seminar im thermal
TRANSCRIPT
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A NONINTRUSIVE THERMAL
MONITORING METHOD FORINDUCTION MOTORS FED BY
CLOSED - LOOP INVERTER
DRIVES
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OVERVIEW
Introduction
Principle
Terminal voltage estimation
Real time signal processing techniques
Experimental validation
Conclusion
References
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INTRODUCTION
Closed loop induction motor drives are widely
used in traction applications and industrial
processes
Accurate thermal monitoring not only protects
the induction machines from overheating, but
also boosts the usage and performance of the
overall drive system
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INTRODUCTION(Contd)
Recently used thermal monitoring schemes forinduction motors are
Embedded temperature sensors
High-order thermal model-based methods Parameter-based methods
Motor-model-based methods
Signal-injection-based methods
The relationship between the resistance and the
temperature is
..(1)
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PRINCIPLE
Fig 1.Simplified diagram of dc current injection in a closed-loop induction
motor drive
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PRINCIPLE(Contd)
Contains an outer low-bandwidth speed-regulating loop and inner high-bandwidth
current-regulating loop.
DC currents can be injected into the three-phasewinding of the induction machine by
superimposing a sine-wave component onto the
current command id*and iq*
id*=Idc cos.....................................(2.a)
iq*= Idc sin .................................(2.b)
is the transformation angle of the dq
reference frame.4
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PRINCIPLE(Contd)
The dc currents injected into the motorswindings are
ia = Idc................................................(3.a)
ib = 0.5Idc.........................................(3.b)
ic = 0.5Idc.........................................(3.c)
Once currents in (2) have been injected into the motorsstator winding, the stator resistance can be calculated asfollows (Yconnection assumed) Rs
Rs= ................................................(4)
and are dc components of Vab and ia
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PRINCIPLE(Contd)
To track the stator temperature over time, thestator resistanceR0 is first estimated at room
temperature t0
The winding temperature ts,
ts = (t0 + k1 )(Rs/Ro)-k1............................(5)
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Fig 2.Estimated stator temperature using the dc injection method
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TERMINAL VOLTAGE
ESTIMATION An accurate extraction of the dc component in
the line voltage vab is critical for calculating the
stator resistance of the induction machine
In typical closed-loop inverter drives,the
terminal voltages are estimated from the
commanded PWM duty cycle and the measured
dc bus voltage asVaN = DaVdc
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TERMINAL VOLTAGE
ESTIMATION(Contd...)
Where Da is the phase-A duty cycle
generated by the current regulator
Vdc is the measured dc bus voltage
VaN is the average phase-A voltage over
a period of the PWM carrier, with
respect to the negative rail of the dc bus
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A. EFFECT OF DEAD TIME ON
DC VOLTAGE ESTIMATION
Fig 3.a)Current flowing outward b)Current flowing inward c)Reducereffective voltage d)Increased effective voltage
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A. EFFECT OF DEAD TIME ON DC
VOLTAGE ESTIMATION (Contd...)
Fig 4.Contribution of dead time on terminal voltage .No dc current offset
Fig 5.Contribution of dead time on terminal voltage .Positive dc current offset11
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A. EFFECT OF DEAD TIME ON DC
VOLTAGE ESTIMATION (Contd...)
Fig 6.Contribution of dead time on terminal voltage. Positive dc
current offset and smaller current amplitude
Equation (6) is therefore modified to
if ia> 0, VaN = (Da Ddt)Vdc
if ia< 0, VaN= (Da+ Ddt )Vdc........................... (7)
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B.EFFECT OF DEVICE VOLTAGE DROP
ON DC VOLTAGE ESTIMATION
Fig 7.a)Current flowing outwards b)Current flowing inwards13
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B.EFFECT OF DEVICE VOLTAGE DROP ON
DC VOLTAGE ESTIMATION(Contd...)
Fig 8.Contribution of device voltage drop on terminal voltage
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B.EFFECT OF DEVICE VOLTAGE DROP
ON DC VOLTAGE ESTIMATION(Contd...)
