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Thread: 3 phase plugs
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9th December 2010, 08:17 AM #31GOLD MEMBER
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your 32v to 24v problem???
its just occured to to me that I service a chiller which has a time delay relay which uses a small synchronous 120v motor on a 240v supply. It has a resistor in series with it which reduces the voltage
and also you could get a 32V - 24V tranny built if expense is not a problem...any transformer manufacturer could do it.
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9th December 2010, 09:59 AM #32
The resistor could work if the load is fairly constant. It will most likely need to me a high wattage resistor though.
Cheers.
Vernon.
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9th December 2010, 10:21 AM #33
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9th December 2010, 10:38 AM #34
Sorry Chris, but Stuart is correct about his "appliance" not needing to meet any defined standards. If he was to manufacture and sell said "appliance", then that's a different story.
However, he could still be liable for any damages/injuries/deaths cause by the "appliance" so it's always wise to put safety first.Cheers.
Vernon.
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9th December 2010, 11:10 AM #35GOLD MEMBER
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eskimo, Vernonv I used to work for a transformer company. I should have grabbed a winding machine A series resistors will work as the load is only a tiny winding inside a clock. Its just I will have to measure the load and do the math. I was hoping someone would have been educated guess. My guess for the load will be something less than 10mA. I doubt the coil would breakdown at 32V anyway but the world might explode if it did, so I better be careful.
Chris
I believe you are wrong.
By your argument at car on a battery charger is part of the grid and has to meant code.
and the extension lead?
I have extension lead. Do I need to have it tested and tagged? No I don't. If someone buys that extension lead from me it's their responsibility to have it tested and tagged if needed.
and the Emergency Evacuation Lighting
Home many houses have Emergency Evacuation Lighting?
Show me the code at applies to my situation....... not a list of standards that most if not all have nothing to do with my situation.
No need for a warning yet. You haven't proven that a suitably qualified electrical engineer/contractor is required in my situation.
Stuart
p.s. Vernonv it appears I still type way to slow lolLast edited by Stustoys; 9th December 2010 at 11:16 AM. Reason: p.s.
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9th December 2010, 11:31 AM #36
I dare not guess at what sort of load the timer will be (do you have a manufacturer name and part number for it?), but for your estimate of 10mA gives the following.
To drop 32V to 24V for a 10mA load would require 800 Ohms. A 1/4 watt resistor will be fine.Cheers.
Vernon.
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9th December 2010, 12:29 PM #37GOLD MEMBER
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Thanks Vernonv
Its by Alstom CH48AC24V
I've just measured the one I have running now.
26V at 5mA
So something in the 1.6kohm range.
Now, should I rummage though my boxes of boards looking for one or go to jaycar for an 8pk for $0.46............ lol jaycar it is. While I am there I can get some bridges for my LED lights
Stuart
p.s. If someone starts in about impedance in AC circuits........................
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9th December 2010, 12:47 PM #38GOLD MEMBER
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9th December 2010, 02:25 PM #39
Hi Stuart,
Vernon has already answered your question, a dropping resistor is the easiest provided the load is constant.
If you had to do the same thing but with a variable load.
In that case a better solution is to use a transformer, BUT rather than getting a custom wound 32-24v transformer, you could use a standard 240v step down transformer that has multiple taps on the secondary and wire it as an auto-transformer.
Hook up your 32 volts across the outside windings of the secondary. Then use a multimeter to pick the tap closest to the voltage you want. I could draw a cct, but you probably already have the idea.
Don't forget to insulate the terminals on the primary side, because they will have high volts.
I think jaycar or dick smith would have something suitable. Look for a frame with adequate VA rating and lots of taps on the secondary.
Regards
Ray
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9th December 2010, 05:08 PM #40
Rays suggestion is certainly a good one and (as he points out) perfect for situations where the load changes.
One thing to be careful of is the voltage rating of the secondary - try and pick a transformer that has a secondary as close to 32 volts as possible. For example if you hook 32 volts across a 12 volt secondary you run the risk of over-saturating the transformer (will cause it to fry sooner or later) as well as causing the primary to produce around 640V.Cheers.
Vernon.
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9th December 2010, 06:17 PM #41GOLD MEMBER
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RayG Now that is a clever idea. I'd always thought of auto tranformers as a stupid idea... until now.
Vernonv Depending on the bobbin layout I should be able to dig the primary out without damaging the secondary.
Thanks guys
Stuart
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9th December 2010, 06:34 PM #42GOLD MEMBER
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9th December 2010, 08:47 PM #43
That's certainly not my experience with doing similar things to what is being suggested here. Also from what I remember reading/studying (and this is a bit sketchy as it was some time ago) over-saturation causes an increase in the current flow, increase in heat generated and can eventually burn it out, even when running very low loads.
Cheers.
Vernon.
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11th December 2010, 09:43 PM #44GOLD MEMBER
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Well I roughed out the control circuit for the shaper today. All worked fine, the hour meter is runnning at 25.9V but thats because the tran is putting out 33.9V. Now to neaten it up and hide it inside the machine base. I even kept the inch button as it was easier to keep than get rid of it.
Plugs and sockets should arrive next week.
Stuart