Mid Sweden University

A technique for measuring the current of a stationaryspot welding unit using a Hall sensor system is implemented. HallEffect sensor is used to sense the strength of the magnetic fieldproduced by the current, flowing through the welding electrodes,on the secondary side of welding transformer. In contrast to acurrent transformer the Hall Effect sensor can read a DC currentand can thus be utilized in direct current welding equipments. Inthis paper the influence of the sensor position and presence of thetools or other materials in the proximity of the sensor that effectthe sensor reading is investigated. COMSOL Multiphysicssoftware is used to investigate these effects and a circuit design isimplemented according to the conclusion drawn from the simulations.

Inverter drive resistance spot welding machines are becoming a good choice of welding because of the increased machine efficiency and output power. The DC link capacitors in spot welding equipment store a large amount of energy. In case of any failure, the IGBT in the inverter has a risk of exhibiting a violent rupture. This rupture can damage the converter, drive down time and personal injury which may lead to the machinery certification problems. IGBT failure detection and solution for protection of these failures in resistance welding machines have not been reported in literature. Literature study of the IGBT failure, rupture, fault detection and protection has been carried out for inverter drives in power applications. On the basis of the findings some protection schemes and important measures in the design of the machine have been adopted which have resulted in the reduced risk of IGBT failure.

In designing switch mode power supply (SMPS), thedesirable feature is to have an efficient and compact design. Themain idea is to increase the switching frequency and reduce thebulky magnetic parts of the converter. This leads to a compactsize, less weight, reduced cost and increased power density of theconverter. This paper presents a high frequency full bridge DC toDC converter, using a multilayer coreless printed circuit board(PCB) step-up power transformer. The converter was simulatedand also implemented on the PCB. The pulse width modulated(PWM) signals were generated, using a microcontroller, to switchthe Metal oxide semiconductor field effect transistor (MOSFET).The design of the converter is tested up to the power levels of 5Watts with the switching frequency in 2 to 3MHz range. Theenergy efficiency of the converter is 74.86% at 2.4 MHz.