Power and energy

EpiSensor current-transformer aperture selector

Match the maximum current per phase and the conductor size to an EpiSensor CT option, with anything outside the verified range sent to our engineers.

Calculate

Measurement duty
A
mm

Worked example

Smallest matching current option

ZEM-65-120 

Option
120 A per-phase split-core CTs, 14 mm aperture
Exact catalogue code
ZEM-65-120
Current margin below the rating
20 A
Aperture margin around the conductor
mm

A catalogue ordering path, not metering-class, insulation or installation approval.

Method and assumptions

Formula

eligible option: rating ≥ maximum current and aperture ≥ measured outside diameter

The output is an ordering-path aid tied to the current catalogue, not CT metering-class or installation approval.

Limits of this result

  • Measure the complete conductor, insulation, lug or cable bundle at the intended CT location; conductor area alone does not determine outside diameter.
  • Mini-CT options are only for the secondary of an existing 1 A or 5 A CT and are not placed around a primary conductor.
  • Confirm waveform, metering class, burden, insulation, CAT rating, protection and installation safety separately.
  • Current is per phase: the rating of each CT or coil, not the total across three phases.
  • The 300 A Rogowski coil closes to about 70 mm across; the 1 kA, 3 kA and 6 kA coils are not fit-selected here because their clear aperture is not yet reviewed for every variant.

Technical sources

  1. Current hardware price and ordering-code sourceEpiSensor · repository-controlled catalogue
  2. Selecting current transformersEpiSensor · 2026-09-14

Put the value to work

Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.

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