Page 1
PG&E’s Emerging Technologies Program ET13PGE1081
Permanent Magnet Alternating Current (PMAC)
Motor Efficiency Comparison – Phase 1
ET Project Number: ET13PGE1081
Project Manager: Jeff Bersini Pacific Gas and Electric Company Prepared By: Brendan P. Dooher PG&E – Applied Technology Services 3400 Crow Canyon Rd. San Ramon, CA 94583
Issued: January 31, 2014
Copyright, 2014, Pacific Gas and Electric Company. All rights reserved.
Page 1
PG&E’s Emerging Technologies Program ET13PGE1081
ACKNOWLEDGEMENTS
Pacific Gas and Electric Company’s Emerging Technologies Program is responsible for this project. It was developed under internal project number ET13PGE1081. Applied Technology Services conducted this technology evaluation for Pacific Gas and Electric Company with overall guidance and management from Jeff Beresini. For more information on this project, contact [email protected].
PG&E would also like to acknowledge George Marx of ABB, Bill Carroll of EMPOWER Sales, and Rick Munz of Marathon Electric for their advice and feedback on this project.
We would also like to thank Brian Woosley and Esteban Rodriguez for their help in constructing the test setup and for their advice and assistance throughout the project. We further wish to thank Manny D’Albora and Adam Fernandez for their help in reviewing the final document. Finally, we would like to thank Jeff Beresini for his advice and support throughout the project.
LEGAL NOTICE
This report was prepared for Pacific Gas and Electric Company for use by its employees and agents. Neither Pacific Gas and Electric Company nor any of its employees and agents:
(1) makes any written or oral warranty, expressed or implied, including, but not limited to those concerning merchantability or fitness for a particular purpose;
(2) assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, process, method, or policy contained herein; or
(3) represents that its use would not infringe any privately owned rights, including, but not limited to, patents, trademarks, or copyrights.
Page 2
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURES
Figure 1. Motor/Generator Test Setup ........................................ 14
Figure 2. Motor/Generator Test Setup (Grey Motor is the
Generator Absorber) ................................................... 15
Figure 3. Schematic of the Motor Test Setup. .............................. 16
Figure 4. Magtrol TM 309 Torque Meter (20 N m) with Rotational
Speed Out ................................................................. 16
Figure 5. ABB ACS 880 VFD Systems, Yokogawa 2533, Yokogawa
1800 WT, and Magtol Meter for TM 309 ......................... 17
Figure 6. Close-Up View of ABB ACS VFD Control Panel ................ 17
Figure 7. 3 HP PEIM – Motor Speed, RPM vs. Efficiency, at
Various Constant Motor Torque, N m ............................ 19
Figure 8. 3 HP PMAC – Motor Speed, RPM vs. Efficiency, at
Various Constant Motor Torque, N m ............................ 19
Figure 9. 3 HP PEIM – Power In, Watts vs. Efficiency, at Various
Constant Motor Speed, RPM......................................... 20
Figure 10. 3 HP PMAC – Power In, Watts vs. Efficiency, at Various
Constant Motor Speed, RPM......................................... 20
Figure 11. 5 HP PEIM – Motor Speed, RPM vs. Efficiency, at
Various Constant Motor Torque, N m ............................ 21
Figure 12. 5 HP PMAC – Motor Speed, RPM vs. Efficiency, at
Various Constant Motor Torque, N m ............................ 21
Figure 13. 5 HP PEIM – Power In, Watts vs. Efficiency, at Various
Constant Motor Speed, RPM......................................... 22
Figure 14. 5 HP PMAC – Power In, Watts vs. Efficiency, at Various
Constant Motor Speed, RPM......................................... 22
Figure 15. 3 HP PMAC – 3D Contour Plot of Efficiency, Torque, N m
(x100 scale) vs. Speed, RPM The PEIM is on the Left,
the PMAC is on the Right ............................................. 24
Figure 16. 5 HP PMAC – 3D Contour Plot of Efficiency, Torque, N m
(x100 scale) vs. Speed, RPM The PEIM is on the Left,
the PMAC is on the Right ............................................. 24
Figure 17. 3 HP PEIM – 2D Contour Plot of Efficiency, Speed, RPM
vs. Torque, N m (x100 scale) ....................................... 25
Figure 18. 3 HP PMAC – 2D Contour Plot of Efficiency, Speed, RPM
vs. Torque, N m (x100 scale) ....................................... 26
Figure 19. 5 HP PEIM – 2D Contour Plot of Efficiency, Speed, RPM
vs. Torque, N m (x100 scale) ....................................... 27
Page 3
PG&E’s Emerging Technologies Program ET13PGE1081
Figure 20. 5 HP PEIM – 2D Contour Plot of Efficiency, Speed, RPM
vs. Torque, N m (x100 scale) ....................................... 28
Figure 21. Comparison of PMAC and PEIM 3 HP Motor Speed RPM
vs. Efficiency, at Various Constant Motor Torque, N m .... 29
Figure 22. Comparison of PMAC and PEIM 5 HP Motor Speed RPM
vs. Efficiency, at Various Constant Motor Torque, N m .... 29
Figure 23. 2D Contour Plot of Efficiency Difference, 3 HP PMAC and
PEIM Speed, RPM vs. Torque, N m (x100 scale) ............. 30
Figure 24. 2D Contour Plot of Efficiency Difference, 5 HP PMAC and
PEIM Speed, RPM vs. Torque, N m (x100 scale) ............. 31
Figure 25. 3 HP PEIM – 3D Contour Plot of Efficiency, Speed vs.
