Standards for efficiency of electric motors permanent magnet synchronous motor technology

Permanent magnet
synchronous motor technology

IEEE INDUSTRY APPLICATIONS MAGAZINE  JAN j FEB 2011  WWW.IEEE.ORG/IAS

B Y A N ´I B A L T . D E A L M E I D A ,
FERNANDO J.T.E. FERREIRA,
˜ O A.C. FONG
& JOA

12

E

LECTRIC MOTORS IN INdustrial applications consume
between 30% and 40% of the
generated electrical energy world-

wide. In the European Union (EU), electric
motor systems are by far the most important
type of load in industry, using about 70% of
the consumed electricity. In the tertiary sector
(nonresidential buildings), although not so relevant, electric motor systems use about one-third of
the electricity consumed. Their wide use makes electric motors particularly attractive for the application of
efficiency improvements. Despite the wide variety of electric motors available in the market, three-phase, squirrel-cage
induction motors (IMs) represent, by far, the vast majority of the
market of electric motors [1], [2].
Higher efficiency electric motors can lead to significant reductions in energy
consumption and also reduce environmental impact. To promote a competitive
Digital Object Identifier 10.1109/MIAS.2010.939427
Date of publication: 12 November 2010

1077-2618/11/$26.00©2011 IEEE

© FOTOSEARCH


of PMSM technology in that respect, which, in general,
are significant.
New Motor Efficiency Classification Standard
IEC 60034-30 [3] is intended to globally harmonize motor
energy efficiency classes in general purpose, line-fed (direct
on-line connection) IMs used in stationary applications,
defined according to IEC 60034-1 [7]. The classification
standard also applies to IMs rated for two or more voltages
and frequencies. IMs in the 0.75–375-kW power range
make up the vast majority of installed motor population
and are covered by this standard. For the application of IEC
60034-30 standard, motor efficiency and losses shall be
tested in accordance with IEC 60034-2-1 [8] using a low
uncertainty method, such as the “summation of losses” test
procedure with stray load losses (SLLs) determined from
residual loss—a procedure similar to IEEE 112-B [11]. The
rated efficiency and the efficiency class shall be durably marked
on the rating plate. In a motor with dual-frequency rating,
both 50- and 60-Hz efficiencies shall be marked for each rated
voltage/frequency combination. Motors with full-load efficiency equal to or exceeding an efficiency class boundary
are classified in that efficiency class. As stated previously,
IE1, IE2, and IE3 classes are normative [3], [4], [10].
Motors covered by this standard may be used in VSD
applications (for further information, see Application Guide

IEC 60034-17); however, in these cases, the marked efficiency of the motor shall not be assumed to apply because of
the increased losses from the harmonic voltage content of
the VSD power supply. Motors specifically built for operation in explosive atmospheres (according to IEC Standards
60079-0 and 61241-1) are also covered by this classification
standard. Some design constraints of explosion-proof motors
(such as increased air gap, reduced starting current, and
enhanced sealing) have a negative impact on efficiency.
Geared motors and brake motors are included, although special shafts and flanges may be used in such motors [10].
According to the IEC 60034-25 standard, motors
specifically made for converter operation with increased
insulation, motors completely integrated into a machine
(pump, fan, compressor, etc.) that cannot be separated from
the machine, and all other nongeneral purpose motors
(such as smoke-extraction motors built for operation in
high ambient temperature environments according to EN
12101-3) are clearly excluded. Special motors required by
applications with a large number of start/stop cycles are
also not covered by this standard. The full-load, continuous-duty efficiency of these special motors is typically
below standard efficiency because of the need to reduce
rotor inertia. In some countries (e.g., Australia and New
Zealand), eight-pole IMs are included in energy efficiency
regulations. However, their market share is already very
low (in Europe about 1% or less). Because of the increasing
acceptance of VSDs and the low cost associated with fourand six-pole standard IMs, it is expected that eight-pole
IMs will further disappear from the general market in the
future. Thus, this standard excludes provisions for eightpole IMs [11].
The 50-Hz values for IE3 class are newly designed and
set about 15% reduced losses above the requirements for
IE2 class. The 60-Hz values were derived from the 50-Hz
values taking into account the influence of supply

