Schneider 3CT-H3-300-C Integrated 3-Phase Current Transformer

The 3CT-H3-300-C is a through-core combined three-phase current transformer of Schneider’s 3CT series (formerly Samwha from South Korea). It is specially developed to match the EOCR series motor protectors. Adopting an integrated three-phase synchronous sampling structure, it is designed for current collection on the main circuit of three-phase motors, meeting demands for motor protection against overload, phase loss and locked rotor as well as current measurement. Equipped with circular through holes for cable threading and compatible with standard 35 mm DIN rail mounting, it greatly saves cabinet wiring and installation space.

1. Step-by-Step Model Code Decoding

3CT-H3-300-C

1. 3CT: Integrated 3-Phase Current Transformer
2. H3: Frame code corresponding to primary current rating of 300 A
3. 300: Rated primary current 300 A
4. C: Circular through-hole structure; models with suffix Z in the same series feature square holes for busbar application

III. Core Technical Specifications

1. Full Model Cross Reference for the Same Series

1. Typical Application Scenarios
2. Complete control cabinets for industrial three-phase asynchronous motors, cooperating with EOCR protectors to realize protection against overload, phase loss, phase unbalance and locked rotor;
3. Current monitoring of 0.4 kV low-voltage power circuits, sampling for ammeters and multi-function meters;
4. Control boxes for high-power motors such as water pumps, fans, air compressors and conveyors;
5. Complete electrical control systems for automatic production lines, HVAC equipment and water treatment facilities.
6. Installation & Operation Maintenance Key Points
7. Thread the three primary-side cables separately through the three circular holes, keep cables centered against the core to avoid sampling errors caused by unilateral offset;
8. Secondary output terminals shall be reliably connected to the EOCR current sampling ports. Never open the secondary circuit, as open-circuit will generate high voltage and damage components;
9. When multiple transformers are connected in parallel for measurement, the total impedance of secondary circuit loads shall not exceed the rated burden limit of 1.25 VA;
10. Operating ambient temperature shall be maintained between -10℃ and +60℃, keep away from strong electromagnetic interference sources such as contactors and inverters;
11. Tighten terminal screws after wiring, conduct regular inspections for cable insulation abrasion, overheating and discoloration.

VII. Troubleshooting Matrix

VIII. Model Replacement Guidelines

1. Same-rating replacement: 3CT-H3-300-Z only adopts square through holes, interchangeable for busbar applications; 3CT-H3-300-C is preferred for cable wiring;
2. Cross-brand replacement: Must match 300/5 A ratio, 1.25 VA burden and integrated 3-phase structure. Separate single-phase standalone transformers cannot be directly substituted, which will trigger abnormal phase-loss protection logic.
3. Safety Precautions
4. Primary rated current shall not exceed 300 A for long-term operation; sustained overload will permanently impair core measurement accuracy;
5. No disconnectable components such as fuses or switches are allowed on the secondary side. Cut off power of the primary main circuit before any maintenance;
6. Reserve heat dissipation gaps during cabinet mounting; do not install closely to heat-generating components including contactors and thermal relays;
7. Only applicable to 50 Hz power frequency low-voltage power circuits; special inverter-type transformers are required for high-frequency variable-frequency circuits;
8. Each product is delivered with an original factory calibration label. Verify the full model before spare part replacement; frames H1/H2/H3 cannot be mixed for use.