Constant Slip Speed Control of 3-Phase ACIM

Constant Slip Speed Control of
3-Phase ACIM
Kartik Liao
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© 2014 Spansion Inc.
Background
 Application
− Lathes, mills, drilling machines
− Conveyers, lifts, cranes
− Compressors, pumps, fans
 ACIM Features
− High reliability
− Less maintenance
− Low cost
 Control Schemes
− V/f control
− Constant slip voltage(V/f, current)control
− FOC
− DTC
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© 2014 Spansion Inc.
Elements of AC Induction Motor
(From Article Library)
Schematic of Slip Speed Control Solution
AC
~
∗ = 0
∗ +

∗
PI
Rectifier
Inv.
Park
DC
PWM
-

∗

+
+
1

IPM
PI
Speed
sensor
 ∗
DC bus voltage
sample
Field
weakening
Software
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ACIM

Speed signal
capture
Hardware
Slip Speed Solution Features
 High efficiency
 Fast dynamics
 Low cost
 Simple control structure
 Easy tuning
Features
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V/f Control
Slip Control
DTC
FOC
Dynamics
Low
Moderate
High
High
Efficiency
Low
High
High
High
Cost
Low
Moderate
High
High
Complexity
Low
Low
Moderate
High
Tuning
Easy
Easy
Moderate
Difficult
© 2014 Spansion Inc.
Control Theory
 Phasor Model of ACIM at Steady State
−  =   +    +  
−  =   +  (  +   ) = 0
 Torque Generation
−  =
=
3
2  
∙
2  2 2 −  2 +2 2

3
2
∙
 2

2  
  +  2 − 
2
+    +  
 Control Target
2

2
 

 

− Slip Speed

− Stator voltage (or V/f, stator current)


Phasor model of AC Induction Motor
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© 2014 Spansion Inc.
1

 


Motor Efficiency and Slip Speed
 MTPA minimizes stator current for a certain load level, which requires
the slip speed to satisfy below equation
−  =


 Maximum efficiency control minimizes copper loss and core loss, which
is realized by setting slip speed as
−  =
1 
√2 
Switching loss [ ]

3-phase
Inverter
Copper loss [ ]
Mechanical loss []
Input Power
[ ]
Output Power
[ ]
AC Induction Motor
Core loss [ ]
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© 2014 Spansion Inc.
Field Weakening and Slip Speed
 High speed operation requires weakening flux level to suppress backEMF under a certain level
 If the load torque is ∗ , the stator flux linkage is determined by slip
speed
−  =
2∗
3
2
∙
 2 +2  2 − 2 +   2
2   2 +   2
2
 Flux level decreases with the
increase of slip speed
Magnitude of stator flux linkage
1.000
Te= 0.5
0.900
0.800
Te= 1.5
0.700
0.600
0.500
0.400
0.300
0.200
0.100
0.000
1
6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96
Slip speed
Slip speed v.s. flux linkage
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© 2014 Spansion Inc.
Related Resources
 Documents
− S6E1A1_AN710-00001-E 3-Phase ACIM Scalar Control
− AN710-00009-1v0-E-3-Phase_ACIM_Scalar_Control_User_Manual
 Find more
http://www.spansion.com/Pages/Default.aspx
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© 2014 Spansion Inc.
www.spansion.com
Spansion®, the Spansion logo, MirrorBit®, MirrorBit® Eclipse™ and combinations thereof are trademarks and registered
trademarks of Spansion LLC in the United States and other countries. Other names used are for informational purposes
only and may be trademarks of their respective owners.
This document is for informational purposes only and subject to change without notice. Spansion does not represent that
it is complete, accurate or up-to-date; it is provided “AS IS.” To the maximum extent permitted by law, Spansion disclaims
any liability for loss or damages arising from use of or reliance on this document.
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© 2014 Spansion Inc.
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