[time-nuts] Line Voltage - USA

[Tim Shoppa]

What modern loads are actually sensitive to high (say, +10 to +20%) line
voltage?

Old incandescent light bulbs were among the most sensitive loads in the
past (so much so, that 130V light bulbs were commonly available from the
industrial suppliers).

I would naively expect the modern CFL's and LED replacements to be fine
with higher line voltage because they have their own built-in switching
regulation.

A lot of modern electronic equipment with switching supplies, are just fine
at +20% line voltage and may even run cooler.

Tim N3QE

On Sun, Jan 1, 2017 at 11:49 PM, Bill Byrom <time at radio.sent.com> wrote:

> There are a couple of recent threads concerning the power line mains
> voltage standards. After a bit of research and thinking, I have found
> that this is a complex topic. The simple answer is:
>
>
> * The standard in the US for the past 50 years has been 120/240 V +/- 5%
>   RMS at the service entrance to the building. This is a range of
>   114/228 V to 126/252 V.
> * The load voltage could be as low as 110/220 V and as high as 125/250 V
>   and be within specifications.
>
>
> There are two voltage measurement points to consider:
>
> (1) Service voltage: This is the RMS voltage measured at the service
>     entrance to the building (at the metering point).
> (2) Utilization voltage: This is the RMS voltage measured at the load.
>     It might be measured at an unused socket in a power strip feeding
>     several pieces of electronic equipment, for example. There are of
>     course many different utilization voltages present in a home or
>     business, depending on where you make the measurement.
>
>
> Most US homes and small businesses are powered by what is commonly
> called a "split-phase" 240 V feed. The final distribution system
> transformer has a 240 V center-tapped secondary. The center tap is
> grounded, and three wires are fed to the building (actually it might be
> up to around 6 houses):
> (1) Leg L1 or phase A (red wire) -- This wire will measure 120 V to the
>     neutral or 240 V to Leg L2.
> (2) Neutral (white wire) -- This wire is grounded at the distribution
>     system and at the service entrance to the building.
> (3) Leg L2 phase B (black wire) -- This wire will measure 120 V to the
>     neutral or 240 V to Leg L1.
>
>
> Large appliances and HVAC systems are usually connected across L1-L2
> (240 V), while most sockets are on circuits either connected across L1-
> neutral (120 V) or L2-neutral (120 V).
>
>
> The voltages I have described are the current standardized values for
> the service voltage which have been in general use for about 50 years
> (120/240 V +/- 5%). I believe that the original systems installed before
> 1940 were designed for a 110/220 V nominal service voltage, but after a
> report in 1949 the nominal service voltage was increased to 117/234 V,
> as specified in ANSI C84.1-1954. After research in actual buildings, in
> the 1960's the nominal service voltage was increased again, to 120/240 V
> in the ANSI C84.1-1970 standard. The purpose is to keep the utilization
> voltage at the load above 110/220 V.
>
>
> The voltage at the service entrance should in most cases be in Range A
> (120/240V +/-5%). On each 120V leg the service voltage should therefore
> be between 114 and 126 V. The utilization voltage at the load should be
> between 110 and 125 V due to losses in building wiring.
>
>
> See details of the current specifications at:
>
> http://www.pge.com/includes/docs/pdfs/mybusiness/
> customerservice/energystatus/powerquality/voltage_tolerance.pdf
>
>
> These voltage specifications were designed for resistive loads and
> measurement of the true RMS voltage. In most electronic equipment built
> over the past 50 years, the power supply input circuitry is basically a
> rectifier connected to a smoothing capacitor. This leads to high input
> current surges during the peaks of the waveform, so that the peak
> voltage is reduced much more by the building wiring resistance than if
> the load was resistive for the same power consumption.
>
>
> So the waveform shape at different utilization locations in a building
> (with active equipment loads) may be different, so the voltage measured
> by different AC measuring instruments can differ. Many meters are full
> wave average measuring but calibrated so they only read RMS voltage
> correctly on pure sinewaves. Other meters are true RMS measuring and
> will read very close the correct RMS voltage even if the waveform is
> distorted.
> --
>
> Bill Byrom N5BB
>
>
>
>
>
> On Sun, Jan 1, 2017, at 12:16 PM, CIW308 VE6OH wrote:
>
> > Mark,
>
> >
>
> > CSA have standards for over and under voltage, Typical no more that 3%
> > over and 5% under if memory serves me.
>
> >
>
> > This might help (
>
> > http://www.safetyauthority.ca/sites/default/files/csa-
> fia3660-voltagedropcalc.pdf
> > )
>
> > The power companies here in Alberta are generally good about fixing
>
> > problems with line regulation.
>
> > There can be problems with industrial areas and big welders or motors
> > staring as I am sure you know.
>
> > I am sure they do not want the bill for replacing equipment that was
>
> > subjected to over voltage.
>
> >
>
> > On UPSs: I am sure you are aware that may of them are not TRUE
> > sine wave
> > so the DMM may not read correctly.
>
> >
>
> > Mitch
>
>
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