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© 2014 UL LLC.

Safety and Performance

Reliability of Electrical

Insulation SystemsMark Raymond

Principal Engineer

Visit us at Booth 3.1/E41

Objectives

• What is an Electrical Insulation System?

• History of Electrical Insulation Systems

• What is UL 1446?

• Performance and Safety

• Future state

Insulation System Definition

Electrical Insulation System

(EIS) – Electrical insulating

structure containing one or

more electrical insulating

materials (EIM) together with

associated conducting parts

employed in an

electrotechnical device

Example - the combination

of a magnet wire, ground

and interwinding insulation,

and impregnating resin in a

transformer

Slide 3

EIS Components

Electrical Insulating Materials

(EIM) – Materials relied on in

the EIS to prevent risk of

electric shock and dielectric

breakdown (formerly known as

Major Components)

Non-electrical Insulating

Materials (NIM) – Materials

used for mechanical or thermal

applications and not relied on to

prevent electric shock or

dielectric breakdown (formerly

known as Minor Components)

Slide 4

History of Electrical Insulation Systems

Need to know

the effects of

Temperature

on Electrical

Insulation

US Navy ships

have limited space

and smaller equip-

ment was needed

to allow for more

room

But how will it

perform?

Compare new

materials with

existing known

service life

materials

1958 US Navy

sponsored

Round Robin

EIS testing

Establish

Thermal

aging test

procedure

to allow

comparison

Slide 5


Functional Evaluation of

Motorette Insulation

Systems - March 1959;

Brancato, Johnson,

Campbell & Walker

Reliability Prediction

Studies on Electrical

Insulation: Navy

Summary Report - July

1977; Brancato, Johnson,

Campbell & Walker

IEEE 117 - IEEE Standard

Test Procedure for

Evaluation of Systems of

Insulating Materials for

Random-Wound AC

Electrical Machinery

Military Specification

MIL-E-917D (Navy),

covering the basic

requirements of

electrical power

equipment for naval

shipboard use

Slide 6


A material that is classified as suitable for a

given temperature may be found suitable for

a different temperature, either higher or lower,

by an insulation system test procedure.

(para. 3.5.2.1.10)“

”

Slide 7


(1) “Material Thermal Class Ratings vs EIS Thermal Class Rating,” Eltek International Laboratories, April 2015.

Study(1) conducted

comparing EIM

ratings vs. EIS

thermal ratings

established by Full

Thermal Aging

Test data from 30 EIS Aging tests were reviewed

15 (50%) were rated higher than the lowest EIM rating

14 (47%) were rated lower than the lowest EIM rating

1 (3%) were rated the same as the lowest EIM rating

This study supports the value in thermal evaluation of an EIS as a complete

system rather than relying upon individual EIM ratings alone to determine

thermal class for the system

Slide 8

What is UL 1446?

Standard of

Insulating

Materials –

General

First Edition

of UL 1446

Published

June 1978

Makes Use of

Existing

Standards for

Evaluation of

EIS and EIM,

predominately

IEC standards

Provides

Guidance on

Substitution

of Materials

UL 1446

Slide 9

Insulation System Compatibility

Magnet

Wire

Tap

es

Lead Wire

Slot

Liners

Layer

Insu

lati

on

Sp

acers

Slot Wedges

Tie

Co

rds

Laminations

Phase

InsulationGround Insulation

Varn

ish

Cross-Over Insulation

Slide 10

Performance and Safety

Magnet

Wire

Tap

es

Lead Wire

Slot

Liners

Layer

Insu

lati

on

Sp

acers

Slot Wedges

Tie

Co

rds

Laminations

Phase

Insulation

Ground Insulation

Varn

ish

Cross-Over Insulation

Chemical interaction

between polymeric

materials at elevated

temperatures may

prematurely degrade

critical insulating

materials

This may eventually cause

potential hazards

• Risk of Fire

• Risk of Electric Shock

• Risk of Injury to Persons

Slide 11


Sustained exposure to heat is a

major cause of polymeric

material degradation

Thermal Aging Test is

conducted to establish a

maximum temperature that an

EIS will operate for the intended

service life of the product

Slide 12

Full Thermal Aging (FTA)

