magnetic chuck control

Certainly *not* the latter -- that would just re-magnetize it with the opposite polarity -- still magnetized.

Hmm ... perhaps the ringing capacitor discharge which I postulated in the other article I just posted.

Enjoy, DoN.

I'm wondering if the thing that looks like a choke might be a transformer used to apply low-voltage AC for degaussing. There are only three terminals in view on the choke/xfmr thingy, but all three of them are more than halfway from center of coil to outside of coil. That makes me wonder if there isn't another winding whose terminals aren't visible in the photos.

That's about all I can deduce from the photos.

There could still be a PTC thermistor in there. They've been around about as long as color TV has. They were used with the degaussing coils that demagnetized the picture tube upon turnon.

Ask easier questions!

Wanna beer? Hot enough for ya? Cold enough for ya? Ja git chur deer? How 'bout them Vikings, eh? Been catchin' enny? Waddya usin fer bait?

That makes sense and explains the electromechanical stuff. Polarity reversals are by definition AC. This is a (very retro) way to achieve AC excitation that diminishes in magnitude over a period of time.

Difficult to sort out from the photos.

The two rectifiers are clearly AC in at the centre and DC out at the ends. Since the the ends of the two rectifier stacks are strapped together they are configured as a full wave bridge rectifier with output to the magnetising coil.

The outer wires of the iron cored component connnect to bridge rectifier AC input so this must be a transformer - it cannot be a choke.

It looks as if there are only three leadouts. The AC input is connected to the centre tag and RH tag(connection at rectifier centre tag) so this makes it an autotransformer - possibly 2:1 stepup for a 230V magnetising coil.

This sounds pretty unlikely unless it is of European origin. However the nameplate lists both 60 and 50 HZ operation so clearly European supplies are a possibility. 230V operation would simply need moving the yellow wire from centre to LH tag.

Jim

Is it likely that the simulated low frequency AC is necessary to get that big magnet to change polarity, and that regular 60Hz is fine for a smaller chuck? This chuck is 30 or 36 inches in diameter and probably weighs 1000 to 1500 lbs. I had a chance to ponder its weight when I crawled under it to check the continuity thru the slip rings and windings.

Ned Simmons fired this volley in news: snipped-for-privacy@4ax.com:

nah... there are magnets the size of a bus that work on 60Hz.

LLoyd

I suspect it is an isolation transformer first off and then has various taps to adapt to a full wave.

I can't see it well - so if the switch is DC to grip and AC on the windings - it might demag the unit while 'off'.

Big time guess - have no idea what the PCB is doing...

Mart> >

Yep - used a monster monster for semiconductor maga hits.

Semi had iron in it - a big NO NO for most fabs - a bad contaminant.

It had a massive metal core that 'focused in cone shape pole. The pole face was an 300mm wafer diameter.

The real problem- where to use it - without ripping walls down.. :-)

Loading dock. It was put there by a massive Hyster forklift that could tilt its wheels in order to make tighter turns.

Moved the loading dock people to another dock. :-)

Mart> Ned Simmons fired this volley in

Well -- to give a partial answer at least:

1) PTC Stands for "Positive Temperature Coefficient" -- when cold the resistance is much lower than when hot. 2) If the cold resistance is low enough and the hot resistance is high enough, it can start out with high current when first switched on, and over a fairly short time decrease to a much lower current as the resistance increases.

This sort of thing was used to degauss color TV tubes when the set was first switched on without continuing to apply an AC magnetic field strong enough to cause wiggling of the image as you watch. (If you switch the set off and back on fairly quickly, you would probably see just that as the PTC resistor heats up again. The presumes that the circuit is designed to drop all power to the PTC and degaussing coil once the current drops below a certain value.

Enjoy, DoN.

Yes, if AC excitation voltage is limited to 115VAC. A large inductance may not accept enough current to demagnetize at 115VAC, 60 Hz.

Difficult to sort out from the photos.

The two rectifiers are clearly AC in at the centre and DC out at the ends. Since the the ends of the two rectifier stacks are strapped together they are configured as a full wave bridge rectifier with output to the magnetising coil.

The outer wires of the iron cored component connnect to bridge rectifier AC input so this must be a transformer - it cannot be a choke.

It looks as if there are only three leadouts. The AC input is connected to the centre tag and RH tag(connection at rectifier centre tag) so this makes it an autotransformer - possibly 2:1 stepup for a 230V magnetising coil.

This sounds pretty unlikely unless it is of European origin. However the nameplate lists both 60 and 50 HZ operation so clearly European supplies are a possibility. 230V operation would simply need moving the yellow wire from centre to LH tag.

Jim

replying to Ned Simmons, ty wrote: need one thats 13 amps 110 vdc output 4000 watts for my blanchard sg.

replying to Ned Simmons, ty wrote: need one thats 13 amps 110 vdc output 4000 watts for my blanchard sg.

Do you really think that he's waited over 11 years for this?