I have an old Walker electromagnet chuck and I really need some help figuring out how to wire this thing..

marino1310

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So I have an old walker 220-240v chuck, no idea how old it is and walker refuses to respond to my multiple emails asking about it. Its mounted to an old Norton surface grinder from the 40s. The original power supply was spliced off the motors 3ph 240v and goes into two large tube rectifiers and a large isolation transformer. None of the old tech works anymore. The isolation transformer is fried as are the 2 tubes. I just want a way to wire this up to its own power or from the machines power, I just want it to work. I went to my friend who is an electrical engineer and he told me Id need an isolation transformer so I dont get shocked and apparently a 1:1 240v isolation transformer is hard to find and very expensive... I was wondering if you guys knew any other way to wire these things
 
i suppose a possible go around would be to use a step up transformer,
or running a step down transformer, in reverse, to achieve the end.
it would still need to be rectified to get the dc to make the magnet work
 
Look into a Neutrofier type of magnetic control, I bought a Chinese unit that is very compact, this was on a 12 X 36" chuck, it has variable hold and neutralizes the residual magnetism so parts are easy to remove from the chuck face and it neutralizes any residual magnetism in the part. I do not know if they are available in 200+ volts, most chucks seem to require 100 V current; I think I got it from KBC or MSC. The machine came with a vacuum tube rectifier, which failed, and the replacement was satisfactory in every way, for over 10 years time.
 
Look into a Neutrofier type of magnetic control, I bought a Chinese unit that is very compact, this was on a 12 X 36" chuck, it has variable hold and neutralizes the residual magnetism so parts are easy to remove from the chuck face and it neutralizes any residual magnetism in the part. I do not know if they are available in 200+ volts, most chucks seem to require 100 V current; I think I got it from KBC or MSC. The machine came with a vacuum tube rectifier, which failed, and the replacement was satisfactory in every way, for over 10 years time.

Ill look into that. But they seem to be very expensive as well. Chinese ones on ebay seem to average $300
 
Usually the transformer is about the last thing to fail. While it's possible that it is gone, it is less likely than other components.

As near as I can tell those old chuck controllers are a full wave, 2 diode rectifier circuit. This would mean a center tapped secondary on the transformer. If the center tap isn't grounded, then it would be a full isolation system. It would also output about 120 VDC max with that wiring configuration.

1543006684448.png

If you were to more or less duplicate the circuit above and use SCRs as opposed to diodes, then drive them with a basic light dimmer circuit it would give you an adjustable output DC supply for your chuck.

This might be worth a read https://www.hobby-machinist.com/thr...ntrol-circuit-wanted.57733/page-2#post-477868
 
Hi Marino,

Just to add to Jim's post, you definitely need to use an Isolation transformer ! Don't even think about running without one.

If you cannot get one then you could use a pair of identical transformers wired back to back, that is 240 in low volts out into the other transformer low volts in high volts out. That will give you the isolation.

However there is a major problem with doing this, whilst it will work, you don't know how much power is involved. If the transformers cannot handle the amount of power needed they will get hot and burn out.

Then you will need to rectify the AC to get DC in order to turn the electromagnet on ! A simple bridge rectifier will do that easily. But again you need to know the amount of current that the electromagnet requires to produce the needed magnetic field. If you are lucky that information will be on a rating plate attached to it.

From there on its just a matter of getting the right rated components and building the power unit to supply the device.
 
A 120 to 240 step up transformer would probably be easier to find. (Or a step down transformer used backwards).
 
Baron is correct, once you know how much current the chuck requires you just build an ac to dc power supply using a transformer and a modern silicon rectifier. Add a variac to adjust the power. Less than 100 $ in parts if you shop around. Marlin P. Jones (www.MPJA.com) is in Florida, they have lots of electronic parts. Ebay too.
Like this:
acdcsup1.jpeg
 
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Baron is correct, once you know how much current the chuck requires you just build an ac to dc power supply using a transformer and a modern silicon rectifier. Add a variac to adjust the power. Less than 100 $ in parts if you shop around. Marlin P. Jones (www.MPJA.com) is in Florida, they have lots of electronic parts. Ebay too.
Like this:
thanks for the parts source Mark :grin:
 
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