8/9/2019 Derating of Induction Motors Due to WaveformDistortion
1/6
1102
IEEE TRANSACTIONS
ON
INDUSTRY APPLICATIONS, VOL. 26, NO.
6.
NOVEMBERIDECEMBER 1990
Derating of Induction Motors Due to
Waveform Distortion
AbstractElectrical motors are designed on the basis ofbalanced
threephase sinusoidal input voltage. Nonsinusoidal voltage hasdetri
mental effects on induction motor performance, and derating ofthe
machine is required. IEEE Standard 519 suggests that no deratingof the
motor would be necessary for a harmonic content of up to
5070.
The
derating of induction motors due to harmonic distortion isdiscussed in
detail.
INTRODUCTION
HE OUTPUT of an induction motor depends mainly on
T eating, and the motor’s life is shortened by overheating.
The temperature rise resulting from losses is, therefore, a
major factor in determining the machine output rating. The
presence of harmonics in the applied voltage can cause
excessive heating.
The amount of voltage distortion, measured by a “distor
tion factor” (DF) and defined by IEE E Standard 519
[l]
as
1 I 2
sum of squares of am plitudes
of all harmonic voltages
square of amplitude of
fundamental voltage
] 1)
F =
I
is used to establish harmonic limits. On industrial power
systems, the voltage distortion is limited to
5 .
However, no
limit is specified in regard to the individual harmoniccontent.
Derating of ‘‘N EM A design B” induction motors of different
output ratings and for two types of enclosures (dripproofand
totally enclosed) due to different cases of harmonic distor
tions are discussed in this paper.
ANALYTICALA CK G RO U N D
General Assump tions
grounded.
ing conditions.
1) The motors are nonskewed, Y connected, and un
2)
The analysis is limited to fullload steadystate operat
3) The principle of superposition applies.
Equivdent Circuit Parameters
The simplified equivalent circuit of a threephase induction
motor is shown
in
Fig. 1. It is to be remembered that this
Paper PID 9029, approved by the Petroleum and ChemicalIndustry
Committee of the IEE E Industry Applications Society forpresentation at the
1989 Petroleum and Chemical Industry Technical Conference, SanDiego,
CA, September 1113. Manuscript released for publicationMarch
8,
1990.
The authors are with the Department
of
Electrical Engineering and
Computer Science, University of Colorado at Denver, 1200 LarimerStreet,
Campus
Box 110
Denver, CO
80204.
IEEE
Log
Number 9038525.
Stator Quantities Rotor Quantities
s x ‘R/s ‘R
2
7
>
I
I 1 4
Magnetic Core
Fig. 1.
Equivalent circuit
of
induction m otor.
equivalent circuit does not take into account any time or
space harmonics. The various resistances and reactances are
referred to the stator winding and are expressed in per unit
(pu) at the machine base. These parameters ( R , ,
R,,
X,
=
W L , , X , , X R , )
are assumed to be constants. This is true
only for a given operating condition. They vary with changes
in motor current, speed, voltage, and temperature
[2].
Motor Losses
The total motor losses (P, , , ) consist of iron, winding,
mechanical, and stray losses.
Iron Losses (Pf,):
For an alternating magnetic field, losses
that occur in the iron consist of hysteresis loss and eddy
current loss. In general, for sinusoidal flux, the losses in
Watt/kg of iron (for a given lamination thickness) can be
expressed as
p f e = k,fBi
+
k, fBm)’
(2 )
where the first term accounts for the hysteresis loss andthe
second term for the eddy current loss. The constants
kh
nd
k ,
depend on the properties of the material.
B,
is the
maximum flux density and is proportional to the airgap
voltage E. If the flux density
B,,,
s uniform over the
crosssectional area
A
of the core,
where
E
is the rms value of the airgap voltage,
C ,
is
a
machine constant, and
f is
the frequency. Substituting
3)
in
(2)
gives
‘fe = [ kh l/f) k k e ] E Cm ) 2 . ( 4 )
Winding Losses Pcu,and Pcu2):
These losses are stator
00939994/90/11001102 01.00
990 IEEE
8/9/2019 Derating of Induction Motors Due to WaveformDistortion
2/6
SEN
AND LANDA:
DERATING
OF INDUCTION MOTORS DUE TO WAVEFORM DISTORTION
1103
and rotor Z2R losses caused by the current flowing through
the respective winding.
