Guide for a Test Procedure for the Measurement of Loss Tangent of Coils and Bars for Machine Windings
|Publication Date:||1 March 1987|
|ICS Code (Components for rotating machines):||29.160.10|
The characteristics of an insulation system can be evaluated in terms of dielectric strength, insulation resistance, dielectric loss, etc.
This report is applicable to a method of measuring dielectric loss properties of the insulation system of the slot portions of new coils or bars for rotating electrical machines having rated voltage UN of 5 kV and above.
The test is applicable to form wound coils or bars in which the insulation is cured before the winding is inserted in the stator.
For tests on post-impregnated machines, see Appendix A.
The uniformity of manufacture is judged to some extent by measurement of the dielectric loss tangent as a function of voltage and by statistical evaluation of the test results.
For a known insulation system, the following properties can be assessed:
- a low loss tangent at low voltage (0.2 UN) indicates a high degree of molecular crosslinking of the bonding medium (degree of resin cure),
- the magnitude of delta tan delta by increase of voltage gives some indication of the void content of the insulation.