Re: 110, 115, 117, 120 or 125 VAC ???
From: David Sharpe[SMTP:sccr4us-at-erols-dot-com]
Reply To: sccr4us-at-erols-dot-com
Sent: Friday, January 02, 1998 11:55 PM
To: Tesla List
Subject: Re: 110, 115, 117, 120 or 125 VAC ???
Tesla List wrote:
> From: Adam[SMTP:absmith-at-tiac-dot-net]
> Sent: Friday, January 02, 1998 7:23 PM
> To: tesla list
> Subject: 110, 115, 117, 120 or 125 VAC ???
> I am curious about mains voltage and equipment ratings. I have
> transformers, computers, and all kinds of appliances that can't seem to
> agree on what voltage they would like to be given. 110, 115, 117, 120
> and 125 seem to be the most popular values, but why so many subtle
> variations? Are these different standards for different parts of the
> country? My home's service clearly measures 120.0 VAC, but my newest
> variac is calibrated for 115V input. That's why I ask.
> Ditto for the 220, 225, 230, 240 VAC appliances.
The IEEE standard for residential power was 117 VAC / 234 VAC
+/- 10% (106-128 / 209-257). Since motor torque is a function
of voltage squared, if the load voltage is too low, motors will
not produce rated horsepower, will be effectively overloaded and
overheat and burn up. If the voltage is too high, incandescent
light bulbs will POP like popcorn, and motors will burn up from
excessive winding currents. At my residence, input voltage is
122 / 245V, since I have a 400A service, and a 34.5kV 3ph underground
feeder about 300' from my house (stiff low impedance source).
Voltage to house depends on many variables, including transformer
impedance, loading on service HV feeders, line losses from nearest
substation, transformer %Z, distribution transformer tap settings,
transfomer loading, etc. etc.
At least in the USA we are all 60Hz, thanks in part to N Tesla.
In Japan, half the country is 50Hz, the other half 60Hz, but their
distribution voltage is 100V!
DAVE SHARPE, TCBOR