Applications of AI-808P

Column: Metallurgical Industry Time:2019-03-25
Keywords: annealing furnace, intelligent programmable controller AI-808P

1. Overview

This paper focuses on the application of new device in the temperature control system of the annealing furnace. The principle, performance and function of the temperature control system will be showed in detail. In this paper, the operating principle 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 which has significant control effects which is widely recommended.

2. The reasons for equipment transformation

The annealing furnace is mainly composed of a roller transmission system and a temperature control heating system. The original annealing furnace temperature control heating system is mainly composed of a contactor and a temperature controller. The annealing furnace heating system has a total power of 546 kW and is divided into 5 heating zones. The heating body is made of iron-chromium-aluminum material, the temperature is about 0~1100℃, the nickel-chromium-nickel-silicon thermocouple is used as the temperature measurement tool, and the temperature display instrument is a circular-type temperature recorder. At the same time, the recorder is used to control the relay heating, and the relay controls the open and close of the contactor, 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), it has large  fluctuations, poor accuracy (±10 degrees), and the heating power is not adjustable, so the energy is wasted which may cause low heating efficiency. Other relay contacts operate frequently, resulting in severe contact wear. The failure rate is risen year by year and has already posed a serious threat to production.

(2) The temperature instrument is seriously aging, there are faults such as control failure, and the accuracy of instrument is also difficult to meet requirements for accuracy of modern production processes. Moreover, this instrument requires daily maintenance.

(3) When the system is running, the noise and 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 cause a fire accident or other electrical faults.

3. Advanced temperature controller

The choice of advanced instruments: In the transformation of the system, we adopted the advanced AI controllers. The AI controller is the core part of the temperature control system. The AI instrument is the first to adopt the platform concept. It converts professional instrument into the platform design product. The AI artificial intelligence adjustment algorithm is based on fuzzy rules. A new algorithm for PID controllers uses fuzzy algorithm to adjust the phenomenon of PID saturation integration when the error is big. When the error is small, the improved PID algorithm is used for adjustment, and the automatic learning and memory can be controlled in the adjustment. Part of the characteristics of the object to optimize the effect.

The self-tuning method is simple and convenient to apply: since the self-tuning is performed by positional adjustment, after 2~3 oscillations, the internal microprocessor of the instrument automatically calculates the period, amplitude and waveform according to the oscillation generated by the position control. M5, P, t and other control parameters. It has the characteristics of no overshoot, high precision, simple parameter determination, and good control effect on complex objects.

In the process of using AI controller combined with PID adjustment, self-learning and fuzzy control technology, the self-tuning / adaptive function, and the precise adjustment without under-tuning, the performance is much better than the traditional PID controller.

3. The composition of the temperature control system

The new temperature-controlled heating system consists of programmable controller AI-808PAI5X3L1L1S4 , three-phase thyristor trigger and paperless recorder AI-3270. The system consists of one incoming line cabinet and three control cabinets, respectively controlling the main power supply system of the annealing furnace and the five-zone heating system and volve (the jog lifting control of the front and rear furnace doors). The specific instructions are as follows:

(1) Incoming cabinet operation includes closing and opening operations. The panel indicates voltage, normal power supply, open separation, and active power metering. (2) The furnace transmission 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. (3) The control power supply mainly provides the  power for the five-zone heating circuit, 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. (4) The five-zone heating circuit operation is divided into single-action and linkage operation. The  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.

5. System control function

We use the temperature controller AI-808PAI5X3L1L1S4: AI-808P is used for occasions that need 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 and 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; Starting and preparing function make program execution more efficient and completed. Function and concept: The segment numbers are range 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 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 reset 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 controller 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.


Program settings:

Program curve arrangement; program table adjuster can be used to automatically change the given value to control the field according to a certain time rule


The program is programmed in the format of [temperature-time-temperature], with 50-segment programming function, which can set the rising and falling slope of the given value of any size; with jump (the target segment is limited to the first 30 segments), running programmable/operable commands such as pause, stop, etc., can be modified during program control operation; have two-way event output function. The alarm output can be used to control other equipment interlocking actions such as: warning lights, fans, and alarms to further improve the equipment automation capability; with power-off processing mode, measured value start-up   preparation function, the program execution is more efficient and completed.

