Higher efficiency electric motors can lead to significant reductions in energy consumption and also reduce environmental impact... In this standard [3], three efficiency classes are prop
Trang 1Permanent magnet
synchronous motor technology
B Y A N I´B A L T D E A L M E I D A ,
F E R N A N D O J T E F E R R E I R A ,
& J O A˜ O A C F O N G
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
rele-vant, electric motor systems use about one-third of
the electricity consumed Their wide use makes
elec-tric motors particularly attractive for the application of
efficiency improvements Despite the wide variety of
elec-tric 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
© FOTOSEARCH
12
Trang 2motor market transformation, a new international standard,
International Electrotechnical Committee (IEC) 60034-30
[3], was approved in November 2008 to globally
harmo-nize motor energy efficiency classes in general purpose,
sin-gle-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
clas-sification], 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
specifica-tion standard, a super-premium efficiency (IE4) is also
pro-posed, 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
high-efficiency 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
low-power levels (up to 7.5 kW), it is clear that moving away
from IM technology and considering emergent
technolo-gies 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
practicabil-ity and technical limits associated with the IE4-class
effi-ciency 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
exist-ing 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
con-troller, 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
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 effi-ciency equal to or exceeding an effieffi-ciency 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 effi-ciency 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 opera-tion 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 spe-cial 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, continu-ous-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 four-and six-pole stfour-andard IMs, it is expected that eight-pole IMs will further disappear from the general market in the future Thus, this standard excludes provisions for eight-pole 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
Trang 3frequency 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
Tech-nologies other than IMs will be required to meet IE4
levels [3]
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 pro-ducing motors for a global market Additionally, custom-ers 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
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 com-pared at the same torque, the 60-Hz efficiency of low-volt-age, 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 effi-ciency [4], [10]
Only large two-pole IMs may experience a reduced efficiency at 60 Hz because of their high share of wind-age and friction losses Another important issue is the load dependency of losses and its impact on the IM effi-ciency When considering EC IMs or PMSMs, those
98 96 94 92 90 88 86 84 82 80 78 76 74 72 70
98 96 94 92 90
88 86 84 82
80
Motor-Rated Power (kW)
Motor-Rated Power (kW)
Four Poles
Four Poles
50 Hz, IE1
50 Hz, IE2
50 Hz, IE3
50 Hz, IE4
60 Hz, IE1
60 Hz, IE2
60 Hz, IE3
60 Hz, IE4
NEMA Premium at 50 Hz NEMA Premium at 60 Hz EPAct at 50 Hz
EPAct at 60 Hz
1
IEC 60034-30 and 31 efficiency levels and NEMA and EPAct minimum efficiency requirements for 60- and 50-Hz,
four-pole IMs [10].
100
90 80 70 60 50 40
30 20 10 0 0.75 1.5 3 5.5 11 18.5
Motor-Rated Power (kW)
30 45 75 110 160 250
Windage and Friction Losses
Core Losses
Stray Load Losses
Rotor I2R Losses
Stator I2R Losses
2
Typical fraction of losses in 50-Hz, four-pole IMs [10].
14
Trang 4efficiency variations are not critical, since frequency can
be set as a function of the needed speed, and the
mag-netizing 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
improve-ment 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
effi-ciency 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
com-mercially 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
effi-ciency This can be done by assuming that the stator core
and windings are optimized in terms of design and
mate-rials, 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]
Line-Start PMSMs with Auxiliary Rotor Cage
In the case of PM rotors with auxiliary squirrel-cage,
con-sidering 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
wind-ing and rotor cage, those effects can be neglected
On the basis of the typical fraction of losses for
four-pole, 50-Hz IMs presented in Figure 2 and the 50-Hz
IE3-class efficiency levels presented in Figure 1, it is possible to
estimate the maximum achievable efficiency level (at 50 Hz) resulting from the reduction of each loss component
The new improved motor-rated efficiency resulting
percent), l is the loss component identification (e.g., rotor
variation of loss component l (in percent)
98
96
94
92
90
88
86
84
82
Four Poles
Motor-Rated Power (kW)
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].
