This document describes the design of an automatic star-delta starter for an induction motor using relays and an adjustable electronic timer. The starter is designed to reduce starting current and prevent issues from low voltage, single phasing, over voltage and under voltage. The circuit uses a 555 timer, transistors, diodes, resistors, capacitors, relays and transformers. It operates by starting the motor in a low-current star configuration, then switching to a delta configuration after a set time using relays controlled by the 555 timer. This provides smooth starting of the induction motor.

1. Presented By
Kumara
Mahesh Hebbar
Jenukumar G S
Somashekar S
DAYANANDA SAGAR ACADEMY OF TECHNOLOGY
& MANAGEMENT
Under the Guidance of:
DR. R V Parimala
Professor & HOD
Dept. of EEE

2. CONTENTS
 Abstract
 Introduction
 Block diagram
 Hardware requirements
 Study of Hardware requirements
 Circuit diagram
 Working
 Applications
 Scope of future work
 Conclusion
 References 1
Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor

3. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Abstract:
• Design of a starter.
• Reduce the starting current.
• In star connection current in different phases while
line voltage is the 3 times the phase voltage.
• In Delta connection the voltage is same as that of
phase voltage.
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4. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Introduction:
• Induction motors are low cost, real efficiency.
• The Star / delta starter used for starting & running of IM.
• IM are very sensitive to low voltage & single phasing.
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5. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
• Under voltage and over voltage cut out.
• Single Phasing prevention.
• Automatic start on resumption of proper condition.
• Specially suited for remote operation of IM.
4

6. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Block Diagram:
5

7. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Hardware Requirements
• Power supply block
• NE555 Timer
• BC547 npn transistor
• BC557 pnp transistor
• Rectifier diodes IN4007
• Switching diode IN4148
• LED’s
• Variable resistor
• Resistor & Capacitors
• Relays
• Transformers
• Induction Motor 6

8. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
555 TIMER:
• The 555 Timer IC is an integrated circuit (chip).
• The original name was the SE555 (metal can)/ NE555
(plastic DIP).
• 20 transistors, two diodes, and 15 resistors on a
silicon chip.
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9. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Pin Diagram Of 555:
• 8 pin DIL package IC.
• Used as a monostable.
• Source or sink 100mA.
• Use supply voltages of 5v
to 15v.
• Disrupt the power supply
8

10. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
9
Transistor BC547
• NPN Epitaxial Silicon Transistor.
• General-purpose switching and amplification.
• NPN General-purpose transistor
• Whenever the base is high, then current flows.

11. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Transistor BC557:
• PNP Epitaxial Silicon Transistor.
• General purpose switching and amplification.
• PNP general purpose transistors.
10

12. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
12
Rectifier Diode
• Converts AC to DC.
• It allows current to pass in the forward direction, while
blocking current in reverse direction.
• Formed by joining a p type and n type semiconductor.

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Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Zener Diode
• Single diode connecting in reverse bias.
• Breakdown in the circuit if voltage applied across
reverse biased current does not flow.
• Applied voltage exceeds an specific amount zener
breakdown takes place.

14. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Variable Resistor
• It is an electronic component.
• Adjusting circuit resistance to control voltage or
current of that circuit or part of that circuit.
• Electrical resistance is varied by sliding a wiper
contact along a resistance track.
• Resistance is adjusted at preset value.
14

15. 15
Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor

16. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Relay:
• It is an electromagnetic switch.
• Used to control the electrical devices.
• Relays are like remote control switches
• It is used in many applications because
of simplicity, long life, and
high reliability.
16

17. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Working :
17

18. 18
Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Transformer
• It is an static machine.
• Transforms electrical power from one circuit to
another circuit without changing frequency.
• Works on the principle of mutual induction.
• 2 windings linked by common magnetic flux.

19. 19
Working :
Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor

20. Design :
20

21. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
21
Result in Star Mode :

22. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
22
Result in Delta Mode :

23. 23
Module:

24. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Area of Application:
• Industries
• Floor mills
• Water Irrigation pumps
• Machine Laboratories
24

25. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Future Scope:
• Compared to the reduced voltage methods it is the
simple and cheapest way of starting the motor.
• But it takes significant inrush currents during the
switching operation.
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26. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
Conclusion:
• An automatic over and under voltage protector system has
been implemented using induction motor starter.
• Consequently, protect them from the danger of being
damaged due to voltage fluctuation.
• It is used for low to medium voltage and light starting torque
motors.
• It is the cheapest way to reduce the starting current, and it is
in the order of 3-4 times that in case of DOL starting of IM
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27. Automatic Star Delta Starter using Relays and
Adjustable Electronic Timer for Induction Motor
References
• INTERNATIONAL JOURNAL OF SCIENTIFIC &
TECHNOLOGY RESEARCH VOLUME 3, ISSUE 5,
MAY 2014.
• B.L. Theraja and A. K. Theraja, A Text Book of
Electrical Technology. S. Chand Company Ltd. New
Delhi, pp. 851-918, 2001.
• [3]. J.D. Edwards, “Electrical Machines”.
• www.electronicsforu.com 27

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