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motor market transformation, a new international standard,
International Electrotechnical Committee (IEC) 60034-30
[3], was approved in November 2008 to globally harmonize motor energy efficiency classes in general purpose, single-speed, line-fed, three-phase, squirrel-cage IMs. In this
standard [3], three efficiency classes are proposed, standard
efficiency (IE1) [the designation of the energy efficiency
class consists of IE (short for International Energy Efficiency
Class), directly followed by a numeral representing the classification], high efficiency (IE2), equivalent to EPAct, and
premium efficiency (IE3), equivalent to National Electrical
Manufacturers Association (NEMA) premium. In addition,
in the last proposal of the IEC 60034-31 technical specification standard, a super-premium efficiency (IE4) is also proposed, intended to be informative, since no sufficient
market and technological information is available to allow
its standardization and more experience with such products
is required. All the IE1, IE2, IE3, and IE4 efficiency levels are
defined for the 0.75–375-kW power range, equivalent to the
1–500-hp range.
Regarding the IE4 class, some European manufacturers
see no technical feasibility to reach the first IE4 proposed
levels with IM technology with the same IEC frame sizes
(defined in [5]) as IE1/IE2-class IMs. However, very highefficiency motors with permanent magnet (PM) rotor
technology are being introduced in the market, which allow
not only reaching but overtaking the proposed IE4 levels.
The IE4 class under consideration can be applied both
to line-fed motors and inverter plus motor units. For lowpower levels (up to 7.5 kW), it is clear that moving away
from IM technology and considering emergent technologies such as PM synchronous motors (PMSMs), either
electronically controlled (EC) or with an auxiliary cage in
the rotor to allow direct line-start mains operation [18],
can allow achieving efficiency levels significantly higher

than those defined by premium IE3 class.
In this article, feasible minimum limits for IE4 class
are analyzed, taking into account the estimated efficiency
limits and rated efficiency for emergent or commercially
best available line-start PMSM technologies. The presented
results can be useful to set up future international standard
super-premium or IE4-class levels/limits. The practicability and technical limits associated with the IE4-class efficiency levels proposed in [4] are addressed, taking into
account technical and economical limitations. It is expected
that advanced technologies will enable manufacturers to
design motors for the IE4-class efficiency levels proposed in
[4], with mechanical dimensions compatible with the existing IMs of lower efficiency classes (e.g., flanges, shaft heights,
or frame sizes as defined in standards EN 50347 [5] and
NEMA MG1 [6]). NEMA frames sizes are larger than the
IEC frame sizes, allowing the use of more active materials. In
addition, 60-Hz operation enables higher power density and
higher efficiency levels with the same frame sizes.
Moreover, in the case of EC PMSMs, the electronic controller, inverter, or variable-speed drive (VSD) efficiency
and its impact on the motor efficiency are taken into
account during efficiency focused analysis.
Since most general purpose IMs are oversized (in the
EU, the IMs’ load factor is, on average, slightly lower than
60% [2]), the part-load efficiency or their load dependency
should be analyzed to underline the potential advantages

13


98

98

96
96

94
92

NEMA Premium at 50 Hz
NEMA Premium at 60 Hz
EPAct at 50 Hz
EPAct at 60 Hz

94
Motor Efficiency (%)

Motor Efficiency (%)

90
88
86
Four Poles

84
82

50 Hz, IE1
50 Hz, IE2
50 Hz, IE3
50 Hz, IE4
60 Hz, IE1

60 Hz, IE2
60 Hz, IE3
60 Hz, IE4

80
78
76
74
72
70
0.1

92
90
88
86
Four Poles
84
82
80
0.1

1
10
100
Motor-Rated Power (kW)
(a)

