Design of Intelligent Motor Protector Based on DSP

Aguilera

Design of Intelligent Motor Protector Based on DSP [Copy link]

Due to the emergence of production automation and various automatic control and sequential control equipment, motors are required to operate frequently in various modes such as frequent starting, braking, forward and reverse transmission, intermittent and variable load. The operation requirements of motors are getting higher and higher. At the same time, since the motor is connected to the supporting machinery, when the motor fails, it often affects the production system. Therefore, it is an important task to effectively protect the motor to ensure the normal operation of the production system.

With the development of science and technology, electronic protection devices are gradually used in motor protection devices. In foreign countries, electronic protection devices have been widely used in power systems and motor protection devices, and they have also begun to be promoted in China. The advantages of electronic protection devices are: they are basically composed of static components. They have fast action speed, no mechanical displacement and wear, and their accuracy and life are generally higher than those of contact relays. They are resistant to impact and vibration and have good reliability. In addition, the electronic circuit has low action power and high sensitivity.

The digital signal processor (DSP) has streamlined operation functions and a single-cycle multiplication structure. The system composed of it can perform spectrum analysis in real time. The high-speed 14-bit A/D converter MAX126 with multi-way switch and sample-and-hold is very suitable for the acquisition of motor signals. In order to achieve reliable protection of the motor, an intelligent motor protector with comprehensive detection and protection functions for common faults such as overload, light load, imbalance, phase failure, overvoltage and undervoltage is proposed with TMS320LF2407 as the core.
1 Basic principles and design ideas of the system

Abnormal operating conditions often occur during motor operation. These abnormal operating conditions include: overload, stall, short circuit, light load, imbalance, phase failure, overvoltage, undervoltage and leakage. Motor protection is based on the detection of three-phase voltages UA, UB, UC, three-phase currents IA, IB, IC and leakage current IL. The specific process is as follows:

(1) Set each number and send control signals from the PC;

(2) Sampling three-phase voltage, three-phase current and leakage current to obtain real-time values;

(3) Use the FFT algorithm to process and calculate the data to obtain the effective value of three-phase voltage and current, active power, reactive power and power factor;

The hardware block diagram of the system is shown in Figure 1. The CPU uses TI's TMS320LF2407, whose rich
hardware resources are fully utilized in the system. Together with a small number of peripheral devices, it forms a functionally
complete, simple and applicable system.

Figure 1 Hardware block diagram
2 System hardware design
2.1 TMS320LF2407 TMS320LF2407, also known as DSP controller, is designed
by TI for the control of motors, inverters, machines, CNC machine tools, etc. [2-4]. TMS320LF2407 uses high-performance static CMOS technology, which reduces the power supply voltage to 3.3V, reducing the power consumption of the controller; the execution speed of 30MIPS shortens the instruction cycle to 33ns (30MHZ), thereby improving the real-time control capability of the controller. It includes two event manager modules EVA and EVB, which can realize: three-phase inverter control; symmetrical and asymmetrical waveforms of PWM; 3 capture units; 16-channel A/D converter. The event manager module is suitable for controlling AC induction motors, brushless DC motors, switched reluctance motors, stepper motors, multi-stage motors and inverters.

基于DSP的智能电机保护器设计.pdf (216.39 KB, downloads: 6)

2019-12-9 21:48 上传

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