| 摘要 |
PROBLEM TO BE SOLVED: To provide a welding power supply which solves the problem that connecting and disconnecting a commercial AC power supply using changeover switches generates spark noise and causes contacts of the changeover switches to deteriorate or to get melted and stuck.SOLUTION: A welding power supply includes a switch for connecting and disconnecting a commercial AC power supply, a DC power supply circuit for generating DC voltage by rectifying and smoothing the commercial AC power, an inverter circuit for converting the DC voltage to high frequency AC voltage, a main transformer for converting an output of the inverter circuit to high frequency AC voltage suitable for arc machining, a secondary rectifier circuit for rectifying an output of the main transformer, and a DC reactor for smoothing the rectified output. Changeover switches for switching the voltage of the commercial AC power are switched at zero-crossings, at which input voltage of the changeover switch is approximately zero. The soft-switching of the changeover switches suppresses occurrence of spark noise and prevents deterioration and melting/adhesion of contacts of the changeover switches. |
