Electrical UL/CSA
Motor Circuit Protection

Of all the branch circuits encountered in the electrical industry, motor branch circuits are some of the most unique.  For a reliable motor branch circuit installation, a thorough understanding of the requirements for various functional parts of motor branch circuits, and their intended purpose, is required.  Below are documents published by Cooper Bussmann to assist with understanding motor branch circuits and associated devices.

Motor Circuit
  • Motor Circuit Protection Tables

    Cooper Bussmann motor protection tables compile sizing requirements for several important motor circuit components.  If you know the voltage and motor horsepower the protection tables can provide you with fuse sizing, switch sizing, starter size and minimum conductor size information.  These recommendations are in accordance with NEC® guidelines.

  • Type 2 Protection Tables

    Type 2 or "No Damage" starter protection can provide a number of benefits to an installation including reduced downtime.  A Type 2 fuse and starter combination has been tested at specific fault levels to ensure that under fault conditions the starter will not be damaged beyond slight contact welding.  A starter without Type 2 protection may see significant damage and have to be replaced shutting down any equipment relying on that circuit.  Here you will find more information on Type 2 protection and a list of tested combinations.

  • Motor Circuit Protection

    This excerpt from the Cooper Bussmann SPD goes into detail on the variety of motor circuit devices and application issues.  Some of these topics include short-circuit and overload protection, voltage unbalance, disconnecting means and NEC® protection requirements.

  • Protection Against Single-Phasing

    Motor single-phasing is a major concern for motor circuits as it can lead to overheating and reduced motor life.  This application paper specifies solutions to the single-phasing threat.

  • Motor Control Circuit Protection

    There are a number of protection requirements for circuits that direct the performance of the main motor power circuit.  This document assists in providing proper protection based on control circuit configuration.

  • Motor Circuit Protective Devices

    This document goes into technical detail on the variety of motor circuit devices, and their limitations and requirements.  This includes short-circuit protective devices, overload protection, disconnecting means and motor controllers.