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A split core current transformer is a type of current transformer whose magnetic core is divided into two or more parts, allowing it to be “clamped” around an existing conductor without disconnecting the circuit. Below is a detailed overview—covering its working principle, classifications, functions, features, application scenarios, and future trends.
The operating principle of a split core current transformer is essentially the same as that of any conventional current transformer—based on electromagnetic induction:
The conductor carrying the current to be measured acts as the primary winding (often a single turn).
The alternating current through this conductor produces an alternating magnetic flux in a high-permeability core.
A secondary winding, wound on the core, picks up that flux and generates a proportional current in its circuit, scaled by the turns ratio.
Because the core is in two (or more) halves, when installed, the halves are closed and clamped, completing the magnetic circuit. Attention must be paid to core alignment and minimizing the air gap between halves, because excessive gaps degrade magnetic coupling and reduce accuracy.
The secondary winding must always remain closed (i.e. loaded) to avoid high voltages on an open circuit.
Once installed, it works just like a solid-core CT: the primary current induces the secondary current in proportion to the turns ratio, allowing measurement or protection equipment to sense high currents safely.
Because the core is split, some additional design care is required to mitigate leakage flux or nonuniform gaps, but modern designs use precise mechanical latches and low-gap magnetic materials to reduce such errors.
Though “split core” itself is a structural classification, split core CTs can also be categorized along several other dimensions:
Mechanism of splitting / closure
Hinged / pivot style (one side opens on a hinge)
Bolt or clip style (two halves joined by screws, snaps, or clamps)
Accuracy class / purpose
General / monitoring class
Metering / billing class (higher precision)
Protection class (able to tolerate short-term overloads)
Current rating & ratio
Low-current ranges (e.g. tens or hundreds of amps)
Higher current ranges (up to thousands of amps)
Secondary outputs of 1 A, 5 A, or lower (milliamp) levels
One such product example is the split core current transformer, which uses this clamping-around design for easier retrofitting.
The essential functions of a split core current transformers include:
Measurement / metering
Converting high primary currents into proportional secondary currents for current meters, power analyzers, or energy metering systems.
Monitoring
Feeding real-time current data into monitoring, control, or protection systems (e.g. SCADA, BMS, energy management systems).
Protection
Serving in overcurrent or fault detection circuits, where the CT feeds relays or protective devices to trigger circuit breakers.
Advantages / Features
Non-intrusive / no interruption
They can be installed around live conductors without disconnecting or rewiring, minimizing downtime.
Ease of installation & retrofit
Ideal for field upgrades, additions, or measurement deployment in existing systems.
Versatility
Available in varied current ratings, sizes, and accuracy classes for wide application coverage.
Split core current transformers are widely used in settings where ease of installation, retrofitting, or minimal disruption is critical. Typical application domains include:
Power distribution / electrical panels
Monitoring branch circuits, feeders, or subcircuits in existing panelboards.
Building energy management & submetering
Installing CTs in existing wiring systems to monitor loads, tenants, or zones in commercial or residential buildings.
Industrial monitoring & load profiling
Measuring currents on motors, drives, pumps, HVAC systems, production lines, etc., often where shutting down is undesirable.
Because of their flexibility, split core CTs are especially valuable in retrofits or expansions, where wiring cannot be easily interrupted.
The field of split core current transformers is evolving as power systems become more complex, distributed, and digital. Some key trends and prospects include:
Higher accuracy & lower error designs
Improved core materials (nanocrystalline, amorphous) and mechanical designs to reduce leakage and gaps, pushing split-core performance closer to solid cores.
Integrated smart electronics
Embedding signal conditioning, amplification, temperature compensation, calibration memory, and digital output (e.g. Modbus, IEC 61850) within the CT body.
Wider bandwidth / high-frequency capability
Designs aiming to better capture harmonic components, fast transients, and non-sinusoidal signals to support power quality analytics.