1
10

100
Motor-Rated Power (kW)
(b)

1

14

frequency on motor efficiency [4], resulting for four-pole
IMs, in the levels presented in Figure 1 for four-pole IMs.
This approach will enable manufacturers to build motors
for dual rating (50/60 Hz).
The levels of the IE4 efficiency class are envisioned
to be incorporated into a future edition of IEC 60034-31
technical specification standard. The goal is to reduce
the losses of IE4 by about 15% relative to IE3. Technologies other than IMs will be required to meet IE4
levels [3].

100

Windage and Friction Losses

90
80

Core Losses

70
Loss Fraction (%)

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IEC 60034-30 and 31 efficiency levels and NEMA and EPAct minimum efficiency requirements for 60- and 50-Hz,
four-pole IMs [10].

60
50

Stray Load Losses
Rotor I 2R Losses

40
30
20

Stator I 2R Losses

10
0
0.75 1.5 3 5.5 11 18.5 30 45 75 110 160 250
Motor-Rated Power (kW)
Typical fraction of losses in 50-Hz, four-pole IMs [10].

2

All efficiency curves are given in mathematical formula
in smooth form to allow for various regional and national
distinctions for frame dimensions and motor sizes.
The approved IEC 60034-30 efficiency classification
standard will harmonize the current different requirements

for IM efficiency levels around the world, hopefully ending
the difficulties that the manufacturers encounter when producing motors for a global market. Additionally, customers will benefit by having access to a more transparent and
easier to understand information.
Efficiency Limits for Line-Start Industrial Motors
The relative importance of the five different kinds of IM
losses depends on motor size, as it can be seen in Figure 2.
In small/medium IMs, I2R losses are dominant. Since I2R
losses remain constant for 50 Hz and 60 Hz as long as the
torque is kept constant, the output power is 20% higher
for the 60-Hz IMs, and although windage, friction, and
iron losses increase with frequency, they play a minor role
in IMs. Therefore, most IMs develop a better efficiency at
60 Hz compared with that at 50 Hz, becoming easier to
reach a high motor efficiency when the motor is designed
for and operated at 60 Hz instead of 50 Hz. The difference
in efficiency between 50 and 60 Hz varies with the number
of poles and the size of the motor. In general, when compared at the same torque, the 60-Hz efficiency of low-voltage, four-pole IMs in the 0.75–375-kW power range is
between 2.5% points (small motors) to less than 0.5% points
(large motors) greater when compared with the 50-Hz efficiency [4], [10].
Only large two-pole IMs may experience a reduced
efficiency at 60 Hz because of their high share of windage and friction losses. Another important issue is the
load dependency of losses and its impact on the IM efficiency. When considering EC IMs or PMSMs, those


In the case of PM rotors with auxiliary squirrel-cage, considering the steady-state, synchronous operation, the rotor
electric and magnetic losses are mainly due to the effect of
negative- and positive-sequence magnetomotive force
spatial harmonics in the cage, inducing stray currents,
which will produce losses, vibration, and parasitic torque
components. Nevertheless, for an optimized stator winding and rotor cage, those effects can be neglected.

On the basis of the typical fraction of losses for fourpole, 50-Hz IMs presented in Figure 2 and the 50-Hz IE3class efficiency levels presented in Figure 1, it is possible to

96

Motor Efficiency (%)

94
92
90
88
86
84
Four Poles
82
0.1

1
10
Motor-Rated Power (kW)

100

IE3 Efficiency Levels for 50 Hz
IE3 Efficiency Levels for 60 Hz
Adapted Ultrapremium Efficiency Levels for 50 Hz
Commercial Ultrapremium Efficiency Levels for 60 Hz

3
Commercially available ultrapremium efficiency 60-Hz,
four-pole IMs [3], [12].

estimate the maximum achievable efficiency level (at 50
Hz) resulting from the reduction of each loss component.
The new improved motor-rated efficiency resulting
from the losses reduction is given by (1) and (2), where gnew
is the new rated efficiency (in percent), gorig is the original
rated efficiency (in percent), Dptotal is the total losses (in
percent), l is the loss component identification (e.g., rotor
I2R losses and stator core losses), pcomp_l is the loss component l (in percentage of total losses), and Dpcomp_l is the
variation of loss component l (in percent).