Mechanical Losses (Pmech):The mechanical losses com
prise of friction and windage losses. They are approximately
proportional to the square of the speed and to the contact
surface area. These losses will be assumed to be unaffected
by voltage harmonic distortion.
StrayLoad Losses (Psr roy):
hese are additional iron and
eddy current losses caused by the increase in airgapleakage
flux with load, and by highfrequency pulsation fluxes.These
losses can be divided into six components as follows:
1
the eddy current loss in the stator copper
W ,
due to slot
(Video) Harmonicsleakage flux (normally neglected);
2) the losses in the motor end structure
We
due to end
leakage flux;
3)
the highfrequency rotor and stator surface losses
W
due to zigzag leakage flux;
4) the highfrequency tooth pulsation and rotor
Z2R
losses
W , , also due to the zigzag leakage flux;
5) the sixtimesfrequency (for threephase machines) ro
tor Z2R losses
w,
due to circulating currents induced
by the stator belt leakage flux;
6) The extra iron losses in motors with skewed slots
W ,
due to skew leakage flux (neglected here because of the
nonskewed assumption).
The equations for these components given
in [3]
are (with
some changes in notation)
We = CeZ:fl 5 )
w,
=
W l
zo)2Bg2
(6)
(7)
w
= Cbk,.,,,R,I;
(8)
W , = C , k , , R , ( C , Z ~ C I Z t )
where
C,, C, , C, , C, , CO,
nd
C ,
are constants that depend
on the m achine and other empirical factors,
k , ,
and
k , ,
are
the skin effect coefficients for the rotor ba rs at the statorslot
harmonic frequency and at the phase belt frequency, respec
tively, B , is the average flux density over the effective
airgap area,
Io
is the noload current, Z is the stator
current, and
f,
s the line frequency. For typical standard
NEMA design
B
machines operating at full load, the losses
can be distributed as [4]
Pmech
0.09
Pcul =
0 . 37
Pcu2 =
0 . 1 8
Pfe =
0.20
Pstray
0 . 1 6
Pdiss=
1 oo
Thermal Stress
[2]
[SI
The allowable hotspot temperature in the stator winding
determined by the insulation class governs the output of a
machine. Assuming a lumped parameter approach, Figs. 2
and
3
show the simplified thermal equivalent circuit of a
dripproof radially cooled and a totally enclosed fancooled
machine.
Air Temp
b)
Thermal network.
Fig.
2.
Dripproof radially cooled squirrelcage motor. (a) Air flow.(b)
R j i .
Air Temp
( b )
Thermal network.
Fig. 3 .
Totally enclosed fancooled squirrelcage motor. (a) Air
f low.
(b)
The temperature rise of the stator winding T is then (for
a dripproof radially cooled machine)
Twl = PculRewl 9)
where
R e w ,
s the thermal resistance of the stator endwind
ing. F or a totally enclosed fancooled machine, thetempera
ture rise is
~ w l
pcu1Ri
+
(PcuI
+
p c u 2
+
Pfe
+
stray) ,
+ (Pcul + Pcu2 + Pfe + Pstray + Pmech) ,
10)
where R i , R j , and R , are the thermal resistances of theslot
insulation, stator backiron (including airgap between the
stator core and outside frame of the motor), and outside
frame and moving air, respectively.
8/9/2019 Derating of Induction Motors Due to WaveformDistortion
3/6
1104
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS. VOL. 26, N O. 6.NOVEMBERIDECEMBER 1990
DERATINGF INDUCTIONMOTORS
UE
O
HARMONICS
Voltage Waveshape
general form as
The nonsinusoidal supply voltage can be expressed
in
a
n
( t )
=
Jz V ,
s i n w t
+ v,sin kwt + 0,) 11)
where
V I
is the fundamental voltage, v k represents har
monic voltages of order k and 6 , is the harmonic phase
angle. The fundamental and the 4,7,
10,
13;
* , [ 3 n +
11,
n
=
1 , 2 ,
* , order voltage harmonics contribute to a
rotating magnetomotive force (MMF)
in
the direction of
motion and hence results in the development of a .positive
torque.
T h e 2 , 5 , 8 , 1 1 ; . . , [ 3 n + 2 ] , n = 0 , 1 , 2 ; * .,
or
der of harmonics results in a rotating MMF in a direction
opposite to the direction of motion of the rotor and hence
contributes to a negative torque. The
3 , 6 , 9 ,
12; e [3n
31,
n
= 0, 1 , 2 , order of harmonics produces no rotating
MMF and, therefore, no torque.
