Current Transformer Shelly 400A Pro (model 3EM-400) — 400 A measurement for energy monitoring

Shelly 400A Current Transformer Pro (3EM-400) is a clamp-style sensor designed to measure alternating current up to 400 A for energy monitoring and integration with Shelly systems. The device provides a non-invasive method to capture real-time current values for metering, load analysis and fault detection. Its compact clamp form allows installation on single conductors in residential and commercial electrical panels without altering the circuit.

Advantages

The current transformer offers accurate AC current sensing up to 400 A with a clamp mechanism that enables quick installation without disconnecting wiring. It is engineered for compatibility with Shelly energy monitoring solutions and supports consistent data collection for load profiling and consumption reporting. The design reduces installation complexity and provides electrical isolation between the measured circuit and monitoring electronics.

Suitable for

• Measuring AC current on single-phase or three-phase circuits (up to 400 A per conductor)
• Integrating with Shelly controllers and energy monitoring systems for consumption tracking
• Load analysis, power distribution monitoring and preventative maintenance
• Residential and small commercial electrical panels where non-invasive measurement is required

Key specifications

• Measurement type: alternating current (AC)
• Maximum measurable current: 400 A
• Form factor: clamp-style (split-core) current transformer
• Output: sensor output compatible with Shelly metering inputs (voltage/current signal for integrative monitoring)
• Installation: non-invasive clamp-on mounting for single conductors
• Application: energy monitoring, load analysis and fault detection

How to use

Place the clamp-style transformer around the conductor to be measured ensuring the core closes fully and the conductor passes through the center of the clamp. Connect the transformer output to the corresponding input on the Shelly monitoring device following the manufacturer wiring diagram and polarity markings. Verify that the monitored circuit does not exceed 400 A and secure the clamp to prevent movement. After wiring, configure the Shelly device in its app or web interface to recognize the current transformer and calibrate the measurement if required.

Usage recommendations

For reliable readings, ensure the conductor passes cleanly through the center of the clamp and avoid bundling multiple conductors inside the clamp. Confirm compatibility with the specific Shelly monitoring model and follow local electrical safety practices: isolate power where necessary, use appropriate personal protective equipment, and consult a qualified electrician for installation in high-current or complex systems.