Contact Tip Inspection

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Contact Tip Inspection These contacts are both considered in good condition (source: ABB Guidelines for Contactor inspection and maintenance). The major difference is that the contacts in photo #1 are the result of very low usage: A contact tip is not worn out just because the surface is rough and discolored. In fact signs of wear are good because this means the contacts are electrically “seated” and match each other better than a new set. Different amounts of contact wear, both between the fixed and movable parts, and between different phases, is normal. Filing, grinding, and other attempts to restore contact surfaces actually cause more harm than good. Maintenance should be limited to inspection for the amount of wear to determine whether or not the contacts need to be replaced before the next inspection.

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Procedure for electrical contact tip inspection

Transcript of Contact Tip Inspection

Page 1: Contact Tip Inspection

Contact Tip InspectionThese contacts are both considered in good condition (source: ABB Guidelines for Contactor inspection and maintenance). The major difference is that the contacts in photo #1 are the result of very low usage:

A contact tip is not worn out just because the surface is rough and discolored. In fact signs of wear are good because this means the contacts are electrically “seated” and match each other better than a new set. Different amounts of contact wear, both between the fixed and movable parts, and between different phases, is normal. Filing, grinding, and other attempts to restore contact surfaces actually cause more harm than good. Maintenance should be limited to inspection for the amount of wear to determine whether or not the contacts need to be replaced before the next inspection.

Contact Tip InspectionLook for the amount of contact tip left. When the contact tip itself is worn out compared to the support, it is time to change out both contact tips and arc chutes. Replace components in complete sets to avoid uneven contact pressure. Photos below show progression.

Early life in squirrel cage motor application:

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Early life in plugging application (5000 make/break operations):

Mid life in squirrel cage application:

Mid life in plugging application (10,000 cycles):

End of life in squirrel cage application. Notice shoulders are gone on contacts on the left:

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End of life in plugging application. Photo at right shows material on arc chutes.

Arc Chute InspectionClean and inspect for contamination. Mark for replacement if there is severe contamination which cannot be removed. Acceptance Criteria (source: ABB 1VAF200013D0015):

1. Surface and hairline cracks that do not penetrate entirely through the inside and outside areas do not require replacement of the arc chute assembly.

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2. Cracks on lower portions and portions outside the area where the arc is extinguished do not require replacement unless they are severe enough to possibly affect the ability of the assembly to stay in position and in one piece.

3. Surface chips, abrasions, and indentations do not require replacement. Chips shown below acceptable. As long as loose pieces do not have a chance to become an impediment to operation of the mechanism, they are acceptable.

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4. When it is apparent that sections of the arc chute have broken off in pieces > ¼” square or there is a gap > 1/16” between sections, the arc chute should be replaced.