[
(Video) ETAP Power Quality  Fundamentals of Harmonicsk = 2
Equivalent Circuit Parameters
Based on assumption 3) , the temperature rise of the motor
can be computed by superposition as if a series of indepen
dent generators were supplying the motor. Each generator
would represent one
of
the voltage terms in (1 1). Each of
these voltages would produced stator and rotor currents.
Evaluation of the reactances and resistances in these series
of equivalent circuits ought to be done at the corresponding
harmonic frequencies.
The actual frequency of the current
in
the stator is
[k
f
]
and in the rotor
[
k * f,
sk],
where
f
is the fundamental
frequency and sk is the slip for the kth harmonic. At these
frequencies, skin and proxim ity effects should beconsidered
in
inductances and resistances. The synchronous speed corre
sponding to the applied frequency [
k * f,
is
[ k N , ] , N ,
being the synchronous speed in revolutions per m inutecorre
sponding to the fundamental (i.e.,
N ,
=
120
.fl
p , p
is the
number of poles). Therefore, the slip sk at any speed N of.
the rotor is given by
kN,
+
N ,
Sk =
( 1 2 )
kNS
The plus sign has been used to account for the fact thatsome
harmonics result
in
rotating MMF’s in the same direction as
the motion of the rotor, while others result in rotating
MMF’s
in
the opposite direction of the motion of the rotor.
In terms of the slip s corresponding to the fundamental),
N
= 1 s ) N , .
(13)
Therefore,
kN, + 1 s ) N , k + (1
S
. (14)
k
=
w s
k
To arrive at appropriate values for the inductances
in
the
circuit with the motor operating with nonsinusoidal voltage,
the effects of harmonic voltage and currents on the degreeof
RSk
‘Sk
Rpk ‘Rk
“k
~
(b )
tion.
(a)
Fundamental. b)
k,
harmonic.
Fig. 4.
Equivalent circuit
for
induction motor with nonsinusoidal excita
saturation must also be considered. The effect of saturationis
to limit the flux
in
the iron of the flux paths, causing a
reduction
in
the inductances.
Eflect of Saturation
To determine the effect of saturation in the noload current
due to harmonic distortion, a new modified magnetizing
reactance is calculated as
Xm,
= Xrn
lMf
(15)
where the factor
M ,
is defined as
M =
/=//
n = O
( 1 6 )
where i , and i , , are the instantaneous magnetizingcurrent
corresponding to the flux density wave for normal and abnor
mal conditions, respectively.
Results of the increase
in
noload current due to saturation
were verified experimentally by lab tests on a 2hpinduction
motor
[ 6 ] .
Determination of Harmonic Currents
When the motor is running near the fundamental syn
chronous speed, the harmonic equivalent circuit is quite
similar to the locked rotor equivalent circuit for theparticular
harmonic being considered. The magnetizing branch may be
neglected since the magnetizing reactance for the kth har
monic
( k X , )
is much greater than the rotor leakage
impedance for the kth harmonic ( Z , , ) . For a similarreason,
the resistors
R
and R , , representing core (and m echanical)
losses for the fundamental and the different harmonics are
also neglected. Fig. 4(a) shows the sim plified equivalent
circuit for the fundamental component and Fig. 4(b) for the
kth harmonic. The kth harmonic current is then given as
‘k
I , =
[ (
R S k
+ R R k
/ ’ I 2
+ ( x . S k +
X R k ) 2 ]
where Vk is the voltage due to the kth harmonic,
R
and
R
the stator and rotor resistances and
x s k
and X , , the
stator and rotor reactances for the kth harmonic. The total
8/9/2019 Derating of Induction Motors Due to WaveformDistortion
4/6
SE N A N D L A N D A : D E R A T I N G
OF
I N D U C T I O N M O T O R S D U E T O W A V E FO R M D I ST OR T I O N
1105
harmonic current is
(18)
Motor Losses
Iron Losses:
The presence of time harmonics results in
higher saturation of the magnetic paths. Consequently, iron
losses will increase. This increase can be estimated bysubsti
tuting the corresponding harmonic voltages and frequencies
in (4).