12 10 8 6 4 2 0 0.75 1.1 1.5 2.2 3.7 5.5 7.5 11 15
Motor-Rated Power (kW)
IE3 Versus Ultrapremium Four-Pole, 60-Hz IMs
4
Loss variation between IE3-class efficiency levels and commercially available ultrapremium 60-Hz, four-pole
Trang 5gnew¼ 104
þ Dptotal 102
ð1Þ
Dptotal¼ 102 R5
l¼1pcomp l Dpcomp l: ð2Þ
In the following analysis, 50-Hz IE3-class efficiency levels are considered the original efficiencies The loss com-ponents, 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:
core losses
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 sta-tor core are maintained constant
On that basis, it is considered that stator core and stator
volume decrease The results for Cases 1, 2, and 3 are pre-sented in Figures 6, 7, and 8, respectively, denoted as above-IE3-class efficiency levels, which evidence the possi-ble 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
60
50
40
30
20
10
0
Motor-Rated Power (kW)
Four Poles, 50 Hz
Rotor I2R Losses Stator I2R Losses
Core Losses
5
Assumed motor loss component fraction (in % of total losses).
100
98
94 96
92
88 90
86
82 84
Motor-Rated Power (kW)
Four Poles, 50 Hz
IE3-Class Efficiency Levels Above-IE3-Class Efficiency Levels (Case 1)
IE4-Class Efficiency Levels
6
Full-load efficiency levels after rotor I 2 R losses elimination in
four-pole, 50-Hz, IE3-class IMs, denoted as above-IE3-class
efficiency levels (Case 1).
TABLE 1 MATERIALS COMPARISON BETWEEN PMSM
AND IE2-CLASS IM [15].
Core Steel (%)
Copper (%)
Magnets (%)
100 98
94 96
92
88 90
86
82 84
Motor-Rated Power (kW)
Four Poles, 50 Hz
IE3-Class Efficiency Levels Above-IE3-Class Efficiency Levels (Case 2) IE4-Class Efficiency Levels
7
Full-load efficiency levels after rotor I 2 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).
16
Trang 6Industrial 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
and reach synchronization In this case, there are additional losses associated with the VSD itself and in the motor be-cause 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
98
94
96
92
88
90
86
VSD-Rated Power (kW)
Four Poles, 50 Hz
Typical Full-Load Efficiency for Standard VSDs Full-Load Efficiency for High-Efficiency VSDs
9
Typical full-load efficiency levels for VSDs.
100
98
94
96
92
88
90
86
82
84
Motor-Rated Power (kW)
Four Poles, 50 Hz
IE3-Class Efficiency Levels
Above-IE3-Class Efficiency Levels (Case 3)
IE4-Class Efficiency Levels
8
Full-load efficiency levels after rotor I2R loss elimination and
stator I 2 R and core loss reduction in 50-Hz, four-pole,
IE3-class IMs, denoted as above-IE3-IE3-class efficiency levels
(Case 3).
100 95 90 85 80 75 70 65 60
VSD Load (%)
1.1 kW Integrated VSD for IM 1.1 kW External VSD for PMSM
11 kW External VSD for PMSM and IM
10
Efficiency for high-efficiency 1.1- and 11-kW VSDs [29].
100 98
94 96
92
88 90
86
82 84
Motor-Rated Power (kW)
Four Poles, 50 Hz
IE3-Class Efficiency Levels Above-IE3-Class Efficiency Levels (Case 4)
IE4-Class Efficiency Levels
11
Full-load efficiency levels for motor-VSD units, considering rotor I 2 R loss elimination and stator I 2 R and core losses reduction in four-pole, 50-Hz, IE3-class IMs, and the VSD efficiency, denoted as above-IE3-class efficiency
Trang 7Considering the impact of the inverter output PWM
vol-tages on the motor efficiency as well as the inverter
effi-ciency decrease (in percentage points)
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 manu-facturers, 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 materi-als 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 com-pared 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 technol-ogy, jumping through the IE3-IM technology
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 signifi-cantly 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
98
94 96
92
88 90
86
82 80 78 76 84
Motor-Rated Power (kW)
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 Four Poles, 50 Hz
12
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].
