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Author Topic: Taming my Shack Voltage From 252Vrms to 240Vrms  (Read 22664 times)
W1BR
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Posts: 4177




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« Reply #15 on: May 15, 2014, 07:43:27 PM »

Someone beat me to it. If your amp is seeing 252 volts, then each side of your breaker box is probably at 125 volts. I'd be incandescent lamps aren't lasting too long Smiley  Call the power company--then can adjust the taps on the pole pig feeding your home... I'd bet your immediate neighbors are having the same issue.

Pete
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N1UK
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Posts: 2219




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« Reply #16 on: May 15, 2014, 08:47:12 PM »

I just have a big 400 amp PCP filled transformer...I don't think it has any taps on it but I could ask

Quote
I'd be incandescent lamps aren't lasting too long

Yes 125 volts on each phase..I just thought 115V light bulbs weren't very good. The ones I had in the UK lasted so much longer then here..lol



Mark N1UK
« Last Edit: May 15, 2014, 09:00:24 PM by N1UK » Logged
K7KBN
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Posts: 3674




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« Reply #17 on: May 15, 2014, 09:34:52 PM »

I just have a big 400 amp PCP filled transformer...I don't think it has any taps on it but I could ask

Quote
I'd be incandescent lamps aren't lasting too long

Yes 125 volts on each phase..I just thought 115V light bulbs weren't very good. The ones I had in the UK lasted so much longer then here..lol



Mark N1UK

PCPs are okay.  Those PCBs, however, are problematic.
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73
Pat K7KBN
CWO4 USNR Ret.
N1UK
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« Reply #18 on: May 16, 2014, 06:57:01 AM »

I meant PCB's. The transformer is from 1974 -1976 but it isn't leaking or burning..so all is good so far


Mark N1UK
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WA2JHS
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Posts: 111




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« Reply #19 on: May 17, 2014, 03:37:14 AM »

Had the same problem here and my vintage collins kws-1 was not happy...I contacted the power company...they said it was normal.. used 2 12 volt 6 amp transformers and wired them to buck both legs of the 250 volt ac...now I have 228 volts and very happy rigs...not hard to do.
Bill
Wa2jhs
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W3RSW
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Posts: 606




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« Reply #20 on: May 17, 2014, 04:38:53 AM »

I used 10 volt 20 amp filament transformer, 220 primary for bucking, wired a couple of outlets in a NEMA box for outlets to run all my older gear including 75a2a from a multi-outlet power strip from one leg.  Other leg goes to 32-V2.

Since I hardly ever use them, they double thank me daily.  Grin
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Rick, W3RSW
N1UK
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Posts: 2219




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« Reply #21 on: May 17, 2014, 07:35:42 AM »

Quote
Had the same problem here and my vintage collins kws-1 was not happy...I contacted the power company...they said it was normal.

How high was your supply voltage?

I will measure the neighbours voltage today or tomorrow. They are on their own (much newer) transformer. So it will be interesting to see the difference.


Mark N1UK
« Last Edit: May 17, 2014, 08:00:05 AM by N1UK » Logged
DL8OV
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Posts: 1051




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« Reply #22 on: May 17, 2014, 12:46:57 PM »

You might be seeing 252V with the amplifier on idle but what supply voltage do you see at your amplifier when transmitting at full power. The mains supply may sag under load.

Peter DL8OV
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N1UK
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Posts: 2219




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« Reply #23 on: May 17, 2014, 01:02:09 PM »

Quote
You might be seeing 252V with the amplifier on idle but what supply voltage do you see at your amplifier when transmitting at full power.

Good point Peter, I will have to check that and but I have a pretty "stiff" supply setup with a 30amp 240V amplifier power spur circuit just to my shack and a 400 amp 240V drop to my whole house. Everything else in the shack runs on a 30 amp 120V spur circuit.

So far I have only measured the supply voltage with the amp lightly loaded on the kitchen table and running on a thin UK 13 amp extension cable This cable runs from my shack to the kitchen table...probably about 30 feet (10m) or so.

There are not that many 240V outlets in an American home..I have more than most I think.


