Research On Arc Velocity Measurement System Of Transverse Magnetic Contact Vacuum Switch

Vacuum circuit breaker has the characteristics of fast breaking speed,low carbon and environmental protection,so it has been widely used in medium and low voltage fields.In order to improve the breaking ability of vacuum circuit breaker,scholars increase the extinguishing ability of vacuum circuit breaker by changing contacts(axial and transverse magnetic contacts).The axial magnetic contact vacuum switch has a large breaking current,however,the manufacturing process of transverse magnetic contact vacuum circuit breaker is simple and the cost is low.In the case of relatively small current(not more than 10 kA class),transverse magnetic vacuum circuit breaker has obvious advantages.In the process of interruption,arc plasma is formed between contacts,current flows through contacts to generate radial magnetic field,vacuum arc rotates at high speed on the surface of contacts under the action of magnetic ampere force.In order to avoid overheating and electrical wear of contact caused by anode bias burning during interruption and increase the service life of switch,it is necessary to study the vacuum arc characteristics of transverse magnetic contact.Based on the analysis of the research status of transverse magnetic vacuum arc at home and abroad,a measuring system of rotational velocity of vacuum arc based on Hall sensor is designed.Compared with the traditional research method,this method is a non-contact measurement.In the hardware part,a speed measurement system of vacuum arc rotating is designed.The time and magnetic field intensity of each arc passing through are recorded by Hall sensor distributed outside the arc extinguishing room.In the software part,the arc measured by Hall sensor is made by mechanism action function,arc voltage capture function and AD conversion function.After the voltage signal passes through the amplifier circuit,it is converted to the main controller by AD circuit to calculate the arc speed.At the same time,the arc image was taken by high-speed camera,and the arc characteristics were compared and analyzed.After the completion of the measurement system,an experimental platform based on synthetic circuit was built to test the interruption of transverse magnetic vacuum switches under different voltages and currents.The arc voltage and current are recorded on the oscilloscope,the time and intensity of the magnetic field passing through the Hall sensor are recorded by the measuring system,and the arc image is recorded by the high-speed camera.After the experiment is completed,the arc rotation speed is calculated by the measuring system according to the average radius of arc rotation and the peak value of Hall sensor output.Factors affecting arc stability by arc rotation speed and image analysis.The results show that the arc voltage of transverse magnetic contact vacuum circuit breaker is 40-130 V and the transverse magnetic field is less than 100 mT.With the increase of arc current,the rotating speed of vacuum arc increases,and there is a positive correlation between them.When the current is small,the arc is in an unstable state and belongs to diffusion arc.It is easy to be extinguished by external interference,and the arc life is short.When the current increases to 10 kA,the arc is in a state of agglomeration and the arc is in a stable state.The speed of arc rotation is faster,which avoids arc burning on the surface of the electrode and increases the breaking ability of the switch.