If you apply dc to any two leads of a delta winding, two phases will be in series, and the third will be in parallel with them. That means one phase will carry twice as much current as the series pair, so it will get much hotter. For the wye connection, only two phases carry current, leaving the third phase cold.
Whether the winding is connected wye or delta, someone must monitor the current and winding temperature, and periodically move the welder leads. Otherwise, parts of the winding may not dry completely, if at all. Welding machines also have a duty cycle that's a lot shorter than the two or three days it might take to dry out one winding!Welding machines are useful when both ends of each phase are brought out as six leads.
An ohmmeter will confirm three separate circuits. In that case, the three phases can be connected in parallel or series, depending on the capacity of the welding machine, and dried simultaneously.The reality is that windings, like anything else placed in an oven, heat up very slowly. Moisture will get out the same way it got in. As the temperature of the winding slowly increases, the moisture (just as slowly) will evaporate.
Although IEEE Standard included an annex with information that may have perpetuated this belief, it was dropped in the next revision cycle.Every day more than 1,900 EASA service centers steam-clean and then bake stator windings—mostly at oven temperatures of . Even though many of them repair thousands of motors annually, there is no evidence that this process has damaged a single winding. Burst insulation due to oven temperatures above is simply not a concern.
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