ASD Control Methods – Creating a flatter
motor efficiency curve for more energy
savings
Dr. Allen Neciosup
LV Drives / Application Engineering
Houston, Texas
Toshiba International Corporation
© 2022 Toshiba International Corporation
Contents
01 Introduction
02 Scalar Control Methods
03 Vector Control and Advanced Algorithms
04 Test Results
05 Summary
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01
Introduction
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Energy Savings
INDUSTRIAL MARKETS AND APPLICATIONS
HVAC
Mining /
Aggregate
Material Handling
Refrigeration & Chillers
Compressors,
Pumps & Fans
Conveyors
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Energy Savings
The need for higher efficiency is being approached by:
• Improved Induction Motors / New designs of Synchronous motors
IE3  IE4
IE4  IE5
(rotor
cage)
(rotor
cage)
All new Synchronous Motors need ASDs to operate
They can’t start directly from the power line
(except hybrid cage designs)
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Controlling the power to the motor
ASDs are becoming “the future” of the electric motors
 Three of five induction motors run on variable speed
 All new Synchronous Motors need ASDs to operate
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Can ASDs make the induction motor efficiency curve flatter?
5 to 7% less efficiency as the load decreases
Up to 10% less at half speed
More modern ASD control algorithms can improve the
reduced load/ speed performance of induction motors
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02
Scalar Control Methods
(Open Loop)
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Scalar Control Methods
 Preset V/f ratios to match constant (CT) and variable torque (VT) load types.
 However V/f constant is applied to most motors indifferently.
Base Speed
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Scalar Control Methods
Challenges of preset V/F constant ratio
• Poor efficiency at reduced load and or speed
 Poor torque capability at reduced speed
Scalar V/Hz ctl methods
10
Volts
Volts x sec
8
6
4
2
0
500
450
400
350
300
250
200
150
100
50
0
7.67
2
6
18
30
42
51
60
Hz
V/Hz=CT
V/Hz=CT Flux
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Scalar Control Methods
Operation challenges of preset VT control
Poor efficiency and torque capability if
VT control is used for P2 and C3 curves
Custom VT Flux can solve both challenges
but still may need manual adjustment
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Scalar Control Methods
More challenges…
.
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Scalar Control Methods
And solutions.
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03
Vector and Advanced Control Strategies
“Closed-Loop Vector”, “Sensor-less Vector”, “Self-Sensing Vector”
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Vector and Advanced Control Strategies
𝑻𝑻𝒆𝒆 =
𝟑𝟑𝟑𝟑
𝟐𝟐
[𝝀𝝀𝒎𝒎 𝒊𝒊𝒒𝒒 + 𝑳𝑳𝒅𝒅 − 𝑳𝑳𝒒𝒒 𝒊𝒊𝒅𝒅 𝒊𝒊𝒒𝒒 ] .
Auto-tuning makes Setup easy - Inductances Ld, Lq, stator resistance and other values are
obtained by drive auto-tuning and used for motor control.
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Vector (r-FOC) and Advanced Control Strategies
Vector Control principle - By using vector control, torque 𝑻𝑻 can be expressed as the product of
rotor flux Ψ𝑑𝑑𝑑𝑑 and motor current 𝒊𝒊𝒔𝒔 in terms of d-q components as follows.
where
𝑻𝑻 =
3 𝐿𝐿𝑚𝑚
𝑃𝑃
Ψ 𝑖𝑖
2 𝑛𝑛 𝐿𝐿𝑟𝑟 𝑑𝑑𝑑𝑑 𝑞𝑞𝑞𝑞
𝑃𝑃𝑛𝑛
number of pole pairs
𝐿𝐿𝑚𝑚 mutual inductance
𝐿𝐿𝑟𝑟 rotor winding self inductance
Vector control have
decoupled 𝒊𝒊𝒔𝒔 space
vector into two
components:
𝑖𝑖𝒔𝒔 =
2
2
𝑖𝑖𝑑𝑑𝑑𝑑
+ 𝑖𝑖𝑞𝑞𝑞𝑞
Ψ𝜑𝜑𝑑𝑑𝑑𝑑
rotor flux Ψ𝑑𝑑𝑑𝑑 = 𝐿𝐿𝑚𝑚 𝑖𝑖𝑑𝑑𝑠𝑠
𝑖𝑖𝑞𝑞𝑞𝑞
q-axis stator current (“torque current”)
𝒊𝒊𝒅𝒅𝒅𝒅
d-axis stator current (magnetizing)
𝒊𝒊𝒅𝒅𝒅𝒅 , 𝒊𝒊𝒒𝒒𝒒𝒒 can be used by vector and advanced
control strategies to optimize efficiency
(reduce the power loss)
𝒑𝒑𝑪𝑪𝒖𝒖 =
3
𝑹𝑹𝒔𝒔 (𝒊𝒊𝟐𝟐𝒅𝒅𝒅𝒅 + 𝒊𝒊𝟐𝟐𝒒𝒒𝒔𝒔 )
2
𝒑𝒑𝑭𝑭𝑭𝑭 = 𝒄𝒄𝟏𝟏 𝝎𝝎𝒆𝒆 (𝒊𝒊)𝝍𝝍𝟐𝟐 (𝒊𝒊) + 𝒄𝒄𝟐𝟐 𝝎𝝎𝟐𝟐𝒆𝒆 (𝒊𝒊)𝝍𝝍𝟐𝟐 (𝒊𝒊)
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Vector and Advanced Control Strategies
Advanced Energy Optimization strategies
𝑖𝑖𝑑𝑑𝑑𝑑
d-axis stator current (magnetizing)
T
∝ 𝒊𝒊𝒅𝒅𝒅𝒅 𝒊𝒊𝒒𝒒𝒒𝒒 (~ area)
𝑖𝑖𝑞𝑞𝑞𝑞
q-axis stator current (“torque current”)
iqs
This area
represents
torque.