Winding Losses: Assuming the skin effect in the stator
winding to be negligible, the stator copper loss on anonsinu
(Video) Gilson Engineering  Basics of Variable Frequency Drives with LSISsoidal supply is proportional to the square of the total rms
current. If R , is the stator resistance, the loss per phaseis
P C U I = C I S R S (19)
I,,, =
JI 1; .
p c u , =
w
1;)
(20)
(21)
Then
where
I f R ,
represents the loss due to the fundamental and
I i R ,
accounts for the losses due to harmonics.
When the rotor conductor depth is appreciable (as in large
machines) skin effect should be taken into account. Loss due
to each harmonic must be considered separately and then
added. In the case of a deep bar machine rotor, the totalrotor
copper loss per phase is
n
pcu2
=
i k R R k k i R R . (22)
k = 2
Here, the first term represents the loss due to harmonics,and
the second term will give the rotor copper loss due to the
fundamental. In orde r to maintain constant output torque,the
last term of (22) will vary an am ount given by (23), whichis
proportional to the resultant torque produced by theharmonic
currents
:
n
T k = z i k R R k / s k .
(23)
k = 2
StrayLoad Losses:
Voltage harmonics significantly affect
these losses. They can be estimated by adapting
(5)(8)
to the
motor with harmonics as follows:
r
n 1
where
ZA
is the noload current corrected for saturation and
I ; is the total stator current including harmonics.
RESULTS ND DI SCUSSI ONS
Using the equations derived in the preceding sections, a
computer program is developed. The temperature rise of
induction motors of different ratings (Table I) and twotypes
TABLE I
THREEPHASENDUCTION M O TO R H A R A C TER I STI C S
7]
Full Resistances and Reactan ces Rotor
Load in Per Unit Based on Full Bar
Rating Slip Load kVA and Rated Voltage Height
(hP) ( ) R.s R R X ,
X.7
X
( m m )
Up to5 4.5
0.055 0.055
1.9 0.048 0.072 15
525 3 .0
0.040 0.04 2 .6
0.064 0.096 25
25200
2.5 0 .030
0.03 3.2 0.068 0.102 35
2001000 1.75 0.025
0.02
3.6 0 .068 0 .102
45
TABLE I1
H A R M O N I CONTENT
F
W A V EF O R M SSED
Waveform Voltage in
of
Harmonic Fundamental
k a b
C
2
3
4
5
6
7
8
9
10
11
12
13
17
19
5.00 0. I7
0.21
0.26
5.00 3.41
0.87
0.25
0.26
0.61
0.26
0.56
0.43
1.21
0.87
0.78
DF =
5 % 5 % 5 %
of enclosures are determined for three different cases of 5%
voltage distortion (Table 11). Triplen harmonics areneglected
in the calculations.
The thermal resistances R ; ,
R j ,
and R , are determined
for a 5hp and for a 100hp machine. The values found for
the 5hp machine are used as representatives of machines
ranging from 0 to 25 hp, and those found for the 100hp
machine f or machines ranging from 25 to
1000
hp. Insulation
class B is assumed for all cases.
Slot leakage inductance reduction d ue to harmonic distor
tion is considered equal to 10 for all waveforms and rotor
slot leakage inductance is taken to be 30% of total rotor
leakage for all machines. In all the computations, an ANSI
M22 steel and 1 OT maximum airgap magnetic flux density
is used.
The results of the increases in temperature with respect to
fullload norm al operating conditions defined by
where TH and TN are the hotspot temperature of the ma
chine when supplied with nonsinusoidal (or harmonic) and
sinusoidal voltages, respectively, are shown in Figs.
5
and 6.
Figs.
5
and
6
reveal that the second harmonic (case a) in a
nonsinusoidal voltage has the most pronouncecl effect on the
temperature rise. The fifth harmonic only or the assorted
higher order harmonics of small magnitudes (cases b and c)
do not have any appreciable effect on the temperature rise
8/9/2019 Derating of Induction Motors Due to WaveformDistortion
5/6
1106
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL.
26,
NO. 6 , NOVEMBERIDECEMBER 1990
17.5
15.0
12.5
H 10.0
7  5
References
a
 harm.
wavefozm a
b  harm. waveform b
c
 harm. waveform C
1
lo oi
(Video) Understanding Power Quality Testing.5
0 5 25 200 1000
OTOR RATINGS
HP)
Temperature increase on dripproof radially cooled inductionmotor.
ig. 5 .
Reference9
b 
harm.
waveform b

harm.
vaveform
C
a
 ham waveform a
a
c
5 25 200 1000
PaTOR RATINGS HP)
Fig. 6 . Temperature increase on totally enclosed fancooledinduction
motor.