8 7 6 5 4 3 2 1 0
Core Steel Steel/IronAluminim
um Copper Magnets
Polymerous
1.1 kW/Four Poles
IE1 IM_al IE2 IM_cu PMSM + VSD IE1 IM + VSD Line-Start PM One-Phase IM_al
13
Materials usage (kg/kW) in different motor technologies (Source: European motor manufacturer.)
18
Trang 8higher costs, have now been rendered
obsolete Therefore, even applications
that were exclusively limited to
asyn-chronous motors for cost reasons can
now profit from the advantages of PM
motors For single-speed applications,
with direct mains operation, the IM
still has a cost advantage, although new
developments in line-start PMs may
be-come a cost-effective alternative
With variable-speed applications,
low-power IMs (with VSD) lose in terms
of energy efficiency, and they have
simi-lar cost to PMs (with VSD), which are
therefore an advantageous option
Since the energy-saving potential
associated with super-premium IE4-class motors is large,
and the technology to achieve such efficiency levels is
already available to be produced in large scale, it makes
sense to promote such motors, by means of proper
classifica-tion and labeling schemes and, in the near future, introducing
upgrade minimum energy performance standard (MEPS),
particularly in the small-medium power ranges
References
[1] A De Almeida, F Ferreira, J Fong, and P Fonseca, “EuP Lot 11
motors, ecodesign assessment of energy using products, final report
for the European Commission, Brussels, Belgium,” ISR-Univ
Coim-bra, Feb 2008.
[2] A de Almeida, Ed., “Improving the penetration of energy-efficient
motors and drives,” ISR-Univ Coimbra, Final Rep for the European
Commission DG-TREN, SAVE Programme, 2000.
[3] Rotating Electrical Machines—Part 30: Efficiency Classes of Single-Speed,
Three-Phase, Cage-Induction Motors (IE-Code), Ed 1, IEC 60034-30,
Nov 2008.
[4] Rotating Electrical Machines—Part 31: Guide for the Selection and
Appli-cation of Energy-Efficient Motors Including Variable-Speed AppliAppli-cations, Ed.
1, Draft Technical Specification, 2/1575/DTS, IEC/TS 60034-31,
Sept 2009.
[5] General Purpose Three-Phase Induction Motors Having Standard Dimensions
and Outputs—Frame Numbers 56 to 315 and Flange Numbers 65 to 740,
EN 50347, 2001.
[6] Motors and Generators, NEMA Standards Publication MG1-2003.
[7] Rotating Electrical Machines—Part 1: Rating and Performance, Ed 12,
IEC 60034-1, 2010.
[8] Rotating Electrical Machines—Part 2-1: Standard Methods for Determining
Losses and Efficiency of Rotating Electrical Machinery From Tests (Excluding
Machines for Traction Vehicles), Ed 1IEC 60034-2-1, Sept 2007.
[9] “EPAct legislation,” in Congressional Rec., Jan 1994.
[10] A Almeida, F Ferreira, J Fong, and B Conrad, “Electric motor
eco-design and global market transformation,” in Proc IEEE Industrial
and Commercial Power Systems Conf., Clearwater Beach, FL, May 4–8,
2008, pp 1–9.
[11] W Cao, “Comparison of IEEE 112 and New IEC Standard
60034-2-1,” in Proc Int Conf Electrical Machines (ICEM’08), Algarve, Portugal,
Sept 2009, pp 259–264.
[12] Siemens, “SD100 TEFC NEMA motors,” Product Tech Catalogue, 2009.
[13] Leroy-Somer, “Synchronous permanent magnet motor,” Product Tech.
Catalogue, 4173en-122007/b, 2009.
[14] J Krotsch, W Mu¨ller, and W Reinhardt, (2009) Fan and blower
drives—A system comparison between asynchronous motors and
elec-tronically commutated motors ebm-papst Mulfingen GmbH [Online].
