News

A dual-loop speed control system is an automatic speed regulation device that works through the coordinated operation of an internal current loop and an external speed loop. Its core structure consists of an internal current loop (inner loop) and an external speed loop (outer loop), and it uses a proportional-integral regulator for closed-loop control [1] [7-8]. The system rapidly regulates the armature current through the current loop to limit sudden current changes and protect the equipment; the speed loop is responsible for precisely controlling the motor speed to ensure steady-state accuracy and anti-load disturbance capability [3] [7]. This hierarchical control strategy enables the system to have fast dynamic response and smooth start-stop processes, while effectively suppressing the impact of grid voltage fluctuations.

A DC motor [1] is an electric motor that converts direct current electrical energy into mechanical energy. Due to its excellent speed regulation performance, it is widely used in power transmission. DC motors are classified into three types based on the excitation method: permanent magnet, external excitation, and self-excitation. Among them, self-excitation is further divided into parallel excitation, series excitation, and compound excitation.
When a direct current power supply supplies current to the armature winding through the brush, the conductors under the N pole of the armature surface can flow in the same direction, and according to the left-hand rule, the conductors will be subjected to a counterclockwise torque; the conductors under the S pole of the armature surface also flow in the same direction, and according to the left-hand rule, the conductors will also be subjected to a counterclockwise torque. Thus, the entire armature winding (rotor) will rotate counterclockwise, and the input direct current energy will be converted into mechanical energy output on the rotor shaft. The stator and rotor are composed of: base, main magnetic pole, commutating pole, brush device, etc.; the rotor (armature): armature core, armature winding, commutator, rotor shaft and fan, etc.

It refers to the study of the laws, phenomena, mechanisms, and models related to the stability of chemical separation or reaction processes.
Stability analysis is a systematic method for researching the stability laws, phenomena, and mechanisms in chemical separation or reaction processes. Its core lies in evaluating the impact of disturbances on the system state and its recovery ability, which directly affects product quality and process safety [3].
This method covers technical directions such as multi-stable phenomenon analysis and dynamic behavior regulation, and commonly used tools include control methods based on Lyapunov stability theory and models of super entropy generation criteria [3-4] [6]. In the verification of measured data from cigarette making process, the accuracy of parameter stability identification reached 72.46% [2]. Nonlinear thermodynamic processes can be determined for stability through the second-order super entropy δ2S as the Lyapunov function [6].
Theoretical research originated from the framework of nonlinear thermodynamic stability analysis. The design of Lyapunov functions combined with sliding mode variable structure control methods improved the control accuracy of pH processes [4]. The establishment of the super entropy generation criterion model provided a universal theoretical basis for the multi-stable analysis of reaction distillation systems [5-6], and the AMMI model significantly enhanced the credibility of variety stability analysis compared to the LR model.

The step response of a system in a given initial state refers to the time evolution of its output when its control input is a Heaviside step function. In electrical engineering and control theory, the step response is the manifestation of a system’s output when the input changes from 0 to 1 within a very short period of time. By using this function and the impulse function, the excitation and response of dynamic circuits can be conveniently described. The impulse response is the derivative of the step response.

Feedback control refers to the process where, after a certain action and task is completed, the actual results are compared, thereby influencing the next action and playing a controlling role. Its characteristics are: it can promptly respond to the objective effects caused by each step of the planned decision during the implementation process, and accordingly adjust and modify the next implementation plan, so that the implementation of the planned decision can be coordinated with the original plan in a dynamic manner. Of course, feedback control mainly refers to the feedback of consequences, while established facts are difficult to change, and replacing the old plan with a new one or the original decision with a new one requires a certain period of time. Due to the system’s inability to adapt to changes in circumstances, it will bring unnecessary losses to the work. This is where feedback control falls short compared to pre-control.

