Permanent Magnet Alternating Current (PMAC) Motor Efficiency … · 2020-01-02 · Munz of Marathon...

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.


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.

mailto:[email protected]


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


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


Figure 11. 5 HP PEIM – Motor Speed, RPM vs. Efficiency, at


Figure 12. 5 HP PMAC – Motor Speed, RPM vs. Efficiency, at


Figure 13. 5 HP PEIM – Power In, Watts vs. Efficiency, at Various


Figure 14. 5 HP PMAC – Power In, Watts vs. Efficiency, at Various


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







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


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


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


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.


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


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

http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/mcs-2013-raree.pdf


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.


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


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


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.


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.


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


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.


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


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


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.


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


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


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


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


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.


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


FIGURE 17. 3 HP PEIM – 2D CONTOUR PLOT OF EFFICIENCY, SPEED, RPM VS. TORQUE, N M (X100 SCALE)


FIGURE 18. 3 HP PMAC – 2D CONTOUR PLOT OF EFFICIENCY, SPEED, RPM VS. TORQUE, N M (X100 SCALE)


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


FIGURE 23. 2D CONTOUR PLOT OF EFFICIENCY DIFFERENCE, 3 HP PMAC AND PEIM SPEED, RPM VS. TORQUE, N M (X100 SCALE)


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


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.


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)


FIGURE 26. 3 HP PMAC – 3D CONTOUR PLOT OF EFFICIENCY, SPEED VS. RPM TORQUE, N M (X100 SCALE)


FIGURE 27 5 HP PEIM – CONTOUR PLOT OF EFFICIENCY, SPEED VS. RPM TORQUE, N M (X100 SCALE)


FIGURE 28 5 HP PMAC – CONTOUR PLOT OF EFFICIENCY, SPEED VS. RPM TORQUE, N M (X100 SCALE)


EQUIPMENT CALIBRATION AND ACCURACY

YOKOGAWA WT1800 POWER SPECTRUM ANALYZER

http://cdn6.us.yokogawa.com/uploaded/BUWT1800_00EN_030.pdf


ABB ACS 880 VARIABLE FREQUENCY DRIVE

http://www.auser.fi/data/attachments/EN_ACS880_single_drives_REVF.pdf


MAGTROL.TM 309 IN-LINE TORQUE TRANSDUCERS

http://www.magtrol.com/manuals/tm300manual.pdf

Permanent Magnet Alternating Current (PMAC) Motor Efficiency … · 2020-01-02 · Munz of Marathon...

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