Burden Resistor calculation: Difference between revisions
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This is how burden resistors are calculated for a given CT and desired range. | |||
==Burden Resistor Formulae== | ==Burden Resistor Formulae== | ||
[[File:Resistor_calculation.png]] | |||
'''R''': Burden resistor value in Ohm<br> | '''R''': Burden resistor value in Ohm<br> | ||
''' | '''Vadc''': ADC reference voltage <br> | ||
'''Nturns''': Number of CT sensor turns (see specs)<br> | :This is 3.3V for all RPICT3T1 RPICT3V1 and RPICT8/RPICT7V1/RPICT4V3 in version 3 and earlier.<br> | ||
'''Irms''': Max current to be read in rms<br> | :This is 4.096V for all RPICT8/RPICT7V1/RPICT4V3 in version 4 and 5.<br> | ||
'''Nturns''': Number of CT sensor turns (see specs). <br> | |||
:SCT-013-000 is 2000 turns.<br> | |||
:SCT-019 is 6000 turns.<br> | |||
:SCT-006 is 800 turns.<br> | |||
:SCT-024 400A/100mA is 4000 turns.<br> | |||
:SCT-031 600A/100mA is 6000 turns.<br> | |||
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.<br> | |||
'''Irms''': Max current to be read in Ampere (rms)<br> | |||
==Current Coefficient Formulae== | ==Current Coefficient Formulae== | ||
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This will compute ICAL. | This will compute ICAL. | ||
[[File:Ical_calculation.png]] | |||
'''ICAL''': Current Coefficient<br> | '''ICAL''': Current Coefficient<br> | ||
'''Nturns''': Number of CT sensor turns<br> | '''Nturns''': Number of CT sensor turns<br> | ||
'''R''': Burden resistor value in Ohm<br> | '''R''': Burden resistor value in Ohm<br> | ||
==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<br> | |||
[[Gen3 Passive Component Setup]]<br> | |||
* For RPICT7V1 RPICT8 and RPICT4V3 in version 4<br> | |||
[[Gen4 Passive Component Setup]]<br> | |||
* For RPICT7V1 RPICT8 RPICT4V3 in version 5 (also RPICT4W3T1 and RPICT4V3T2 and RPICT4T4 v5)<br> | |||
[[Gen5 Passive Component Setup]]<br> | |||
Latest revision as of 16:28, 17 February 2022
This is how burden resistors are calculated for a given CT and desired range.
Burden Resistor Formulae
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: 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
- For RPICT7V1 RPICT8 and RPICT4V3 in version 4
- For RPICT7V1 RPICT8 RPICT4V3 in version 5 (also RPICT4W3T1 and RPICT4V3T2 and RPICT4T4 v5)