Application of Yudian Intelligent Instrument AI-808 in Constant Temperature Control System

1. Overview

With the increasing use of electric heating equipment in industrial production, various control methods have been introduced to manage temperature in automated systems. The traditional approach typically involves contactors that switch the main circuit on and off to regulate temperature. However, this method has several drawbacks. It lacks precision, leading to temperature fluctuations. Moreover, frequent switching of the AC contactor can cause wear and tear, resulting in contact damage or sticking, which may lead to loss of temperature control. In addition, the repeated operation of the contactor can cause voltage fluctuations in the power grid and potentially damage the heating elements, negatively impacting the economic efficiency of the enterprise. To address these issues, our company has adopted advanced temperature control solutions using intelligent instruments from Yudian Automatic Technology Co., Ltd., specifically the AI series, along with thyristor triggers and bidirectional thyristors. These components provide a more reliable and efficient way to manage temperature control. Intelligent power regulators are widely used in various electric heating applications, such as hot rolling mills, electric ovens, drying chambers, and other industrial equipment. They offer flexible control modes, easy manual-to-automatic conversion, and high-precision temperature regulation. The system is composed of an AI-808 intelligent instrument, thyristor modules, trigger circuits, and fast fuses. By utilizing non-contact control, it enhances resistance to vibration, corrosion, and interference, ensuring high stability and reliability. Its compact design makes installation and maintenance convenient, making it an ideal replacement for older temperature control systems in industries like heat treatment, chemicals, textiles, food processing, automotive, and electronics.

2. System Structure and Working Principle

The temperature control system includes an air switch, thyristor, trigger, and smart meter (refer to Figure 1 for the control schematic). The thyristor is mounted on a heat sink, and a fan and temperature switch are also installed on the same heat sink to manage the cooling process, preventing overheating and ensuring safe operation. The thyristor is a bidirectional device equipped with varistor or RC absorption protection and a fast fuse for added safety. The selection of specific components should be based on the relevant technical manual. The intelligent power regulator functions as a "zero-voltage switch" controller. When the AC voltage crosses zero, the thyristor conducts for a set number of cycles and then turns off for another set. This duty cycle adjustment allows precise control of the load power. By triggering at the zero crossing point, the load receives a complete sine wave, reducing harmonic distortion and minimizing interference with the power grid. This results in a higher power factor and greater energy efficiency compared to phase-shifting regulators. The AI-808 temperature controller integrates an embedded system with PID self-tuning capabilities. It can be programmed to control temperature rise or fall based on user requirements. It supports various types of temperature sensors, including thermocouples, resistance temperature detectors, and linear signals. The output can be configured to standard signals like 0–10V, 1–10mA, or 4–20mA, with the output power directly proportional to the control signal. The controller supports both position control and AI-based fuzzy logic PID control, allowing for closed-loop or open-loop operations. Users can manually adjust the setpoint via a potentiometer to achieve desired temperature control. Additionally, the AI-808 offers segmented power limitation and multi-curve programming features. A communication module enables data acquisition and control across multiple temperature control cabinets through a networked system.

3. Application Conditions

- Load Type: Capacitive or inductive loads - Power Supply: Three-phase four-wire 380V ±10% at 50Hz, or single-phase 220V - Ambient Temperature: -10°C to +45°C - Environment: No conductive dust, no corrosive gases, no severe vibrations The electrical control cabinet must have proper ventilation to ensure adequate heat dissipation for the thyristor.

4. System Debugging and Precautions

4.1 Input and Output Circuit Check

Before commissioning, verify all wiring according to the system schematic. Pay special attention to the correct connection of the trigger circuit. The meter should be properly configured before use, with input settings adjusted based on the type of on-site temperature sensor. The output type should also be set depending on the control signal received by the trigger.

4.2 Dummy Load Test

During testing, if no actual load is available, connect a light bulb to the main circuit output. Set the meter to manual mode and use the “>” or “<” keys to adjust the brightness. Observe if the bulb dims smoothly, confirming that the trigger circuit and overall wiring are correctly connected.

4.3 Manual Adjustment and Self-Tuning

In real-world applications, users often need to control temperature within specific ranges based on process requirements. The AI-808’s intelligent tuning function uses fuzzy logic PID control for accurate temperature regulation. With its auto-tuning feature, one or two self-tuning cycles can be performed to achieve optimal control. Different temperature profiles can be programmed for different time periods to meet varying control objectives.

5. Conclusion

Since its implementation, the temperature control cabinet produced by our company has demonstrated excellent performance, meeting all user requirements and operating reliably without any maintenance issues for several years. It continues to be a trusted solution for industrial temperature control.

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