ReplyOn miller welders. pin B is a voltage input supplies voltage to a circuit.
a simple functional equivalent circuit. think of a relay inside the welder.
one leg of the relay is connected to circuit common. "G" and the supply voltage comes from pin "A" out to feeder and comes back to "B" other leg of the relay is connected to "B". The Miller Deltaweld is wired this way.
Place meter on "A" to "B" and read 24 vac. because the meter sees common through the relay coil. No current flow , no voltage drop.
SO assuming the welder has only a 115 volt supply at weld voltage. you will connect your transformer to that to get your 24vac for the contactor. then you make and brake this voltage to turn the contactor on and off. Now comes the problems. does the welder only produce 115 volts at low speed and and turn it off at weld speed.
Have a 100Hz plug for weld lights. but your transformer might burn up with that power. If it produces 115 at weld speed, just connecting the transformer might draw enough current to lock the welder in high speed and it will never idle down.
You need a welder that produces 115 volts at low and high speeds and stays at 60Hz. But these welders with have a remote control receptacle.
NOT knowing the model you want to do this do can't be anymore help.
Need full model name and serial number. That way I can see the correct manual.
Miller has made many different types of engine drive welders. all with different power set ups.