(less than 5 ). It is also clear that, for dripproofradially
cooled machines, the percentage variation of temperaturerise
reduces as the size increases (negative slopes in Fig. 5 ) ,
whereas it increases in totally enclosed fancooled machines
(positive slopes in Fig.
6 ) .
Based on the initial results, it is decided to calculate the
derating due to second harmonics (case a) only. T odetermine
the derating, a computer program reduces the output power
of the machine until the temperature due to the abnormal
condition is less than or equal to the normal operating
temperature corresponding to class B insulation. Thederating
due to harmonic distortion is then calculated as
29)
pout H
derating,
= 1
ou t
where Pout
and Pout re the output power
of
the machine
1.00 t
I 1
0.95
D:
0.90
Lr
0.85
z
* 0.80
W
CI
0 70
4
I
I
I
c
0 5
25
200 1000
MOTOR RATINGS HP)
Derating factors due to harmonic voltage distortion. Dottedlines:
dripproof radially cooled motor. Solid line: totally enclosedfancooled
motor.
Fig. 7.
when supplied with nonsinusoidal and with sinusoidal volt
age, respectively. The results are shown in Fig.
7.
When supplied with waveform a, machines of both types
of enclosure and for all ratings would require derating at
5
harmonic distortion. Fig. 7 also shows the derating due to
8 % second harmonic.
CONCLUSION
While, in the cases of harmonic waveforms b and c,
5
limitations on harmonic content is acceptable, results forcase
a are significant. We find that a restriction for the second
harmonic should be included on the harmonic distortion
limits estab lished by IEEE Standard 519 [l], and derating
in
some cases should be considered for less than 5 % harmonic
distortion.
8/9/2019 Derating of Induction Motors Due to WaveformDistortion
6/6
SEN AND LANDA: DERATING O F INDUCTION M OTORS DUE TO WAVEFORMDISTORTION
1107
Dripproof machines are found to be less affected by
harmonic distortion than the totally enclosed machines. Ef
ficiency plays a very important role in the degree ofderating.
Less
efficient machines would require
a
higher derating. It is
also clear that smaller machines (less than 5 hp) areaffected
more by the harmonics than are larger machines.
REFERENCES
IEEE Guide
f o r
Harmonic Control and Reactive Compensation
of Static Power Converters, ANSIIIE EE Standard 519, Apr.1981.
E. Levi , Polyphase
Motors:
A Direct Approach to Their Design.
New York: Wiley, 1984.
P. L. Alger, G. Angst, and E. J . Davies, “Strayload lossesin
polyphase induction machines,” AIEE Trans. Power App . Syst .,
vol. 78, pt. 111A, pp. 349357, June 1959.
J . C. Andreas,
Energy Ejicient Electric
Motors. New York:
Marcel Dekker, 1982.
Optimization
of
Induction
Motor
Ejic iency , vol. 1 EPRI, Univ.
of Colorado, Boulder, July 1885.
H. A. Landa, “Derating of induction motors due to harmonicsand
voltage unbalance,” M.S. thesis, Univ. of Colorado, Denver,Nov.
1987.
E. Clarke, Circuit Analysis of AC Power Systems. London: Wi
ley, 1950.
B. N. Gafford, W. C. Duesterhoeft , Jr . , and C. C. Mosher,111,
“Heat ing of induction m otors on unbalanced voltages,” AIEETrans.
P o w er A p p . Sy s t . , pp. 282288, June 1959.
E.
A. Klingshirm and H. E. Jordan, “Polyphase induction motor
performance and losses on nonsinusoidal voltage sources,”IEEE
T rans . P ow e r A p p . S y s t . , vol. PAS87, pp. 624631,M ar. 1968.
P. G . Cummings, “Estimating effect of system harmonics onlosses
and temperature rise of squirrelcage motors,” IEEE paperno.
PCIC857, 1985.
Pankaj K.
Sen
(S’71M ’74SM ’90) received the
B
S E E degree (with honors) from Jadavpur Uni
versity, Calcutta, India, and the M.E and Ph D
degrees in electrical engineering from the Techni
cal University of Nova Scotia, Halifax, NS.
