A Closed-loop Chopper Start DC Holding Electromagnetic Appliance Control System

Abstract

The invention relates to a closed-loop chopped-wave starting direct current-retained electromagnetic electrical appliance control system. The system comprises a singlechip microcomputer control module, a pulse width modulation (PWM) module, a three-way current monitoring circuit and the like, duty cycle and breakover period number of PWM voltage at two ends of a coil are fast regulated directly by taking the coil current as feedback amount through closed-loop chopped-wave control, thus achieving the purpose of regulating the current of the coil, being capable of fast regulating the starting current in the starting process and achieving the purpose of reasonably matching the dynamic process. In closed stage, different direct-current-retained power supplies can be selected according to different capacities, thus realizing energy-saving silent running.

Description

technical field [0001] The invention relates to the field of intelligent control of instruments, in particular to a closed-loop chopper-starting and DC-maintaining electromagnetic appliance control system. Background technique [0002] As a traditional electrical appliance, electromagnetic appliances are widely used in control systems, such as electromagnetic contactors, electromagnetic relays, electromagnetic releases and so on. With the continuous improvement of system automation level, higher requirements are put forward for the performance indicators of electromagnetic appliances. [0003] Ordinary electromagnetic appliances have the following characteristics in operation: [0004] (1) The closing phase angle affects its pull-in dynamic characteristics. For the electromagnetic mechanism powered by AC and the electromagnetic mechanism powered by pulsating DC, the randomness of the closing phase angle leads to the random change of the excitation current, the magnetic flu...

AI Technical Summary

Problems solved by technology

The dispersive characteristics of the action time of the electromagnetic mechanism exist both for AC electromagnetic appliances and DC electromagnetic appliances, which makes it difficult to control electromagnetic appliances, and the impact is more obvious for electromagnetic circuit breakers that require fast action.

Although the time of the microprocessor control system is within microseconds, the dispersion of mechanism action time often leads to control failure

Moreover, with the frequent operation of switching appliances, factors such as wear of the contact system and aging of the mechanism will lead to changes in the action time

Therefore, the unidirectional open-loop control mode cannot effectively complete the intelligent control of electromagnetic appliances

[0006] (3) Narrow working voltage range

The AC electromagnetic appliances with single-phase control power supply will generate vibration and noise in the holding state. Therefore, it is necessary to design and install the sub-magnetic ring. The sub-magnetic ring often becomes the weakness of the AC electromagnetic appliance. The phenomenon that the mechanical life of electrical appliances ends is relatively common. Moreover, for single-phase AC electromagnetic appliances such as air-conditioning and refrigeration industries, it is also a design difficulty to design an ideal magnetic separation ring to reduce working noise.

[0008] (5) There is hysteresis eddy current loss in the magnetic circuit

[0012] First of all, it is impossible to solve the problem of dispersion of electromagnetic electrical appliances caused by the influence of the mechanism, and the problem of change in the action time caused by the wear of the contact system;

[0013] Secondly, in the electromagnetic mechanism, it is the magnetic potential in the magnetic circuit that directly affects the work of the mechanism. Since the AC electromagnetic mechanism is connected to the DC excitation power supply, the magnetic reactance in the magnetic circuit (caused by hysteresis and eddy current loss), and the magnetic reactance in the circuit The reactance does not exist, then the current in the coil will increase significantly

During the control process, the switching tube of the starting circuit will bear a huge current impact, especially for large-capacity electrical appliances, it is very difficult to control the starting process by using the control principle of voltage regulation

[0014] Third, it is necessary to monitor the current change law in the coil of the electromagnetic appliance in real time, so as to realize the optimal control of the whole process, which is difficult to achieve by using the voltage control scheme.

[0015] Fourth, in the high-voltage start-up and low-voltage maintenance scheme, two power electronic switches are required for high-low level conversion, and the high-voltage start-up power electronic switch increases rapidly with the increase in the capacity of electromagnetic appliances, the voltage and current stress, and the cost also increases rapidly

In this mode, due to the change of the working air gap, the parameters such as AC inductance change during the whole movement process, and the voltage, current, magnetic flux, flux linkage, displacement, speed and suction in the system during the dynamic process and other parameters change with time, resulting in difficult control

After the mechanism is closed, the magnetic state of the open position is very different. Therefore, this control mode using changing voltage cannot effectively and real-time control the excitation magnetic potential in the magnetic circuit.

[0017] Sixth, at the end of the starting process and turning to the holding stage, due to the rapid cut-off of the holding circuit and the starting of the holding circuit, it will cause inrush current and operating overvoltage

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