Triacs and Optocouplers

[Ken Benedict]

+1

[plasmadrive]

And going back to RMS, and the importance of terminology, even on positive only waveforms, there is usually a difference between RMS and average value.

 

Take a sawtooth waveform, 220V at peak, declining to zero, and immediately repeating.  This has an average voltage of 110V.  But it has an RMS voltage of 126 V RMS

 

If I place this across a 126 ohm resistor, do I get 1A of current, or do I get 0.873 A?   Am I dissipating 126 W, or 96.03W?    Or are you doing more adjustments to finally get back to 126W, or do you think it is  some other level of power dissipated?

klb, 

I believe that in this case given your values for RMS and AVG,  Pavg = Vrms x Irms  If I got that correct, then in this case, 126W is the AVG power.   You get 1 amp of RMS current....

 

But, to be honest about this, I don't remember for sure... been a very long time since I had to do any of these calcs. 

 

You have hit my ceiling for brain power... We now return you to your regularly scheduled program.

 

[-klb-]

But I thought in response to me talking about RMS of rectified sine waves a few days ago that you said that using RMS for dc waveforms was incorrect, and that only average applied for DC waveforms?

[plasmadrive]

But I thought in response to me talking about RMS of rectified sine waves a few days ago that you said that using RMS for dc waveforms was incorrect, and that only average applied for DC waveforms?

You mean this?  "The RMS value is useful only for AC as the avg value of and AC sign wave is 0.  The RMS value does give you the usable power equal to the Avg of the pulsating DC.  That I agree on.  But Avg is used for DC and RMS for AC.  Terminology counts".