METHOD OF AND DEVICE FOR FORMING EXTERNAL VOLT-AMPERE CHARACTERISTIC OF DC WELDING GENERATOR Russian patent published in 2002 - IPC

FIELD: mechanical engineering; welding appliances. SUBSTANCE: according to proposed method field winding current value of electric generator is changed means of feedback circuit. For this purpose constant reference voltage is set and first control signal is formed in proportion to this voltage. Output of generator is measured and converted into voltage which is then compared with reference voltage. If converted voltage value exceeds reference voltage value, second signal is formed whose initial value is set equal to value of first control signal. Value of second control signal is changed in reverse proportion to change of measured value of regenerator output current. First control signal is cut off. If value of output current drops below preset value of first control signal, initial value is restored, and second control signal is cut off. Thus steepness of external volt-ampere characteristic of welding generator is increased and its no-load voltage remains constant over entire welding arc current control range. In proposed device series starting circuit consists of push-button 34 with normally open contacts and resistor 33 connected to common wire of device. Feedback circuit 16 is formed by arc current sensor 7 and field winding current sensor 9, voltage-to-current converters 18 and 19 and threshold amplifiers 20, 21. voltage stabilizer 13 is connected in parallel with output of three-phase rectifier 4 and is connected with input of reference voltage source 15 connected at output to noninverting inputs of two threshold amplifiers 20, 21 and current inputs of voltage-to-current converters 18, 19. measuring inputs 17 are connected with arc current sensor 7 and field winding current sensor 9, and outputs are connected to adjusting resistors 30 and 32 and integrating capacitors 29 and 31 connected with common wire of device. Voltage-to-current converters are connected through threshold amplifiers 20, 21 to inputs of pulse-length modulator 24 unitied by NON-OR circuit. Output 25 of modulator 24 is connected with field winding 2 and series starting circuit through power amplifier 26. EFFECT: enlarged operating capabilities. 3 cl, 2 dwg