To account for the effect of device voltage drop,(7) is further improved to
if ia> 0, VaN= (Da Ddt)Vdc (Da Ddt)VIGBT(ia) (1 Da+ Ddt)Vdiode(ia)
if ia< 0, VaN= (Da+ Ddt )Vdc+(Da + Ddt)
Vdiode(ia)+ (1 Da Ddt )VIGBT(ia)............ (8)
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C. EFFECT OF DIFFERENT
DEVICE TURN-ON/TURN-OFF
TIME DELAY
Fig 9. Contribution of different turn-ON/turn-OFF delay on terminal
voltage.
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C. EFFECT OF DIFFERENT
DEVICE TURN-ON/TURN-OFF
TIME DELAY(Contd...) To account for the effect of device turn-
ON/turn-OFF time difference, (8) is furtherimproved to
if ia > 0, VaN = (Da Ddt+ Ddly)Vdc
(Da Ddt+ Ddly)VIGBT(ia)
(1 Da+ Ddt Ddly)Vdiode(ia)
if ia< 0, VaN = (Da+ Ddt Ddly)Vdc+ (Da+ Ddt Ddly)Vdiode(ia)
+ (1 Da Ddt+ Ddly)VIGBT(ia)...(9)
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REAL-TIME SIGNAL
PROCESSING TECHNIQUES
Fig. 10. Signal process techniques for extracting dc current and voltage. (a) DC
current extraction. (b) DC voltage extraction.
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EXPERIMENTAL VALIDATIONA.EXPERIMENTAL SETUP
Fig. 11. Experimental setup for the proposed thermal monitoring method.
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B. MEASURED MOTOR WAVEFORMS
Fig. 12. d- and q-axis current before and during dc current injection. (a) id
reference and measurement. (b) iq reference and measurement.
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MEASURED MOTOR WAVEFORMS(Contd...)
Fig. 13. Stator voltage and current before and during dc current injection.
(a) Waveform of vab . (b) Waveform of ia
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MEASURED MOTOR WAVEFORMS(Contd...)
Fig. 14. DC components of stator voltage and current. (a) DC component
of vab . (b) DC component of ia .
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MEASURED MOTOR WAVEFORMS(Contd...)
Fig. 15. Motor torque and speed before and during dc current injection. (a)
Electromagnetic torque. (b) Measured motor speed.
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C TEMPERATURE ESTIMATION AT
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C. TEMPERATURE ESTIMATION AT
A SINGLE OPERATING
CONDITION
Fig. 16. Stator winding temperature estimation at constant operating
condition.
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D TEMPERATURE ESTIMATION
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D. TEMPERATURE ESTIMATION
WITH VARIABLE OPERATING
CONDITIONS
Fig. 17. Stator winding temperature estimation with variable load level.
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TEMPERATURE ESTIMATION
WITH VARIABLE OPERATING
CONDITIONS(CONTD.....)
Fig. 18. Stator winding temperature estimation with variable motor speed.
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TEMPERATURE ESTIMATION
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TEMPERATURE ESTIMATION
WITH VARIABLE OPERATING
CONDITIONS(CONTD...)
Fig. 19. Stator winding temperature estimation with variable dc bus
voltage.27
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CONCLUSION
A simple method is proposed for injecting dccurrent into closed-loop drive-fed induction
machines without interrupting normal operation.
The major technical difficulty of dc-injection-based thermal monitoring, which is
inconsistency in resistance estimation, has been
overcome by carefully analyzing and
compensating for the effects of inverternonidealities.
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ADVANTAGES
Nonintrusive
Easy to use
Accurate
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REFERANCES
[1] Siwei Cheng, Yi Du, Jose A. Restrepo,Pinjia Zhang, andThomas G. Habetler, ANonintrusive Thermal Monitoring Method
for InductionMotors Fed by Closed-Loop Inverter Drives,IEEE
Trans. Power Electron.,vol. 27, no. 9, Sept. 2012.
[2] A. Boglietti, A. Cavagnino, M. Lazzari, and M. Pastorelli, A
simplified thermal model for variable-speed self-cooled industrialinduction motor,IEEE Trans. Ind. Appl., vol. 39, no. 4, pp. 945
952, Jul./Aug. 2003.
[9] IEEE Standard Test Procedure for Polyphase Induction Motors
and Generators, IEEE Standard 112-2004 (Revision of IEEE
Standard 112-1996),pp. 179.
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