12
10
Losses Reduction (%)

Line-Start PMSMs with Auxiliary Rotor Cage

98

IE3 Versus
Ultrapremium
Four-Pole, 60-Hz IMs

8
6
4
2
0
0.75 1.1 1.5 2.2 3.7 5.5 7.5 11
Motor-Rated Power (kW)

15

4
Loss variation between IE3-class efficiency levels and
commercially available ultrapremium 60-Hz, four-pole
IMs [10], [13].

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efficiency variations are not critical, since frequency can
be set as a function of the needed speed, and the magnetizing flux can be properly regulated to maximize
the efficiency.
Excluding the use of amorphous steel sheets in the stator
and rotor cores, which means that copper is used in the stator
windings and conventional ferromagnetic steel sheets are
used in the stator and rotor cores, the efficiency improvement of the industrial motors can be achieved mainly by
improving the design and changing the rotor materials.
The use of copper in the rotor cage was an important
step toward premium efficiency levels, maintaining the
typical wound stator and frame size. However, if the frame
size is respected, such material change is not enough to
reach super-premium levels although it allows to reach efficiency levels slightly higher than IE3 class. Ultrapremium
efficiency IM models are already commercially available, as
can be seen in Figure 3 [12]. The efficiency gain over
NEMA premium or IE3-class efficiency levels is nearly one
percentage point for the 1–10-hp power range, meaning
that losses were lowered from 6.2 to 11.4% (Figure 4) by
means of improved design and use of copper in the rotor
cage. As expected, the efficiency gain decreases with the

rated power. This clearly shows the efficiency improvement
potential limits associated with IMs, if standard frame sizes
are respected.
Nevertheless, new promising technologies are being
investigated, such as the single-speed non-EC line-start
PMSMs (with auxiliary cage) and the EC PMSMs [16]–
[31]. The last technology is currently commercially
available [13]–[19], but the first one is not yet commercially available (at least in large scale) because of
the inherent problems related with starting torque and
synchronization effectiveness reported in a number of
studies [20]–[31].
Considering PMSM technology as the best candidate
for line-start, single-speed, super-premium motors, it is
important to estimate the maximum achievable efficiency. This can be done by assuming that the stator core
and windings are optimized in terms of design and materials, regarding cost-effectiveness issues and large-scale
manufacturing technological restrictions (e.g., the type of
stator winding used). On that basis, only the rotor can be
improved or changed. In the case of PM rotors, there are
two main options: with or without auxiliary squirrel-cage
to allow line-start capability [18]. Within the PM rotors,
there are several types with surface or interior PMs, with
or without rotor saliency, and conventional or claw-pole
geometry [18], [32].

15


h

iÀ1

gnew ¼ 104 Á gorig Á 104 þ Dptotal Á 102 À gorig
ð1Þ

Loss Component Fraction (% of Total Losses)

60

Rotor I 2R Losses
Stator I 2R Losses
Core Losses

50

Dptotal ¼ 10À2 Á R5l¼1 pcomp l Á Dpcomp l :

40

30

20

10
Four Poles, 50 Hz
0
0.1

1
10
Motor-Rated Power (kW)

100

5
Assumed motor loss component fraction (in % of total losses).

TABLE 1. MATERIALS COMPARISON BETWEEN PMSM
AND IE2-CLASS IM [15].

