| Author |
Any idea about the concept of Instantaneous RMS values of Currents/Voltages of AC supply
|
|
| R&D Enginers and Scientist 2005-08-19, 6:21 am |
| Does anyone help me in understanding the practical idea about concept
of Instantaneous RMS values of Currents/Voltages of AC supply under
both balanced and unbalanced cases.
Thanking you in advance
| |
| Polymath 2005-08-19, 5:21 pm |
| There isn't such a concept because the "M" in "RMS"
stands for "Mean" - an averaging over a full cycle.
Therefore it is meaningles to talk about instantaneous RMS
R&D Enginers and Scientist wrote:
> Does anyone help me in understanding the practical idea about concept
> of Instantaneous RMS values of Currents/Voltages of AC supply under
> both balanced and unbalanced cases.
>
> Thanking you in advance
| |
| TimPerry 2005-08-22, 11:21 pm |
|
"Polymath" <aiyr.r.bean@lycos.co.uk> wrote in message
news:1124481789.407648.194330@g44g2000cwa.googlegroups.com...
> There isn't such a concept because the "M" in "RMS"
> stands for "Mean" - an averaging over a full cycle.
>
> Therefore it is meaningles to talk about instantaneous RMS
>
given varying or fluctuating voltage or current it will have instantaneous
values.
a practical example would be the supply current to tower mounted aircraft
beacons. the AC to the top beacon is interrupted by a "flasher" yet the side
lights remain constant. the current switches from high to low a certain
number of time per minute.
in addition the load varies slightly as the lamp filaments heat up and cool
down
the primary practical interest in this case will be the peak current for
proper sizing of wires and fuses.
> R&D Enginers and Scientist wrote:
>
| |
| TokaMundo 2005-08-22, 11:21 pm |
| On Mon, 22 Aug 2005 21:37:03 -0400, "TimPerry"
<timperry@noaspamadelphia.net> Gave us:
>
>"Polymath" <aiyr.r.bean@lycos.co.uk> wrote in message
>news:1124481789.407648.194330@g44g2000cwa.googlegroups.com...
>
>given varying or fluctuating voltage or current it will have instantaneous
>values.
But they are NOT referred to as "instantaneous RMS values". They
are merely instantaneous readings.
| |
| TimPerry 2005-08-24, 1:21 am |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:a01lg11uegbo2crhcom88cetdd3q3ffcv4@4ax.com...
> On Mon, 22 Aug 2005 21:37:03 -0400, "TimPerry"
> <timperry@noaspamadelphia.net> Gave us:
>
instantaneous[color=darkred]
>
> But they are NOT referred to as "instantaneous RMS values". They
> are merely instantaneous readings.
| |
| TimPerry 2005-08-24, 1:21 am |
|
"TokaMundo" <TokaMundo@weedizgood.org> wrote in message
news:a01lg11uegbo2crhcom88cetdd3q3ffcv4@4ax.com...
> On Mon, 22 Aug 2005 21:37:03 -0400, "TimPerry"
> <timperry@noaspamadelphia.net> Gave us:
>
instantaneous[color=darkred]
>
> But they are NOT referred to as "instantaneous RMS values". They
> are merely instantaneous readings.
this may be a minor quibble but as long as one properly defines the working
parameters so that another engineer or tecno understands what you mean it
might be very useful to "talk about instantaneous RMS values"
another example might be speaker power. a non-sinusoidal non-repetitive
waveform, whose power, voltage, and currents are measured in RMS values is
presented to a resistive + reactive load.
adding the designation "instantaneous" to peak power or peak voltage gives
it a precise meaning to wit: one defined point in time. (first time i've
used "to wit" in a sentence i think. just finished re-reading some sherlock
holmes stories)
| |
| TokaMundo 2005-08-24, 7:21 am |
| On Wed, 24 Aug 2005 00:12:48 -0400, "TimPerry"
<timperry@noaspamadelphia.net> Gave us:
>
>this may be a minor quibble but as long as one properly defines the working
>parameters so that another engineer or tecno understands what you mean it
>might be very useful to "talk about instantaneous RMS values"
No. It MIGHT be useful to call them instantaneous value readings
taken to determine an RMS value.
|
|
|
|