Testing of Motors and Generators
Today’s machines are subjected to extremely high electrical and mechanical stresses and therefore have shorter life spans as compared to yesterday’s bulky machines. Furthermore, unfavorable operating conditions may lead to unexpected troubles, which can have harmful effects on machine life. The insulation system is extremely important and therefore should be checked on a regular basis. IEEE standard 1415-2006, IEEE Guide for Induction Machinery Maintenance Testing and Failure Analysis provides maintenance testing and failure analysis guidance for form-wound, squirrel cage, induc- tion motors rated up to 15 kV. It addresses the stator (winding and core) rotor (winding and core) vibration and noise bearings and shafts structure, frame ventilation, and accessories. This guide is intended to be used by personnel responsible for the operation and maintenance of large induction machines. Table 10.1 of the IEEE standard 1415-2006, IEEE Guide for Induction Machinery Testing and Failure Analysis, gives a list of the various tests that are in wide- spread use in the industry for testing induction machines. This table lists the test description, effectiveness, typical frequency, and the pertinent IEEE standard reference for each test. The IEEE Table 10.1 is represented in Table
10.10 for reader’s reference. The reader is urged to consult this table and the IEEE standard 1415-2006 when performing test on induction machinery.
The tests listed in Table 10.10 are all encompassing, and many of the nonelectrical tests are not in the scope of this book. The reader should refer to the last column of the Table 10.10 for additional information on the tests not covered in this chapter. The state of the machine insulation can be checked by means of the tests discussed below:
Insulation Resistance and Dielectric Absorption Tests
The simplest and most basic tests for checking insulation integrity of machines are the insulation resistance and dielectric absorption (DA) tests. Refer to Chapter 2 for details on how to perform these tests.