RPM Torque, N m (x100 scale) ..................................... 33
Figure 26. 3 HP PMAC – 3D Contour Plot of Efficiency, Speed vs.
RPM Torque, N m (x100 scale) ..................................... 34
Figure 27 5 HP PEIM – Contour Plot of Efficiency, Speed vs. RPM
Torque, N m (x100 scale) ............................................ 35
Figure 28 5 HP PMAC – Contour Plot of Efficiency, Speed vs. RPM
Torque, N m (x100 scale) ............................................ 36
TABLES
Table 1. Estimates of Motor Sales and Potential Savings in the
PG&E Service Territory, Ranked by Size Category............. 5
Table 2. Estimates of Motor Sales in California and PG&E Service
Territory ................................................................... 10
Table 3. Estimates of Motor Sales in the PG&E Service Territory,
Ranked by Size Category. ........................................... 10
Table 4. Estimates of Motor Sales in the PG&E Service Territory,
Ranked by Motor Size and Motor Size Category .............. 11
Table 5. Estimates of Annual Savings in the PG&E Service
Territory, Ranked by Motor Size and Motor Size
Category ................................................................... 12
Table 6. Motors Evaluated and Their Properties .......................... 18
Page 4
PG&E’s Emerging Technologies Program ET13PGE1081
CONTENTS
FIGURES _______________________________________________________________ 2
TABLES ________________________________________________________________ 3
CONTENTS _____________________________________________________________ 4
EXECUTIVE SUMMARY _____________________________________________________ 5
INTRODUCTION __________________________________________________________ 7
BACKGROUND __________________________________________________________ 7
MARKET OPPORTUNITY: ESTIMATES OF MOTOR USE AND SALES IN THE PG&E SERVICE TERRITORY
______________________________________________________________________ 9
TEST METHODOLOGY ____________________________________________________ 13
Assessment Objectives .......................................................... 13
Methodology ......................................................................... 14
Measurement Equipment ........................................................ 15
Products Evaluated ................................................................ 18
RESULTS_______________________________________________________________ 18
Comparison Between PEIM and PMAC ...................................... 18
DISCUSSION AND RECOMMENDATIONS _______________________________________ 31
3-D CONTOUR CHARTS OF MOTOR EFFICIENCIES _______________________________ 33
EQUIPMENT CALIBRATION AND ACCURACY ___________________________________ 37
Yokogawa WT1800 Power Spectrum Analyzer ........................... 37 ABB ACS 880 Variable Frequency Drive .................................... 40 Magtrol.TM 309 In-Line Torque Transducers ............................ 41
Page 5
PG&E’s Emerging Technologies Program ET13PGE1081
EXECUTIVE SUMMARY This is the final report for 2013 phase (Phase I) of the Permanent Magnet Alternating
Current (PMAC) motor testing performed at PG&E’s Applied Technology Services (ATS).
ATS, under the funding and direction of PG&E’s Emerging Technologies Group (ET) within
the Customer Energy Solutions (CES) organization. conducted an evaluation of a potentially
energy saving technology known as PMAC motors. ATS would develop methodology and
evaluate several manufacturers’ PMAC motors in a first phase effort.
High efficiency Permanent Magnet AC (PMAC) Motor systems are of extreme interest in
order to increase motor efficiencies in the lower HP region, where overall efficiencies lag
behind the approximately 94% for high efficiency, high HP motors. The claim is that PMAC
motors will give energy savings when compared against Premium Efficiency induction
motors (PEIMs) in variable speed applications.
For Phase 1 of this project, to assess the potential overall savings of the technology, two
PMAC motor sizes were initially tested (3 HP and 5 HP) and compared against premium
efficiency induction motors of the same size as our controls in order to assess the overall
testing methodology and obtain efficiency comparisons with this initial limited sample. The
PMAC motor tested are designed to be able to replace a standard frame size motor.
As part of this effort ATS estimated the total number of sales per motor size category and
then estimated the potential savings in moving from a PEIM to a PMAC motor. As can be
seen in Table 1, the potential savings are substantial on a yearly basis. Since this is an
estmate based on some very simple estimators, it is expected that savings would be even
greater than estimated below, if all motors were upgraded to PMAC types. Of course, some
estimate of % market penetration would have be made to evaluate final projected savings.
TABLE 1. ESTIMATES OF MOTOR SALES AND POTENTIAL SAVINGS IN THE PG&E SERVICE TERRITORY, RANKED BY SIZE
CATEGORY.
Size Category (HP) Average Distribution of
Motor Shipments 2014 PG&E Service
Territory Motor Shipment Estimates
Annual Potential Savings in the PG&E
Service Territory MWh
1 to 5 53.41 % 44,761 3,272.5
6 to 20 28.30 % 29,322 9,635.3
21 to 50 11.02 % 11,418 7,959.7
51 to 100 4.17 % 4,321 5,977.3
101 to 200 2.30 % 2,383 5,102.9
201 to 500 0.80 % 829 3,460.6
The findings presented in this report indicate that PMAC motors have the potential to save
substantial energy in variable speed applications, even when compared to a high efficiency
NEMA PEIM. The Phase 1 test setup was able to show that PG&E can assess and compare
various motors. However, it is recommended that in a Phase 2 we complete testing of
motors in the 3 to 10 HP range, and examine other manufacturer motors, such as NEMA D
and other motors used in the PG&E Service Territory.
PEIM and PMAC data collected to develop performance curves for both 3 HP and 5 HP
motors show that the PMAC motors have superior abilities to keep high efficiency at
Page 6
PG&E’s Emerging Technologies Program ET13PGE1081
constant torque loadings when compared to the control PEIM. The substantial increase in
efficiency at typical motor operations suggests that significant energy savings can be
realized, especially when examined in light of the yearly sales of motors in the PG&E Service Territory.
