miller generator/welder. at 1800 rpm, the generator portion should output 60 hz, 120v. . its 4 pole. output is 65v at 40 hz.. will output 60hz and 120v at about 3400 rpm. . the welder portion is a separate stator, it also outputs half the voltage and HZ. i suspected a bad pole on the rotor,. as a half assed test, i applied 12v to the slip rings. inserting a thin welding rod at each pole showed the same magnentic attraction. i was expecting a dead pole. . ohms out at 18 ohms, which is correct. on the 240 volt plug, i get read 60 v, 40hz from one leg to neutral or ground, . 120v and 40hz from hot to hot. . . runs like a 2 pole unit. im really stuck . . i ran it at 3400, and i get 60hz, but thats way to high rpm. for a moment, i saw the fluke spike to 130hz, but when i set it to min max it didnt do it again. . i can send a schematic. the fact that it has a generator stator and a welder stator that has the same issue makes me think its somehow the rotor. if it is, its a goner. i hope not. it spent a lot of time getting it to run like a top, now this. any thoughts?

Model and year of Miller unit?Could be RPM problem. Some are 3600.

A separate stator requires a revolving field. If the D.C. isn't pure (read failed exciter rectifier) then RPM count and stator voltage would be affected. This really should be diagnosed with a handheld oscilloscope.

rectifier tests good. i also disconnected the bridge and ran pure 12v straight from the battery to the brush holder. still low HZ. at the same rpm, the output voltage would be reduced with only 12v, but the HZ should still be 60

ok. just looked at it. inserted thru the back a long 1/4 inch steel rod into the opening between a pole and the stator. with 12v on the brushes, you cant even pull out the rod. disconnect the 12v and the rod releases. it does the exact same thing on all 4 poles, equally. i think that rules out the rotor. i ran the machine at 2200 rpm with 12v on the brushes. 39-40 hz, about 30v ac . with the power to the slip rings disconnected, i still get 39-40 hz just from the residual magnetism, but of course very low AC, 1.5 volts. put back to normal with a new bridge rectifier brings me back to the orig problem, 39-40 hz, 70 volts AC at 2200 rpm. should be over 60hz and 120v. what else could it be? the stator is two windings with a center tap. both X and w outputs on the stator exhibit the same condition. you see the same acrosss X and Y. which are the hot legs for 220 v. there i ger the same 40 Hz, and around 120v. WTF could it be?

May want to read through this:Miller troubleshooting

generator/welder issue. | Good Sam Community

MEXICOWANDERER
Explorer
Dec 04, 2022
One of 3 phases open on the secondary stator winding will also affect Hz
enblethen
Nomad
Dec 04, 2022
May want to read through this:
Miller troubleshooting
mhooker32
Explorer
Dec 04, 2022
ok. just looked at it. inserted thru the back a long 1/4 inch steel rod into the opening between a pole and the stator. with 12v on the brushes, you cant even pull out the rod. disconnect the 12v and the rod releases. it does the exact same thing on all 4 poles, equally. i think that rules out the rotor. i ran the machine at 2200 rpm with 12v on the brushes. 39-40 hz, about 30v ac . with the power to the slip rings disconnected, i still get 39-40 hz just from the residual magnetism, but of course very low AC, 1.5 volts. put back to normal with a new bridge rectifier brings me back to the orig problem, 39-40 hz, 70 volts AC at 2200 rpm. should be over 60hz and 120v. what else could it be? the stator is two windings with a center tap. both X and w outputs on the stator exhibit the same condition. you see the same acrosss X and Y. which are the hot legs for 220 v. there i ger the same 40 Hz, and around 120v. WTF could it be?
mhooker32
Explorer
Dec 04, 2022
rectifier tests good. i also disconnected the bridge and ran pure 12v straight from the battery to the brush holder. still low HZ. at the same rpm, the output voltage would be reduced with only 12v, but the HZ should still be 60
MEXICOWANDERER
Explorer
Dec 04, 2022
A separate stator requires a revolving field. If the D.C. isn't pure (read failed exciter rectifier) then RPM count and stator voltage would be affected. This really should be diagnosed with a handheld oscilloscope.
enblethen
Nomad
Dec 04, 2022
Model and year of Miller unit?
Could be RPM problem. Some are 3600.

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generator/welder issue.

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