The 3NJ6930-3BG23 is the legal-for-trade calibrated variant in the SENTRON 3NJ6930 family — compact NH1 bushing current transformers for 3NJ62/63 in-line fuse-switch-disconnectors. With 250/5 A ratio and Class 0.5 factory calibration, it brings billing-grade measurement to space-constrained NH1 distribution panels.

Why does the legal-for-trade version have a smaller cable opening?

The 3BG23 accepts cables up to 14 mm diameter through a 15.2 mm bushing opening — smaller than the 21 mm opening on the standard 3BG22. The calibration components and additional winding precision needed for legal-for-trade conformity occupy internal space, reducing the available bushing diameter. The trade-off is physical: you gain billing certification at the cost of maximum cable size. Ensure your feeder cable outer diameter is ≤14 mm before specifying this variant.

How does the 3NJ6930 series differ from the larger 3NJ6940 CTs?

The 3NJ6930 family serves NH1 (3NJ62/63) switch disconnectors up to 250 A, while the 3NJ6940 family serves the larger 3NJ6 platform up to 600 A. Key differences: smaller footprint (44 × 65 mm vs 70 × 88.5 mm), lower burden rating (2.5 VA vs 5 VA), and a maximum cable diameter of 21 mm vs 32 mm. Choose the 3NJ6930 when your disconnector is NH1 size; choose the 3NJ6940 for NH2/NH3 applications above 250 A or when you need 1 A secondary options.

Frequently Asked Questions

Is this CT plug-and-play with any 3NJ62 or 3NJ63 disconnector?

Yes. It plugs directly onto the outgoing cable side of 3NJ62 and 3NJ63 in-line fuse-switch-disconnectors. No tools or separate mounting hardware required.

What meter burden can this CT drive?

With a 2.5 VA rating, the total connected burden — meter input plus cable losses — must not exceed 2.5 VA at rated current. A typical digital energy meter draws 0.2–0.5 VA per phase, leaving ample headroom for standard control cabling over short to moderate distances. For long cable runs, calculate the total burden to confirm compliance.