A very common defect found with small crimp lugs is a high resistance termination.

A crimp lug often used for small electric motors with cable size 6mm^2 or below are color coded with a preformed insulation barrel.

The Insulation barrel extends beyond the underlying internal metal barrel which makes the termination.

When making the compression with a crimp tool a common mistake is the alignment of the anvil in the crimp tool to the metal barrel. The result is a partial or full miss of the compression zone which creates a high resistance termination.

As the insulating material is compressed along with the Metal barrel it is difficult to see if the termination has been made correctly. If not aligned correctly or not checked once compressed the high resistance termination heats up under start conditions.

This heat (Losses I^2R) oxidizes the copper surface and loss of copper annealing and the copper strands. Become brittle. The oxidation further causes resistance increase and problem escalates to a failure.

Embrittlement of the copper due to the heat also risks a strand break adding to the resistance defect.

Motor Testing experience shows this type of defect occurs in approximately 20% of small motors. What often saves the situation is they are lightly loaded, and can last quite some time before failure.

As a result crimp terminations in industry are quite poor, often wrong sized lugs are used as in the case resulting in not enough surface area (Current carrying Area).

A number of possible causes are at hand being, awareness, skills, tools, or pressure to get job done quickly. Rushing the job is false economy as the this will end in repeat failures.  Skills, awareness and tools are easy fixes a simple skill sheet and a toolbox meeting often get results.

The Awareness comes from finding these defects and sharing the results. Motor Circuit Analysis is a very easy method of finding high resistance terminations and should form part of every Electrical Preventative maintenance program.

The other types of common defects are Loose nut between Motor Lead and the Link, incorrectly torque settings, arrangement so Motor Lead, Link and Supply lead have washers or nuts in the current path, debris between termination faces.

When you add up all these commons defects they account for 94% of Motors in industry.

That means the vast majority of Motors can see improvements in Reliability and Energy savings.

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