IEEE 117:2015 pdf free download – IEEE Standard Test Procedure forThermal Evaluation of Systems ofInsulating Materials for Random-Wwound AC Electric Machinery
5.1.1 Motorette general construction
This subclause suggests appropriate test specimens for evaluating insulating systems that may be usefullysubjected to the exposures outlined in 5.2, to simulate their behavior in service. It is considered that one typeof motorette, as defined in the following, will adequately represent random-wound machines of both frac-tional and integral horsepower of 600-V rating or less. Other types of specimens will be required to representmachines with operating voltages other than 600 V and with other than random-wound insulation systems.Procedures for evaluating such other types of insulation fall outside the scope of this standard.(See IEEE Std1107-1996 [B15]and IEEE Std 1776 [B16].)
5.1.2 Motorettes
The model shall be made to embody all of the elements and should be, as nearly as possible, representativeof a complete winding insulation system.Specifically, it is recommended that for the purposes of testing ran-dom-wound motor insulation a motorette be employed, as shown in Figure 1, Figure 2, and Figure 3.At least10 motorettes shall be subjected to each of a series of test exposures outlined in 5.2.
Figure 1 shows typical components of a motorette before final assembly, while Figure 2 shows the assembledmotorette, and Figure 3 shows the motorette frame dimensions. Each of these components should be subjectedto separate screening tests to establish uniformity and normality before they are assembled.For example, anumber of representative samples of the wire, slot, and phase insulation, as well as wedges, all of which maybe broken down by ac high-potential tests or other means. It should be recognized that the number of tests thatare required to establish the acceptable temperature limit in service will increase greatly, if the performance ofindividual components varies over a wide range.Therefore, everything possible should be done to assure thatthe individual components are uniform and representative of the materials used in actual service.
The finished motorette consists of a rigid supporting metal stand with four suitable stand-off porcelain insula-tors bolted to one end and with a slot portion, made from an inner and outer plate, bolted to the other end.Thesupporting stand has holes for mounting the fixture during vibration testing.The slot sections are fabricatedfrom US Standard#16 gauge (1.52 mm [0.060 in]) steel sheets such as AISI 1010 cold rolled steel.The assem-bled slot portion contains two coils of magnet wire insulated from ground by slot insulation, insulated fromeach other by phase insulation, and held in place with slot wedges.These components are typical parts used inactual motors. The coils are each wound with two parallel wires (bifilar wound) so that conductor-to-conduc-tor electrical tests may be made.They can be machine wound on pins or forms, as in ordinary shop practice.
In special cases, the construction and processing procedures may be modified to simulate the intended use.
5.1.3.1 Overview of preparation
The following is a detailed description of the preparation of the motorette test samples for this standard testmethod.This motorette description is based on historic industry-wide testing.As noted in the last sentence of5.1.2, modifications may be made to more clearly simulate the intended use, provided the control and candi-date test specimens are modified in the same manner.The methodology for testing of multiple materials on onemotorette specimen has not been standardized and has not been established as part of this standard.