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Re-winding solenoids.

Thank you for your information.

It changes nothing. The original solenoid develops about 12,000 ampere turns at 480 Volts. The replacement needs to develop 12,000 ampere turns at 240 volts.

If this were a customer, such as a extended care center where I originally bought the used generator from and replaced their original automatic transfer switch with a new compatible one I would have (and did) take proper steps to insure everything worked within the confines of a life-safety application.

This is a manual transfer switch with some control logic to determine if all the power is present prior to switching. What in essence it does is not allowing you to switch to a non-existent source.

I asked for an opinion that ampere turns was the right direction I was headed in to change an operating solenoid from 480 to 240 volts.

I did not ask form someone such as yourself to presume that I totally lack the ethics to endanger life with a crap modification.

Ya know, the way this transfer switch operates, I can just as easily add the optional "manual handle" on the side of the box to switch from normal to emergency power and throw away all the complicated stuff inside.

As far as life safety is concerned, this is to handle a loss of power at the shop I operate. Simple. "The power failed." Go outside, start the generator and once it's running go back and flip the transfer switch. When the utility power returns and stays on, flip the siwtch aback and then go outside and turn the generator off.

This really isn't rocket science.

Jeff-1.0

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus
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Well as long as your bitching at me for leaving something out....

The original coil is being fed through a bridge rectifier (mentioned elsewhere in the thread). So the AC impedance is less of an issue.

Using the proline scripting, I came up with 80 mH using #28 AWG wire,

1988 turns and 1.54" outside diameter with 42.63 ohms.

I come up with 11192 ampere turns. I've got some wiggle room to increase the bobbin size a bit. So rest well good sir, we are at a point that is "close enough" to wind up a prototype and see if works properly.

If it does, then it gets potted in Epoxy to match the original physical dimensions and we call it a success.

Jeff-1.0

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus

I always find something to complain about. It's part of my standard usenet protocol. Nothing personal.

Bad news. 60Hz is still AC. The AC current, is determined by the AC impedance also known as Z. Fortunately, most of it comes from the resistance of the wires, making the coil specs easier to guess.

You cheated by going over the OD by 0.04". Assuming you can pack the windings in as tight as the original, that shouldn't be a problem. I'm not all that confident you can do it. Use a mandrel and a slow turning lathe.

It will probably work. I just hate to say that as I'm sure you'll blame me when it explodes and sprays coil bobbin parts all over the shop. It might help to immolate an old solenoid on the barbeque as a burnt offering to the god of electric power for a favorable outcome.

Right. Hide the evidence. Be sure to embalm the windings in yellow Kapton (Polyimide) high temp tape before potting. I learned that the hard way after trying to pot some radios. The epoxy shrinks as it hardens, which likes to tear wires away from their attachment points. The tape provides an easy air space for the epoxy to shrink.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

Well of course, I've known you long enough now to fully understand the protocol. ;-)

The physical demisions after the epoxy potting are 1.55, instead of my guess of 1.375), and 1.66 rather than my also guess of of 1.50.

Isn't that also standard Usenet protocol?

I still have several rolls here at the shop from when I'd rewind surplus wall warts for laughs.

Jeff-1.0 the other other one.

Having a vacuum pot and temperature chamber helps make stuff "right" when you do it. I kind of prefer a polyurethane for potting myself.

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus

Yes. The first step to analyzing a failure is to blame someone.

I like to use Bondo, because it doesn't shrink.

Way back in the days when I still received a regular paycheck, the company had a "modular products" division that sold data converters into such non-critical applications like missiles and air traffic control systems. Instead of just dumping the electronics into a potting shell and filling it with epoxy, they would first fill it almost to the pour hole with sand and then top it off with epoxy. The thermal conductivity of epoxy is slightly better than lousy. The sand gives an even temperature distribution, protects against mechanical shock, and is cheaper than epoxy. It also makes post-potting repair somewhat possible. Filling the bobbin with sand before potting isn't going to do anything useful for your solenoid, but I thought I would mention it for future applications.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

You said in an earlier post that the current in the coil needs to be around

5 amps, and you propose to use 28 AWG wire to wind it. AWG 28 wire has a rated ampacity for chassis wiring (inside a bundle, similar to your solenoid coil), is only 1.4 amps. I doubt that your coil would last very long with that amount of current. More investigation is necessary. Might be less painful to spring for the proper solenoid from the manufacturer. 
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David
dgminala at mediacombb dot net
Reply to
Dave M

OOps.. I got that wrong.. That figure was the capacity in free air... The capacity of AWG28 wire in an enclosed space is 0.83 amps.

