project epq

8/7/2019 Project EPQ

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As we know, once a supply is connected to a

three phase induction motor a rotating

magneticfield will be set up in the stator, this

will link and cut the rotor bars which in turn will

induce rotorcurrents and create a rotor field

which will interact with the stator field and produce rotation. Ofcourse this means that the

three phase induction motor is entirely capable

of self-starting.The need for a starter therefore is

not, conversely enough, to provide starting but

to reduceheavy starting currents and provide

overload and no-voltage protection.There are a

number of different types of starter including

The Direct On-line Starter, The Star- Delta

Starter, Auto-Transformer and Rotor

resistance.

IV. Direct-on-LineDirect-on-line (DOL) is the simplest form motor

starting method had being used. It is a traditionally

started and stopped by applying and removing the

supply from the circuit. During starting, the full

voltage are acceptable to used, but to avoid large

starting current from occur, the voltage starter need to

be reduced. The DOL starter comprises a switch and

an overload protection relay as shown in figure1.

Figure 1.Direct-On-Line motor starter.

The switch may be manual or automatically depends

on the user. In previous, manually operated load

break switch are used, but more commonly an

electromagnetic contactor are used which can be

opened by thermal overload relay. Contactors

arecontrol by separated star and stop button and

auxiliary contact used to hold the supply when the

start button is release. By applying full line voltage to

the motor winding during motor starting, it will draw

a very high inrush current up to 6 to 7 times rated

motor current and sometimes it may increase up to 9

to 10 times the rated current exist. Using this starting

method, will produce a very high starting torque and

usually higher than required for most application.For

a very short time, to establish the magnetic field in

the iron. This inrush current are valued in between

V. Star-DeltaStar-delta motor starting method are also known as

soft starting method. Star-delta starting is when the

motor in connected in STAR connection during

starting sequence. The motor then connected to

DELTA when it accelerated to close to the normal

running speed. In order to allow the motor to start,

the motor windings are configured in a star formation

to the supply voltage. The voltage is supply to the

individual motor windings therefore it reduced by a

factor of this connection amounts to

approximately 30% of the delta values. By using this,

it reduced to one third of the direct starting current

(DOL). Due to the reduction of starting torque, the

star-delta connection is suitable for drives with high

inertia mass but a resistance torque which is low or

only increased speed. After motor run-up, in most

cases an automatic timing relay controls the switch-over from star to delta. The run-up using star

connection should last until the motor reach the

operational value. During the switching from star to

delta, the will be an occurrence of high current as

seen with direct-on-line starting. During delta

connection, the full mains voltage is applied to the

motor windings. To enable a switch-over from star to

delta, the six ends of the motor winding are

connected onto terminals. Figure 2 shows the star-

delta motor starting wiring.


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Figure 2: Star-delta motor starting wiring

This method can only be used if when the starting

works is light loaded. If the motor start in heavily

loaded there will not be enough torque to accelerate

the motor up to speed required.

VI. AutotransformerAn autotransformer starter uses an auto transformer

to reduce the voltage applied to a motor during start.

By having a number of output taps such as 50%, 65%

and 80% to be set-up to provide a single stage starter

or a multistage starter enable the motor to be started

at one or more of these settings. There are two ways

of connecting an autotransformer starter, first, by

applying full voltage to the transformer via a

contactor and connect the motor to the tap by means

of the contactor. The tap contactors will opens or

disconnecting the motor from the transformer and

another contactor closes connecting the motor to the

supply when the motor has accelerated to full speed

or has run out of acceleration torque. This is known

as an open transition starter and it is less than ideal

due to the fact that the motor is disconnect for a short

period of time during the start period. While the

motor is connected and accelerating, it also acts as a

generator until the rotor field decays. The voltage

generated by the motor is not synchronized to the

supply, and so on reconnection to the supply, the

voltage across the contactor at closure can be as

much as twice the supply voltage resulting in a veryhigh current and torque transient. The transition

switching or known as auto-reclose effect as it yields

similar characteristic to opening and closing a

breaker on a supply to the motor. By using

autotransformer motor starting method, it can reduce

the torque as the square of the applied voltage. Figure

3 shows the autotransformer motor starting wiring.

Figure 3. Autotransformer motor starting wiring

VII. Result & Discussion

In this paper the power quality event that occur in

the system due to the different motor starting are

review by using the PSCAD (Power System CAD)

software.There are three type of motor starting are

being consider in this paper which is Direct-On-

Line(DOL), Star-Delta and Autotransformer.

During DOL motor starting, the motor are connected

direct to the load and having a breaker function as a

switch and a transformer used to isolate the motor

circuit from the power supply as shown in figure 4

below. The motor torque are fixed to 5NM and speed

of motor van be varied from 0 to 10 rad/s.