The program instrument self-tuning sets the first program to the normal temperature or the highest temperature to start the auto-tuning, and the time stops running.

The thyristor trigger adopts the phase shifting trigger. The AIJK6 series is an intelligent three-phase phase shifting trigger and a cycle zero-crossing trigger using the single-chip technology. It is powerful and reliable, and can adapt to various resistance wires and silicon. The carbon rod and the load are various types of industrial electric furnaces such as silicon molybdenum rods and tungsten wires which are stepped down by transformers, and can also be used for the control of soft start of the motor. Main performance of AIJK6: 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; AIJK6 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. AIJK6 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).

Module over voltage protection:

Generally, the two methods of RC absorption and varistor are used together. For an overvoltage with short absorption time and low voltage, a method of parallelizing the RC absorption circuit at both ends of the device is generally adopted, and the absorbing capacitor turns the electromagnetic energy of the overvoltage into In addition to preventing the oscillation of the circuit, the electrostatic energy storage can also limit the turn-off loss and large di/dt value of the capacitor to the thyristor when the turned-off thyristor is turned on again. For a longer duration, energy is generated. Large overvoltages, such as overvoltages caused by lightning strikes, will use varistors to absorb overvoltages.

Component selection: When selecting a varistor, which is the voltage across the varistor when it flows through 1 mA. After sensing the grid fluctuation and the safety factor, the general 380V power supply uses 1000V; the 220V power supply uses 630V varistor. The flow capacity of the varistor should be greater than the actual inrush current of the circuit, generally 3 to 15 KA. Common specifications: single-phase zero-crossing 40A or more varistor 20D751K 750V; phase shifting using RC RC varistor 20D751K, cement resistor RX27-1/8W/6.8Ω, capacitor 0.22uF/ 275V ~ iv high-voltage capacitor.

Broken-coupled over-temperature alarm phase loss protection:

Control the AC contactor to cut off the heater power during the over temperature alarm. Even if the thyristor is broken down, it can protect the electric furnace. For phase loss protection, it is recommended to use a three-phase phase loss protector for independent use. AI series control cabinets Compared with electric furnace control cabinets with equivalent functions, the AI series has the simplest line and modular structure, and it is very convenient from maintenance to expansion.

Wiring method and neutral line:

The wiring of each heating device is different. If the load is a heating furnace and the load may not be equal (such as a silicon carbide furnace), the three-phase four-wire system has better flatness than the three-phase three-wire system. And when a phase load is open, the three-phase four-wire system can automatically monitor and alarm (AIJK3). Therefore, the three-phase four-wire system are better than the three-phase three-wire system, but it must be noted that the zero line is correctly selected. In conventional applications, if the three-phase load is fully balanced, it is customary for the neutral line to use a much smaller wire diameter than the phase line. However, for the three-phase four-wire phase modulation trigger, when the phase shift angle is less than 60 degrees, the current of the neutral line is the sum of the three phase line currents (the three-phase load turns on, the current flows through the zero line, and the mutual current is completely impossible. Offset), when the phase shift angle is 60~120 degrees, the neutral current is only 0 when the thyristor is fully turned on and the three-phase load is balanced. Therefore, when the ordinary resistance wire is a load, the neutral line must adopt the same wire diameter as the phase line. For a load whose resistance will change with temperature or with aging, such as a silicon carbon rod electric furnace, since it often works at a small phase shift angle, the neutral line should be thicker than the phase line, preferably the phase line safe load, it is about 2-3 times higher than the flow rate. The neutral line from the cabinet of the power supply transformer should be thick, so as to ensure the safety of the neutral line and avoid excessive loss of electrical energy on the zero line.

High frequency interference:

Since the phase shift trigger will bring a strong interference in the frequency range of 1~100KHZ, the phase shifting trigger should be installed at a position away from the thyristor, but it should be kept at a certain distance from the power line, and the trigger line should be shortened as much as possible。

Instrument control is divided into single action and linkage, in the case of instrument power and transformer, the instrument inside each cabinet is open in the combined state, select single-action / linkage button switch in the 2# cabinet, the instrument can be perform in the form of single-action or linkage operations. 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, whether in single or linkage operation.


Parameter settings, debugging methods:

According to the requirements of the system, we can choose various instrument types such as AI-808PAI5X3L1L1S4 with Thristor AIJK3, and use the main output of AI-808P as the control signal of AIJK6 to control the heating output.

