How do you determine Peak current in Sine Wave 1

[drax]

I always heard that you multiply 2.2 by the RMS value but how is this derived?

thanks,
mark

 

[drax]

I meant to say how do you determine peak to peak, I've been told to mult rms by 2.3. where does 2.3 come from?

thanks,
Drax

 

[scottf]

RMS means root mean squared, i.e. you multiply the RMS value by the square-root of 2, which is 1.41.

 

[Lewish]

If you mean, by "peak to peak" the maximum instantaneous current at two peaks in a single cycle sinewave, then it is 2 times the square root of 2. Or in otherwords, 2.8284.

 

[Lewish]

Ooops, I didn't get the second sentence finished. It should say -

Or in otherwords, 2.8284 times the RMS current value.

 

[drax]

Thanks for all of your help. An engineer at work finally explained the 2.3 multiplier. He showed me a graph using a 8.8 X/R ratio that translates to the 2.3 number instead of the 2.82 number.

thanks again

 

[1x1x1x]

Drax,

Like the others said in normal condition the peak of the sinusoidal current is equal the rms current * sqrt (2).
The peak sinusoidal current only depends on the X/R ratio when short circuit happens. During short circuit the first few cycle will have a DC component, which will add to the sinusoidal current. This current is called asymmetrical short circuit current. The peak and the duration of the asymmetry depend on the X/R (Inductive reactance /Resistance) ratio of the AC circuit.

 

[drax]

thanks 1x1x1x for explaining that, even though he showed me a chart, I still didn't understand until your email. I'm a mechanical engineer trying to learn the electrical side.
thanks a million,

Drax