College of Engineering and Technology
Electrical and Control Engineering Department
Automated Industrial Systems I
EE512
EX1: Direct Online Motor Starter
Lecturer name: ……………..……………………………………………….…..…………………………...….……
Student name : .…………………………………………….…………………..……………………………………..
Registration # : …..……..………………………………………………………………………………………………
Prepared By: Prof. Hamdy Ashour
September 2014
Eng. Ahmed Al Bashir
Mr. Mohamed Samir
Mr. Wael Mohamed
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ge
Experiment 1
Direct Online Motor Starter
1- Objective
To start and stop a three phase induction motor by Direct On Line (DOL) Starter.
2- Theory
A Direct On Line (DOL) or across the line starter applies the full line voltage to the motor terminals.
This is the simplest type of motor starter. A DOL motor starter also has protection devices and, in
some cases, condition monitoring. Smaller sizes of direct on-line starters are manually operated;
larger sizes use an electromechanical contactor (relay) to switch the motor circuit. Solid-state direct
on line starters also exist.
A direct on line starter can be used if the high inrush current of the started motor does not cause
excessive voltage drop in the supply circuit. The maximum size of a motor allowed on a direct on
line starter may be limited by the supply utility for this reason. For example, a utility may require
rural customers to use reduced-voltage starters for motors larger than 4KW (5HP).
DOL starting is sometimes used to start small water pumps, compressors, fans and conveyor belts.
In the case of an asynchronous motor, such as the 3-phase squirrel-cage motor, the motor will draw
a high starting current until it has run up to full speed. This starting current is typically 6-7 times
greater than the full load current. To reduce the inrush current, larger motors will have reducedvoltage starters or variable speed drives in order to minimize voltage dips to the power supply, or
series resistance and inductance can be added.
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3- Instruments & Equipments
Three phase induction motor
Main and Sub feeder isolating circuit breakers
(board #5)
Power and control circuits fuses
(board #6)
Three phase electromagnetic contactor with
bi-metal overload relay
(board #2)
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Indicating lamps and Pushbuttons
(board #1)
Multimeter
Digital stroboscope
Wattmeter
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4- Connection
Q2
L1
L2
L3
L1
C.B
Fuse
F6
13
13
Pushbutton Start
S1
Circuit Breaker
C.B
Q1
K1
14
Pushbutton Stop
S0
Fuses
F1 F2 F3
14
11
12
95
Overload
F4
Contactor
K1
96
A1
Overload
F4
Contactor
Coil
T1
T2
H1
K1
X2
A2
T3
Fuse
3φ
IM
X1
F7
C.B
N
Q2
Power Circuit
Control Circuit
Power and Control circuits connections diagram
5- Procedure
a.
b.
c.
d.
Connect the circuits as shown in the diagram.
Switch on the main and sub feeder isolating circuit breakers (Q1, Q2).
Use the start and stop pushbuttons for motor operation.
Measure the currant, voltage, power and the no load speed of the motor.
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6- Results
Current =.………..………..A
Voltage =…………………..V
Power =……………….….W
Speed =……………….....FPS
7- Connect the power and control circuits on the following figure
8- Add your own comments
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9- Use internet resources to provide advantages, disadvantages and then discuss different
applications of DOL motor starter circuit
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