Current Transformer

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Current Transformer

The CT benefits include safety agency isolation and isolation required by circuit needs. High current is sometimes difficult to monitor directly. It is easy using an appropriate CT. The CTHT series of current transformers are usable up to 90 Amps peak.

Current transformers (CT’s), like traditional transformers, convert voltages and currents based on their turns ratio. The most important relationship for CT's is primary amp-turns equaling secondary amp-turns (Ip Np = Is Ns). This series of CT's uses a customer supplied single turn primary through the center to carry the large circuit current. An appropriate turns ratio and terminating resistor are selected to supply a voltage, Vs = Is Rb, for the monitoring circuit.


  • Low Cost Encapsulated Transformer
  • Designed for Use Over a Wide Frequency Range
  • Sensitivity Can Be Set to Match Your Specific Requirements
  • Can be Provided with Installed Primary for Easy PCB Installation
  • Other Configurations Available Upon Request - Contact Precision
Model Turn Inductance mHy (Min) DCR Ohms (Max) Rb** Ohms
CTHT-17100-0500 50 5 0.50 50
CTHT-17100-1000 100 20 1.40 100
CTHT-17100-1500 150 45 3.00 150
CTHT-17100-2000 200 80 4.50 200
CTHT-17100-3000 300 180 11.0 300
CTHT-17100-4000 400 320 18 400
CTHT-17100-5000 500 500 30 500
CTHT-17100-7500 750 1150 57 750

Design Criteria

To match your monitoring circuitry to a specific CT, you need to know the CT characteristics in relationship to input current, turn ratio, and frequency range. The Rb referenced in the curves below is defined as Rb = 1 Volt/Is, the value which will yield one volt per amp output, where Is=(Np/Ns) Ip. To assist with choosing Rb, see graphs below. Lower or higher Rb values can be used for your specific requirements. Contact a Precision engineer for assistance (See buttons below).

Note: All results shown assume a square waveform for the current, where Ton=0.5T. Other wave forms are supported to slightly higher peak currents.