A permanent magnet synchronous motor is a type of synchronous motor that uses permanent magnets to generate a magnetic field. The rotational speed of the rotor in this motor is synchronized with the frequency of the current in the stator windings.
A permanent magnet synchronous motor consists of components such as the stator, rotor, and end cover. The stator is similar to that of an ordinary induction motor, using a laminated structure to reduce iron loss during operation. The rotor can be made solid or can be laminated [9]. The armature winding can be of a centralized equal pitch type, or a distributed short pitch type and unconventional types [11].
The working principle of a permanent magnet synchronous motor is based on the interaction between the rotating magnetic field generated by the stator and the magnetic field generated by the permanent magnets on the rotor. The rotor is equipped with pre-magnetized permanent magnets, which can generate a strong magnetic field when rotating, thereby providing a greater output torque. The motor’s control system precisely regulates the current to ensure that the motor rotor can rotate synchronously with the rotating magnetic field, maintaining a stable operating state [8].
The permanent magnet synchronous motor is a widely used type of motor, with advantages such as high efficiency, good dynamic response performance, and low noise [10]. It is widely applied in electric vehicles, robots, and other fields that require high efficiency, high dynamic performance, and low noise.

Multi-break arc extinguishing is a bridge-type contact device with a dual-breakpoint structure [1-2], which is applied in relays, contactors, load switches, medium and low-voltage circuit breakers and other switchgear [2]. When the contacts are separated, two breakouts generate mutually connected arcs. Under the action of electric force, they move towards both sides, causing the arcs to elongate and cool down and extinguish [4].
This type of contact has two effective arc-extinguishing areas. For small-capacity AC contactors with a rated voltage of 380V or less and a current of 20A or less, arc extinguishing can be achieved using the near-cathode effect when the current naturally crosses zero. When the current is 20-80A, an arc starter plate or the use of circuit electric force blowing arc in combination with the dual-breakpoint arc extinguishing is required. The gap of the dual-breakpoint contact is small and the structure is compact, but it needs to be made of silver or silver-based alloy materials, which is costly [3], and the contact pressure and higher closing force need to be increased [5].

An AC contactor is an automatic switching electrical device that connects or disconnects the main circuit of an electric motor or load. It is an electrical appliance that uses electromagnetic force to close or open the switch, suitable for frequent operation, long-distance control of strong electrical circuits, and has protection performance of low-voltage release. It is used for long-term and high-frequency switching of AC main circuits and control circuits, and has the advantages of automatic operation, voltage loss and under-voltage protection, large capacity operation, strong stability, and low maintenance requirements. [2]
The contactors usually adopt three arc-extinguishing methods: double-break arc-extinguishing, longitudinal seam arc-extinguishing and grid plate arc-extinguishing. These methods are used to eliminate the arcs generated during the opening and closing of the moving and static contacts. Contactors with a capacity of 10A or above all have arc-extinguishing devices. The contactors also have auxiliary components such as counteracting springs, buffer springs, contact pressure springs, transmission mechanisms, bases and terminal posts. [1]

The working principle of a thermal relay is that the current flowing through the heating element generates heat, causing the bimetallic strip with different expansion coefficients to deform. When the deformation reaches a certain distance, it pushes the connecting rod to act, disconnecting the control circuit, thereby de-energizing the contactor and breaking the main circuit, achieving overload protection for the motor.
As an overload protection component for motors, the thermal relay has been widely used in production due to its small size, simple structure, and low cost.

Motor protection refers to technical measures implemented to trigger alarms or provide protection when a motor experiences faults such as overload, phase loss, locked rotor, short circuit, overvoltage, undervoltage, leakage, three-phase imbalance, overheating, bearing wear, rotor-stator eccentricity, etc. These measures are achieved through thermal relays, electronic protectors, and intelligent protection devices. The protection devices monitor parameters such as current, voltage, and temperature, and use techniques like three-phase true effective value calculation and winding heating model simulation to determine the fault state, thereby triggering power disconnection or triggering alarms. The protection range covers overcurrent, short circuit, and other operating conditions. Important motors often integrate current display, temperature monitoring, and local reset functions [1-3].
Traditional thermal relays have gradually been replaced by electronic protectors due to their low sensitivity. The latter achieve overload protection through inverse-time characteristics. Intelligent protectors integrate parameter display functions and support industrial communication protocol conversion [1] [3]. The “Made in China 2025” initiative proposes that by 2025, 100% of power transmission and transformation complete equipment will be fully intelligentized, promoting the application of intelligent protection devices in automated production lines. The selection should take into account motor parameters, load characteristics, and environmental conditions. For ordinary working conditions, electronic protectors can be selected, while in smart grid scenarios, devices with sensor integration features should be configured [1] [4].