Dear Reza,

I had done some work on the phase angle effective voltage relationship and developed following array. It is for sinusoidal supply waveforms and resistive load. This array has 100 elements each representing the relative effective voltage at a firing angle. The first value is for firing angle at 45 degrees second at 45.9 degrees third 46.8 degrees and so on thus 100th element power when firing angle is 135 degrees.

uchar code rmsfactor[100]={255, 254, 253, 253, 252, 251, 250, 249, 248, 247,
							 246, 246, 244, 243, 242, 241, 240, 239, 238, 237,
							 235, 234, 233, 232, 230, 229, 228, 226, 225, 223,
							 222, 220, 219, 217, 216, 214, 213, 211, 209, 208,
						     206, 204, 202, 201, 199, 197, 195, 193, 192, 190,
							 188, 186, 184, 182, 180, 178, 176, 174, 172, 170,
							 168, 166, 164, 161, 159, 157, 155, 153, 151, 148,
							 146, 144, 142, 140, 137, 135, 133, 131, 128, 126,
							 124, 122, 119, 117, 115, 113, 110, 108, 106, 103,
							 101,  99,  97,  94,  92,  90,  88,  85,  83,  81 };

Hope this helps.

Remember the above table is only for resistive loads with sinus voltage applied. For inductive, capacitive load or Non Sinus waveforms the above table wont work.

Best Regards,
Prahlad Purohit