Canada
He is currently an Associate Professor of Elec
trical Engineering at the University of Colorado,
Denver His research interests include application
problems in machines and power systems and
power engineering education
Dr Sen is a Registered Professional Engine er in the State ofColorado
Hector
A . Landa (S’87M’87) was born in
Paysandu, Uruguay, in 1956 He received the B S
degree in electromechanical engineering from the
University of Concepcion del Uruguay, Argentina,
and the M
S
degree in electrical engineering from
the University of Colorado, Denver
Since 1988 he has been employed by the U S
Government Bureau of Reclamation
in
the Electric
Power Branch as a Research Electrical Engineer
His areas of special interest are power systems
harmonics and computer simulation
Mr. Landa is a member of Eta Kappa Nu
FAQs
What is the effect of harmonic distortion parameter on 3 phase induction motor? ›
Harmonics distortion raises the losses in AC induction motors in a similar way as in transformers and cause increased heating, due to additional copper losses and iron losses (eddy current and hysteresis losses) in the stator winding, rotor circuit and rotor laminations.
What are the effects of harmonic distortion on motors? ›First, harmonics reduce the motor's efficiency. Harmonic content makes it harder to magnetize the copper and iron in the motor's stator and rotor, causing higher eddy current and hysteresis losses. If harmonic frequencies exceed 300 Hertz, the skin effect compounds these losses.
How do you reduce third harmonics? ›Explanation: Certain methods can be used to reduce harmonics they are: Adding a line reactor or transformer in series will significantly reduce harmonics, as well as provide transient protection benefits. Isolation transformers provide a good solution in many cases to mitigate harmonics generated by nonlinear loads.
How current distortion affects the voltage distortion under the presence of harmonics? ›This voltage distortion affects the current harmonics emitted by the electronic loads. Depending on the voltage waveform characteristics (magnitude and phase angle of the harmonics), harmonic emission of electronic loads can increase or decrease [59].
How much harmonic distortion is acceptable? ›While there is no firm limit in the US, IEEE 519 recommends that general systems like computers and related equipment have no more than 5% total harmonic voltage distortion with the largest single harmonic being no more than 3% of the fundamental voltage.
How to reduce the total harmonic distortion in power system? › KRated Transformers. ANSI Standard C57. ...
 Measuring KFactor. In any system containing harmonics, the Kfactor can be measured with a power quality analyzer (see Figure 1). ...
 Circuit Load. ...
 Harmonic Mitigating Transformers. ...
 DeltaWye Wiring. ...
 Zigzag Windings.
In order to reduce the harmonics, filters are connected in either series or parallel to the load side and/or supply side. Shunt active filter (SAF) is generally used to reduce the harmonics in the power system.
How do you reduce harmonics in a motor? ›To reduce the harmonics in induction motor drives, there are two main approaches: passive and active. Passive methods use passive components, such as filters, reactors, and chokes, that are connected in series or parallel with the power system or the motor to block or absorb the harmonics.
What causes high total harmonic distortion? ›Harmonic distortions are usually caused by the use of nonlinear loads by the end users of electricity. Nonlinear loads, a vast majority of which are loads with power electronic devices, draw current in a nonsinusoidal manner.
How do you get rid of harmonic distortion? › Position the nonlinear loads upstream in the system.
 Group the nonlinear loads.
 Create separate sources.
 Transformers with special connections.
 Install reactors.
 Select the suitable system earthing arrangement.
What is the method to suppress harmonics? ›
Harmonics in distribution systems can be suppressed with reactive devices, switching compensators and hybrid devices built of reactive devices and a switching compensator.
What reduces the second harmonic distortion? ›What reduces the second harmonic distortion? Explanation: The second harmonic distortion can be reduced by transistor switch arrays. The switch arrays are implemented in a pseudodifferential configuration. This design of the transistor switch arrays as a side effect reduces the second harmonic distortion.
What causes waveform distortion? ›Typical causes.
Voltage waveform distortion typically relates to electronic equipment, which has an internal switchmode power supply (SMPS) that draws a nonlinear current waveform. Whereas a linear load produces a sine wave current, the SMPS draws current pulses at only one portion of the applied voltage waveform.
Distortion refers to change or deformation of an audio signal's waveform. The most common type of change is called clipping. This happens when the signal level goes above the maximum a system can handle. It's called clipping because the tops of the waveforms get chopped off abruptly at the maximum.
How do you reduce voltage distortion? ›Use of reactors
Reactors or inductors are used in loads such as variable and speed drives. Because of this, the AC line reactor reduces the total harmonic voltage distortion on its line side.
