This document presents a method to estimate the operating power factor (PF) of an induction motor using only the measured motor current and manufacturer data. The method involves estimating the reactive current component from nameplate data and then calculating PF based on the measured current and assumed constant reactive current. Experimental results on a test motor show the PF estimated using this current-only method has an error of around 0.04 compared to methods using voltage and current measurements, with higher error only at no-load condition. This low-cost method provides an alternative to monitor PF without voltage sensors.
The cosine of angle made between the voltage and current is called the power factor.
In AC circuits, there is always the phase deference between the voltage and current, which is calculated in terms of power factor.
If the load is inductive the current lags behind the voltage and the power factor is lagging.
If the load is capacitive the current leads the voltage and the power factor is leading.
The value of power factor can never be more than unity.
In electrical engineering, a synchronous condenser (sometimes synchronous capacitor or synchronous compensator) is a device identical to a synchronous motor, whose shaft is not connected to anything but spins freely.
The topic mainly deals about different methods of high power Underground transmission systems currently implemented across the world as well as about the modern GIL systems.
It also explain about the advantages, construction and features of GIL (Gas Insulated Transmission Lines) by highlighting its future scope as well.
The cosine of angle made between the voltage and current is called the power factor.
In AC circuits, there is always the phase deference between the voltage and current, which is calculated in terms of power factor.
If the load is inductive the current lags behind the voltage and the power factor is lagging.
If the load is capacitive the current leads the voltage and the power factor is leading.
The value of power factor can never be more than unity.
In electrical engineering, a synchronous condenser (sometimes synchronous capacitor or synchronous compensator) is a device identical to a synchronous motor, whose shaft is not connected to anything but spins freely.
The topic mainly deals about different methods of high power Underground transmission systems currently implemented across the world as well as about the modern GIL systems.
It also explain about the advantages, construction and features of GIL (Gas Insulated Transmission Lines) by highlighting its future scope as well.
Winding
What is Armature winding?
Terms related to armature winding.
Single layer and double layer windings.
Comparison between closed and open windings.
Types of DC armature winding.
Types of AC armature winding.
This presentation outlines the different storage technology options available to cope up with the intermittent nature of the Renewable energy like wind and solar.
AC Induction motor (IM) are used as actuators in many industrial processes. Although IMs are reliable, they are subjected to some undesirable stresses, causing faults resulting in failure. Monitoring of an IM is a fast emerging technology for the detection of initial faults. It avoids unexpected failure of an industrial process. Monitoring techniques can be classified as the conventional and the digital techniques.
1.1 PROTECTION SCHEME OF INDUCTION MOTOR
Classical monitoring techniques for three-phase IMs are generally provided by some combination of mechanical and electrical monitoring equipment. Mechanical forms of motor sensing are also limited in ability to detect electrical faults, such as stator insulation failures. In addition, the mechanical parts of the equipment can cause problems in the course of operation and can reduce the life and efficiency of a system.
It is well known that IM monitoring has been studied by many researchers and reviewed in a number of works. Reviews about various stator faults and their causes, and detection techniques, latest trends, and diagnosis methods supported by the artificial intelligence, the microprocessor, the computer and other techniques in monitoring unbalanced voltage inter turn faults, stator winding temperature and microcontroller based digital protectors have been recently studied subjects. In these, while one or two variables were considered together to protect the IMs, the variables of the motor were not considered altogether. Measurements of the voltages, currents, temperatures, and speed were achieved and transferred to the computer for final protection decision.
A programmable integrated circuit (PIC) based protection system has been introduced using Microprocessors and the solutions of various faults of the phase currents, the phase voltages, the speed, and the winding temperatures of an IM occurring in operation have been achieved with the help of the microcontroller, but these electrical parameters have not been displayed on a screen.
Nowadays, the most widely used area of programmable logic controller (PLC) is the control circuits of industrial automation systems. The PLC systems are equipped with special I/O units appropriate for direct usage in industrial automation systems. The input components, such as the pressure, the level, and the temperature sensors, can be directly connected to the input. The driver components of the control circuit such as contactors and solenoid valves can directly be connected to the output.
Waste-to-energy technologies convert waste matter into various forms of fuel that can be used to supply energy. Waste feed stocks can include municipal solid waste (MSW); construction and demolition (C&D) debris; agricultural waste, such as crop silage and livestock manure; industrial waste from coal mining, lumber mills, or other facilities; and even the gases that are naturally produced within landfills.
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Estimation of induction motor operating power factor.