16

Copper
(%)

Magnets
(%)

PMSM

40

42

100

IE2-Class IM

100

100

0

In the following analysis, 50-Hz IE3-class efficiency
levels are considered the original efficiencies. The loss components, in percentage of total losses, are assumed as in
Figure 5. Using (1) and (2), three cases were analyzed in
terms of efficiency gains by means of losses reduction:
2
n Case 1: elimination of rotor electric I R losses
2
n Case 2: case 1 and 58% reduction in stator I R losses
n Case 3: case 2 and 60% reduction in the stator
core losses.
The percentage reduction of stator electric I2R and core
losses is adapted from the expected/typical motor active
material volume reduction from IE2-class IMs to PMSMs,
according to Table 1 [15], assuming that the current density
in stator windings and the magnetic flux density in the stator core are maintained constant.
On that basis, it is considered that stator core and stator
I2R loss reduction is directly proportional to the respective
volume decrease. The results for Cases 1, 2, and 3 are presented in Figures 6, 7, and 8, respectively, denoted as
above-IE3-class efficiency levels, which evidence the possible efficiency gains associated with line-start PMSMs with
auxiliary cage.
Line-Start Electronically Controlled PMSMs

In the case of PM rotors without auxiliary squirrel cage, the
effects referred to in the “Efficiency Limits for Line-Start

100
98
100

96

IE3-Class Efficiency Levels
Above-IE3-Class Efficiency
Levels (Case 1)
IE4-Class Efficiency Levels

96
Motor Efficiency (%)

98

Motor Efficiency (%)

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Core Steel
(%)

ð2Þ

94
92

94
92
90
88

90
86
88
84
Four Poles, 50 Hz

86
82
0.1

84
Four Poles, 50 Hz
82
0.1

1
10
Motor-Rated Power (kW)

1
10
Motor-Rated Power (kW)

IE3-Class Efficiency Levels
Above-IE3-Class Efficiency Levels (Case 2)
IE4-Class Efficiency Levels

100

6

2

100

Full-load efficiency levels after rotor I R losses elimination in
four-pole, 50-Hz, IE3-class IMs, denoted as above-IE3-class
efficiency levels (Case 1).

7
2

Full-load efficiency levels after rotor I R losses elimination
and stator I2R losses reduction in 50-Hz, four-pole, IE3-class
IMs, denoted as above-IE3-class efficiency levels (Case 2).


Industrial Motors: Line-Start PMSMs with Auxiliary Rotor
Cage” section do not exist, and therefore, the rotor losses are
extremely low. However, the motors with such rotors have
to be EC by inverters (or VSDs) to be able to properly start

100
98

and reach synchronization. In this case, there are additional
losses associated with the VSD itself and in the motor because of the PWM voltage-related harmonic losses.
When integrated in the system, although the energy
savings potential associated with speed regulation, VSDs
have a negative impact on the full-load efficiency motor
system because of their internal losses and to the additional

high-frequency losses in the motor. In Figures 9 and 10,
the VSD efficiency typical levels and variation of efficiency
with load are presented.

100

94

95
92
90
VSD Efficiency (%)

Motor Efficiency (%)

96

90
88
86

80
75
1.1 kW Integrated VSD for IM
1.1 kW External VSD for PMSM
11 kW External VSD for PMSM
and IM

70

84
Four Poles, 50 Hz
82
0.1

85

1
10
Motor-Rated Power (kW)

65

100

60

IE3-Class Efficiency Levels
Above-IE3-Class Efficiency Levels (Case 3)
IE4-Class Efficiency Levels

0

20

40
60
80
VSD Load (%)

100

120

10

2

Full-load efficiency levels after rotor I R loss elimination and
stator I2R and core loss reduction in 50-Hz, four-pole, IE3class IMs, denoted as above-IE3-class efficiency levels
(Case 3).