A 0.5% THD ratio means that the harmonics produced by the distortion represent 0.5% of the total output of the mic. You can find THD specifications not only for microphones but also in preamps and loudspeakers for example. With tube mics or preamps, the story is a bit different. Tubes want to be driven.
Can total harmonic distortion be over 100%? ›Total Harmonic Distortion. The control unit calculates total harmonic distortion related to the fundamental value THD, and total harmonic distortion related to RMS values THDR for voltages and currents. The current THD can be higher than 100%.
Is total harmonic distortion 0.1% good? ›How much THD is acceptable? As long as THD is less than one percent, most listeners will not hear any distortion. Some musicians and audiophiles, however, may notice that level of distortion.
Which device is used to control harmonic distortion? ›There are a number of devices available to control harmonic distortion. They can be as simple as a capacitor bank or a line reactor, or as complex as an active filter.
Is higher or lower total harmonic distortion better? ›The lower the THD percentage, the better.
In an ideal situation for use with headphones, speakers, and earphones, you would be looking for a total harmonic distortion level as close to zero as possible.
How do you reduce the cogging effect of an induction motor? ›
In order to reduce or eliminate cogging or teeth locking in the induction motors, the number of stator slots are never made equal to or an integral multiple of the rotor slots. In the squirrel cage induction motors, the cogging can also be decreased by using skewed rotor.
What causes harmonics in induction motors? ›Space harmonics fluxes are produced by the windings, slotting, magnetic saturation, inequalities in the air gap length. These harmonic fluxes induce voltages and circulate harmonic currents in the rotor windings.
How do you control the frequency of an induction motor? ›Volts/Hz speed control of an induction motor. The speed of an induction motor can be easily controlled by varying the frequency of the 3phase supply; however, to maintain a constant (rated) flux density, the applied voltage must also be changed in the same proportion as the frequency (as dictated by Faraday's law).
Which of the following will be provided to reduce the harmonics? ›Filters are provided on the AC side of the converter of the HVDC transmission line, to reduce the harmonic current and voltage of the AC side.
What is the standard for harmonic distortion? ›The IEEE 5192014 standard defines the voltage and current harmonics distortion criteria for the design of electrical systems. The existed voltage and current waveforms in every part of the system are explained in this standard, and the waveform distortion goals for the system designer are established.
What is the major cause of harmonics? ›Harmonics are the result of nonlinear loads that convert AC line voltage to DC. Harmonics flow into the electrical system because of nonlinear electronic switching devices, such as variable frequency drives (VFDs), computer power supplies and energyefficient lighting.
What are the types of harmonic distortion? › Amplitude distortion.
 Frequency distortion.
 Phase distortion.
 Intermodulation distortion.
 Cross over distortion.
 Rightclick on the Sound icon in the bottom right of your screen on the desktop.
 Click on Recording Devices. Rightclick on the microphone.
 Click on Properties.
 Click on the Enhancements tab.
 Check the 'Disable' box inside the box.
 Click 'Ok'.
One of the way out to resolve the issue of harmonics would be using filters in the power system. Installing a filter for nonlinear loads connected in power system would help in reducing the harmonic effect. The filters are widely used for reduction of harmonics.
What are the three types of harmonics? ›Harmonics are usually classified by two different criteria: the type of signal (voltage or current), and the order of the harmonic (even, odd, triplen, or nontriplen odd); in a threephase system, they can be further classified according to their phase sequence (positive, negative, zero).
Which of the following will reduce the harmonics in the voltage waveform? ›
Smoothing Reactors are serially connected reactors inserted in DC systems. They reduce harmonic currents and transient over currents and/or current ripples in DC systems.
Do capacitors reduce harmonics? ›Capacitors — Capacitors operate as sinks to increased harmonics and harmonic frequencies. Supply system inductance can resonate with capacitors at some harmonic frequencies, causing large currents and voltages to develop at these frequencies.
Which feedback reduces distortion? ›Negative feedback applied to an amplifier linearizes the transfer characteristic of the amplifier and reduces the distortion of the input signal that is generated by the nonlinearity. The gain of the amplifier at an operating point is also reduced accordingly.
How to control harmonic distortion in neutral connection as per rule? › Modifications to the installation.
 Stardelta transformer.
 Transformer with zigzag secondary.
 Reactance with zigzag connection.
 Third order filter in the neutral.
There are five main types of waveform distortions: DC offset, harmonics, interharmonics, notching and noise.
