Re-winding solenoids.

Beware that some coils are dual coils with diodes potted in them.

WHen a diode fails in one of these, they tend to generate some noise when energized. This is because one coil is pushing both directions against the other that isn't.

Basically what this means is, the coil is designed to operate in a DC state.

What we have done in the past if we suspected a shorted diode in one of these types is to put a bridge rectifier in front of it.

But I can tell you this, if the construction of core around this coil in the device that is using it has a laminated type layers, chances are, you have a simple coil and there is some form of shading device near the contact point where the accouter makes contact with it.

What is this thing? A ratcheting three position device? being ASCO, it sounds like some kind of valve.

Jamie

Make, model, and photograph?

Is there a copper D-ring on the top end of the solenoid?

If the coil it dead, try disolving the epoxy.

It will also make a useful coil form.

If you know the core dimensions and the wire guage, you can estimate the number of turns.

Check eBay?

--
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

This is a simple multi-layer solenoid. It is fed with 480 VAC via an external bridge rectifier.

It is a pull up actuated 100 amp 3-pole contactor.

It is physically identical to this one, with the excption of being 3-poles rather than 2.

The solenoid is at the top left of the contactor with the bridge rectifier on the side.

Jeff-1.0

--
"Everything from Crackers to Coffins"

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

This is the coil itself from ASCO.

Nope.

Coil works perfectly with 480 VAC applied to the bridge recitfier. My task is to wind a new coil that will work at 240 VAC.

I did that, see the initial posting. Using DC resistance, physical size and measured inductance.

They have the contactors available from $750 and up, and complete units for $1500 and up.

No solenoids only.

Jeff-1.0

--
"Everything from Crackers to Coffins"

do you see the part number on this list? Seems considerably cheaper:

Tell him something he DOESN'T already know.

--
You can't have a sense of humor, if you have no sense.

Why don't you use a simple step up transformer for the coil? you won't need a large one.

JAmie

To add to that, a 1:1 control transformer of a very small size can be wired as a buck boost to operate that coil.

Jamie

Um, however briefly, the transformer needs to supply

5.2 amps at 480 volts to successfully energize the coil.

That's 2500 VA Even a 500 VA control transformer that I have sags too much to properly actuate the transfer switch.

Jeff-1.0

--
"Everything from Crackers to Coffins"

As I mentioned previously, the solenoid requires a 5.2 amp pulse to properly actuate the contactor mechanism.

With a 240/240 control transformer wired up in boost mode that would need at 1000 VA transformer as a bare minimum.

Jeff-1.0

--
"Everything from Crackers to Coffins"

Heh, thanks Michael. What I don't know and would like to know is if my thinking with regards to ampere turns is correct. Because I CAN wind a new solenoid coil with a

1/2 pound spool of wire for about $20.

Jeff-1.0

--
"Everything from Crackers to Coffins"

I find it hard to believe that coil is using that much? Are you sure it's in proper working order? We have 500 amp contactors with

120V coils that only require about 2 amps to pull in. Something just does not sound right, but what ever.

Jamie

Yes I am sure. And yes I know what some contactors take to actuate the coils in a steady state holding condition.

To repeat. This is a pulsed operation. The auxiliary contacts on the transfer switch contactor interrupt the source from the solenoid as it actuates.

The solenoid core pulls up on a link that rotates the armature of the contactor assembly from normal to emergency position. Each time it is pulsed, it rotates it one way, then the other way.

The actual amount of time (I haven't measured it) this takes is under a second roughly.

Jeff-1.0

--
"Everything from Crackers to Coffins"

Do you have good reason to believe that AWG 30 is the proper gauge, and that your calculations are correct? If so, then buy the wire and do it. If it doesn't work, you're out only $20 and the time it took to wind the coil.

I don't know enough about solenoids to properly judge your calculations. But I don't see anything obviously wrong.

Then it must be pushing a large load a long distance.

at that current, you looks like you have ~ 100 ohm coil.

which means the wire in the coil is rather a large gauge since this is DC going to it.

I would start around 20awg and see what the DCR 1M is on the chart. Then see if that will physically fit on the form.

Jamie.

Did you read the details from my original posting? (Se below)

roughly 100 ohms, yes.

This is NOT a constant pull and hold solenoid. This is a pulsed operation.

Based on: Ampere turns = (Applied voltage * number of turns)/(coil resistance)

Both estimations of the needed number of turns and wire size seem correct.

This tends to indicate that ampere turns is indeed the magic number as 6000 is not enough to actuate a mechanism that appears to require 12,000.

Jeff-1.0

--
"Everything from Crackers to Coffins"

Yields both the correct inductance and DC resistance with #30 AWG for the assumptions I've made for the physical size of the coil bobbin.

And that's why I thought I'd ask here. I was hoping to find someone that _is_ familiar enough to at least tell me, "Yeah, you seem to be heading in the right direction."

Jeff-1.0

--
"Everything from Crackers to Coffins"

You didn't say this solenoid was part of a transfer switch. This raises the stakes substantially. Transfer switches are used to switch the mains supply to a generator when mains power is interrupted. They serve two main purposes: to keep critical equipment functioning when mains power is interrupted, and to deenergize the power line so that workers can assume it is deenergized when they work on it.

Now, the transfer switch was tested to meet specifications with the designed solenoid installed. Knowing nothing of the design or construction of the component, you propose to roll your own and stick it in.

Which would be fine, if no one's life depended on its working. And if the vendor would stand behind your handicraft.

I don't think Asco could reasonably foresee that someone would use a program that gives the number of turns for an air-core inductor to design a part for a life-safety application.

You left that out of your initial rant. First sentence should be what the [deleted expletive] you're trying to accomplish.

What you want is an equal amount of magnetic force (i.e. gilberts) or ampere-turns for both the 480VAC and 240VAC coils.

480VAC coil = 125mH and 95 ohms XL = 2*Pi*60*125*10^-3 = 47 ohm Total impedance is the vector sum of 95 ohms and 47 ohms = Z = sqrt(95^2 + 47^2) = 105 ohms Current is: I = 480VAC / 105 ohms = 4.5A 2500 turns * 4.5A = 11,250 AT Ok, you got that part correct.

Trying a different gauge for 240VAC. The hard part will be keeping the max diameter to under 1.5" OD.

For #29awg, 75mH, 1990 turns, 51 ohms resistance. XL = 2*Pi*60*75*10^-3 = 28 ohm Z = sqrt(51^2 + 28^2) = 63 ohms I = 240VAC / 63 ohms = 3.8A 1990 turns * 3.8A = 7580 AT

For #28awg, 60mH, 1759 turns, 37 ohms resistance. XL = 2*Pi*60*60*10^-3 = 22.5 ohm Z = sqrt(51^2 + 37^2) = 63 ohms I = 240VAC / 63 ohms = 3.8A 1759 turns * 3.8A = 6700 AT

Ok, that's not going to work. Most of the impedance is coming from the DC resistance of the wire. Decreasing the gauge decreases this resistance, but also decreases the number of turns that will fit on a the spool to a maximum OD of 1.5". This isn't working. I give up for tonite.

--
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