100
98
96
Motor Efficiency (%)

100

98

VSD Efficiency (%)

96

94

IE3-Class Efficiency Levels
Above-IE3-Class Efficiency
Levels (Case 4)

IE4-Class Efficiency Levels

94
92
90
88
86

92

84
90

88

86
0.1

Four Poles, 50 Hz
82
0.1

Typical Full-Load Efficiency
for Standard VSDs
Full-Load Efficiency for
High-Efficiency
Four VSDs
Poles, 50 Hz
1
10

VSD-Rated Power (kW)

100

11

100

9
Typical full-load efficiency levels for VSDs.

1
10
Motor-Rated Power (kW)

Full-load efficiency levels for motor-VSD units, considering
rotor I2R loss elimination and stator I2R and core losses
reduction in four-pole, 50-Hz, IE3-class IMs, and the
VSD efficiency, denoted as above-IE3-class efficiency
levels (Case 4).

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8

Efficiency for high-efficiency 1.1- and 11-kW VSDs [29].

17

Considering the impact of the inverter output PWM voltages on the motor efficiency as well as the inverter efficiency, the overall efficiency is given by (3), where gvsd is
the VSD efficiency (in percent), gorig is the original efficiency of the motor (in percent), gnew is the motor-VSD
unit efficiency (in percent), and Dgorig is the motor efficiency decrease (in percentage points).


gnew ¼ 10À2 Á gvsd Á gorig À Dgorig :

ð3Þ

Using (3), Case 4 is analyzed in terms of efficiency
reduction due to the efficiency of the VSD, and the results
are presented in Figure 11. In this case, the impact of the

VSD output PWM waveforms in the motor efficiency is
not considered.
Comparison of Standard
and Commercial Efficiencies

Some manufacturers sell integrated PMSMþVSD solutions,
which achieve full-load efficiency values significantly higher
than IE3 class. In Figure 12, the full-load efficiency of
commercial PMSMþVSD units from two different manufacturers, as well as the estimated maximum achievable
full-load efficiency levels for PMSMþVSD units, is shown.
It can be seen that, for the low-power range, efficiency
improvements are still possible.
Materials Usage

IE2-class IMs incorporate more active materials than PMSMs,
as can be seen in Table 1 and Figure 13. According to two
PMSM manufacturers, PMSMþVSD units and IE2-class

IMþVSD units have an equivalent manufacturing cost.
However, IE3-class IMþVSD units incorporate more materials and have a higher cost. Moreover, considering that copper
is not used in the rotor, IE3-class premium IMs incorporate
much more material than IE2-class IMs.
Therefore, in variable-speed applications, when compared with IE3-class IMþVSD units, PMSMþVSD units
use less active materials. Even considering the additional
rotor magnet cost, PMSMþVSD have lower costs, and they
achieve significant energy savings, thus being more
environmentally friendly. As a consequence, in low-power
range variable-speed applications, it seems advantageous to
shift the market directly to IE4-class levels using PM technology, jumping through the IE3-IM technology.

98
Four Poles, 50 Hz
96
94

18

Motor Efficiency (%)

90
88
86
84

Conclusions
Growing environmental concerns and high energy costs
emphasize the importance of considering the life-cycle costs
of nonstandard technologies. PM motors prove to be significantly more efficient than IMs, particularly in the low-power

range. Moreover, they have higher power factor and cooler
operating temperature. Former disadvantages, such as the

82
80
78
76
0.1

1

10

100

Motor-Rated Power (kW)

1.1 kW/Four Poles

8
IE3-Class Efficiency Levels
IE4-Class Efficiency Levels
Estimated Maximum Efficiency for
EC-PMSM (Case 4)
Brand A, Four-Pole, EC-PMSM
Brand B, Four-Pole, EC-PMSM
Brand C, Ultrapremium-Class IM,
Adapted to 50 Hz
Brand D, Four-Pole, NonECLINE-Start PMSM

IE1 IM_al
IE2 IM_cu
PMSM + VSD
IE1 IM + VSD
Line-Start PM
One-Phase IM_al

7

kg (kW)

