Split core current transformer

Output voltage of a split-core current transformer feeding a voltmeter with finite internal resistance, computed from the given primary current and core parameters.

Engineering Problem

How can the output voltage of a split-core current transformer be found?

Answer

Only part of the winding is represented in the 2D geometric model; the remaining winding length is represented as an equivalent resistance in the external circuit, in series with the voltmeter's 100 kΩ input resistance.

Typical Applications

Split-core current transformers
Clamp-on current sensors
Non-invasive current measurement

Simulation Problem

Problem Type

Plane-parallel AC Magnetics

Geometry

Model z-direction length 10 mm, core 60 mm × 50 mm, with two air gaps at the joint.

Given

Input AC current 100 A, frequency f = 50 Hz
Secondary winding turns N = 122, wire cross-section Sc = 0.1964 mm², copper conductivity σ = 58.5 MS/m
Core permeability μ = 1000, with 2 air gaps of 0.1 mm each at the core joint
Voltmeter internal resistance 100 kΩ

Task

Compute the transformer's output voltage.

Solution

Only part of the winding is represented in the 2D geometric model; the missing part is represented as a resistance in the circuit.

Mean turn length 43.2 mm; the total length of the winding segments in the geometric model is 10 mm + 10 mm.

Resistance of the remaining portion: R = (1/σ) · N · (43.2 − 10 − 10) / Sc = 0.246 Ω.

Results

Output voltage 1.3 V.