights. Before the linkage and single-action operation, the power-opening and control-opening of each zone are in the joint position.
2.1.5 Paperless Recorder (EN880)
The main functions of EN880 are: rich display screen; powerful setting function; perfect flow processing; practical disk operation function; convenient data statistics function; flexible alarm function; reliable communication function;
2.1.6 Yudian AI-808PAXI2 temperature control table
2.1.6.1 Yudian AI-808PAXI2 temperature control table performance:
The AI-808P program type instrument is used when it is necessary to automatically change the set value for control according to a certain time rule. It has powerful programming and operation capabilities to further increase the automation of the control device. It has a 50-segment programming function, which can set the rising/lowering slope of a given value of any size; with programmable/operable commands such as jump, run, pause and stop, the program can be modified during program control operation; Event output function. The alarm output can be used to control the interlocking action of other devices to further improve the automation capability of the device; the operation of the program can be executed by running an external switch to suspend or synchronize the operation or convenient operation; Start function and prepare function to make program execution more efficient and complete.
2.1.6.2 Functions and concepts:
Block: The segment number can be from 1-30, and the current segment (STEP) indicates the segment currently being executed.
Set time: refers to the total time of the block setting operation, the unit is min, the valid value is from 1-9999.
Running time: refers to the running time of the current segment. When the running time reaches the set time, the program automatically skips a running period.
Jump: The program block can be programmed to automatically jump to any of the 1-30 segments for loop control. Jumps can also be achieved by modifying the value of STEP.
Run/HoLd: When the program is running, it is timed and the setpoint changes according to the pre-programmed program curve. When the program is in the pause state, the timer is stopped and the set value remains unchanged. The meter can be programmed to pause in the block, or it can be paused/runned at any time. The meter still maintains the adjustment function during the pause state.
Stop (stoP): Executing a stop operation will stop the program. At this time, the run time is cleared to 0, the event output switch is reset, and the control output is stopped. When the running operation is executed in the stop state, the instrument will start the running program from the segment number set by STEP. The function of automatic stop can be programmed in the block and the STEP value of the running segment number can be set at the same time. It is also possible to perform a stop operation at any time (STEP is set to 1 after execution, but the user can modify it).
Event output: Occurs by program orchestration. The 2-way alarm switch can be controlled during program operation to facilitate synchronization or interlocking of various external devices.
Power outage/power-on event: refers to the instrument is connected to the power supply or unexpected power failure during operation, and can provide a variety of processing options for the user to choose. The user can set the meter's parameter (run) to set the running status of the meter after power-on.
Preparation (rdy) / measured value start function: When the start running program has a deviation between the temperature of the furnace body and the initial temperature set by the meter, and the difference is greater than the positive (or negative) deviation alarm value (dHAL and dLAL), The meter does not immediately perform a positive (or negative) deviation alarm, but first adjusts the measured value to a value less than the deviation alarm value. At this time, the program also pauses the timing and does not output the deviation alarm signal until the positive and negative deviations meet the requirements. Only start the program again. The Ready/Measured Value Start function is also useful for setting up segments that cannot predict the rise/lower time. To allow or cancel the preparation/measurement value start function, set it in the run parameter. The preparation/measurement value start function ensures the integrity of the entire program curve. The preparation/measurement value start function is used to solve the uncertainty caused by the inconsistency between the measured value and the set value at the start-up operation. Efficiency, completeness and compliance with user requirements.
2.1.7 Yudian AIJK3 Phase Shift Trigger
Yudian AIJK3 series is an intelligent three-phase phase shift trigger and cycle zero-crossing trigger using single-chip technology. It is powerful and reliable. It can adapt to various resistance wires, silicon carbon rods and load transformers. Various types of industrial electric furnaces such as silicon molybdenum rods and tungsten wires can also be used for the control of motor soft start.
Main performance of AIJK3: 0-20mA (0-5V) / 4-20mA (1-5V) signal compatible input; computerized linearization power correction, when the load is resistive, its output power is proportional to the input signal ; phase loss detection, overcurrent detection and alarm function; AIJK3 also has thyristor breakdown and load open circuit detection function; automatic synchronization function, no phase sequence is required when connecting thyristor trigger line; AIJK3 does not even need polarity With all-optical isolation and "burning not bad" technology, the reliability is very high, causing little interference to the input end; the current feedback or delay time adjustable soft start / soft stop function, adapt to silicon molybdenum rod, tungsten wire, motor and Inductive load; contains switching power supply, can be directly powered by 220VAC power supply, and has 5V and 24V two sets of DC power output.
