Elevators

The use of high frequency testing can determine if the insulation is starting to deteriorate around the “turns” of the armature or field coils. The high frequency (TDR) excites the insulation and, if there are anomalies present, they can be detected on a very fast oscilloscope.

This testing differs from conventional testing (i.e. megger, high pot or polarization index) in that it uses high frequency as the methodology. TDR will discover problems in the insulation (after-potentials) before they are detectable with conventional testing.

Clients are supplied with a summary report on all elevators tested (armature & field coils). The computer will generate a failure percentile giving the percentage of motors that have failed in one year with a given profile.

This has proven to be extremely beneficial as it relates to gearless/geared machines and generator sets before they are modernized. If a static drive is going to be installed to power the motor, the square tooth wave that will be emitted from the controller will quickly deteriorate a compromised field coil. Therefore, they will most likely burn out after modernization. When compromised armatures or field coils are detected using TDR, they can be rewound during modernization.

The testing takes about 1 hour per unit (armature/field coils) and the results are available in approximately one week. For more information on TDR testing for elevators please review the case studies below.

Otis Elevator Case Study

Otis Type 77 Eevator Field Study