Mr. Luddite wrote:
On 10/12/2018 11:02 AM, Wayne.B wrote:
On Fri, 12 Oct 2018 08:23:18 -0400, Keyser Soze
wrote:

I happen to have that info handy because I looked it up last week when I
had to replace a dead microwave oven. Here's how it is figured:

A 1200 watt output microwave takes 10. The typical formula for this is..
P = VI.. I = P/V = 1200 /120 =10 A. Hence, one would think that the
answer is 10 A.. However, this formula applies only for DC current. For
AC current,. P=VI cos (theta). where theta is the phase difference
between V and I.. This phase difference is created by the inductances
inside the microwave oven.

===

Whoo hoo! 'Airree discovered Power Factor, well known to EEs of
course, which is why most high powered AC electrical devices are
rated in KVA instead of KW. For bonus points explain why inductors
create a phase difference between voltage and current.



Eli the ice man.

For even extra credit Harry, please explain when current leads voltage
and when voltage leads current and what types of loads causes this.

For our purposes of the microwave discussion, it can pretty much be
ignored anyway. Power Factor becomes a concern in manufacturing
plants when there are, as you say, many high powered electrical devices
to be used.




Works well for me. I do art welding, and do not see much difference in my
electric bill from the welder. I think the power factor is off enough to
not register on the meter. New meter for the solar may be different.