Burden Resistor calculation

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This is how burden resistors are calculated for a given CT and desired range.

Burden Resistor Formulae

Resistor calculation.png

R: Burden resistor value in Ohm
Vadc: ADC reference voltage

This is 3.3V for all RPICT3T1 RPICT3V1 and RPICT8/RPICT7V1/RPICT4V3 in version 3 and earlier.
This is 4.096V for all RPICT8/RPICT7V1/RPICT4V3 in version 4 and 5.

Nturns: Number of CT sensor turns (see specs).

SCT-013-000 is 2000 turns.
SCT-019 is 6000 turns.
SCT-006 is 800 turns.
SCT-024 400A/100mA is 4000 turns.
SCT-031 600A/100mA is 6000 turns.

Nturns can be deduced dividing primary current by secondary current. For example the SCT-013-000 is rated as 100A/50mA. Therefore we get 100/0.05 = 2000 turns.
Irms: Max current to be read in Ampere (rms)

Current Coefficient Formulae

This will compute ICAL.

Ical calculation.png


ICAL: Current Coefficient
Nturns: Number of CT sensor turns
R: Burden resistor value in Ohm

Application

You will find tables of pre-calculated resistors values in the links below.

  • For RPICT3T1 RPICT3V1 RPICT4T4v2.5 and also RPICT8/RPICT7V1/RPICT4V3 in version 3 and RPICT4T4 v2

Gen3 Passive Component Setup

  • For RPICT7V1 RPICT8 and RPICT4V3 in version 4

Gen4 Passive Component Setup

  • For RPICT7V1 RPICT8 RPICT4V3 in version 5 (also RPICT4W3T1 and RPICT4V3T2 and RPICT4T4 v5)

Gen5 Passive Component Setup