Recent power sources are based on inverter technology and now becoming more popular. First of all, lot of developments are being done on this technology by many experts all over the world. Inverters are designed to operate on three-phase as well as single-phase 50/60 Hz input supply. Output current range is from 100 ampere to 1200 ampere. Open circuit voltage is less than 100 V, and depends on the welding process. This current range covers almost all applications of fabrication industry such as SMAW, GMAW, AC TIG, DC TIG, saw, gouging and cutting. If one studies the population of welding electrodes in the field for manual welding process, 400 ampere inverter welder is more than enough to meet almost 80 per cent requirements of the market. Population of these machines is more in the field. Same is the case for GMAW process. 1.2 mm MS wire and flux cored wire is used in large quantity by fabrication industry. For SAW process, 3.2/4.0 mm wire is used in large quantity and current range required is 600 to 1200 ampere. The duty cycle should be 100 per cent for this process because it is continuous and automated process. Process characteristic such as CC or CV and combined CC/CV are achieved through electronic circuits.
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Single phase inverter power source working on 220/230 mains supply is more popular. Single phase supply is available at all places where one can carry out repairing work. 2.5 mm and 3.2 mm diameter electrode are regularly used by welder. This power source weighing 8 to 9 kg is very compact and useful for repair and light fabrication. The machine is portable and can carry very easily to any desired location. Output current range is 100 to 200 ampere DC. Above 200 ampere, inverter power source is working on 415 volts, three phase, and 50/60 Hz supply.

Inverters are using IGBT and MOSFET as main power switching active device. These power devices are now easily available at competitive prices. Design engineers are familiar with associated switching and drive circuits. Quality and reliability of design is improved. Customer is also showing confidence in inverter power sources. Today, customer is inquiring for inverters machines. Spare parts of inverter power source are available at affordable price. Service is offered by supplier regularly. Failure rates have reduced. The prices of inverter welders are competitive. Delivery and lead time is improved and further have contributed to more demand of inverter welders in the market.

Inverter welder over conventional welder
Why inverter welding power sources are compact, light-weight, portable and consume less energy?

It’s because of frequency of operation. High frequency has reduced the size of main step down transformer, output inductance and cooling fan. High frequency has reduced size of magnetic core, primary no of turns, secondary no of turns and no of turns of inductance. Inverter output is AC with square waveform which gives good quality DC output voltage after rectification. Secondary rectifier diodes with fast recovery time and ultra-fast recovery time are used for rectification of 20 Khz square wave secondary voltage. The time
required for single cycle is 50 micro second. Therefore, correction is fast.

Input supply is directly rectified with three-phase full wave rectifier and DC link voltage is acting as battery voltage for inverter. Switching frequency is generated by PWM control circuit. It is a closed loop control which regulates either output current or voltage by modulating pulse width.

Authored by
R.K.Patwardhan
ACE Weld Engineers
Email: aceweld2008@rediffmail.com