Using Current Transformer In Core Saturating Mode Enables DC Current Measurements

Focus:

Current transformers (CTs) are among the most effective isolated current sensors and can measure up to thousands of amperes. Besides providing immunity to common-mode noise and low power dissipation, a CT does not require separate converters supplying isolated dc voltage to power up the sensor input circuitry. Normally, CT-based current sensors are only intended for monitoring of ac or pulsing currents with zero minimum levels. However, utilizing the transformer’s saturation mode and a special technique for detection of the dc component can expand CT-based sensor usage to enable dc current monitoring. This article studies an opportunity for adopting such a technique and presents design considerations for CT-based dc current monitoring.

What you’ll learn:

• How to measure dc current using a current transformer operating in saturation mode
• How to measure a dc current applied to a current transformer’s primary by applying a sawtooth waveform on the secondary and detecting demagnetization of the core

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Author & Publication:

Viktor Vogman, Power Conversion Consulting, Olympia, Wash., How2Power Today, Oct 14 2022

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