Methods and apparatus for calibrating a thermomagnetic trip unit of a circuit breaker

摘要

Methods, apparatus, and systems are provided for calibrating a thermomagnetic trip unit in a circuit breaker base assembly. An apparatus for calibrating a trip unit includes a calibration nut, an extended armature guide pin having a threaded portion, a spring disposed on the calibration nut and coiled around the extended armature guide pin, and an armature disposed on the spring and adapted to be held by an electromagnet. The calibration nut is threaded on the threaded portion of the extended armature guide pin and adapted to translate up or down depending on rotation of the extended armature guide pin to compress or decompress the spring against the armature. The extended armature guide pin includes a slotted end that is accessible when the apparatus is installed in the circuit breaker base assembly. The calibration nut is also accessible when the apparatus is installed in the circuit breaker base assembly.

主权项

1. An apparatus for calibrating a trip unit, the apparatus comprising:
a calibration nut; an extended armature guide pin having a threaded portion; a spring disposed on the calibration nut and coiled around the extended armature guide pin; and an armature disposed on the spring and adapted to be pulled by an electromagnet, wherein one end of the spring contacts the calibration nut while other end of the spring contacts the armature and wherein the calibration nut is directly accessible for calibration such that a length of the spring is adjusted by holding the calibration nut rotationally stationary and rotating the extended armature guided pin, wherein the calibration nut is threaded on the threaded portion of the extended armature guide pin and adapted to translate up or down depending on rotation of the extended armature guide pin to compress or decompress the spring against the armature.