DEFINITIONS FOR COMMUTATOR CONDITION INDICATORS
Total Indicated Runout (TIR)
The Total Indicated Runout for commutator and slip ring tests is the difference between the minimum bar or segment height and the maximum bar height. The TIR is also referred to as 'out of roundness'.
Maximum Bar-to-Bar Variance (MBTB)
The Maximum Bar-to-Bar Variance for commutator and slip ring tests is the maximum height difference between two consecutive bars or segments.
Undercut depth is the depth of the insulating mica between the bars or segments. High micas occur when there appears to be no gap between two consecutive bars.
(Thanks to National for use of the above slides.)