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Old 9th December 2009, 10:11 AM   #1
tubo is offline tubo  Philippines
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Default mains overvoltage what to do?

hi,

my mains voltage is up to about 125vac and my power trannys primary is only rated at 115vac and that causes my B+ supply to be higher.

i did put a 10ohm 10watt resistor on each Hot and Neutral and it lowered the voltage down to 116vac.

1. is this the right way of lowering down the mains voltage?
2. will it cause problems?
3. will a bucking transformer be better?if so what?

thanks

ivan
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Old 9th December 2009, 10:14 AM   #2
AndrewT is offline AndrewT  Scotland
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your 115Vac transformer should be designed to work with the normal range of mains voltages.

Your B+ is the problem. Sort after the transformer.

Check your voltmeter accuracy and if your mains is always high, ask the supplier to investigate.
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Old 9th December 2009, 01:41 PM   #3
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ANSI C84.1 limits the long-term voltage at your panel to +/-5% (114-126). So technically there is nothing wrong with your voltage, but 125V over a period of days is a tad hot, IMO. Incandescent lighting has a shortened life this high.

It is my experience that the utility is able to both hold regulation better than +/-5%, and can adjust taps so your nominal is closer to 118V. You may consider making a phone call; it costs you nothing, and the utility is required by the PSC to at least investigate.

I did this very thing a week ago, but my voltage was ranging between 113-116V at the panel, with harmonic distortion in excess of 5%. Some of my equipment was running near 108V after my isolation transformer. They are planning on correcting this.
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Old 9th December 2009, 02:29 PM   #4
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What is the topology of your PS filtering? CLC, CRC, etc......
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Old 11th December 2009, 12:20 AM   #5
jjman is offline jjman  United States
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OP is listed as in the Philippines. I don't know the exact voltage range they consider acceptable nor if making any calls to the authorities would be fruitful. I've heard of varying degrees of success with such phone calls in the USA. I'm at 123 and have read 127 at times here in NJ.
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Old 11th December 2009, 08:53 AM   #6
Ian444 is offline Ian444  Australia
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Makes one wonder if a SMPS delivering B+ regulated might become welcome in the valve amp world?
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Old 11th December 2009, 10:45 AM   #7
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Quote:
Originally Posted by Ian444 View Post
Makes one wonder if a SMPS delivering B+ regulated might become welcome in the valve amp world?
Ay, this is my philosophy. Switch mode doesn't come without a brain storming tag plus EMC. The performance is excellent but to keep the whole darned thing to size in a chassis is the main challenge. The best tackle is to use SMD to reduce space but I don't like working submin with strong glasses.

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Old 11th December 2009, 10:49 AM   #8
AJT is offline AJT  Philippines
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Quote:
Originally Posted by tubo View Post
hi,

my mains voltage is up to about 125vac and my power trannys primary is only rated at 115vac and that causes my B+ supply to be higher.

i did put a 10ohm 10watt resistor on each Hot and Neutral and it lowered the voltage down to 116vac.

1. is this the right way of lowering down the mains voltage?
2. will it cause problems?
3. will a bucking transformer be better?if so what?

thanks

ivan
hi,
you can always file a complaint with Meralco,or your service providser, they are under obligation to correct the line voltage.....are you in the Clark, Pampanga area? afaik, that is the last remaining place where such service is maintained due to previous presence of american military bases in that area...
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