AI-808P intelligent controller adds 30+20 programming control function, the first 30 segments can be programmed as automatic jump execution, realize loop control, adopt advanced modular design, and have 5 function module sockets: auxiliary input, main Output, alarm, auxiliary output and communication,

The input mode of the controller can be freely set to thermocouple, thermal resistance and linear current (voltage). The specific module functions are as follows;

X3: Photoelectric isolation high precision linear current output;

S4: Photoelectric isolation RS485 communication interface module with isolated power supply;

L1: relay contact switch output module;


AIJK6 series is an intelligent three-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 silicon molybdenum with transformer voltage drop. Rods, tungsten wires, etc. Also, it can be used in various types of industrial electric furnaces and for thes control of motor soft start. The main features include:

0-20mA (0-5V) / 4-20mA (1-5V) signal compatible input;

The computerized technology is used for 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; AIJK6 also has thyristor breakdown and load open circuit detection function;

Automatic synchronization function, the phase sequence is not required when connecting the thyristor trigger line; AIJK6 does not even need polarity;

The use of money photoelectric isolation and "burning not bad" technology, the reliability is very high, causing little interference to the input;

Soft start/soft stop function with adjustable current feedback or delay time, which can adapt to silicon molybdenum rod, tungsten wire, motor and inductive load;

It includes a switching power supply, which can be directly powered by 220VAC power supply, and has two sets of DC power output of 5V and 24V;


The instrument's adjustment function uses an advanced AI artificial intelligence PID adjustment algorithm. The AI artificial intelligence adjustment algorithm is a new algorithm that uses fuzzy rules for PID adjustment. When the error is large, the fuzzy algorithm is used to adjust to eliminate the PID saturation integral phenomenon. When the error is small, the improved PID algorithm is used to adjust. And can automatically learn and memorize some features of the controlled object in the adjustment to optimize the effect. It has the characteristics of no overshoot, high precision, simple parameter determination, and good control effect on complex objects. The improved PID parameters are represented by U-specific M 5, P, t and other control parameters.


Debugging mode: Pid controller AI-808PX3L1L1S4, three-phase zero-crossing trigger control.


Debugging method:

After the parameter is set, it must first be self-tuned. The AI artificial intelligence adjustment algorithm is a new algorithm that uses fuzzy rules for PID adjustment. When the error is large, the fuzzy algorithm is used to adjust to eliminate the PID saturation integral phenomenon. When the error is small, the improved PID algorithm is used to adjust. And it can automatically learn and memorize some features of the controlled object during the adjustment to optimize the effect. It has the characteristics of no overshoot, high precision, simple parameter determination, and good control effect on complex objects.


The AI series adjustment instrument also has a parameter self-tuning function. When the AI artificial intelligence adjustment mode is used for the first time, the self-tuning function can be activated to assist in determining the control parameters such as M 5, P, and t. When the auto-tuning is started for the first time, the controller can be switched to the display state. To set the setting value, press and hold the semi-circular arc button for about 2 seconds. At this time, the display under the controller will flash to display the word “At’. The words indicate that the controller has entered into the self-tuning state. After 2~3 oscillations, the internal microprocessor of the instrument automatically calculates M 5, P, t, etc. according to the oscillation generated by the position control, analyzing its period, amplitude and waveform. If you want to abandon the auto-tuning in advance during the auto-tuning process, you can press and hold the semi-circular arc button for about 2 seconds to stop the display under the instrument from flashing “At”. Depending on the system, the time required for self-tuning can vary from a few seconds to several hours. After the self-tuning of the instrument is completed successfully, the parameter CtrL will be set to 3 or 4, so that the auto-tuning cannot be started from the panel by pressing the button again in the future, which can avoid the artificial misoperation to start the auto-tuning again. A controller that has started a self-tuning function. If you want to start auto-tuning in the future, you can start it by setting the parameter CtrL = 2. The specific operation should refer to the instruction manual.


