▲Lee Taek-gi, Professor at Kyunghee University

■Please give readers a brief explanation of industrial motors and motor control technology .

It is no exaggeration to say that electric motors account for the majority of power sources in the industrial world. In the past, direct current (DC) motors were used for control purposes, but now alternating current (AC) motors are used. Although DC motors have many advantages, AC motors are used instead of DC motors due to limitations in maintenance. In order to use these AC motors, a power conversion device is essential and an inverter is used for control.

■In order to control industrial motors, it is thought that various engineering knowledge such as mechanical engineering in addition to electronic engineering will be required. What advice would you give developers on the basic knowledge and study methods they need to have for industrial motor control?

As mentioned earlier, an inverter is needed to control an AC motor. Therefore, it is essential to understand the structure and basic principles of an inverter. An inverter is a device that converts direct current into alternating current. Since the power we use is AC, a rectifier that converts AC to DC is attached to the front of the inverter. Since this power conversion device is composed of power semiconductor devices, it is necessary to understand the characteristics of both traditional RLC and power semiconductor devices.

Therefore, in order to control a motor, it would be good to first understand the operating principles of a power conversion device made of power semiconductor devices, and then learn the equations and control methods that represent the basic characteristics of the motor.

■Regarding the above question, I am curious about what you focus on when teaching students. I would like to hear about your own educational philosophy.

I think that in any discipline, if you stick to the basics, it is relatively easy to apply. I think that it is absolutely necessary to acquire sufficient basic knowledge in motor control as well.

Therefore, I think it is a priority to understand the characteristics of the motor based on several equations that represent the characteristics of the most basic DC motor. In addition, understanding the basic principles of generators and transformers will be of great help.

■Motor control technology has also developed along with the development of power semiconductor devices. What are your thoughts on this?

The development of motor control is closely related to the development of power conversion devices. Starting with the thyristor in the past, the motor drive system is composed of power conversion devices that mainly use IGBT devices. The application of power semiconductor devices is used in various fields, not just motor control.

For example, power supplies are used in everything from small home appliance chargers, such as the cell phone chargers we use, to electric vehicle chargers and wireless electric vehicle chargers. In the future, electric vehicle control is expected to develop further, and examples of motor control using power conversion devices, that is, power semiconductor devices that we commonly see in electric vehicles, subways, and high-speed railways, etc.

The basis of motor control is current control, and furthermore, speed control, position control, and torque control are performed. For example, in the case of electric vehicles, various motors are used, so control technology that matches the characteristics of each motor is expected to be developed. It is expected that the development of such control technology will be accompanied by the development of microprocessors and digital control technology.

■What knowledge is needed for motor control?

I think that understanding the characteristics of the motor is a priority for motor control. Based on the characteristics of the DC motor, the characteristics of the AC motor are understood, and as mentioned earlier, understanding the operation of the power conversion device must be included. AC motor control can generally be divided into scalar control and vector control. For this, the equivalent circuit of the motor and mathematical modeling are required. The controller is configured based on equivalent circuit and mathematical modeling.

■Please explain the content that will be covered at the '2022 e4ds Industrial Motor Control Technology Conference' to be held on July 22nd.

The Industrial Motor Control Technology Conference will be an opportunity to learn the fundamentals of motor control, including the basic characteristics of RLC circuit elements, the basic characteristics of PI controllers based on an understanding of motor characteristics and power conversion devices, and especially the operating principles of rectifiers and inverters, and control methods through mathematical modeling of AC motors in the synchronous coordinate system.

■Please give a final word to e4ds news readers.

I would like to thank the readers who took the time out of their busy schedule to attend the Industrial Motor Control Technology Conference . I am honored to be able to participate as well. I hope that this conference will help you understand the basics and methods of motor control. If you have any questions, please leave a question and I will answer you sincerely. For more detailed information on motor control, please contact the Korean Institute of Power Electronics.

thank you

The 2022 e4ds Industrial Motor Control Technology Conference, which presents a structural development modeling and latest technology trends seminar for motor control developers, will be held on July 22nd in the main auditorium of the Korea Conference Center (Gangnam Station).