PROGRESS ON IEC 60034-18-42 FOR QUALIFICATION OF
STATOR INSULATION FOR MEDIUM-VOLTAGE INVERTER
Copyright Material IEEE
Paper No. PCIC-2007-6
Senior Member, IEEE Fellow, IEEE
GE Consumer & Industrial
107 Park Street North
2-1 Westside Dr.
Peterborough, Ontario K9H 7A4
D. L. Bogh
Senior Member, IEEE
GE - Motors
18628 – 182nd Ave NE
Woodinville, WA 98077
Toronto, ON M9C 1B2
Abstract - There is an industry need for suitable methods
to qualify medium- and high-voltage stator insulation systems
for inverter duty applications. Technical Specification (TS) IEC
60034-18-42 is being written to address the unique
requirements of form-wound micaceous systems to withstand
inverter pulses, characterized by elevated voltage, fast rise
times, and high frequency impulse repetition rates. These
machines do not operate under the same ageing conditions
as those supplied by sinusoidal power or as random windings
supplied by pulse-width modulated (PWM) drives. Depending
on the specific waveform characteristics observed at the
machine terminals, the groundwall insulation, turn insulation,
corona suppression and endwinding voltage grading systems
are significantly affected by ageing factors such as partial
discharge (PD) and elevated temperature. The TS offers
technically sound guidelines to manufacturers and users
describing test procedures to prove the electrical and thermal
reliability of these components. Like IEC 60034-18-41 (for low
voltage systems) it will significantly impact construction and
testing of NEMA motors. This paper describes the theoretical
and practical considerations of the specification.
ASD’s are an integral part of the industrial world. There is
wide recognition that motors and drives need to be
coordinated as a system to assure reliable, long-lived
installations. Drive systems for low voltage machines are well
documented; NEMA and IEC have published application
guides. NEMA published , which addresses issues
associated with adjustable speed drive (ASD) and motor
installations. It is currently being updated and the new edition
will likely reference IEC 60034-18-41. IEC has also published
, which covers low voltage applications only.
IEEE has recently published , a performance standard for
medium voltage drives and motors used in the petrochemical
industry. The standard says nothing about the interaction
between power converter pulses and medium voltage motor
insulation systems. This is a difficult subject, which has not
received the same attention as low voltage insulation
IEC 60034-18-41 covers Type I insulation systems, which
are generally low voltage and by definition are designed to
operate without PD. The document provides the technical
foundation for both technical specifications . The IEC voted
1-4244-1140-8/07/$25.00 ©2007 IEEE
this document as a technical specification In 2006. IEC
60034-18-42 is still draft. There is a good chance that it will be
voted to a standard in 2007.
IEC TS 60034-18-42 addresses Type II insulation systems.
Type II insulation systems are designed to experience PD
over their lifetime. The coils are usually form wound and rated
more than 2400 volts. PD and elevated temperatures
experienced during service limit the life of the insulation
system. IEC TS 60034-18-42 employs comparison to an
insulation system having “acceptable service life” as the basis
for qualification of a candidate inverter duty system.
In the authors’ experience, medium voltage machine
insulation systems generally have fared quite well when
matched with medium voltage ASD’s. Form wound motor
stator coils with micaceous insulation systems are fully
impregnated by vacuum-pressure impregnation (VPI) or press
cured using resin rich tapes.
Medium voltage drives are generally based on multi-step
PWM voltage source power conversion. IEC TS 60034-18-42
formally covers only motors associated with PWM voltage
source inverters. These pose more of a risk to insulation
systems than other ASD architectures. Motor insulation
requirements are based on expected waveforms at the motor
terminals, giving the TS very broad applicability.
IEC TS 60034-18-42 gives a consistent definition of
medium voltage machine insulation systems applied to ASDs.
Its careful descriptions of system qualification tests and
production acceptance tests will provide a basis for an
increased understanding of insulation system performance.
II. FORM WOUND COIL INSULATION SYSTEMS
The Type II insulation system described by IEC TS 60034-
18-42 is expected to be form wound, typically used in stators
rated 2400 V and above. Figure 1 shows a diagram of a form
wound coil. The insulation system consists of:
• Stranded conductors to improve the efficiency of the
motor by reducing eddy current and skin effect losses.
The insulation used on the strands is typically a film
coating and/or a Dacron and glass covering.
• Turn insulation to isolate the copper turns from each
other. In modern motors the turn insulation is usually a
Dacron and glass composite or mica paper (mica
platelets on a film- or Dacron-and-glass backing tape).
The authors would like to acknowledge the tremendous
effort of Dr. Jeremy Wheeler, who is convener of the IEC
working group writing IEC 60034-18-42.
Meredith Stranges holds degrees in Chemistry and
Metallurgical Engineering from Brock University and
McMaster University, respectively. She joined General
Electric in 1997, and in 2004 became the Lead
Insulation Engineer for GE Peterborough. Meredith
specializes in qualification of insulation systems and
materials for large industrial motors, and she has
authored or co-authored several papers. She is active in
the IEEE Dielectrics and Insulation Society, and is a
contributing member to international standards working
groups for the IEEE Standards Association and IEC
Technical Committee 2 on Rotating Machines. She is a
Professional Engineer in the province of Ontario.
Greg. C. Stone has a PhD in Electrical Engineering
from the University of Waterloo, Canada. For 17 years
he was with Ontario Hydro, a major Canadian utility,
where he was involved in motor and generator testing.
Since 1990, he has been a Dielectrics Engineer at Iris
Power, a manufacturer of machine test equipment. He is
past President of the IEEE Dielectrics and Electrical
Insulation Society, and has published 2 books and
numerous papers. He is a Professional Engineer in
Dennis L. Bogh has a BS in Electrical Engineering
from the University of Washington, Seattle, WA, USA.
He has been employed by General Electric since 1975 in
various capacities including
management, sales and application engineering. He is a
member of the API 547 committee, and a registered
Professional Engineer in the state of Washington.