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David
dgminala at mediacombb dot net
Reply to
Dave M

I'm sure that it is. The original coil at 480 volts draws 5.2 amps and is wounnd with #30 AWG.

Guess I need to repeat this. It is PULSED not STEADY operation.

Jeff-1.0

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus

You know, at this point, you pretty much don't care I would assume how ever, have you thought about constructing a voltage double rectifier instead of that bridge rectifier to drive that coil?

+-------+-------++ | | | + | | D1 - | | ^ | | | | + C1 + + C| 240 AC in | --- C| 480 Solenoid || | ---C2 C| +---+-||+------+ + | || + | + | | | - | | D2 ^ | | 240 AC in + | | | + | +-------------+-------++-------+ (created by AACircuit v1.28.6 beta 04/19/05
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I suppose if you had to motor caps around you could use those, the large ones of course.

What ever. Jamie

Reply to
Jamie

Good idea. The caps will need to be charged by the 240VAC line voltage in a few cycles in order to get any kind of usable response time for pulsed operation. That means the caps are going to be rather big. A rough guess would be:

AC impedance of the coil is roughly: 480VAC / 5A = 96 ohms To get C2 up to about 90% of full charge in 2 cycles, the capacitive reactance of C1 would need to be about: Xc = 96 * 0.1 = 9.6 ohms At 60Hz, that's 276 uF. 330uf 600VDC caps should work. I'm not very confident with my crude approximations. Therefore, I would feed the model to LTSpice and see what it's really going to do.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

You're charging to the peak values, not RMS, so it's going to be 680 volts at a minimum, and probably more like 750 for some margin of safety.

Caps of that size and rating will end up costing as much as the coil itself.

Jeff

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus

You're right. I don't. Because my original question was in regards to ampere turns and rewinding a solenoid for a different operating voltage.

Because so far, with one notable exception, everyone has insisted on coming up with some Rube Goldberg solution or accusing me of trying to murder widows and orphans.

Jeff-1.0

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus

I wish that that had been your original question, which was a rambling stream of consciousness. Your reference to a program for calculating aircore inductors made me think you were using "solenoid" in the sense of "helical coil."

Your desire to save $380 in the belief that ASCO was screwing its customers with jacked-up prices seemed a bit unreasonable, the more so when you revealed the true application for the solenoid actuator.

But your juryrig would merely produce widows and orphans, not kill them. Only the lineman trying to restore power would be killed if your Rube Goldberg solution failed to work.

Reply to
spamtrap1888

Can't follow a thread, can you? It's for his workshop.

--
You can't have a sense of humor, if you have no sense.
Reply to
Michael A. Terrell

Since you seem to be so good at divination....Pray tell me just exactly how a three-pole double throw transfer switch can connect the emergency power to the line rather than the load.

The ONLY thing this switch can do if the solenoid fails is to NOT actuate the switch from one position the other.

But I'm sure you have a reasonable explanation on how that can not be the case here.

Jeff-1.0

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus

I must say, you are an idiot!

How is the device itself any less dangerous than using an alternate to operate it?

Jamie

Reply to
Jamie

I see that only the ASCO 4000 and 7000 series are closed-transition switches, i.e. break before make, not the Series 940 -- which I had to look up from the replacement part number you gave.

My bad, I suppose.

Reply to
spamtrap1888

o

If the alternate does not operate sufficiently like the original.

If he could explain how the actuator works and what the important parameters were, we could speculate as to all the possible failure modes.

Reply to
spamtrap1888

You can speculate all you want. You sound like an attorney looking for work or closely related to one.

If you read the blog, you would see what he is using if for, and if he really wants you to know, I am sure he'll refresh your memory.

Jamie

Reply to
Jamie

I suppose. The solenoid coil listed is for the series 940. It is also used for several other series. Specifically, in my case, the Series 386 manual transfer switch.

And in case you missed it earlier, here is the link for an eBay auction showing picturs of the transfer switch contactor.

A similar model. 2-pole 120 VAC rather than 3-pole 480 VAC.

And if you go to the partsasco.com website and look up the replacement part numbers for the model 300 or 386, it directs you to the coil marked as being for the series 940.

This is the coil itself from ASCO.

But again, you're making all sorts of asumption looking to find fault. You've done nothing what so ever to answer the question on rewinding a solenoid to operate at 240 volts rather than 480.

Jeff-1.0

--
"Everything from Crackers to Coffins"
Reply to
Jeffrey Angus

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