For the 3 HP efficiency difference between PEIM and PMAC motors, the difference in
efficiency ranges from 2% to 24%, in a fairly linear distribution across the motor speed. For
the 5 HP efficiency difference between PEIM and PMAC motors, the range is from 4% to
24%, in a fairly linear distribution across the motor speed. Both are siginificant
improvements, and would have significant impacts on a Customized or Deemed program. It
is discussed later in the report, when comparing the power usage of the PMAC and NEMA
Premium Efficiencies, that we use an estimated adjustment factor of 0.68 to account for
situations where the system was not under full speed or load. It is apparent that PMAC
motors high constant efficiency will have a significant positive impact on power savings,
lead larger overall cost savings and faster payback for systems that require a VFD; this
should be examined in detail based on example field based cases used as an example of system performance.
For Phase 2, we plan on expanding the motors examined as part of this test. This will
include outreach and interaction with both the manufacturers and our customers to try to
understand how these technologies would best be introduced, including analyzing impact on
customers and how PMAC technologies may best be able to help them reduce their energy
costs. For example, how would new 30, 40 and 50 hp PM motors compare to new premium
efficiency and NEMA D motors in oilfield pump applications? We plan on considering
improvements in the expected ranges, in motor operating hr/yr, kW load, kWh/yr
consumption, motor equipment cost, motor labor cost and motor operating cost.
Page 7
PG&E’s Emerging Technologies Program ET13PGE1081
INTRODUCTION This is the final report for 2013 phase (Phase I) of the Permanent Magnet Alternating
Current (PMAC) motor testing performed at PG&E’s Applied Technology Services (ATS).
ATS, under the funding and direction of PG&E’s Emerging Technologies Group (ET) within
the Customer Energy Solutions (CES) organization. conducted an evaluation of a potentially
energy saving technology known as PMAC motors. ATS would develop methodology and
evaluate several manufacturers’ PMAC motors in a first phase effort.
High efficiency Permanent Magnet AC (PMAC) Motor systems are of extreme interest in
order to increase motor efficiencies in the lower HP region, where overall efficiencies lag
behind the approximately 94% for high efficiency, high HP motors. The claim, from both
academic literature and from manufacturers testing results, are that PMAC motors will give
energy savings when compared against National Electrical Manufacturers Association
(NEMA) Premium Efficiency induction motors in variable speed applications. Part of the
savings comes from the system not having to induce a magnetic filed in the rotor as is done
in induction motors. Due to this, the efficiency does not degrade as rapidly as the rotation is
reduced from the standard design point (1800 rpm or 3600 rpm) as is found in induction
motors. This makes the system more flexible across a wide range of rotational speeds and
torques.
For Phase 1 of this project, to assess the potential overall savings of the technology, two
PMAC motor sizes were initially tested (3 HP and 5 HP) and compared against premium
efficiency control motors of the same size in order to assess the overall testing methodology
and obtain some efficiency comparisons with this limited sample. The PMAC motor tested is
designed to be able to replace a standard frame motor. The Premium Efficiency Induction
Motors (PEIM) were also tested with a VFD first to work out system bugs and to act as a
control. Finally, we compared the efficiency of PEIM versus PMAC.
The primary goal of this phase of the motor testing research at ATS has been to support the
CES project office to justify either adding lower HP super-premium efficiency motors
(beyond Title 24 NEMA Premium) to the PG&E Deemed program or encouraging their use in
the Customized Incentive Program.
Overall, the PMAC motors provided a higher efficiency than the premium efficiency motors
over all of the tested operating parameters. Annual energy savings estimates are dependent
on motor operation, and are discussed in detail below.
BACKGROUND Energy use in the United States is heavily tied to electric motors, as they are used in HVAC
systems, manufacturing, energy, and water distribution systems, among others. It is
estimated that motor usage accounts for over 40% of U.S. energy usage.
It is useful to describe the two basic motor technologies that are being tested. Induction
motors rely on the external windings of the stator to induce a magnetic field on the rotor. In
PMACs, magnets are part of the rotor, so that they produce the magnetic field, which then
couple with the motor's current-induced, magnetic fields generated by electrical input to the
stator windings, as would be found in an AC induction motors. Due to this, secondary circuit
Page 8
PG&E’s Emerging Technologies Program ET13PGE1081
rotor I2R losses are essentially eliminated, resulting in higher efficiency and better power
factors.
The terms PMAC, PM synchronous, and brushless dc are essentially synonymous terms. For
most PMAC type motors, a VFD is required to run the motor, although there are several
manufacturers that are working on technologies that would allow the PMAC motor to be
“self-starting” and to operate in a similar fashion to an induction motor. Due to the use of
permanent magnets, manufacturers have more options for physically designing the motor
itself, and it must be expected that there will be many, slightly different technologies that
will make their way to market.
Rare-earth elements are used in most PMAC motors. Rare-earth magnets are created
through a manufacturing process that results in in magnetic fields ranging more than twice
the field strength of traditional ferrite magnets (generating fields up to 1.4 Tesla in some
cases.) Despite the term, rare earths are relatively abundant, but discovered mineable
concentrations have lagged behind other ores (USGS, 2013)1. The USGS states that the
undiscovered resources are large relative to the expected demand. Although rare-earth
materials are used in the majority of commercial PMACs, due to their strength and the
simplicity of design, they can be designed with traditional ferrite magnets. These designs
take advantage of advanced numerical analysis that allows significantly better
understandings of the EMF interactions.