𝑻𝑻 ∝ 𝒊𝒊𝒅𝒅𝒅𝒅 𝒊𝒊𝒒𝒒𝒒𝒒
Motor
current
𝒑𝒑𝑪𝑪𝒖𝒖 =
3
𝑹𝑹𝒔𝒔 (𝒊𝒊𝟐𝟐𝒅𝒅𝒅𝒅 + 𝒊𝒊𝟐𝟐𝒒𝒒𝒔𝒔 )
2
𝒑𝒑𝑭𝑭𝑭𝑭 = 𝒄𝒄𝟏𝟏 𝝎𝝎𝒆𝒆 (𝒊𝒊)𝝍𝝍𝟐𝟐 (𝒊𝒊) + 𝒄𝒄𝟐𝟐 𝝎𝝎𝟐𝟐𝒆𝒆 (𝒊𝒊)𝝍𝝍𝟐𝟐 (𝒊𝒊)
iqs
Motor
current
ids
ids
Advanced Energy Saving control
(reduced iqs, ids)
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Vector and Advanced Control Strategies
Traditional Field Oriented Control (T-FOC)
3 𝐿𝐿𝑚𝑚
𝑃𝑃
Ψ 𝑖𝑖
2 𝑛𝑛 𝐿𝐿𝑟𝑟 𝑑𝑑𝑑𝑑 𝑞𝑞𝑞𝑞
Ψ𝑑𝑑𝑑𝑑 = 𝐿𝐿𝑚𝑚 𝑖𝑖𝑑𝑑𝑑𝑑
3 (𝐿𝐿𝑚𝑚 )2
𝑻𝑻 = 𝑃𝑃𝑛𝑛
𝑖𝑖 𝑖𝑖
𝐿𝐿𝑟𝑟 𝑑𝑑𝑠𝑠 𝑞𝑞𝑞𝑞
2
Flux-Speed Law
𝑻𝑻 =
imr,R
𝒊𝒊𝒅𝒅𝒅𝒅 , 𝒊𝒊𝒒𝒒𝒒𝒒 -two degrees of
freedom to produce torque
𝑻𝑻𝑭𝑭𝑭𝑭𝑭𝑭,𝑳𝑳 = 𝒌𝒌𝒕𝒕 𝒊𝒊𝒎𝒎𝒎𝒎,𝑹𝑹 𝐼𝐼𝐿𝐿2 − 𝒊𝒊𝟐𝟐𝒎𝒎𝒎𝒎,𝑹𝑹
T-FOC choice is to constraint to one degree of freedom and achieve maximum flux
for every speed up to base
𝑪𝑪𝑪𝑪 Flux-Speed Law
𝑭𝑭𝑭𝑭 Flux-Speed Law
𝒊𝒊𝟐𝟐𝒅𝒅𝒅𝒅 + 𝒊𝒊𝟐𝟐𝒒𝒒𝒒𝒒 ≤ 𝑰𝑰𝟐𝟐𝑳𝑳


𝒊𝒊𝒎𝒎𝒎𝒎,𝑹𝑹 = constant = Rated
𝒊𝒊𝒎𝒎𝒎𝒎,𝑹𝑹 = field weakening (CPSR)
≤ 𝑰𝑰𝟐𝟐𝑳𝑳 Constraint due to motor current limit
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Vector and Advanced Control Strategies
T-FOC
𝒊𝒊𝟐𝟐𝒅𝒅𝒅𝒅 + 𝒊𝒊𝟐𝟐𝒒𝒒𝒒𝒒 ≤ 𝑰𝑰𝟐𝟐𝑳𝑳
𝑻𝑻𝑭𝑭𝑭𝑭𝑭𝑭,𝑳𝑳 = 𝒌𝒌𝒕𝒕 𝒊𝒊𝒎𝒎𝒎𝒎,𝑹𝑹 𝐼𝐼𝐿𝐿2 − 𝒊𝒊𝟐𝟐𝒎𝒎𝒎𝒎,𝑹𝑹
T-FOC choice of using 𝒊𝒊𝒎𝒎𝒎𝒎,𝑹𝑹= constant can cause a lower efficiency for a lower torque T*
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Vector and Advanced Control Strategies
MTPA (Maximum Torque Per Amp)
isq
∗
𝑖𝑖sd
=
∗
𝑖𝑖sq
Minimized is
=
𝑇𝑇 ∗
𝑘𝑘𝑡𝑡
isd
𝑻𝑻𝑭𝑭𝑭𝑭𝑭𝑭,𝑳𝑳 = 𝒌𝒌𝒕𝒕 𝒊𝒊𝒎𝒎𝒎𝒎,𝑹𝑹 𝐼𝐼𝐿𝐿2 − 𝒊𝒊𝟐𝟐𝒎𝒎𝒎𝒎,𝑹𝑹
𝑻𝑻𝑴𝑴𝑴𝑴𝑴𝑴𝑴𝑴,𝑳𝑳 = 𝒌𝒌𝒕𝒕 𝒊𝒊𝟐𝟐𝒎𝒎𝒎𝒎,𝑹𝑹
MTPA improves efficiency by minimizing stator current (pj)
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Vector and Advanced Control Strategies
Loss distribution for the different control strategies
TL = 3.5 N.m (1.1kw motor, 400V, 4 poles)
Loss reduction (%) over an Extended TL range
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04
Test Results
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Test Results
Test data of 200V-4P-2.2kW air handling fan motor
Energy Savings of
Pt=4&5 is effective at
low Sp (air flow).
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Test Results
Motor Efficiency Comparison
and Efficiency Gain
(from 40% up to 100% rated speed)
100.0
100.0
80.0
90.0
60.0
80.0
40.0
70.0
20.0
7.5
3.9
60.0
2.2
1.9
0.0
-0.1
-0.1
0.0
50.0
-20.0
40
50
60
70
5eta2
3eta2
80
90
100
Eff Gain3
10HP, 4poles, NEMA Premium Efficiency induction motor
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Test Results
Motor Efficiency Comparison
and Efficiency Gain
(from 40% up to 100% rtd Sp)
Motor Efficiency Comparison
and Efficiency Gain
