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Burden Resistor and Current Transformer Math

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Introduction

This is a list of the burden resistors for SCT-0750, SCT-1250, SCT-2000 and SCT-3000 series transformers used to ensure a 333mVAC output at max rated current. The current transformer math will be defined as an aide to calculate alternate voltage outputs or alternate max rated current limits.

UCT series transformers are customizable Series resistance burden tables are not published.

Transformer features; Operates from 50 Hz to 400 Hz, Rated input from 0 Amp to 3000, Amp Phase angle < 1 degrees measured at 50% rated current, custom voltage max 1.00V AC output at rated current, Accuracy ± 1%, UL recognized, Accuracy at 10% to 130% of rated current.

SCT Series Burden Resistor Tables

SCT-0750 SERIES SPLIT CORE CT
Rated Current amp Resistor Ohms
5 490
10 245
15 163
20 123
25 98.1
30 81.7
50 49.0
60 40.9
70 35.0
100 24.5
150 16.3
200 12.3

 

Current Transformer MathIn order to calculate the number of turns based on the burden resistor charts the following equation may be used:N=I(pri)/[ RxV ]Where:R = Burden Resistor in Ohms
V = 0.333V which is the secondary output voltage
I(pri) = Primary Current
N = Number of turnsAssuming the number of turns will remain constant alternate equations for V – Secondary Output Voltage and I(pri) – Rated Current can be calculated using the following formulas. I(pri) = N*[ V/R ]V=[ I(pri) / N ] x R

SCT-1250 SERIES SPLIT CORE CT
Rated Current amp Resistor Ohms
50 48.9
70 34.9
100 24.4
150 16.3
200 12.2
250 9.78
300 8.15
400 6.11
600 4.07

 

SCT-2000 SERIES SPLIT CORE CT
Rated Current amp Resistor Ohms
100 24.5
200 12.3
300 8.17
400 6.13
600 4.09
800 3.06
1000 2.45
1200 2.04
1500 1.63

 

SCT-2000 SERIES SPLIT CORE CT
Rated Current amp Resistor Ohms
400 8.67
600 5.78
800 4.33
1000 3.47
1200 2.89
1500 2.31
2000 1.73
2500 1.39
3000 1.16