Vanguard CT-7500 - Manual (Page 56)

MODEL CT-7500 OPERATING INSTRUCTIONS
50
Rev 2 Jan 2001
9.14. Breaker Travel Analysis
The CT-7500 travel analysis includes breaker stroke, over-travel, bounce-back, and contact-
wipe distances, and contact velocity calculation.
9.14.1 Breaker Stroke
The CT-7500 uses a digital transducer to measure a breaker's contact stroke, over-travel, and
bounce-back. The digital transducer output is 200 counts per linear inch of travel; the resolution is
accurate to 1/200 inch. The output resolution is ±0.01 inch on the test result report.
Unlike slide-wire transducers, the CT-7500 transducer needs no calibration or setup. A user
verifies transducer function by selecting a diagnostic test for the transducer (paragraph 9.19).
9.14.2 Breaker Over-travel Distance
Over-travel is a distance the contact moves beyond the resting position. Over-travel is typically
found in the Close Operation.
9.14.3 Breaker Bounce-Back Distance.
Bounce-back is the distance the breaker contact moves before the resting position after over-
travel. Again, bounce-back is typically found in the Close Operation.
9.14.4 Contact Wipe.
Contact wipe is the distance measured from the close position to the contacts touching (or
parting). In the Close Operation, contact wipe is measured from the contacts touching position to
the final close position.
In the Open Operation, contact wipe is measured from the close position to contact break (or
parting) position.
NOTE
Contact wipe is measured during operation. This measurement may not be as accurate as
measurement done using the slow close mode. It is recommended the user use the Slow
Close Test (paragraph 9.18) to verify wipe measurement if required.
9.14.5 Breaker Velocity
The CT-7500, when used with a travel transducer, calculates the breaker contact velocity
through the arc zone. Users must program the calculation points (analysis points) on the travel
curve for the unit to calculate contact velocity. Analysis points selection and setup are discussed
in the following paragraphs.
9.14.6 Analysis Point Selections.
Analysis points are used to calculate average contact speed through the contact's arc zone.
The analysis points are usually specified by the breaker manufacturers. The analysis points are
fully programmable in the Timer by the user. The Timer will store two setups for calculating
velocity (one each for open and close). These setups remain in the Timer's RAM memory until
changed by the operator.