On Friday, December 03, 2010 02:54:37 am Chuck Anderson wrote:
Here's a question for you. How do you calculate the total current & power capacity of a L21-20 or L21-30, and how do you do the calculations in order to balance the load between the phase legs? This seems like it would be a trivial thing to do, but given that the three legs are 120 degrees out of phase with each other, I don't think you can just do normal addition.
You would be correct. A pretty good three-phase calculation reference can be found at http://www.3phasepower.org/3phasepowercalculation.htm It is vector addition, and with the angles involved you end up multiplying and dividing by the square root of 3 a lot. Also see the wikipedia article, and here's a few others: http://www.gavinelectrical.com/content/threephase.htm http://www.servertech.com/uploads/documents/0000/0236/3-Phase_Power_in_the_D... That last PDF is directly related to this discussion, and a good read.