Currently, PMAC motors require special synchronous VFDs to operate; they are not designed
for across-the-line starting, although that technology is coming. These VFDs are designed to
work with the permanent magent motor, allowing for tighter torque control. Care must be
taken in setting up the motor and drive controller, since as the rotor spins (with or without
power applied to the windings) the mechanical rotation generates a voltage. It is this
capability which allows a PMAC to be used as a generator as well, which, without proper
saftey interlocks, can result in the drive being damaged if line power is cut to the system.
For this reason, a circuit breaker controlled by line current is placed between the drive and
the motor, so in the event of a power failure, the line circuit between the drive and motor is
broken.
In PMAC motors, speed is an exact function of frequency, with the motors rotating at the
same speed (synchronously) as the magnetic field produced by the stator windings. For a
given input frequency, the rotor exactly matches that frequency. This is an advantage of the
PMAC, giving fine control over the rotor speed without slip under torque as happens in
induction motors.
The system input frequency and motor speed are related through the number of magnetic
poles. For a ten pole motor (such as the PMAC motor used in these tests), the motor's input
frequency from the drive must be 150 Hz to obtain 1,800 rpm. The motor user does not
need to calculate this, however the number of poles must be known as it is required by the
drive set up routine for efficient operation.
Cogging in PMACs is a mechanical jerking that results during motor rotation that can occur
during start up due to harmonics. It is caused by the there not being enough driving EMF to
overcome the attraction of permanent magnets and the stator's steel structure. Cogging in
turn causes noise, vibration, and non-uniform rotation. Most motor and drive systems are
designed to reduce this issue, but care should be taken when a motor is driven at low
rotational speeds,
1 http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/mcs-2013-raree.pdf
Page 9
PG&E’s Emerging Technologies Program ET13PGE1081
Since there is no need to induce a magnetic field on the stator in a PMAC, the efficiency is
higher than for an induction motor. Due to the permanent magnets, the PMAC motor will
have higher power density than an equivalent induction motor, allowing for smaller
systems, and more flexibility in the physical design configuration of the PMAC as compared
to the IM. At low loads, the EMF begins to approach similar field levels to that of the input
voltage, also reducing the efficiency.
PMAC systems can be run using motor monitoring with signals fed back to the drive control,
which allows the drive to exactly track the rotor position and to allow for very exacting
torque control across a wide range while having very exact frequency control.
PMAC motors have capabilities that may work well as replacements for higher-end
applications where precision is required in torque, speed, or positioning. Permanent-magnet
fields are, by definition, constant and not subject to failure, except due to demagnetization
by overheating or shock induced breakage.
MARKET OPPORTUNITY: ESTIMATES OF MOTOR USE
AND SALES IN THE PG&E SERVICE TERRITORY The following discussion was an initial assessment performed in order to evaluate the
market and energy savings potential for PMAC motors in the PG&E service territory. In order
to estimate the number of premium efficiency motors sold in the State of California, and
specifically in PG&E Service Territory, the method of Schare et al. 2013 was adapted. They
based the number of premium motors sold in the Pacific Northwest on CEE and US DOE
motors. They then developed a methodology to extend 2009 numbers to 2012. This was
used to find the approximate number of PEIMs (Type I) expected to be sold in 2014 in
California and the PG&E Service Territory. These estimates are found in Table 2 and Table 3.
Page 10
PG&E’s Emerging Technologies Program ET13PGE1081
TABLE 2. ESTIMATES OF MOTOR SALES IN CALIFORNIA AND PG&E SERVICE TERRITORY
2009 CEE Sales Estimates 2014 Sales
Premium Non-Premium Total Sold OEM Sales Adjusted
DOE Growth Est
Subtype I Estimate
Northwest 24,190 13,785 37,975 62,993 135,565 99,912
California 24,486 76,163 100,649 166,956 359,301 264,805
PG&E Service Territory 9,582 29,804 39,385 65,332 140,599 103,622
United States 201,933 628,118 830,051 1,376,890 2,963,156 2,183,852
TABLE 3. ESTIMATES OF MOTOR SALES IN THE PG&E SERVICE TERRITORY, RANKED BY SIZE CATEGORY.
Size Category (HP) Average Distribution of Motor
Shipments 2014 PG&E Service Territory Motor
Shipment Estimates
1 to 5 53.41 % 44,761
6 to 20 28.30 % 29,322
21 to 50 11.02 % 11,418
51 to 100 4.17 % 4,321
101 to 200 2.30 % 2,383
201 to 500 0.80 % 829
Page 11
PG&E’s Emerging Technologies Program ET13PGE1081
TABLE 4. ESTIMATES OF MOTOR SALES IN THE PG&E SERVICE TERRITORY, RANKED BY MOTOR SIZE AND MOTOR SIZE
CATEGORY
Common Motor Size
(HP)
Distribution of Motor Shipments
Estimate of 2014 PG&E Service Territory Motor
Shipments
Estimate of Percent Motors Sold In Motor Size Range (2014)
Estimate of Total Motors Sold In Motor Size Range (2014)
1 13.76% 14,259
53.41% 44,761
1.5 11.35% 11,766
2 9.91% 10,266
3 8.17% 8,471
5 10.22% 10,588
7.5 8.79% 9,104
28.30% 29,322 10 7.67% 7,944
15 6.33% 6,555
20 5.52% 5,719
25 3.21% 3,322
11.02% 11,418 30 2.94% 3,047
40 2.57% 2,658
50 2.31% 2,391
55 1.17% 1,208
4.17% 4,321 60 1.12% 1,159
75 1.01% 1,043
100 0.88% 910
125 0.85% 877
2.30% 2,383 150 0.78% 804
200 0.68% 702
250 0.16% 164
0.80% 829
300 0.15% 151
350 0.14% 140
400 0.13% 131
450 0.12% 124
500 0.11% 118
Table 4 shows estimates by Common Motor Size from 1 HP to 500 HP. These estimates
were based on discussions with a major US motor manufacturer. A power fit equation was
developed to describe motor sales. The manufacturer used a rough estimate of the number
of ½ HP motors sold, and then roughly described that the numbers of 1 HP sold were
approximately 2/3 times the number of ½ HP motors sold; that the number of 3 HP sold
were approximately 2/3 times the number of 1 HP sold; that the number of 5 HP were
approximately 1.25 times the number of 3 HP sold; and that the number of 10 HP were 1/3
times the number of 5 HP sold. This forms a rough power law that can be extrapolated
Page 12
PG&E’s Emerging Technologies Program ET13PGE1081
outwards towards 500 HP, and when summed by category, was fairly close to the final
percentages for each motor range as found in Schare et. al, 2013 and seen in Table 3. The
power law estimates were then adjusted on a per range basis to give the final estimate of
premium motors sold in the PG&E Service Territory as seen in Table 4.
