# Derating of Induction Motors Due to Waveform Distortion - [PDF Document] (2023)

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1102

IEEE TRANSACTIONS

ON

INDUSTRY APPLICATIONS, VOL. 26, NO.

6.

NOVEMBERIDECEMBER 1990

Derating of Induction Motors Due to

Waveform Distortion

Abstract-Electrical motors are designed on the basis ofbalanced

three-phase 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 (drip-proofand

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)

3) The principle of superposition applies.

Equivdent Circuit Parameters

The simplified equivalent circuit of a three-phase induction

motor is shown

in

Fig. 1. It is to be remembered that this

Paper PID 90-29, 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 11-13. 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

.

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 air-gap

voltage E. If the flux density

B,,,

s uniform over the

cross-sectional area

A

of the core,

where

E

is the rms value of the air-gap 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

0093-9994/90/1100-1102 01.00

990 IEEE

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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.

eddy current losses caused by the increase in air-gapleakage

flux with load, and by high-frequency 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) Harmonics

leakage flux (normally neglected);

2) the losses in the motor end structure

We

due to end

leakage flux;

3)

the high-frequency rotor and stator surface losses

W

due to zig-zag leakage flux;

4) the high-frequency tooth pulsation and rotor

Z2R

losses

W , , also due to the zig-zag leakage flux;

5) the six-times-frequency (for three-phase 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 

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

air-gap area,

Io

is the no-load 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 

Pmech

0.09

Pcul =

0 . 37

Pcu2 =

0 . 1 8

Pfe =

0.20

Pstray

0 . 1 6

Pdiss=

1 oo

Thermal Stress



[SI

The allowable hot-spot 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

drip-proof radially cooled and a totally enclosed fan-cooled

machine.

Air Temp

b)

Thermal network.

Fig.

2.

Drip-proof radially cooled squirrel-cage motor. (a) Air flow.(b)

R j i .

Air Temp

( b )

Thermal network.

Fig. 3 .

Totally enclosed fan-cooled squirrel-cage motor. (a) Air

f low.

(b)

The temperature rise of the stator winding T is then (for

Twl = PculRewl 9)

where

R e w ,

s the thermal resistance of the stator end-wind-

ing. F or a totally enclosed fan-cooled 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 air-gap between the

stator core and outside frame of the motor), and outside

frame and moving air, respectively.

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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 Harmonics

k = 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 no-load 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

were verified experimentally by lab tests on a 2-hpinduction

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

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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 LSIS

soidal 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

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 no-load 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

THREE-PHASENDUCTION 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

5-25 3 .0

0.040 0.04 2 .6

0.064 0.096 25

25-200

2.5 0 .030

0.03 3.2 0.068 0.102 35

200-1000 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 5-hp and for a 100-hp machine. The values found for

the 5-hp machine are used as representatives of machines

ranging from 0 to 25 hp, and those found for the 100-hp

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

M-22 steel and 1 O-T maximum air-gap magnetic flux density

is used.

The results of the increases in temperature with respect to

full-load norm al operating conditions defined by

where TH and TN are the hot-spot 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

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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 drip-proof 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 fan-cooledinduction

motor.

(less than 5 ). It is also clear that, for drip-proofradially

cooled machines, the percentage variation of temperaturerise

reduces as the size increases (negative slopes in Fig. 5 ) ,

whereas it increases in totally enclosed fan-cooled 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:

drip-proof radially cooled motor. Solid line: totally enclosedfan-cooled

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.

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SEN AND LANDA: DERATING O F INDUCTION M OTORS DUE TO WAVEFORMDISTORTION

1107

Drip-proof 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, “Stray-load lossesin

polyphase induction machines,” AIEE Trans. Power App . Syst .,

vol. 78, pt. 111-A, pp. 349-357, June 1959.

J . C. Andreas,

Energy Ejicient Electric

Motors. New York:

Marcel Dekker, 1982.

Optimization

of

Induction

Motor

Ejic iency , vol. 1 EPRI, Univ.

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. 282-288, June 1959.

E.

A. Klingshirm and H. E. Jordan, “Polyphase induction motor

performance and losses on non-sinusoidal voltage sources,”IEEE

T rans . P ow e r A p p . S y s t . , vol. PAS-87, pp. 624-631,M ar. 1968.

P. G . Cummings, “Estimating effect of system harmonics onlosses

and temperature rise of squirrel-cage motors,” IEEE paperno.

PCIC-85-7, 1985.

Pankaj K.

Sen

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.

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’87-M’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

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 non-linear 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 [5-9].

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? ›

Five Ways to Reduce Harmonics in Circuits and Power Distribution Systems
1. K-Rated Transformers. ANSI Standard C57. ...
2. Measuring K-Factor. In any system containing harmonics, the K-factor can be measured with a power quality analyzer (see Figure 1). ...
4. Harmonic Mitigating Transformers. ...
5. Delta-Wye Wiring. ...
6. Zigzag Windings.
May 24, 2021

How do you reduce harmonics in an induction motor? ›

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? ›

Basic solutions to mitigate harmonics
1. Position the non-linear loads upstream in the system.
3. Create separate sources.
4. Transformers with special connections.
5. Install reactors.
6. Select the suitable system earthing arrangement.
Jun 22, 2022

### 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 pseudo-differential 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 switch-mode 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.

How does distortion change a 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.

What is a 0.5% total harmonic distortion? ›

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 THD-R 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 3-phase 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 519-2014 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 energy-efficient lighting.

What are the types of harmonic distortion? ›

In general, there are five types of harmonic distortion that can be observed when looking at a waveform:
• Amplitude distortion.
• Frequency distortion.
• Phase distortion.
• Intermodulation distortion.
• Cross over distortion.

How do you remove distortions? ›

Fixing A Distorted Microphone
1. Right-click on the Sound icon in the bottom right of your screen on the desktop.
2. Click on Recording Devices. Right-click on the microphone.
3. Click on Properties.
4. Click on the Enhancements tab.
5. Check the 'Disable' box inside the box.
6. Click 'Ok'.
Mar 24, 2022

How can you decrease the harmonics in a wave form? ›

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 non-triplen odd); in a three-phase 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? ›

Measures to eliminate harmonic currents
1. Modifications to the installation.
2. Star-delta transformer.
3. Transformer with zigzag secondary.
4. Reactance with zigzag connection.
5. Third order filter in the neutral.
Mar 25, 2016

What are the four primary types of waveform distortion? ›

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 squirrel-cage rotor to run at speeds as low as one-seventh of their synchronous speed. This phenomenon is known as the crawling of an induction motor.

What is meant by harmonic effect on three-phase 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 three-phase bridge converter? ›

Output of 3-phase bridge inverter at 180° mode is connected to 3-phase star RL-Load which is non-sinusoidal 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 energy-efficient lighting.

What is the difference between 2nd and 3rd harmonic distortion? ›

Second-order or 'even' harmonics are even-numbered multiples of the fundamental frequencies and create a rich, pleasing sound. Third-order or 'odd' harmonics are odd-numbered multiples of the fundamental frequencies, which give the signal an edgier, more aggressive sound.

Why 3rd harmonics is undesirable in 3-phase 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? ›

Equipment failure and misoperation
• 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? ›

Examples of equipment malfunction and failure linked to harmonics in a power supply include the following symptoms:
• 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.

What problems can harmonics cause? ›

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.

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