According to Mark Lloyd :
I was wondering why the SPECIFIC value of 117V was mentioned in an
earlier post.
That's what I was answering.
I seem to recall somewhere seeing that 117V is the exact calculated
RMS value from some specific regulatory "peak" _nominal_ voltage.
In college I was taught that peak voltage = 1.414 * RMS voltage. In
that case, 117V RMS would equal 165V peak. The post I responded
mentioned "110 to 120", supposedly referring to the permitted range of
supply voltages. This differs from 165V.
You're getting confused. 110 to 120 (or more actually like 130)
is the permitted _RMS_ supply voltage range. The sinusoidal peak is
indeed in the 165V range.
The point being that because of resistive losses and power station
management, it is _allowed_ (by code and power regulations) to vary
a fair bit. This means in practise there's a considerable variation
in the voltage present on a given outlet, moreso when you figure that
many voltmeters aren't very accurate on AC RMS voltages either.
BTW, The voltage numbers I remember hearing about are 110V, 115V,
117V, 118V, 120V, 120V and 220V, 230V, 235V, 240, 250V.
For some unknown reason, 250V got neglected when I made that list so I
fixed the omission.
Okay....
Think about them as being dialects of "power speak", all meaning the
same thing in the end.
One of the reasons for that is pragmatic - Eg: motor HP and current draw
are often specified at the lower end of the permitted range, because
that's worst-case for heat generation/ultimate limits on the device.
If the permitted range is still 110V to 130V, the lower end is not
117V.
I wasn't saying that 117V was the lower range. I was actually referring
to the practise of many motors having a _plate_ rating of thus-and-so
Amps at 110V.
Since the text from , that I responded to got
snipped, here it is below. I was wondering where the specific number
of 117 came from:
IIRC, if you calculate the actual rms voltage, a "110" or "120" volt
line is actually 117v. Of course this is nominal, since it excludes
noise and IR drops.
You answered that yourself.
--
Chris Lewis,
Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.