TABLE 5. ESTIMATES OF ANNUAL SAVINGS IN THE PG&E SERVICE TERRITORY, RANKED BY MOTOR SIZE AND MOTOR
SIZE CATEGORY
Common Motor Size
(HP)
Average NEMA
Efficiency
Reported/ Estimated
PMAC Efficiency
Average Annual
Hours of Operation
Average Per-Unit Savings
kWh
Estimated Annual
Shipments PG&E
Service Territory
Annual Potential
Savings in the PG&E
Service Territory
MWh
Annual Potential Savings
size range) in the
Territory MWh
1 85.5% 86.8% 2745 24.4 14,259 347.80
3,272.5
2 86.5% 86.1% 2745 *
2 86.5% 86.5% 2745 *
3 89.5% 91.7% 2745 112.0 8,471 948.56
5 89.5% 91.7% 2745 186.6 10,588 1,976.17
7.5 91.7% 93.0% 3,391 196.7 9,104 1,790.50
9,635.3 10 91.7% 93.6% 3,391 380.8 7,944 3,024.88
15 92.4% 93.6% 3,391 358.0 6,555 2,346.70
20 93.0% 94.1% 3,391 432.4 5,719 2,473.21
25 93.6% 94.5% 4,067 524.8 3,322 1,743.20
7,959.7 30 93.6% 94.5% 4,067 629.8 3,047 1,918.65
40 94.1% 95.0% 4,067 830.8 2,658 2,208.56
50 94.5% 95.3% 4,067 873.6 2,391 2,089.27
55 94.5% 95.2% 5,329 1,212.4 1,208 1,464.74
5,977.3 60 95.0% 95.7% 5,329 1,264.2 1,159 1,465.66
75 95.4% 96.0% 5,329 1,433.8 1,043 1,495.49
100 95.4% 96.0% 5,329 1,704.7 910 1,551.39
125 95.4% 95.9% 5,200 1,902.3 877 1,668.22
5,102.9 150 95.8% 96.3% 5,200 2,105.0 804 1,693.15
200 96.2% 96.6% 5,200 2,481.6 702 1,741.57
250 96.2% 96.6% 6,132 3,346.2 164 549.57
3,460.6
300 96.2% 96.6% 6,132 3,733.4 151 562.40
350 96.2% 96.5% 6,132 4,095.5 140 573.47
400 96.2% 96.5% 6,132 4,437.3 131 583.23
450 96.2% 96.5% 6,132 4,762.5 124 591.98
500 96.2% 96.5% 6,132 5,073.4 118 599.91
* The PMAC Vendor reports that in the current design of their motors the efficiency is less or equal to the NEMA premium rating at
these sizes.
Page 13
PG&E’s Emerging Technologies Program ET13PGE1081
This estimate of motors (based on major HP motors sold in each range), and not including
specialty HP levels, can act as a guide to deliver an estimate of the potential for future
savings that PG&E may be able to see through supporting customers to consider using a super-premium motor such as a PMAC.
Annual energy consumption for a motor may be assessed as the product of the following factors:
1) Motor horsepower multiplied by the kW conversion factor of 0.746 kW/hp;
2) Annual run-time hours;
3) Motor loading factor;and 4) The difference of the inverse of the two motor type efficiencies.
Annual run-time hours are based on numbers presented for the various motor ranges as
reported in Schare et. al, 2012, and are shown in Table 5. The motor loading factor is
estimated to be 0.68, and is an adjustment factor that takes into account that the motor is
unlikely to run at full loading through all hours of operation. Efficiencies up to 40 HP are
based on reported values from the PMAC Vendor for one production line of motors.
Efficiencies beyond that are estimates based on a power law estimate of the difference
between NEMA efficiency and PMAC efficiency, extrapolated to 200 HP. Although it is an
extrapolation, the numbers look reasonable compared to various reports in the academic
literature as well as being in line with the Marathon SyMax estimates. This does not take
into account that PMAC motors have better efficiencies at lower speeds. That would actually
cause an increase in the actual savings.
The hypothetical energy savings due to use of a more efficient PMAC motor is then the
difference in energy consumption between the NEMA PEIM efficiency and and the reported
or estimated PMAC motor efficiency. Table 5 presents per-unit energy savings due to the
use of premium efficiency motors in the PG&E Service Territory. The largest savings are in
the 7.5 to 20 HP and 25 to 50 HP range. However, considering the small number of motors
in the 55 to 500 HP range, a significant savings may be attained with a small amount of
effort. However, it should be stated that ATS has not investigated the manufacturing or
sales in that range yet. Since there are manufacturers that have built standard frame
motors up to 40 HP, the range of 7.5 HP to 40 HP would be useful to pursue.