Mark N1UK
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WA2ISE
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Posts: 1280




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« Reply #24 on: May 17, 2014, 01:15:58 PM »

About 20 years ago I found that I had 132V on each leg of my powerline, or 264V total.  Called the power company (Pubic Service Electric and Gas) and they checked the voltage, and checking for bad neutrals (a bad neutral can make one side too hot, but not both at the same time).  It took them some time at the substation to change some caps, they called us (we had the same DVM they used, and they knew we knew how to measure), no change.  Turns out the town had a severe imbalance of the loading of the three phase distribution system, once they fixed that the voltage is now normal.  

As for 240V outlets, I have several of these old style 3 pin outlets in the house, here fed with 240V@15A.  Turns out these are the same size and shape as Australian powerpoints, and I have a couple of antique Aussie tube radios plugged into them, and they are perfectly happy with 60Hz, and as their radios used power transformers, both lines being hot with 120V doesn't matter to them.
« Last Edit: May 17, 2014, 01:19:59 PM by WA2ISE » Logged
K2OWK
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Posts: 1279




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« Reply #25 on: May 17, 2014, 03:43:25 PM »

I do not know if they are still made, but the company I worked for many years ago used a device called a regulating transformer made by Solar. It was used for exactly what you want. Selecting the required voltage to regulate the line. They came in various VA values. The higher ones were quite expensive. I would guess you could get them on EBay or at a ham fest.

Hope this helps.

73s

K2OWK
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KD8MJR
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Posts: 5530




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« Reply #26 on: May 17, 2014, 05:13:56 PM »

Your power company is feeding you a BS story.
Write them an email telling them that items in your house are running hot and your afraid a fire may break out. That will get their attention from a liability standpoint and I suspect they will fix the problem ASAP.
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“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
N1UK
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Posts: 2219




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« Reply #27 on: May 17, 2014, 06:21:35 PM »

Thank you for the picture of the radio..a lovely appliance. The Australian plugs are interesting.

I have some of these in my shack..

http://www.ebay.com/itm/SELECTRIC-2-GANG-SWITCHED-13-AMP-SOCKET-METAL-CLAD-WITH-BACKBOX-LG9098MB-/271056508667

http://www.meteorelectrical.com/switches-and-sockets_metalclad-range_13amp-2-gang-metalclad-switched-socket.html

Mark N1UK
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W1BR
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Posts: 4177




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« Reply #28 on: May 21, 2014, 06:32:48 AM »

You might be seeing 252V with the amplifier on idle but what supply voltage do you see at your amplifier when transmitting at full power. The mains supply may sag under load.

Peter DL8OV

I'd rather see the AC line voltage fairly stable. The only reason amps work better on 220 volts is generally because the I squared R losses between the breaker panel and AC outlet are much lower at the 220 volts vs. 110. Running higher than normal AC voltage to compensate for voltage sag in the house wiring is piss poor engineering.

Pete
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KH6AQ
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Posts: 7761




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« Reply #29 on: May 22, 2014, 07:45:14 AM »

The voltage drop between the breaker panel and the amp is exactly halved at 240 vs. 120 VAC, assuming the instantaneous load current exactly halves (the load is purely resistive). And because the working voltage is doubled, the voltage drop - as a fraction of the working voltage - is 1/4 of what it was. If the voltage drop was 10% at 120 VAC it's 2.5% at 240 VAC. So, the AC wiring contribution to HV sag under load is reduced by 4X.

How about the HV transformer? When running 120 VAC the two transformer primary windings are connected in parallel and when running 240 VAC the two primary windings are connected in series, thereby increasing the transformer primary resistance by 4X. The current is halved at 240 VAC and so the transformer primary voltage drop is 2X. But because the transformer ratio is halved there is no change in the transformer primary resistance contribution to HV sag under load. Nothing has changed on the HV winding and so its contribution to sag has not changed. So, the HV transformer does not enter into the HV sag equation when changing from 120 to 240 VAC.

This is a first-order analysis as there's more to it. There's the effect of the rectifier capacitor input filter, transformer magnetizing current (this drops out of the equation and does not contribute) and the transformer leakage inductance (I think this drops out too).
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