Available: www.ebmpapst.com
[15] Lafert Group (2009) Innovation, Presentation Slides [Online]
Avail-able: www.lafert.com
[16] D Idles-Klumpner, “Small permanent magnet synchronous motor
technology—An overview,” invited paper, in Proc PCIM Europe Conf.,
Nuremberg, Germany, May 27–29, 2008.
and control of interior PM synchronous machines,” in Proc IEEE Annu Meeting, IAS Tutorial Notes, Oct 2004, pp 2.1–2.22.
[18] M Melfi, S Evon, and R McElveen, “In-duction vs permanent magnet motors,” IEEE Ind Applicat Mag., vol 15, no 6, pp 28–35, Nov./Dec 2009.
[19] J Mazurkiewicz (2009) AC vs DC brush-less servo motor Baldor Electric [Online] Available: www.motioncontrolonline.org/files/ public/
DCvsACBrushless.pdf [20] G Yang, J Ma, J Shen, and Y Wang,
“Optimal design and experimental verification
of a line-start permanent magnet synchronous motor,” in Proc Int Conf Electrical Machines and Systems, China, 2008, pp 3232–3236.
[21] F Libert, J Soulard, and J Engstrom, “Design
of a 4-pole line start permanent magnet syn-chronous motor,” Proc Int Conf Electrical Machines, Belgium, Aug 25–28, 2002 Paper 153.
[22] K Kiurihara and M Rahman, “High-efficiency line-start interior permanent magnet synchronous motors,” IEEE Trans Ind Applicat., vol 40, pp 789–796, May/June 2004.
[23] T Miller, “Synchronization of line-start permanent-magnet ac motors,” IEEE Trans Power App Syst., vol PAS-103, pp 1822–1509, July 1984.
[24] Z Bingyi, Z Wei, Z Fuyu, and F Guihong, “Design and starting process analysis of multi polar line start PMSM,” in Proc Int Conf Electrical Machines and Systems, Korea, Oct 2007, pp 1629–1634.
[25] J Soulard and H Nee, “Study of the synchronization of line-start permanent magnet synchronous motors,” in Proc Industry Application Conf., Oct 2000, vol 1, pp 424–431.
[26] L Lefevre and L Soulard, “Finite element transient start of a line-start permanent magnet synchronous motor,” in Proc Int Conf Electri-cal Machines, Finland, Aug 2000, vol 3, pp 1564–1568.
[27] T Marcic, B Stumberger, G Stumberger, M Hadziselimovic, P Virtic, and D Dolinar, “Line starting three- and single-phase interior permanent magnet synchronous motors—Direct comparison to induc-tion motors,” IEEE Trans Magn., vol 44, no 11, pt 2, pp 4413–
4416, Nov 2008.
[28] T Ding, N Takorabet, F Sargos, and X Wang, “Design and analysis of different line-start PM synchronous motors for oil-pump applications,” IEEE Trans Magn., vol 45, no 3, pp 1816–
1819, 2009.
[29] A Takahashi, S Kikuchi, K Miyata, S Wakui, H Mikami, K Ide, and A Binder, “Transient torque analysis of line-starting permanent-magnet synchronous motor,” in Proc Int Conf Electrical Machines, Por-tugal, Sept 2008, pp 1–6.
[30] C Lee and B Know, “Design of post-assembly magnetization system
of line start permanent magnet motors using FEM,” IEEE Trans Magn., vol 41, no 5, pp 1928–1931, May 2005.
[31] C Lee, B Kwon, B Kim, K Woo, and M Han, “Analysis of mag-netization of magnet in the rotor of line start permanent magnet
ac motor,” IEEE Trans Magn., vol 39, no 3, pt 1, pp 1928–1931, May 2003.
[32] F Ferreira, M Cistelecan, and A de Almeida, “Voltage unbalance impact on the performance of line-start permanent-magnet synchro-nous motors,” in Proc 6th Int Conf Energy Efficiency in Motor Driven Systems (EEMODS’09), Nantes, Sept 2009, Paper 53.
Anı´bal T de Almeida (adealmeida@isr.uc.pt), Fernando J.T.E Ferreira, and Joa˜o A.C Fong are with the University of Coim-bra, 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
THE RELATIVE IMPORTANCE OF THE FIVE DIFFERENT KINDS
OF IM LOSSES DEPENDS ON MOTOR SIZE.
19