TEST METHODOLOGY
ASSESSMENT OBJECTIVES
The goal of this study was to develop the capability for PG&E to assess motor efficiencies
under VFD conditions for advanced motor systems, and to set up a motor test operation at
ATS. In Phase 1, ATS experimentally measured motor efficiency over a full range of
operating conditions for 3 HP and 5 HP motors, comparing PEIM and PMAC systems. These
findings may be used by the ET program to assist PG&E in offering its customers additional
options for energy savings technologies, and to help PG&E understand the efficiency
differences between a Premium Efficiency Motor and developing next generation Super High
Efficiency Motors, which incorporate magnetic materials into their construction.
Page 14
PG&E’s Emerging Technologies Program ET13PGE1081
METHODOLOGY All testing was performed in the Water Heater Evaluation Laboratory at PG&E’s San Ramon
Technology Center located at 3400 Crow Canyon Rd. in San Ramon, CA. ATS initially
intended to use its flow loop at ATS’s Advanced Technology Performance Laboratory (ATPL)
in San Ramon as a load source for testing the motor efficiency, by matching the motor with
a pump and then adjusting back-pressure on the flow loop. After significant effort was made
to find centrifugal pumps that would match the motor characteristics across a wide range of
input power, RPM, and torque, this effort was abandoned. Beyond the difficulty of finding
the correct pump and being able to control the system to get good results in a timely
fashion, the effort was found to be not easily scalable to larger sizes.
Instead, PG&E considered using the same sort of technology that is currently being used in
electric vehicles. This uses a special variable frequency or speed drive (VFD or VSD) that
can control a normal induction motor as a generator/absorber. The VFD was purchased from
ABB, and is one of its next generation VFD lines. A matching VFD is used to control the
motor. Power generated by the generator/absorber is fed back into the motor VFD, reducing
the overall system power required to just that required to make up losses in the overall
motor/generator system. The system also allows the generator output to be used as a DC source with a load bank, if that is required.
FIGURE 1. MOTOR/GENERATOR TEST SETUP
Page 15
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 2. MOTOR/GENERATOR TEST SETUP (GREY MOTOR IS THE GENERATOR ABSORBER)
MEASUREMENT EQUIPMENT
The test system setup uses a Baldor IDNM2238T 10 HP motor, allowing for a total test
range of between 1 HP and 10 HP, a speed range of 0 to 5000 RPM, a maximum rated torque range of 40 Nm, and power limit of 7.45 kW. Test equipment are listed below:
o Yokogowa 2533 Power Meter
o Yokogowa 1800 Power Quality Analyzer
o Magtrol TM 309 Torque Meter (20 N m) with rotational speed out
o Agilent Data Logger
o ABB ACS880 10 HP VFD Controllers (with power regeneration and
Induction/Permanent Magnet Motor option)
o ABB/Baldor IDNM2238T (10HP used as generator/load)
This setup was for initial testing purposes, and we expect that there will be further iterations
on the test setup in future efforts. The motor absorber setup is shown in Figure 1 andFigure
2. Figure 3 shows the test setup schematic. Figure 4 through Figure 6 show components of the data acquisition system.
Page 16
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 3. SCHEMATIC OF THE MOTOR TEST SETUP.
The Yokogawa 2533 Power Meter was set up on the line input to collect total power input
into the VFD, while the Yokogawa 1800WT Power Quality Analyzer was placed in line
between the input VFD and the motor under test. Output power was collected with the
Magtrol, and compared to power input into the motor. The Yokogawa 1800WT can also be
used to collect power fed back into the system from the generator/absorber. For the
purposes of this test, ATS focused on collecting daa only using the Yokogawa 1800WT and Magtol torque transducer (Figure 4).
FIGURE 4. MAGTROL TM 309 TORQUE METER (20 N M) WITH ROTATIONAL SPEED OUT
Page 17
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 5. ABB ACS 880 VFD SYSTEMS, YOKOGAWA 2533, YOKOGAWA 1800 WT, AND MAGTOL METER FOR TM 309
FIGURE 6. CLOSE-UP VIEW OF ABB ACS VFD CONTROL PANEL
Page 18
PG&E’s Emerging Technologies Program ET13PGE1081
PRODUCTS EVALUATED Four motors were evaluated. These included two NEMA Premium and two PMAC motors.
The properties of the motors were very close to each other, and the PMAC motors were
easily switched out with the PEIM controls.
TABLE 6. MOTORS EVALUATED AND THEIR PROPERTIES
3 HP PEIM 5 HP PEIM 3 HP PMAC 5 HP PMAC
Power 2.237 kW 3.728 kW 3 HP/2.237 kW 5 HP/3.728 kW
Voltage 208-230/460 V 208-230/460 V 460 V 460 V
Current 9-8.4/4.2 A 13.9-13.4/6.7 A 3.8 6.4
Speed 1760 RPM 1750 RPM 1800 RPM 1800 RPM
Frame 182T 184T 182T 184T
Frequency 60 Hz 60 Hz 150 Hz 150 Hz
Efficiency 89.5% 89.5% 91.7% 91.7%
PF 75 78 80 80
Temp. Rise @ Rated Load 40 C 40 C 40 C 40 C
Full Load Torque 12.04 N m 20.20 N m 11.86 N m 19.80 N m
RESULTS
COMPARISON BETWEEN PEIM AND PMAC
All motors were evaluated as downstream efficiencies. Although input power was measured
to assess full system efficiencies, as part of the Phase 1 evaluation it was decided to focus
on the motor efficiencies alone, outside of the drive efficiencies, in order to gain an
understanding of the test system and to examine how the motors react at various speeds
and torques. Further testing will be able to evaluate system efficiencies, as well as look at
the impact of different drives on the motor efficiency as well as overall system efficiency.
