A Rogowski coil is a helical wire coil wrapped around a toroidal (often flexible) former, used to measure AC current in conductors without making electrical contact. Unlike a current transformer, a Rogowski coil has no iron core—its air core makes it light, linear and safe for high-current measurements.
This guide covers how Rogowski coils work, key parameters, typical applications, and how they compare with current transformers and hall sensors.
Shaanxi SiRui Technology Co., Ltd. manufactures Rogowski coils and current sensors for power monitoring, motor drives and protection applications. Contact: sales@sirui-tech.com | Web: www.sirui-tech.com
1. How a Rogowski Coil Works
The coil measures the magnetic field around a current-carrying conductor. Induced voltage is proportional to di/dt. An integrator circuit converts this to a signal proportional to actual current: V_out = M × I_measured.
- No saturation: air core means no magnetic saturation even at very high currents
- Linear output: perfectly linear over the entire range
- Wide bandwidth: 0.1 Hz to 10 MHz depending on design
- Safe open circuit: unlike CTs, no dangerous voltage spike
2. Comparison with Other Sensors
| Feature | Rogowski | Current Transformer | Hall Sensor |
|---|---|---|---|
| Core | Air (no iron) | Iron / ferrite | Iron core + hall |
| Saturation | Never | Can saturate | Can saturate |
| Bandwidth | 0.1 Hz–10 MHz | 50 Hz–20 kHz | DC–100 kHz |
| Measures DC | No | No | Yes |
| Open circuit | Safe | Dangerous | Safe |
3. Key Parameters
- Range: 1 A to 10,000 A typical
- Accuracy: class 0.5 to class 1 standard, class 0.1 for revenue metering
- Coil diameter: must fit around the conductor, 50–300 mm typical
- Integrator: required external circuit, or integrated smart module
4. Common Applications
- Power quality monitoring in switchgear and distribution panels
- Motor current measurement in VFDs and drives
- Leakage current and ground fault detection
- Harmonic analysis (wide bandwidth)
- Portable / temporary measurements (flexible clamp-around)
- High-current busbars and welders
5. Sirui-Tech Products
- Rigid Rogowski coils: high accuracy, permanent installation
- Flexible Rogowski: clamp-around, portable measurements
- Integrated sensors: coil + integrator in one package
- Custom sizes: wound to customer ID and current range
Conclusion
Rogowski coils are the safe, linear and lightweight solution for AC current measurement. They never saturate and are safe to use open-circuit. They do not measure DC—use hall sensors for that.
Need a Rogowski coil? Contact Sirui-Tech at sales@sirui-tech.com with your current range and accuracy requirements.