Investigation of the magnetic system design influence on the parameters of the pulses controlling the transfer of the electrode metal

Abstract

As a result of the analysis of the literature data, it was found that up to 20% of the electrode metal is lost to waste and spattering caused by short circuits of the arc gap with large drops and their explosion. To reduce losses, the frequency of droplet transition is forcedly increased by current pulses, mechanical pulses, magnetic field pulses. To transfer droplets by pulses of the electrode wire feed speed, a 5 W synchronous electric motor is used. When using a mechanical oscillatory circuit, and overcoming the cavitation threshold at a frequency of more than 270 Hz, 2 W power is supplied to the excitation winding. When a drop is transported by an axial magnetic field, current pulses with an amplitude of 2500 A are required. They are provided by the energy of a capacitor charged up to 800 Volts. High currents require reliable switching devices, and high voltages require reliable insulation to protect the welder from electric shock. Therefore, the task to investigate the effect of design parameters on the magnitude of the magnetic field in the drop formation zone was set in order to reduce the parameters of control pulses. To fulfil the research, an inductor with a ferromagnetic coil without the cheek in its upper part was made. There is a winding on the coil, the current in which is regulated by the rectifier voltage. The segment of the electrode is located symmetrically to the magnetic circuit, that’s why it is possible to measure the magnetic induction in the upper and lower parts of the inductor. Measurements have shown that the induction at the top of the inductor is twice as high as at the bottom. This is due to the fact that the ferromagnetic coil cheek shunts the downward magnetic flux. When replacing the non-ferromagnetic current lead with a ferromagnetic one, the magnetic field induction in the upper part of the inductor has become three times higher as compared to its lower part. To increase the magnetic induction, the air gap was replaced with a ferromagnetic cylinder with a cone. The magnetic induction in the drop formation zone has increased up to 900 mTs, at only
500 ampere-turns. To create such a field in the known inductor, the ampere turns made up 2500 A × 28 = 70,000 ampere-turns, therefore, a decrease in the resistance of the magnetic circuit made it possible to reduce the magnetizing force by a factor of 100-140 and maintain the magnitude of the control pulses. To get it, it is necessary to reduce the air gaps to a minimum and swing the inductor 180°