Specific VFDs must be used with PMAC systems, although most manufacturers are now
marketing drives that can work with induction motors as well as synchronous motors.
It is apparent immediately that the PMAC motors showed significantly more linear efficiency
curves than PEIM systems for any given torque. Figure 7 and Figure 8 shows the efficiency
curve for the 3 HP systems under constant torque for a given motor speed (RPM). The PMAC
keeps an almost linear efficiency across the frequency domain. Figure 9 and Figure 10 show
efficiency curves for Input Power (Watts) for constant motor frequencies. The efficiencies
remain high for all Input Power, significantly higher than the PEIM at low speeds. Figure 11 through Figure 14 show the same curves for 5 HP, with similar results.
Page 19
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 7. 3 HP PEIM – MOTOR SPEED, RPM VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR TORQUE, N M
FIGURE 8. 3 HP PMAC – MOTOR SPEED, RPM VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR TORQUE, N M
Page 20
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 9. 3 HP PEIM – POWER IN, WATTS VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR SPEED, RPM
FIGURE 10. 3 HP PMAC – POWER IN, WATTS VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR SPEED, RPM
Page 21
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 11. 5 HP PEIM – MOTOR SPEED, RPM VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR TORQUE, N M
FIGURE 12. 5 HP PMAC – MOTOR SPEED, RPM VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR TORQUE, N M
Page 22
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 13. 5 HP PEIM – POWER IN, WATTS VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR SPEED, RPM
FIGURE 14. 5 HP PMAC – POWER IN, WATTS VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR SPEED, RPM
Page 23
PG&E’s Emerging Technologies Program ET13PGE1081
An attempt was made to create a multivariable polynomial curve fit in order to directly
compare the efficiencies of the system (as was done in a similar test by others on a
different PMAC motor). However, close examination showed that the curves significantly
deviated at the higher frequencies, and although the fit had high R2 residuals, the specific
fit was a poor representation of the original data. Instead, the data was fit using first a
method known as kriging, and then smoothed using a piecewise polynomial curves using
SURFER, a 3-D analysis tool. Significantly better results were obtained, and are shown in
Figure 15 and Figure 16 for 3-dimensional contours of efficiency plotted by motor speed
(RPM) and torque (N m, x100 scale). These figures are read much the same way a map is
read in Google Maps when “Terrain” is chosen. Larger figures are shown at the end of the
report (Figure 25 through Figure 28). The 3-dimensional images allow for a different type
of comparison that goes beyond what can be shown in an ordinary x-y chartallowing the entire efficiency curve regime can be examined and compared directly.
Figure 17 through Figure 20 show the same plots as more traditional 2-D contours maps,
with the countours set at 0.02% efficiency intervals.. Once again, it easy to see that the
efficiency drops off significantly less with the PMAC motors, as opposed to the PEIM. The
PMAC motors have more linear torque, with changes in efficiencies for any one torque level
changing very little across the motor speed. The data generated here allows for more direct
comparison of speed and efficiency per torque level.
Figure 21 show a comparison for the 3 HP PEIM and PMAC motor at 2 N m and 11 N m,
while Figure 22 shows a similar comparison of the 5 HP PEIM and PMAC motor at 2 N m, 10
N m, and 19 N m. These summary figures show the significant drop in efficiency for a PEIM
in comparison to the PMAC motor for the various levels of motor torque. This translates as
significant energy savings for a given energy input and motor torque output – less power is
lost as the system frequency is reduced and the motors supply greater equivalent torque
per motor speed. Figure 23 and Figure 24 show 2-dimensional contour plots of the
difference in efficiencies between the 3 HP PMAC and PEIM and the 5 HP PMAC and PEIM.
Again, the delta efficiency is shown in 0.02% contours. For the 3 HP efficiency difference,
the range is from 2% to 30%, in a fairly linear distribution across the motor speed. For the
5 HP efficiency difference, the range is also from approximately 2% to 30%, in a fairly linear
distribution across the motor speed. Both are siginificant improvements, and would have significant impacts on a Customized or Deemed program.
As per theory, the PMAC showed very exact speed control and stability when compared to
the PEIM, so for systems that demand high stability at a given speed, a PMAC is very much of an improvement in overall system control.