(worst case of CT control)
100.0
100.0
100.0
100.0
80.0
90.0
80.0
90.0
85.0
60.0
80.0
40.0
70.0
7.5
60.0
50.0
95.0
40
20.0
3.9
50
2.2
60
5eta2
1.9
70
3eta2
0.0
80
Eff Gain3
-0.1
90
-0.1
100
60.0
80.0
75.0
70.0
40.0
18.4
65.0
0.0
-20.0
20.0
7.9
5.9
5.3
60.0
3.5
2.8
2.5
0.0
55.0
50.0
40
50
60
5eta2
70
0eta2
80
90
100
-20.0
Eff Gain0
10HP, 4poles, NEMA Premium Efficiency induction motor
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Test Results
Motor Loss Reduction in %
(from 40% up 100% rtd Sp)
Motor Loss Reduction in %
(added worst case of CT control)
70.0
70.0
60.0
50.0
50.0
40.0
30.0
30.0
20.0
10.0
10.0
0.0
-10.0
40
50
60
70
80
90
100
-10.0
40
50
60
70
5 vs 3
80
90
100
5 vs 0
10HP, 4poles, NEMA Premium Efficiency induction motor
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Test Results
Motor Loss Reduction in %
(added worst case of CT control)
Motor Efficiency Comparison
and Efficiency Gain
(worst case of CT control)
100.0
95.0
90.0
85.0
80.0
75.0
70.0
65.0
60.0
55.0
50.0
18.4
7.9
5.9
5.3
3.5
70.0
2.8
2.5
100.0
60.0
80.0
50.0
60.0
40.0
40.0
30.0
20.0
20.0
0.0
40
50
60
70
5eta2
0eta2
80
Eff Gain0
90
100
-20.0
10.0
0.0
-10.0
40
50
60
70
5 vs 3
80
90
100
5 vs 0
10HP, 4poles, NEMA Premium Efficiency induction motor
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05
Summary & Conclusion
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Summary & Conclusion
• Without incurring any additional hardware or cost, ASDs control methods can
improve the efficiency of Induction and new Synchronous Motors
• We have focused in obtaining efficiency improvement results for fans and pumps
and at this time we have presented the results in the low HP range
• Using an Induction motor with a off the shelf ASD with the proper control
algorithm can (next slide) :
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Summary & Conclusion
• Increase the efficiency of the variable load/speed application.
• At steady state, ASDs can provide motor optimal air gap flux or the
ids, iqs combination at each operating point for energy savings and
the required dynamics for the application,
• Minimize the motor current for less motor copper losses (MTPA), or
• Maximize the efficiency (MTPW) for less input power consumption
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Thank You
Presenter: Dr. Allen Neciosup
To learn more about Toshiba, please visit our website at www.toshiba.com/tic.
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