Quantitative current data allows localization of ground. To perform these tests obtain a test signal from a power source and insert an ammeter between source and probe. Provide a return lead to the source from the motor frame.
In Figure 6-25, connecting the probe to point “A,” which is closest to the grounded coil will provide a higher current flow then when connected to Points “B” or “C.”
Figure 6-25 - Localizing Ground with Ammeter
It is harder to localize grounds in delta configured windings because current differences aren’t as great due to multiple flow paths.
Contains descriptions, explanations of and case studies illustrating 12 diagnostic tests performed during motor manufacturing and repair, including entirely new and extremely valuable test method involving use of polarization index curves called Polarization Index Profile Analysis for determining the condition of insulation systems in all sizes and types of motors in service as well as during restoration short of total rewind.