# Any idea about the concept of Instantaneous RMS values of Currents/Voltages of AC supply

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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.
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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.
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On 8/19/05 1:17 AM, in article snipped-for-privacy@g44g2000cwa.googlegroups.com, "R&D Eng> Does anyone help me in understanding the practical idea about concept
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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 Eng> Does anyone help me in understanding the practical idea about concept
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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.
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On Mon, 22 Aug 2005 21:37:03 -0400, "TimPerry" Gave us:
But they are NOT referred to as "instantaneous RMS values". They are merely instantaneous readings.
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instantaneous
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instantaneous
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)
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On Wed, 24 Aug 2005 00:12:48 -0400, "TimPerry" Gave us:
No. It MIGHT be useful to call them instantaneous value readings taken to determine an RMS value.

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