Shock Hazard: Unburdened CT's should never be handled with primary current applied!

CT Calculation Helper

Enter the information below to calculate the burden resistor required for Current Transformers that do NOT contain a built-in burden resistor.

Do I need a burden resistor?

Some CT's contain a built-in burden resistor.  If the CT is rated in Volts per Amp (for example 0.333V at 100A) then it already contains a built-in burden resistor.

If a CT is rated as a turns ratio, then it likely does NOT contain a burden resistor.  The calculator below can be used to determine the desired burden resistor value.

CT Operation

A CT encloses a primary current (Ip) and produces a secondary current (Is) through the seconday winding of N turns (the turns ratio). 

The voltage produced across the burden resistor (R) is given by the accompanying equation.

The following calculator can be used to determine a suitable burden resistor for use with the Z3 NetMeter:

Burden Resistor Calculator
(Amps RMS)
(Volts RMS)
(Number of turns of the secondary winding)