Thermal

Endurance

Test

Actual Operating Part:

• Motors

• Transformers

• Solenoid Coils

Non Functional

Test Specimens

General Purpose Model (GPM)

Slide 13

Full Thermal Aging (FTA) – General Purpose

Model (GPM)

Slide 14

Thermal Aging Test Program

Oven(Conditioning)

Cold(Conditioning)

Vibration(Conditioning)

Moisture(Conditioning)

Turn to Turn (Proof Testing)

Ground, Interwinding

and Encapsulant(Proof Testing)

Slide 15

Thermal Aging Test Program

Conditioning• Oven

• Vibration

• Cold

• Moisture

Proof Testing• Turn to Turn

• Ground, Interwinding and Encapsulant

Slide 16

UL’s Electric Insulation System Categories

OBJY

Primary category for

manufacturers of EIS in

their products. i.e. Motor

and transformer

manufacturers

OBJS

Category established for

supplier of materials used

in EIS by the OBJY

manufacturer. i.e. plastic

and impregnating resin

manufacturers

Slide 17


Evaluation of an EIS allows for

Efficient use of

materials

Reduction in

size and weight

of the device

Leverage

availability of

supply chain

materials

Greater

Confidence in

Reliability and

Performance

Slide 18

Future State of Electrical Insulation Systems

Current UL 1446

Standards Technical

Panel activities

• Removed voltage

reference in Scope

• Improve definition of

Terms

• Add equivalent IEC

test as preferred

method for existing

ASTM methods

Proposal to revise the organization of UL 1446

• Thermal aging of EIS

• Substitution guidelines

• Magnet Wire and Coatings

• Varnishes and Impregnating Resins

• Specific Ground and Interwinding Requirements

• Molding requirements for Ground Insulation

• Integral Ground Insulation

• Flexible Laminate Requirements

• Laminate Construction Details for Insulation

Systems - Component

Slide 19


Improved Test Method for High

Voltage Transformer EIS

• Current method IEEE C57.12.60

• IEC 61857-41

• 2016-06-10 closing date for

voting New Work Item Proposal

Form-wound Pre-insulated High

and Medium Voltage Motor

and Generator EIS

• IEC 60034-18-31

• IEC 61858-2 Form-wound EIS

substitution

Use of extended Field History of EIS

in lieu of Thermal Aging

IEC 61857-41

• If approved and published it will

immediately be available for use

under UL 1446 standard because UL

1446 references IEC 61857 (All Parts)

• EIS thermal rating is based upon a

voltage stress level, i.e. kV/mm and

may be used in a variety of transfor-

mer designs that use the same mate-

rials tested and the voltage stress

level is at or below the level tested.

Slide 20


Short Term Thermal Aging

of EIS for use in Motors

• IEC 60335-1 Annex C

• Test on actual motor using

locked rotor and monitor

winding temperature

• Elevate winding

temperature above

anticipated Thermal Class

• Test time takes

approximately 50 days

Slide 21

Example of STTA Test

Desired rating is Class B 130ºC

Shortest test time is achieve using test temperature 55ºC above thermal class i.e. 185ºC

Use 6 motors for test

Thermal couple the windings and lock the rotors

Apply voltage to increase the temperature of the windings to 185ºC

When temperature is stable, maintain for 250 hours (cycle)

After 1st cycle measure the leakage current, requirement <0,5mA

Repeat 3 more times, after last humidity conditioning conduct electric strength test

using value 50% of the required test voltage for device’s voltage rating

Then 48 hour humidity conditioning 93 ± 3% RH.

Slide 22

Short Term Thermal Aging of EIS for use in Motors

Primary Benefits

Reduced time-to-

market due to an

accelerated (two

month) evaluation

Less expensive than

Full Thermal Aging

program

Reduced sample

preparation costs

and time due to

actual motor testing

Slide 23

Key Take Away

The importance of thermal aging evaluation of the electrical insulation system

as a whole to determine thermal classification

What should you DO if you do nothing else

Be aware of IEC Standards Developments and get involved with your National

Committee

Slide 24

Thank you!

Any Questions?

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