The parameter values obtained by the system under different set values are not exactly the same. Before executing the auto-tuning function, the set value should be set to the most common value or intermediate value (for the AI-708P/808P program type instrument, The set value can be changed to meet the requirements by modifying the current block value. If the system is an electric furnace with good insulation performance, the set value should be set at the maximum value used by the system, and then the operation function of starting the auto-tuning should be performed. The setting of parameters CtI (control cycle) and dF (hysteresis) also have an effect on the self-tuning process. Generally speaking, the smaller the set values of these two parameters, the higher the accuracy of the theoretical self-tuning parameters. However, if the dF value is too small, the meter may cause a misalignment of the position adjustment near the given value due to the input fluctuation, which may instead set a completely wrong parameter. It is recommended that CtI = 0-2 and dF = 2.0. In addition, based on the reason for learning, the first time after the end of auto-tuning, the control effect may not be optimal, and it takes a period of time (usually the same time as auto-tuning) to get the best results.


In use, the AI regulator combines PID adjustment, self-learning and fuzzy control technology to achieve self-tuning/adaptive function and precise adjustment without under-adjustment. The performance is far superior to the traditional PID controllers.

6. AI-2070C/3070 split paperless recorder function

The data was recorded using an AI-2070C/3070C split paperless recorder. The main functions are: rich display screen; powerful setting function; perfect data processing; practical U disk and CF card recording data function; convenient data statistics function; flexible alarm function; reliable communication function; Management software.

Data logging function application:

The data recording function has developed rapidly, from paper recording to paperless recording; paperless recording analog input to digital paperless recorder; since electric furnace control cabinet is a digital adjustment instrument with communication function to control electric furnace thyristor, it needs Record the temperature control curve of the electric furnace.

The digital AI-2070S/3070S paperless recorder is installed in the control cabinet. It can be easily used with the AI intelligent program type PID temperature regulator through the RS485 communication interface and the upper and lower position.

In the electric furnace program temperature control, the hyperbolic running diagram can be displayed on the touch screen, the 15-segment lifting and lowering program can be stored in the screen, and the program graphics can be re-displayed; the setting can be set, read, and the temperature rise, constant temperature and cooling program can be set up and down; Instrument graph.

Control the operating program instrument on the screen [Start] [Stop] [Pause], switch the [Manual/Automatic] status in the running state, manually control the output; modify the [Segment No.] in real time, specify the running segment; and modify the instrument control parameters. And other functions; recall the recorded temperature curve data. Printing of data reports and alarm reports

1. PC data processing

In the data logger, you can set the data sampling time, storage interval and whether to save the record and data to the CF card and other functions according to the actual needs of the customer to meet different needs. The sampling time defaults to 6 seconds, and the time range that the user can set is 6 to 3600 seconds;

The CF card of the touch screen is externally inserted to save data; electronic hard disk with 1 GB volume is standard. Expandable CF card have storage space for 1~4G; Data, report and curve can be printed through micro printer; or store data through CF card. Use card reader to copy data packet on PC and then dispay and read data with graphics software; The COM2 port backs up the Excel spreadsheet data to the host computer. CF card: [AL] The data packet is the alarm report; [DL] The data packet is the data report; the data source file is saved by year/month/day/hour. It can display the open record data and the alarm record file or the data that the user has queried from the CF card, and display it in the form of a report;  The saving data is encrypted and must be read by specific Yudian PC graphics software.


View Curve: Click the [View Curve] button to display the data that has been queried in the report and displayed in the report mode in the form of a curve. The curve shown above can be divided into several parts:

1. Micro printer mode

With a micro printer, you can print historical data and curves by directly clicking the print button on the touch screen.

2. Data curve query printing: manually set the report time based on the content of the query, print 5 groups of data per line;

3. Data curve instant printing: manually print the content of the report that has just been collected which can print 5 groups of data per line, and continuously wrap;



Due to the excellent measurement and control performance of the AI artificial intelligence controller in the retrofitting of the heating furnace, the use of thyristor control has brought unprecedented convenience to the retrofitting design of the electric furnace control cabinet. For example, its output can be equipped with a thyristor trigger module, which can directly trigger various unidirectional, bidirectional thyristors and power modules with time proportional zero crossing, cycle zero crossing or phase shifting, not only reduce costs, simplify installation and increase reliability.

In recent years, with the development of electrical control technology, the automatic control system of electric heating furnace has been rapidly developed. The function of digital paperless recorder has been continuously improved, and the control system has been well applied and developed. The electric heating furnace automatic control system adopting the digital communication control instrument with touch screen digital paperless recorder is developed, which makes the technical transformation of the electric heating furnace more advanced.