SCR Phase Angle Voltage Measurement Page


Metering SCR or Triac controlled circuits requires the user to know the phase angle of conduction and the relationship between the peak to rms value of the waveform at that conduction angle (commonly called the "Crest Factor"). Also, included in this page is the ratio of peak to average and rms to average values. To use the table below, define the degrees of conduction (based on full conduction angle of 180 degrees). Then find the three ratios comparing rms, average, and peak values. The following table was calculated using MATHCAD Software. For a copy of the mathcad file, please email me at tom's mail box.


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Chart of Ratios of RMS, Average, and Peak Values for Various Conduction Angles of SCR/Triac Controlled AC circuits.
DEGREES OF CONDUCTION RATIO OF PEAK TO RMS(Crest Factor) RATIO OF PEAK TO AVERAGE RATIO OF RMS TO AVERAGE
1 13.42 180 13.42
2 12 120 10
3 10.76 89.99 8.366
4 9.796 71.98 7.348
5 9.042 59.97 6.632
6 8.434 51.39 6.093
7 7.931 44.95 5.668
8 7.507 39.94 5.321
9 7.143 35.93 5.031
10 6.826 32.65 4.784
11 6.547 29.92 4.57
12 6.299 27.6 4.382
13 6.076 25.61 4.215
14 5.875 23.89 4.067
15 5.691 22.38 3.932
16 5.524 21.05 3.81
17 5.369 19.86 3.699
18 5.227 18.8 3.597
19 5.094 17.84 3.503
20 4.971 16.98 3.415
21 4.855 16.19 3.334
22 4.747 15.47 3.258
23 4.645 14.81 3.188
24 4.549 14.2 3.121
25 4.458 13.63 3.058
26 4.372 13.11 2.999
27 4.29 12.63 2.943
28 4.212 12.17 2.89
29 4.138 11.75 2.84
30 4.066 11.36 2.792
31 3.998 10.98 2.747
32 3.933 10.63 2.703
33 3.871 10.3 2.662
34 3.81 9.991 2.622
35 3.752 9.696 2.584
36 3.696 9.416 2.547
37 3.643 9.151 2.512
38 3.59 8.899 2.478
39 3.54 8.658 2.446
40 3.491 8.43 2.414
41 3.444 8.211 2.384
42 3.398 8.002 2.355
43 3.353 7.803 2.327
44 3.31 7.612 2.299
45 3.268 7.428 2.273
46 3.227 7.252 2.247
47 3.187 7.083 2.223
48 3.148 6.921 2.199
49 3.11 6.764 2.175
50 3.073 6.614 2.152
51 3.036 6.468 2.13
52 3.001 6.328 2.109
53 2.966 6.193 2.088
54 2.932 6.062 2.068
55 2.898 5.936 2.048
56 2.866 5.813 2.029
57 2.834 5.695 2.01
58 2.802 5.58 1.991
59 2.771 5.469 1.973
60 2.741 5.361 1.956
61 2.711 5.256 1.939
62 2.681 5.154 1.922
63 2.653 5.055 1.906
64 2.624 4.958 1.89
65 2.596 4.865 1.874
66 2.568 4.774 1.859
67 2.541 4.685 1.844
68 2.514 4.598 1.829
69 2.488 4.514 1.815
70 2.461 4.432 1.8
71 2.435 4.351 1.787
72 2.41 4.273 1.773
73 2.385 4.196 1.76
74 2.36 4.121 1.747
75 2.335 4.048 1.734
76 2.31 3.977 1.721
77 2.286 3.907 1.709
78 2.262 3.838 1.697
79 2.238 3.771 1.685
80 2.215 3.706 1.673
81 2.192 3.641 1.662
82 2.168 3.578 1.65
83 2.145 3.516 1.639
84 2.123 3.456 1.628
85 2.1 3.396 1.617
86 2.077 3.338 1.607
87 2.055 3.28 1.596
88 2.033 3.224 1.586
89 2.011 3.169 1.576
90 1.989 3.114 1.566
91 1.967 3.062 1.556
92 1.947 3.01 1.546
93 1.927 2.961 1.537
94 1.907 2.913 1.528
95 1.888 2.867 1.518
96 1.87 2.822 1.509
97 1.852 2.779 1.5
98 1.835 2.737 1.491
99 1.819 2.697 1.483
100 1.803 2.657 1.474
101 1.787 2.619 1.466
102 1.772 2.583 1.457
103 1.758 2.547 1.449
104 1.744 2.513 1.441
105 1.73 2.479 1.433
106 1.717 2.447 1.425
107 1.704 2.415 1.417
108 1.692 2.385 1.409
109 1.68 2.355 1.402
110 1.669 2.327 1.394
111 1.657 2.299 1.387
112 1.647 2.272 1.38
113 1.636 2.246 1.373
114 1.626 2.221 1.366
115 1.617 2.196 1.359
116 1.607 2.172 1.352
117 1.598 2.149 1.345
118 1.589 2.127 1.338
119 1.581 2.105 1.332
120 1.573 2.084 1.325
121 1.565 2.063 1.319
122 1.557 2.044 1.312
123 1.55 2.024 1.306
124 1.543 2.006 1.3
125 1.536 1.987 1.294
126 1.529 1.97 1.288
127 1.523 1.953 1.282
128 1.517 1.936 1.276
129 1.511 1.92 1.271
130 1.506 1.905 1.265
131 1.5 1.89 1.259
132 1.495 1.875 1.254
133 1.49 1.861 1.249
134 1.485 1.847 1.243
135 1.481 1.834 1.238
136 1.477 1.821 1.233
137 1.472 1.808 1.228
138 1.469 1.796 1.223
139 1.465 1.785 1.218
140 1.461 1.773 1.214
141 1.458 1.762 1.209
142 1.454 1.752 1.204
143 1.451 1.742 1.2
144 1.448 1.732 1.196
145 1.446 1.722 1.191
146 1.443 1.713 1.187
147 1.441 1.704 1.183
148 1.438 1.696 1.179
149 1.436 1.688 1.175
150 1.434 1.68 1.171
151 1.432 1.672 1.168
152 1.43 1.665 1.164
153 1.429 1.658 1.16
154 1.427 1.651 1.157
155 1.426 1.645 1.154
156 1.424 1.639 1.151
157 1.423 1.633 1.147
158 1.422 1.627 1.144
159 1.421 1.622 1.142
160 1.42 1.617 1.139
161 1.419 1.612 1.136
162 1.418 1.608 1.134
163 1.418 1.604 1.131
164 1.417 1.6 1.129
165 1.417 1.596 1.127
166 1.416 1.593 1.125
167 1.416 1.59 1.123
168 1.415 1.587 1.121
169 1.415 1.584 1.119
170 1.415 1.582 1.118
171 1.415 1.579 1.116
172 1.415 1.578 1.115
173 1.414 1.576 1.114
174 1.414 1.574 1.113
175 1.414 1.573 1.112
176 1.414 1.572 1.112
177 1.414 1.572 1.111
178 1.414 1.571 1.111
179 1.414 1.571 1.111
180 1.414 1.571 1.111

Notes:
#1. These values are for educational purposes only.
Due to the wide range of circuit applications, the author assumes no responsibility for the application of these values.

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