Motor maintenance testing & diagnostics on-line, off-line

In recent years there have been significant advances in diagnostic technologies to detect early signs of degradation in motor electrical components. Such information allows corrective actions to be taken before failures occur and thus significantly improve motor reliability. This is particularly true in the case of on-line diagnostic techniques. This paper discusses the following on and off-line diagnostic test techniques, as well as visual inspections, as they apply to ac motors with voltage ratings of 2300 V and above. ldr Partial discharge ldr Current signature analysis Off-Line Tests and Inspections ldr Insulation resistance (IR) and polarization index (PI) ldr Surge ldr Hi pot ldr Power Factor or Dissipation Factor Tip-Up ldr Partial Discharge ldr AC Pole Drop ldr Stator core ldr Visual inspections The on-line tests are performed with the motor running under normal operating conditions while the remainder deal with tests and inspections that require the motor to be shut down and in some cases be partly or completely disassembled.