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Define frame size, sensor, sensor plug, and rating plug for Masterpact and Powerpact P and R breakers

Published date: 10 June 2020

What is meant by frame size, sensor, sensor plug, and rating plug for Masterpact and Powerpact P and R breakers with Micrologic trip units, and how are they used to determine breaker amperage?

Product Lline:
Masterpact ajnd Powerpact P and R frame circuit breakers with Micrologic trip units.

  • Breaker frame has three general meanings. It is difficult to know what is being meant by “frame” without additional information and context.
    • The industry defines frame as the maximum current rating of a circuit breaker of a particular construction. 
    • Breaker families are called “frames” such as P frame, R frame, W frame, etc. 
    • Frame is also used to indicate the maximum setting possible for a particular circuit breaker.  For example, a PJ800 or PJ1200, or a 2000 A or 4000 A frame.
      In some cases though, this is misleading and frame designation alone does not necessarily indicate the maximum setting. 
  • The sensor is an air-core Rogowski CT and is a permanent part of the circuit breaker; it cannot be changed out in the field or in the factory. The same Rogowski CT may be used in different breaker frames and amperages.
  • The sensor plug is a plug fitted into the trip unit base under the trip unit and it sets the breaker’s maximum current setting. It can be replaced with the same type of sensor plug and in most cases can be changed out to another amperage.
  • The rating plug fits over the long time pickup and delay dials, and contains the multipliers that may be applied to the sensor plug to give the breaker its current rating. It is interchangeable and may be replaced with one with different multipliers to achieve different breaker ampacities.
Breaker amperage is the product of sensor plug value multiplied by the long time (Ir) setting.  The Ir setting is determined by which value on the rating plug the Ir dial is pointing to.

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