1. Estimation of Induction Motor
Operating Power Factor From
Measured Current and
Manufacturer Data
2. Estimation of IM Operating PF From Measured Current and Manufacturer Data
index
Sl
No
Tittle Page
No
1 Introduction 02
2 Background Information 04
3 Current –Only, Pf Estimation 06
4 Power Factor: From Voltage, Current ZC 11
5 Power Factor: From Instantaneous Power 14
6 Discussion Of Results 16
7 Conclusion 20
8 References 21
1
3. Estimation of IM Operating PF From Measured Current and Manufacturer Data
introduction
“ THREE-PHASE induction motors (IM) are industrial work-horses,
responsible for consumption of 40–50% of generated
electrical power. ”
2
4. Estimation of IM Operating PF From Measured Current and Manufacturer Data
Recently there has been a lot of focus on IM
protection at LV, &MV levels.
These protection devices typically monitor the
motor current and/or voltage to provide the motor
protection functionalities
One of the interesting parameters to monitor is the
operating power factor (PF)
Traditionally, to monitor the operating PF of the IM,
one would require both the voltage and the current
A low cost method of determining the operating PF
of the IM using only the measured current and the
manufacturer data is developed.
3
5. Estimation of IM Operating PF From Measured Current and Manufacturer Data
BACKGROUND INFORMATION
IM equivalent circuit.
Leakage reactance
I1 = Im+I1 ’ Load
v1
I1
r1 X1
rC Xm
I1’
X2’
r2’
s
component
Exciting
component
Im
core-loss
resistance
magnetizing
reactance
stator
Rotor
4
6. Estimation of IM Operating PF From Measured Current and Manufacturer Data
Power Factor and Motor Load
휽ퟎ in the range 75 –85
ie, stator PF at no load may
be as low as 0.1–0.3.
Typically, stator PF of
about 0.8–0.9 at 80–100% of
the full-load
I1’ N1= I2’ N2
5
7. Estimation of IM Operating PF From Measured Current and Manufacturer Data
CURRENT –ONLY, PF ESTIMATION
Total input electrical apparent power , 푷 = ퟑ푽푰
Active power, for supplying the load ,푷 = ퟑ푽푰 cos ∅
PF =
푷
푷
= cos ∅ Eqn 1
I= 푰풂풄풕풊풗풆
ퟐ + 푰풓풆풂풄풕풊풗풆
ퟐ
푰풂풄풕풊풗풆 = I cos ∅ , 푰풓풆풂풄풕풊풗풆= I sin ∅
푰풓풆풂풄풕풊풗풆=I sin cos−ퟏ(푷푭) Eqn 2
PF = 푐표푠 ∅ = 1 − 푠푖푛∅2 = 1 − (
퐼푟푒푎푐푡푖푣푒
퐼
)2 Eqn 3
6
8. Estimation of IM Operating PF From Measured Current and Manufacturer Data
푰풓풆풂풄풕풊풗풆 remains constant, it can be estimated from
nameplate data using 푰풓풆풂풄풕풊풗풆= I sin cos−ퟏ(푷푭)
At no-load condition, there is no active current flow.
So, at no-load, I= 푰풓풆풂풄풕풊풗풆 PF = 0 (
퐼PF= 1 − (
푟푒푎푐푡푖푣푒
퐼
)2 )
As motor load increases the PF will increase toward
unity.
Motor
load
increases
Total
motor I
increase
푰풓풆풂풄풕풊풗풆
remains
constant
(
푰풓풆풂풄풕풊풗풆
푰
)ퟐ
Decreases
Physically, at no-load, there is not much mechanical
resistance, so the whole circuit is mostly inductive due to
the stator coils, causing low PF.
7
9. Estimation of IM Operating PF From Measured Current and Manufacturer Data
Basic Algorithm
Estimate the 푰풓풆풂풄풕풊풗풆 from the nominal PF out of
the nameplate data. ( 푰풓풆풂풄풕풊풗풆=I sin cos−ퟏ(푷푭))
Estimate the operating PF from measured motor
current & constant 푰풓풆풂풄풕풊풗풆
“ It would not require synchronized voltage and
current measurement like in the displacement PF
measurement principle.”
8
10. Estimation of IM Operating PF From Measured Current and Manufacturer Data
experimental setup
Load
supply
Motor
supply
ABB
Lv drive
IM 3 ph
Load
Motor
(7.5kw)
Test Motor
(2.2 kw)
two pole
pairs IM,
M2AA LA4
Motor
current
measureme
nt
Main supply (50 Hz)
IM 3 ph
9
11. Estimation of IM Operating PF From Measured Current and Manufacturer Data
NAME PLATE RATING OF THE
TEST MOTOR TYPE ABB M2AALA4.
