Re: [CAD_CAM_EDM_DRO] Re: What is Rms?

turbulatordude wrote:

>I was under the impression that RMS only applied to sine wave type
>power (or half wave) but not to square wave. After all, isn't duty
>cycle used to calculate current ?
>
>
>

No, RMS can apply to any waveform. Ordinary voltmeters are corrected
for sine waves, only, and will give incorrect AC readings on anything other
than a sine wave. Duty cycle can be used simply to calculate the average
voltage or current. But, if a square wave voltage is applied to a resistive
device, the power delivered will not match the duty cycle * voltage. That
is because power is volts X amps. When the voltage goes up, the current
ALSO goes up, by the same factor. Therefore, a change in voltage causes
a change in power equal to the SQUARE of the change in voltage. This is the
whole key to the thing.

So, if you were to apply 120 V DC to a 120 Ohm resistor, it would draw
one amp, and dissipate 120 Watts. If you applied 240 V 50% of the time,
it would draw 2 A, and dissipate 480 W during the on time, and of course
zero during the off time. The average power dissipation would be 240 W
(480 / 2). So, although the average VOLTAGE is the same 240/2 = 120,
the average POWER is twice as large, in this example.

Jon