May 04, 2006
Motor Testing Tip
Developing Winding Shorts
Electric motor shorts are not instantaneous. They normally start with some type of weakness or defect between conductors that is aggravated by the electrical environment, contamination, starts and stops or aging. In the first stage, small changes to the capacitance of the insulation cause a small change in phase angle and or current/frequency response readings with MCA. As the change continues, the fault becomes more reactive and, in the second phase of a developing winding short, the phase angle and/or current/frequency test result changes are greater as the capacitive values of the insulation system changes more and the motor may begin ‘nuisance tripping.’ In the final stages of winding shorts, the fault area becomes less resistive as the fault temperature increases, at some point, the copper may vaporize between conductors, coils or from conductors to ground. This final stage is the only point where insulation testers and multi-meters can detect the fault, while MCA can detect the earlier stages up to months in advance, in systems under 600 Volts.
Tip provided by ALL-TEST Pro, LLC
http://www.alltestpro.com
Tel: 860.395.2988
May 04, 2006
Human Error Tips
Practice makes permanent, not perfect. Many organizations today depend on OJT (On-The-Job-Training) which is fine if the “teacher” is doing the job correctly. In many cases the teacher has bad habits that are passed on to the students and those bad habits spread. Many believe that you should WRITE WHAT YOU DO and DO WHAT YOU WRITE. The potential flaw is, what you write may not be correct! However, if we follow the incorrect information, we would be in compliance.
Tip provided by the Reliability Center Inc.
Tel: 804-458-0645
http://www.reliability.com
Human error caused loss of Mars orbiter