NOMINAL VOLTAGE 4 00V
NOMINAL CURRENT 4.9A
RATED POWER 2.2KW
RATED PF 0.81
RATED SPEED 1430 RPM
푰풓풆풂풄풕풊풗풆=I sin cos−ퟏ(푷푭)
= 4.9* Sin (cos−1 0.81)
=2.87
MEASURED I,CALCULATED PF
FROM
CURRENT-ONLY METHOD AT
DIFFERENT LOAD
Measured
CURRENT
I(A)
I/푰풏풐풎풊풏풂풍 (%) PF
3.01 61.43 .30
3.23 65.92 .46
4.37 89.18 .75
5.21 106.33 .83
6.21 126.73 .89
PF= 1 − (
퐼푟푒푎푐푡푖푣푒
퐼
)2=
2.87
3.01
1 − (
)2 = 0.3
10
12. Estimation of IM Operating PF From Measured Current and Manufacturer Data
Power Factor: From Voltage, Current ZC
Basic Algorithm
Synchronized measurement of the supply voltage and
the motor current are done.
Displacements in the ZC timings between the voltage
(taken as reference) and the current signals are
estimated.
Estimate the PF using the equation ±x ms : Deviation between the current
ZC w.r.t. the voltage ZC,
풇ퟎ ∶ 퐒upply frequency.
PF=풄풐풔(
풙
(
ퟏ
풇ퟎ
)
X ퟑퟔퟎퟎ)
The current ZC deviation is positive or negative w.r.t.
The voltage would decide whether the PF is lagging
or leading.
11
13. Estimation of IM Operating PF From Measured Current and Manufacturer Data
experimental setup
Load
supply
Motor
supply
ABB
Lv drive
IM 3 ph
Load
Motor
(7.5kw)
Tektronix Voltage probe
Current hall-sensor probe
Test Motor
(2.2 kw)
two pole pairs IM,
M2AA LA4
Main supply (50 Hz)
oscilloscope
Agilent
IM 3 ph
12
14. Estimation of IM Operating PF From Measured Current and Manufacturer Data
PF MEASUREMENT USING
DISPLACEMENT IN THE ZC OF THE
SYNCHRONIZED SUPPLY VOLTAGE
AND MOTOR CURRENT AT 66%
CURRENT LOAD.
±x ms : 3.4 ms ,풇ퟎ =
ퟓퟎ
Pf =풄풐풔(
풙
(
ퟏ
풇ퟎ
)
X ퟑퟔퟎퟎ)
=cos(
3.4
20
푿 ퟑퟔퟎퟎ) =
0.48
RMS CURRENT,TIME DEVIATION
BETWEEN ZC OF VOLTAGE
&CURRENT, PF FROM
DISPLACEMENT METHOD AT
DIFFERENT LOAD
RMS
current
I(A)
ZC time
difference
(ms)
PF
2.97 4.6 0.12
3.00 3.4 0.48
3.54 2.8 0.64
4.24 2.1 0.79
5.23 1.6 0.87
13
15. Estimation of IM Operating PF From Measured Current and Manufacturer Data
Power Factor: From Instantaneous Power
Basic Algorithm
Estimate instantaneous power per phase (i.e., point-by-
point multiplication of the two waveforms) from
the synchronized supply voltage and the motor
current
Average power (푃 ) per phase from the
measurement in the scope.
Estimate the PF using the equation : PF =
푃
푉퐼
14
16. Power factor measurement using
instantaneous power from the measured
synchronized supply voltage and the
motor current at 66% current load.
푃 =328.525 V=230 I=3
PF =
푃
푉퐼
=
328.525
230 푋 3
= 0.476
RMS CURRENT,RMS VOLTAGE ,
INSTANTANEOUS POWER ,POWER
FACTOR AT DIFFERENT LOAD
RMS
current
(A)
RMS
voltage
(v)
Instantaneou
s power(w)
PF
2.97 230 72.86 0.1
1
3.00 230 328.53 0.4
8
3.54 230 547.48 0.6
7
4.24 230 774.67 0.7
9
5.23 230 1014.32 0.8
4
Estimation of IM Operating PF From Measured Current and Manufacturer Data
15
17. Estimation of IM Operating PF From Measured Current and Manufacturer Data
DISCUSSION OF RESULTS
METHOD I(A) PF I(A) PF
From Measured Current 3.00 0.221 4.24 0.71
From Voltage, Current ZC 3.00 0.48 4.24 0.79
From Instantaneous
3.00 0.48 4.24 0.79
Power
“The PF estimation error using the current-only method is
about +0.04 , except at the no-load condition, where it is
about−0.18 . This could be because, the sensitivity of the
motor current measurement module might not be very perfect
at no-load condition.”
16
18. Estimation of IM Operating PF From Measured Current and Manufacturer Data
The proposed method relies on the fact that the
inductance of the total circuit remains constant.
This rule might be violated if the motor is supplied via a
variable speed drive.
Most modern drive systems usually measure both voltage
and current and can provide PF measurement . Hence, no
need for cheaper calculation of PF.
it is assumed that manufacturers comply with the
relevant IM manufacturing standards, providing rated
values with acceptable accuracy.