Page 24
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 15. 3 HP PMAC – 3D CONTOUR PLOT OF EFFICIENCY, TORQUE, N M (X100 SCALE) VS. SPEED, RPM THE PEIM IS ON THE LEFT, THE PMAC IS ON THE RIGHT
FIGURE 16. 5 HP PMAC – 3D CONTOUR PLOT OF EFFICIENCY, TORQUE, N M (X100 SCALE) VS. SPEED, RPM THE PEIM IS ON THE LEFT, THE PMAC IS ON THE RIGHT
Page 25
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 17. 3 HP PEIM – 2D CONTOUR PLOT OF EFFICIENCY, SPEED, RPM VS. TORQUE, N M (X100 SCALE)
Page 26
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 18. 3 HP PMAC – 2D CONTOUR PLOT OF EFFICIENCY, SPEED, RPM VS. TORQUE, N M (X100 SCALE)
Page 27
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 19. 5 HP PEIM – 2D CONTOUR PLOT OF EFFICIENCY, SPEED, RPM VS. TORQUE, N M (X100 SCALE)
Page 28
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 20. 5 HP PEIM – 2D CONTOUR PLOT OF EFFICIENCY, SPEED, RPM VS. TORQUE, N M (X100 SCALE)
Page 29
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 21. COMPARISON OF PMAC AND PEIM 3 HP MOTOR SPEED RPM VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR TORQUE, N M
FIGURE 22. COMPARISON OF PMAC AND PEIM 5 HP MOTOR SPEED RPM VS. EFFICIENCY, AT VARIOUS CONSTANT MOTOR TORQUE, N M
Page 30
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 23. 2D CONTOUR PLOT OF EFFICIENCY DIFFERENCE, 3 HP PMAC AND PEIM SPEED, RPM VS. TORQUE, N M (X100 SCALE)
Page 31
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 24. 2D CONTOUR PLOT OF EFFICIENCY DIFFERENCE, 5 HP PMAC AND PEIM SPEED, RPM VS. TORQUE, N M (X100 SCALE)
DISCUSSION AND RECOMMENDATIONS
PEIM and PMAC data collected to develop performance curves for both 3 HP and 5 HP
motors show that the PMAC motors have superior abilities to keep high efficiency at
constant torque loadings when compared to the control PEIM. The substantial increase in
efficiency at typical motor operations suggests that significant energy savings can be
realized, especially when examined in light of the yearly sales of motors in the PG&E Service
Territory. Tested motors matched well to the specifications of the manufacturer at maximum speed and load.
The findings presented in this report indicate that PMAC motors have the potential to save
substantial energy in variable speed applications, even when compared to a high efficiency
NEMA PEIM. The Phase 1 test setup was able to show that PG&E can assess and compare
various motors. However, it is recommended that in Phase 2 we complete testing of motors
in the 3 to 10 HP range, and examine other manufacturer motors, such as NEMA D and
Page 32
PG&E’s Emerging Technologies Program ET13PGE1081
other motors used in the PG&E Service Territory. The system can be automated to that a
single test can be done daily, using automatic feedback controls to the computer data
acquisition system. This was not done in Phase 1 due to lack of time and funds during this
phase. For future consideration, we could purchase and install an automated 10 HP to 100
HP test apparatus to examine large motors. Since this will be essentially a sized up version
of the current 1-10 HP test setup, no further development costs will be required. We could
then perform efficiency testing for up to 100 HP PMAC motors, including performing
dynamic testing. Finally, this testing should take place with an added PG&E industrial power meter to assess if the system is accurately being measured under harmonic influences.
For the 3 HP efficiency difference, the range is from 2% to 30%, in a fairly linear
distribution across the motor speed. For the 5 HP efficiency difference, the range is also
from approximately 2% to 30%, in a fairly linear distribution across the motor speed. Both
are siginificant improvements, and would have significant impacts on a Customized or
Deemed program. It was discussed earlier in the report when comparing the power usage
of the PMAC and NEMA Premium Efficiencies, an adjustment factor of 0.68 was used to
account for situations where the system was not under full speed or load. It is apparent that
PMAC motors high constant efficiency will have a significant positive impact on power
savings, lead larger overall cost savings and faster payback for systems that require a VFD;
this should be examined in detail based on example field based cases used as an example of system performance.
Finally, in Phase 2 we should interact with both the manufacturers and our customers to try
to understand how these technologies would best be introduced, including analyzing impact
on customers and how PMAC technologies may best be able to help them reduce their
energy costs. For example, how would new 30, 40 and 50 hp PM motors compare to new
premium efficiency and NEMA D motors in oilfield pump applications? We should consider
the expected ranges in motor operating hr/yr, kW load, kWh/yr consumption, motor
equipment cost, motor labor cost and motor operating cost.
Page 33
PG&E’s Emerging Technologies Program ET13PGE1081
3-D CONTOUR CHARTS OF MOTOR EFFICIENCIES
FIGURE 25. 3 HP PEIM – 3D CONTOUR PLOT OF EFFICIENCY, SPEED VS. RPM TORQUE, N M (X100 SCALE)
Page 34
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 26. 3 HP PMAC – 3D CONTOUR PLOT OF EFFICIENCY, SPEED VS. RPM TORQUE, N M (X100 SCALE)
Page 35
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 27 5 HP PEIM – CONTOUR PLOT OF EFFICIENCY, SPEED VS. RPM TORQUE, N M (X100 SCALE)
Page 36
PG&E’s Emerging Technologies Program ET13PGE1081
FIGURE 28 5 HP PMAC – CONTOUR PLOT OF EFFICIENCY, SPEED VS. RPM TORQUE, N M (X100 SCALE)
Page 37
PG&E’s Emerging Technologies Program ET13PGE1081
EQUIPMENT CALIBRATION AND ACCURACY
YOKOGAWA WT1800 POWER SPECTRUM ANALYZER
http://cdn6.us.yokogawa.com/uploaded/BUWT1800_00EN_030.pdf
Page 38
PG&E’s Emerging Technologies Program ET13PGE1081
Page 39
PG&E’s Emerging Technologies Program ET13PGE1081
Page 40
PG&E’s Emerging Technologies Program ET13PGE1081
ABB ACS 880 VARIABLE FREQUENCY DRIVE
http://www.auser.fi/data/attachments/EN_ACS880_single_drives_REVF.pdf
Page 41
PG&E’s Emerging Technologies Program ET13PGE1081
MAGTROL.TM 309 IN-LINE TORQUE TRANSDUCERS
http://www.magtrol.com/manuals/tm300manual.pdf
Page 42
PG&E’s Emerging Technologies Program ET13PGE1081
Top Related