# How can I compute envelope for three phase current?

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Rajeev Kumar on 24 Sep 2022
Edited: Rajeev Kumar on 26 Sep 2022
I stuck in a very small step i.e. the envelope identification of three phase current signal. In matlab when I used the predefined envelope function, it computed the three individual envelope plots instead of one plot for three phase current signal.
Please guide me, how can I plot the single envelope for all the three phase wave?.

Star Strider on 24 Sep 2022
I am not certain what you want.
Perhaps this —
Fs = 0.0001;
t = linspace(0, 1, 1/Fs)/Fs;
s = sin(2*pi*t*60 + deg2rad([0; 120; 240]))
s = 3×10000
0 0.0377 0.0753 0.1129 0.1502 0.1874 0.2243 0.2609 0.2971 0.3329 0.3682 0.4029 0.4372 0.4707 0.5037 0.5359 0.5673 0.5980 0.6277 0.6566 0.6846 0.7116 0.7376 0.7625 0.7863 0.8091 0.8307 0.8510 0.8702 0.8882 0.8660 0.8466 0.8259 0.8041 0.7811 0.7570 0.7318 0.7056 0.6784 0.6502 0.6211 0.5911 0.5603 0.5287 0.4963 0.4632 0.4295 0.3952 0.3603 0.3248 0.2890 0.2527 0.2160 0.1791 0.1418 0.1044 0.0669 0.0292 -0.0085 -0.0462 -0.8660 -0.8843 -0.9012 -0.9169 -0.9313 -0.9444 -0.9561 -0.9665 -0.9755 -0.9831 -0.9893 -0.9941 -0.9975 -0.9994 -1.0000 -0.9991 -0.9968 -0.9931 -0.9880 -0.9815 -0.9736 -0.9643 -0.9536 -0.9416 -0.9282 -0.9135 -0.8975 -0.8803 -0.8618 -0.8420
[seu,sel] = envelope(s, 1, 'peak')
seu = 3×10000
0 0.0377 0.0753 0.1129 0.1502 0.1874 0.2243 0.2609 0.2971 0.3329 0.3682 0.4029 0.4372 0.4707 0.5037 0.5359 0.5673 0.5980 0.6277 0.6566 0.6846 0.7116 0.7376 0.7625 0.7863 0.8091 0.8307 0.8510 0.8702 0.8882 0.8660 0.8466 0.8259 0.8041 0.7811 0.7570 0.7318 0.7056 0.6784 0.6502 0.6211 0.5911 0.5603 0.5287 -0.2482 -0.2316 -0.2148 -0.1976 -0.1801 -0.1624 -0.1445 -0.1263 -0.1080 -0.0895 -0.0709 -0.0522 -0.0334 -0.0146 0.0042 0.0231 -0.8660 -0.8843 -0.9012 -0.9169 -0.9313 -0.9444 -0.9561 -0.9665 -0.9755 -0.9831 -0.9893 -0.9941 -0.9975 -0.9994 -1.0000 -0.9991 -0.9968 -0.9931 -0.9880 -0.9815 -0.9736 -0.9643 -0.9536 -0.9416 -0.9282 -0.9135 -0.8975 -0.8803 -0.8618 -0.8420
sel = 3×10000
0 0.0377 0.0753 0.1129 0.1502 0.1874 0.2243 0.2609 0.2971 0.3329 0.3682 0.4029 0.4372 0.4707 0.5037 0.5359 0.5673 0.5980 0.6277 0.6566 0.6846 0.7116 0.7376 0.7625 0.7863 0.8091 0.8307 0.8510 0.8702 0.8882 -0.4330 -0.4233 -0.4129 -0.4020 -0.3905 -0.3785 -0.3659 -0.3528 -0.3392 -0.3251 -0.3106 -0.2956 -0.2802 -0.2643 -0.2482 -0.2316 -0.2148 -0.1976 -0.1801 -0.1624 -0.1445 -0.1263 -0.1080 -0.0895 -0.0709 -0.0522 -0.0334 -0.0146 0.0042 0.0231 -0.8660 -0.8843 -0.9012 -0.9169 -0.9313 -0.9444 -0.9561 -0.9665 -0.9755 -0.9831 -0.9893 -0.9941 -0.9975 -0.9994 -1.0000 -0.9991 -0.9968 -0.9931 -0.9880 -0.9815 -0.9736 -0.9643 -0.9536 -0.9416 -0.9282 -0.9135 -0.8975 -0.8803 -0.8618 -0.8420
figure
plot(t, s)
hold on
plot(t, max(seu), '-r', 'LineWidth',2)
plot(t, min(sel), '-g', 'LineWidth',2)
hold off
xlim([0 250])
figure
plot(t, s)
hold on
plot(t, max(s), '-r', 'LineWidth',2)
plot(t, min(s), '-g', 'LineWidth',2)
hold off
xlim([0 250])
.
Rajeev Kumar on 26 Sep 2022
Edited: Rajeev Kumar on 26 Sep 2022
I have a two array
A = [1,2,3,4,0,6,7,0,9,10,11,0,13,14,15];
t=[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
Now skip the zeros form the array A and also skip the crossponding index form the time (t) array. and make a plot in between them?

Sam Chak on 24 Sep 2022
You can try if the envelope function works for you.
https://www.mathworks.com/help/signal/ref/envelope.html