Estimation of IM operating PF could be used for PF
compensation
17
19. Estimation of IM Operating PF From Measured Current and Manufacturer Data
Under no-load condition, the referred reactance of the
rotor
X2’ would be absent.
The no-load current would comprise of the magnetizing
current only. ie the no-load current would not be a good
representative of the total reactive current
So, the reactive current estimated from the rated
condition, would not miss any inductive elements.
For bigger IMs with low I(no−load)/I(rated) ratio, the
assumption to use I reactive = constant for light loads
might lead to high errors in the PF estimation.
Higher power machines usually come with MV or LV drives
already provided with the PF computation.
18
20. Estimation of IM Operating PF From Measured Current and Manufacturer Data
Measured current (A)
Underload protection using motor current & power factor
Measured current (A)
푁표푚푖푛푎푙 푐푢푟푟푒푛푡 (퐴)
Power factor
Measured current (A)
푁표푚푖푛푎푙 푐푢푟푟푒푛푡 (퐴)
At low loads the nonlinear curve of the PF provides better
resolution
It challenging to accurately measure the low current change
from small load change at low loading.
19
21. Estimation of IM Operating PF From Measured Current and Manufacturer Data
CONCLUSION
Low cost method of determining the operating PF
of the IM using only the measured current and the
manufacturer data typically available from the
nameplate and/or datasheet.
This would provide a cheaper solution to under
load protection, e.g., in pump applications, using
the operating PF, without requiring the voltage
sensors.
Operational PF can also be used for PF
compensation to improve the power quality.
20
22. Estimation of IM Operating PF From Measured Current and Manufacturer Data
REFERENCE
P.S.Bimbhra, electrical machinery. New delhi, india:
khanna publishers,,
“Identification of induction motor equivalent circuit
parameters
using the single-phase test,” IEEE trans. Energy
convers.
Abb. (2009). Manual for low voltage motor.
Http://www.Abb.Com/motors.
Abb. (2010). LV drives, model ACS800.
Www.Abb.Com/drives
D. Sharon, “power factor definitions and power
transfer quality in no sinusoidal situations,”ieee trans.
Instrum.
“Power-factor compensation of electrical circuits,”
IEEE control syst.
21
24. Estimation of IM Operating PF From Measured Current and Manufacturer Data
ANY
QUESTION
S?
23
Editor's Notes
in Fig. 5. In Fig. 5, we have a test motor (2.2 kW) [12] supplied
from the 50-Hz mains. There is a second motor of slightly bigger
size (7.5 kW) [12] directly coupled to the test motor, acting as a
loading motor to the test motor. The loading motor is supplied
via an ABB drive [13] so that the torque of the loading motor
can be changed in order to test different loading conditions for
the test motor. In order to load the test motor, the direction of
rotation of the loading motor should be opposite to that of the
test motor. This can be done via the drive, as indicated in Fig. 5.
The test motor is an ABB three-phase, two pole pairs IM, type
M2AA LA4 [12]. Fig. 6 shows the nameplate ratings of the test
motor. Stator winding of the motor was connected in star (Y).
The effective nameplate ratings are given in Table I.
For the proposed PF measurement, the motor current of the
test motor is measured using a motor current measurement
module. To validate the proposed current-only PF estimation,
the actual PF also needs to be measured. For that purpose, a
high-resolution oscilloscope from Agilent [14] is used to make
synchronized measurement of the supply voltage and the motor
current. The oscilloscope has four input channels. So, two phases
of the supply voltage and two phases of the motor currents are
in Fig. 5. In Fig. 5, we have a test motor (2.2 kW) [12] supplied
from the 50-Hz mains. There is a second motor of slightly bigger
size (7.5 kW) [12] directly coupled to the test motor, acting as a
loading motor to the test motor. The loading motor is supplied
via an ABB drive [13] so that the torque of the loading motor
can be changed in order to test different loading conditions for
the test motor. In order to load the test motor, the direction of
rotation of the loading motor should be opposite to that of the
test motor. This can be done via the drive, as indicated in Fig. 5.
The test motor is an ABB three-phase, two pole pairs IM, type
M2AA LA4 [12]. Fig. 6 shows the nameplate ratings of the test
motor. Stator winding of the motor was connected in star (Y).
The effective nameplate ratings are given in Table I.
For the proposed PF measurement, the motor current of the
test motor is measured using a motor current measurement
module. To validate the proposed current-only PF estimation,
the actual PF also needs to be measured. For that purpose, a
high-resolution oscilloscope from Agilent [14] is used to make
synchronized measurement of the supply voltage and the motor
current. The oscilloscope has four input channels. So, two phases
of the supply voltage and two phases of the motor currents are