6
5
4
3
2

12

1
us
ym

er
o

et
s
Po
l

ag
n
M

pe
r
op
C

in
im
um

ro
n

um

Al

ee
l/I

St

St

ee
l

0
or
e

Comparison between IE3-class and IE4-class efficiency
levels, commercial EC PMSMs full-load efficiency
(considering the VSD efficiency), precommercial non-EC
line-start PMSM prototypes full-load efficiency, and the
estimated maximum efficiency levels for EC PMSMs
(considering the VSD efficiency), corresponding to the
above-IE3-class levels (Case 4) presented in Figure 11 [3],
[4], [12]–[15].

C

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92

13
Materials usage (kg/kW) in different motor technologies.
(Source: European motor manufacturer.)


[17] N. Bianchi and T. Jahns, “Design analysis
higher costs, have now been rendered
and control of interior PM synchronous
obsolete. Therefore, even applications
THE

RELATIVE
machines,” in Proc. IEEE Annu. Meeting, IAS
that were exclusively limited to asynTutorial Notes, Oct. 2004, pp. 2.1–2.22.
chronous motors for cost reasons can
[18] M. Melfi, S. Evon, and R. McElveen, “InIMPORTANCE OF
duction vs permanent magnet motors,” IEEE
now profit from the advantages of PM
Ind. Applicat. Mag., vol. 15, no. 6, pp. 28–35,
motors. For single-speed applications,
THE FIVE
Nov./Dec. 2009.
with direct mains operation, the IM
[19] J. Mazurkiewicz. (2009). AC vs DC brushDIFFERENT KINDS
still has a cost advantage, although new
less servo motor. Baldor Electric [Online].
Available: www.motioncontrolonline.org/files/
developments in line-start PMs may beOF IM LOSSES
public/
come a cost-effective alternative.
DCvsACBrushless.pdf
With variable-speed applications,
[20] G. Yang, J. Ma, J. Shen, and Y. Wang,
DEPENDS ON
low-power IMs (with VSD) lose in terms
“Optimal design and experimental verification
of energy efficiency, and they have simiof a line-start permanent magnet synchronous
MOTOR SIZE.
motor,” in Proc. Int. Conf. Electrical Machines
lar cost to PMs (with VSD), which are
and Systems, China, 2008, pp. 3232–3236.

therefore an advantageous option.
[21] F. Libert, J. Soulard, and J. Engstrom, “Design
Since the energy-saving potential
of a 4-pole line start permanent magnet synassociated with super-premium IE4-class motors is large,
chronous motor,” Proc. Int. Conf. Electrical Machines, Belgium, Aug.
25–28, 2002. Paper 153.
and the technology to achieve such efficiency levels is
already available to be produced in large scale, it makes [22] K. Kiurihara and M. Rahman, “High-efficiency line-start interior
permanent magnet synchronous motors,” IEEE Trans. Ind. Applicat.,
sense to promote such motors, by means of proper classificavol. 40, pp. 789–796, May/June 2004.
tion and labeling schemes and, in the near future, introducing [23] T. Miller, “Synchronization of line-start permanent-magnet ac
upgrade minimum energy performance standard (MEPS),
motors,” IEEE Trans. Power App. Syst., vol. PAS-103, pp. 1822–1509,
July 1984.
particularly in the small-medium power ranges.

References

Anı´bal T. de Almeida (), Fernando J.T.E.
Ferreira, and Joa˜o A.C. Fong are with the University of Coimbra, Portugal. Ferreira is also with the Engineering Institute of
Coimbra, Polytechnic Institute of Coimbra, Portugal. de Almeida
and Ferreira are Senior Members of the IEEE. This article first
appeared as “Standards for Super-Premium Efficiency Class for
Electric Motors” at the 2009 Industrial and Commercial Power
Systems Technical Conference.

IEEE INDUSTRY APPLICATIONS MAGAZINE  JAN j FEB 2011  WWW.IEEE.ORG/IAS

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