The present invention discloses a method and related apparatus for compensating a gain mismatch between a first DAC and a second DAC. In a stator 2 for a dynamo-electric machine comprising a stator core 32 having a plurality of slots 35, and a stator winding installed in the slots 35 and comprising a plurality of conductors 33 joint end portions 33a thereof joined to each other, joint portions of the joint end portions 33a comprise a molten metal 33g, 33 fof a lower melting point than that of the conductors 33. Inside the steam generator, the water is heated to steam.