What are the 3 common distortion patterns? ›There are three common distortion patterns, pronation distortion, lower cross syndrome, and upper cross syndrome. Each of these patterns can either be exhibited by themselves, or people can have multiple at the same time.
What are two possible causes of the signal distortion? ›The three main reasons for signal distortion in transmission impairment are environmental parameters, properties of the transmission medium, and distance between the transmission end and receiving end.
What are the two types of distortion? ›Two common types of distortion. In barrel distortion (left), magnification decreases with distance from the centre of the image; in pincushion distortion (right), magnification increases with distance.
What is the most efficient way to reduce voltage? ›The simplest way to reduce voltage drop is to increase the diameter of the conductor between the source and the load, which lowers the overall resistance. In power distribution systems, a given amount of power can be transmitted with less voltage drop if a higher voltage is used.
What causes reduction in voltage? ›A voltage drop in an electrical circuit normally occurs when a current passes through the cable. It is related to the resistance or impedance to current flow with passive elements in the circuits including cables, contacts and connectors affecting the level of voltage drop.
What is the easiest way to reduce voltage? ›
To reduce voltage in half, we simply form a voltage divider circuit between 2 resistors of equal value (for example, 2 10KΩ) resistors. To divide voltage in half, all you must do is place any 2 resistors of equal value in series and then place a jumper wire in between the resistors.
What does presence of harmonics in induction motor causes? ›Crawling: The crawling in the induction motor is caused by harmonics developed in the motor. Crawling is the tendency of particularly squirrelcage rotor to run at speeds as low as oneseventh of their synchronous speed. This phenomenon is known as the crawling of an induction motor.
What is meant by harmonic effect on threephase converter? ›The harmonic is the distortion in the waveform of the voltage and current. It is the integral multiple of some reference waves. The harmonic wave increases the core and copper loss of the transformer and hence reduces their efficiency. It also increases the dielectric stress on the insulation of the transformer.
What are the effects of harmonics in a threephase bridge converter? ›Output of 3phase bridge inverter at 180° mode is connected to 3phase star RLLoad which is nonsinusoidal and contains some amount of harmonics. Load current contain harmonics which causes noise copper loss, vibration loss and pulsating torque.
What does harmonic distortion do? ›Harmonic distortion is the addition of new tones to the audio signal. These distortion products occur at integer multiples of the original signal's frequency and are harmonically related to the original tone.
What are causes of producing harmonics in three phase induction motor? ›Harmonics are the result of nonlinear loads that convert AC line voltage to DC. Harmonics flow into the electrical system because of nonlinear electronic switching devices, such as variable frequency drives (VFDs), computer power supplies and energyefficient lighting.
What is the difference between 2nd and 3rd harmonic distortion? ›Secondorder or 'even' harmonics are evennumbered multiples of the fundamental frequencies and create a rich, pleasing sound. Thirdorder or 'odd' harmonics are oddnumbered multiples of the fundamental frequencies, which give the signal an edgier, more aggressive sound.
Why 3rd harmonics is undesirable in 3phase power system? ›Generally, power system harmonics increase the current in the circuit rapidly. The rapid increase in electric current exactly happens at the 3 r d harmonic making it dangerous for circuits. These harmonics cause malfunctioning of devices and heating.
Does harmonic distortion affect power factor? ›Total harmonic distortion (THD) is an important aspect in power systems and it should be kept as low as possible. Lower THD in power systems means higher power factor, lower peak currents, and higher efficiency.
What are the major problems due to harmonics? › Overheating (motors, cables, transformers, neutrals)
 Motor vibrations.
 Audible noise in transformers and rotating machines.
 Nuisance circuit breaker operation.
 Electrical fires.
 Voltage notching.
 Erratic electronic equipment operation.
 Computer and/or PLC lockups.
What are the disadvantages of harmonic distortion? ›
 Heating up (motors, cables, transformers, neutrals)
 Motor tremors.
 Transformers and whirling devices make audible noise.
 Nuisance operating a circuit breaker.
 Lightning strikes.
 Notching of voltage.
Harmonic currents increase the r.m.s. current in electrical systems and deteriorate the supply voltage quality. They stress the electrical network and potentially damage equipment. They may disrupt normal operation of devices and increase operating costs.
What is the main source of harmonic distortion? ›Harmonic distortions are usually caused by the use of nonlinear loads by the end users of electricity. Nonlinear loads, a vast majority of which are loads with power electronic devices, draw current in a nonsinusoidal manner.