Figure4. Direct-On-Line motor starting circuit

From figure 4, loads are connected in parallel to the

motor. A volt meter and ammeter are connected to

the load and when motor starting it results voltage

sag to the loads. During motor starting, the inrush

current occurs in the induction motor starting and it


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causes the voltage and current terminal to drop in

magnitude. Graph 1 and 2 shows the voltage and

current output at load.

Graph1. Voltage Sag occur in DOL motor starting

Graph2. Current Sag occur in DOL motor starting

In star-delta motor starting connection, the same load,

motor and transformer are used from DOL motor

starting connection as shown in figure 5. The

difference is that, these circuits are using two breaker

functions as switch to change connection from star

supply for motor starting and to delta supply when

the motor reach the operation speed.

Figure 5.Star-Delta motor starting circuit

Once again a volt meter and ammeter are connected

to the load connection to measure the voltage and

current flow through load. As shown in graph 3 and

4, the voltage and current sag are still occur but this

time it less than the DOL voltage and current sag.

Graph 3 and 4 also shows that waveform drop for a

moment and then back to the normal when the motor

already reach the operational speed.

Graph 3.Voltage sag occur in star-delta motor starting

Graph 4. Current sag occur in star-delta motor starting

Same as star-delta starting connection, this circuit

still using same motor, transformer, breaker and load.But this time, three autotransformer are added to the

circuit function as a supply to the motor as shown in

6.


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Figure 6.Autotransformer motor starting circuit

As shown in graph 5 and 6, the voltage and currentsag still occur at the load but this time drop value are

less compare with the other two starting method.

Graph 5. Voltage sag occur in autotransformer motor starting

Graph 5.Current sag occur in autotransformer motor starting

VIII. ConclusionElectrical power quality which is one of the topics for

several power utilities all over the world, and its

becoming an important and challenging issue for the

power engineers. There is no unique model can be

used to assess the power quality problem and to

identify and classify them properly.

By using PSCAD software to create power quality

event (voltage sag) due to different motor starting

method, shows that out of three methods, the star-delta method are the one that only method that

produce small amount of voltage and current sags

and at the same time it repair back the signal compare

with the other two method.

In order to repair or solve back this problem, a few

solutions have being suggested due to problem

occurred. By installing an Uninterruptable Power

Supply (UPS) will help the system to maintain the

supply when there is any disturbances occur in the

system. There is several types of UPS are available

depending on the problem such as Standby UPS,

Online UPS, and Hybrid UPS. Each UPS has its own

advantage and disadvantage but Standby UPS are

commonly used out of the other two types of UPS.


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REFERENCES

[1] D.Saxena, K.S. Verma and S.N. Singh, Power Quality Event

Classification: An Overview and Key Issues,

InternationalJournal of Engineering, Science and Technology,

Vol.2, No. 3, 2010, pp.186-199.

[2]John Stones and Alan Collinson , Special Feature: IntroductionPower Quality, Power Engineering Journal April 2001.

[3] Amaya Barona, Francisco Ferrandis, Javier Olarte and Jose L.

Iribarren, New Power Quality Solutions Especially Designed for

Industrial Application, 9th

International Conference, Electrical

Power Quality and Utilization, Barcelona, 9-11 October 2007.

[4] T.L. Tan, S. Chen, S.S. Choi, An Overview of Power Quality

State Estimation.

[5] Christopher J. Melhorn, Mark F. McGranaghan, Interpretation

and Analysis of Power Quality Measurement.

[6] MasoudAliakbarGolkar, Electric Power Quality: Types and

Measurement, 2004 IEEE International Conference on Electric

Utility Deregulation, Restructuring and Power Technologies

(DRPT2004) April 2004 Hong Kong

[7] DharshanaMuthumuni, PSCAD Essential Tutorials: Getting

Started and Basic Features, dm/Tutorial_gettingstarted.doc,

Revision 2, Feb 16, 2007

[8] A. El Saeed, M. Tantawi, K. Youssef, Power Quality

Phenomena in Academic Building, Paper accepted for

presentation at PPT 2001,2001 IEEE Porto Power Tech

Conference, 10th

13th

September,Porto,Portugal.

[9] Barry W. Kennedy, Power Quality Primer McGraw-Hill,2000

[10]Henk de Swardt,Star-DeltaStarting and Dual VoltageMotors

Explained.Vector is the Journal of the Institution of Certified

Mechanical and Electrical Engineers and the Journalof South

African Institute of Electrical Technician Engineer,10/2007

[11] Rockwell Automation,Basic for pratical operation: Motor

Starting.

[12]Allen-Bradley, Rockwell Software,WYE-DELTA AND SOLIDSTATE STARTER APPLICATIONGUIDEEXPLANATION AND

ASSISTANCE FOR APPLYINGSOLID STATE SOFT STARTERS IN

TRADITIONALREDUCED VOLTAGE APPLICATIONS

[13]Ana Iacob,Electrical Power Quality Improvement

using a DSP Controlled Active Power Filter,9th

International

Conference, Electrical Power Quality and Utilisation.

Barcelona,9-11 Oct 2007

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