IEEE 1776-2008 pdf download IEEE Recommended Practice for Thermal Evaluation of Unsealed or Sealed Insulation Systems for AC Electric Machinery Employing Form- Wound Pre-Insulated Stator Coils for Machines Rated 15 000 V and Below
1. Overview
1.1 Scope
This recommended practice outlines test procedures for comparing two or more unsealed or sealedinsulation systems in accordance with their expected life at rated temperature. The procedure is limited tonsulation systems for AC electrical machines using form-wound pre-insulated stator coils rated 15 000 Vand below.
The intent of this test procedure is to evaluate unsealed insulation systems for use with air cooling underusual (normal) service conditions, or sealed insulation systems for use under severe environmentalconditions (where the insulation is exposed to conducting contaminants). This procedure does not coverspecial requirements, such as those for machines enclosed in gas atospheres or machines subjected tostrong chemicals, metal dust or submersion in liquid, etc.
The procedure includes instructions for testing candidate systems in comparison with known referencesystems, of the same type, having a proven record of service experience and interpreting the results of thesetests.
1.2 Purpose
The purpose of this procedure is to classify unsealed or sealed insulation systems for the machinery used inusual (normal) service or machinery used in severe environmental conditions (and falling within the scopeof this recommended practice) in accordance with their temperature capabilities by test, rather than bychemical composition. Data from such tests may be used to establish the temperature classification of newinsulation systems before they are service-proven.
In order to provide data from which a base of reference for temperature classification can be established.
service-proven (reference) unsealed or sealed systems should also be tested according to this test procedure.
This document combines the procedures given in IEEE Sd 275TM-1992 (for unsealed systems) with thoscofIEEE Std 429TM-1994 (for sealed systems).
1.3 General conditions
The concepts implemented in this recommended practice are based on IEEE Std 9g TM
The intent of this procedure (Combination of IEEE Std 275-1992 and IEEE Std 429-1994) is to classifycandidate insulation systems by comparing them to reference insulation systems in machines with service-proven classifications in the Class A, B, F, H, N, S, R or C categories. The temperatures for classification ofinsulation systems are 105 “C, 130 C,155 C,180 C, 200 C, 220 C,240 C and over 240 C.respectively. lt is expected that the several insulating materials or components that form any insulationsystem to be evaluated by these procedures will first be screened by the appropriate test procedures for eachtype of material Thermal indexes for insulating materials can be obtained by following the proceduresshown in IEEE Std 98TM
Thermal indexes of insulating materials cannot be used to classify insulation systems. They are to beconsidered only as screening tests for this system test
1.4 Methods of evaluation
This test procedure describes test models suitable for use in insulation tests. The procedure recommends aseries of heat exposures to which the test models may be subjected to represent, under acceleratedconditions, the cumulative effects of long service. Procedures are given for applying periodic voltagechecks, preceded by periods of mechanical stress and moisture, to establish the end point of insulation lifeby electric failure.
To obtain an acceptable statistical average, for each chosen temperature of heat exposure, an adequatenumber of samples should be carried through the test procedure until failure occurs, lt is recommended thatthe tests on the samples be performed at a minimum of three different aging (exposure) temperatures foreach insulation system to be evaluated.
IEEE 1776-2008 pdf download
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