The Siemens 3VA9677-0NA11 is an external current transformer for the neutral conductor, designed as a field-installable accessory for 3VA6 and 3VA2 molded case circuit breakers. It mounts externally to the breaker assembly, not inside the breaker housing, so panel layout must accommodate the additional footprint alongside the breaker.
Compatibility and current ranges
This CT is specified for use with 3VA6 breakers rated 600 A, 1000 A, or 1200 A, and with 3VA2 breakers rated 630 A, 1000 A, or 1250 A. The neutral CT provides the residual-current measurement path for the electronic trip unit; without it, the breaker cannot detect ground faults on the neutral leg. Verify the breaker frame rating matches one of the listed values before ordering — the CT is not a universal fit across the entire 3VA family.