AIJK3 alarms when the main circuit is disconnected or missing phase; the main circuit contactor is disconnected; the varistor pressure sensitive absorption is damaged (does not affect heating).
2.1.8 Instrument Control
The instrument control is divided into single action and linkage. When the instrument power supply and the transformer are normal, the instruments in each cabinet are open and closed. In the 2# cabinet, select the single-action/linkage button switch, and the instrument can perform single-action or Linkage operation. The instrument control is controlled by three states: RUN, STOP, and HOLD.
The single-operation operation of the instrument is used to control the operation of one instrument in one zone, and the linkage operation is used to control the operation of all instruments in zones 1 to 5. The three states of the instrument operation can be converted by pressing and holding the linked temperature control instrument button under the single-action or linkage operation. The conversion is shown in Figure 1:
Figure 1: Instrument running state transition diagram in single-action and linkage state
When the contactor is powered on in the stop state, the meter will automatically switch to the STOP state. When the main circuit is connected, the instruments in each zone can enter the running heating state under single-action or linkage operation. This is for the protection of the contactor mechanism and contacts. . Because the load state contactor pulls in, it will cause electric shock to the contactor contact, and the ablation contact will reduce the service life.
3. Temperature control system operation principle
3.1 operating principle shown in Figure 2:
Figure 2: Schematic diagram of the temperature control system operation
When the AI-808PAXI2 meter was first run, the auto-tuning function was enabled, and the best MPT parameters were found faster. The self-tuning process uses the position control to adjust the system. After the system oscillates 2-3 times, the microprocessor inside the instrument automatically calculates the M5 according to the oscillation generated by the position control and analyzes its period, amplitude and waveform. P, T and other control parameters. The introduction of the expert self-tuning system in the AI ​​series instrument not only reduces the labor intensity of the operator, but also facilitates the operation and further improves the control quality of the control system.
The use of zero-crossing triggering is mainly caused by zero-crossing triggering and phase-shifting triggering, which has minimal harmonic pollution to the power grid, and minimally affects the reliable operation of other electrical equipment in the power grid.
3.3 AI-808PAXI2 instrument related operations
3.3.1 Oven operation
After the furnace body or the heating body is overhauled, in order to ensure the long-term safe and reliable operation of the furnace body and the heating body, and to improve the service life of the heating body, it is generally necessary to perform the oven operation on the heating furnace, which requires adjustment of the oven curve. Oven. The oven curve is set according to the relevant regulations of the heating furnace. Generally, it is operated in a multi-temperature zone. It experiences a temperature rise at a certain temperature rise rate. After rising to the first temperature section, it is kept for a certain time. In the second and third temperature ranges of the cycle, Finally, the oven oven ends and enters the operational phase. When adjusting the oven curve, press the “Cycle setting button†twice under the power-on window to enter “STEP X†and change the X value to 5. Operating the instrument control button allows the instrument to operate and enter the oven. After the oven is completed, the meter automatically switches to the production phase and maintains the last set production temperature. In this case, it is necessary to first set the initial production temperatures C01 and C02 to prevent the device from exhibiting an abnormal temperature state after the end of the oven.
3.3.2 Process production setting of the instrument
When the setting value is needed under the power-on window, press “Left Arrow†to enter “C01 XXXXâ€, and “Up†or “Downâ€
Set XXXX to the production set value, and then press the “Down Arrow†to “C02 XXXX†to make XXXX the production temperature set value. In the keep warm state, the set temperature set by the two set values ​​is the same, so that the meter enters. Operating status. Repeat the above operation to change the temperature value by changing the XXXX setting value.
in conclusion
This temperature control system has been running for half a year, and the system works reliably. Xiamen Yudian's AI-808P and AIJK series triggers play a vital role in this system, and the temperature control accuracy is extremely high (±1°C in steady state). ), the temperature control has no overshoot and high precision control, and has achieved maintenance-free and trouble-free operation. The system is easy to adjust and operate, economical and reliable, and saves energy. And the system has strong anti-interference, which greatly improves the production efficiency of the enterprise and greatly improves the automation level of the enterprise. The temperature control system is a new type of temperature control device that is widely used, economical, and has a remarkable control effect and is widely recommended.
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