Mains voltage - what do you do when it's too high?

[Family Hoof]

Air conditioner season is at it's peak in NYC and the mains voltage in my apartment is is running way too high. Just now I measured 160V RMS on all of the outlets! Previous measurements had never gone past 124 (supposed to be 120, of course). A piece of gear that runs on a simple IC regulator supply like the kind we often build here was refusing to drop all this extra votlage and I'm afraid to run anything that isn't on one of those universal switchers.

How do you cope with mains voltage getting so high? How do you design a power supply that is up to the task? I was thinking put a 130V thermistor across the mains inlet but this doesn't seem safe somehow.

 

[NewYorkDave]

Get a variac--you can pick one up at Leeds in Brooklyn. They have a 3.8-amp model listed on this page for $25. Just make sure that whatever you buy, it's rated for 60Hz operation. There are some 400Hz variacs (intended for use on aircraft) floating around on the surplus market, if you'll excuse the pun.

 

[gyraf]

And make sure that it's not your voltmeter that's in need of new batteries.. Been there, tried that.. :razz:

Jakob E.

 

[idylldon]

Here's a simple solution:

http://www.geofex.com/Article_Folders/vintvolt/vintvolt.htm

Cheers,
--
Don

 

[bcarso]

160V!!! That is insane! More than just audio equipment would be disturbed by that.

They used to crank up the voltages in Chicago during CES anticipating the big loads. A startup called Frox was getting some powered speakers from JayBL that were hastily designed and constructed using automotive amps inside. Unfortunately the amp chips shut down at 18.0V dc in, and the line voltage ahead of the transformers got high enough to cause this to be exceeded. Nothing worked for the first couple of days until somebody figured out what was going on and trucked in a bunch of variacs.

Much loss of face.

 

[Svart]

what to do when mains voltage is too high.. have it sit down in a cool, darkened room, eat doritos and watch The Wall until it's a bit more under control


:green:

 

[CJ]

put a big capacitor in sereis.
reactive resistor=no heat :razz:

 

[Family Hoof]

I mean't to say varistor, not thermistor. Whoops!

Svart, that is an excellent suggestion. It did go back down to 124V sometime this afternoon. Apparently Con Edison, the local electric company, was hit yesterday with the biggest demand they've ever experienced and started overcompensating last night.


I know abouts variacs, but what would you all recommend in terms of "automatic" mains voltage limiting for a linear supply which might be subjected to these conditions on a regular basis?

Thanks!

 

[NewYorkDave]

There are "constant voltage" transformers (noisy, expensive) and automatic AC voltage regulators that use multitap transformers and fast relay switching (also noisy and expensive). Honestly, a variac with a dedicated meter is your best option unless you have a large budget and a lot of space.

 

[bradb]

woah, never thought about investigating this... yesterday we set a consumption record beating some day in 2001 (if i remember correctly)

 

[Family Hoof]

Dave,

A variac requires a person to operate it. I'm talking about something you would install permanently inside the chassis as part of the design.

 

[Family Hoof]

[quote author="bradb"]woah, never thought about investigating this... yesterday we set a consumption record beating some day in 2001 (if i remember correctly)[/quote]
Yeah, that's exactly what caused this problem I'm talking about.

 

[CJ]

Call Emron. :grin:

 

[NewYorkDave]

Dude, the point I'm trying to make is that trying to regulate the line voltage automatically inside of the unit is not feasible. There is no easy, small, inexpensive way to regulate AC (and you don't even want to bother with cheap means of "regulation" that involve lopping off the tops/bottoms or otherwise chop up the waveform--unless you want your **** to be really noisy). You're better off redesigning the PSU (at the secondary side) to be insensitive to higher-than-usual input voltages.

 

[Family Hoof]

Gotcha! :thumb: :sam:

Back to the books...

 

[cayocosta]

http://www.tripplite.com/products/product.cfm?productID=2832

 

[Butterylicious]

160 VAC wall voltage is way too high. A. make sure your meter is callibrated, B. Call the utility company.

Residential grade electrical equipment is rate for 250V, and code there's that word again says 150 volts to ground MAX in dwellings. Nope, you can't have 480 or delta in a house. But seriously, if you truly do have 160V, it needs to be reported and fixed.

 

[Svart]

not much you are going to be able to do. what you are talking about involves an active ingredient.. you'll have to resort to switching powersupply and inverter techniques to get what you want.. I agree with NYD that what you need to do is design your PSUs to handle the extra voltage on both sides, such as making sure the VA is high enough(which it should be much higher than needed to have a quieter PSU..) and regulation parts that will take the extra secondary voltage. You might try high power TVS devices before the regulators..

 

[NewYorkDave]

Just wondering, you measured between hot and neutral, right? Measure also between neutral and ground while you're at it. Make sure there's no sizable offset there. And of course, as everybody else mentioned, make sure your meter is accurate.

 

[Family Hoof]

[quote author="NewYorkDave"]Just wondering, you measured between hot and neutral, right? Measure also between neutral and ground while you're at it. Make sure there's no sizable offset there. And of course, as everybody else mentioned, make sure your meter is accurate.[/quote]
Offset was only a few volts. I used two different meters. That 150 - 160 business was real, but didn't last long. It's cruising at 124 now.