ISSN: 2277-3754

ISO 9001:2008 Certified

International Journal of Engineering and Innovative Technology (IJEIT)
Volume 5, Issue 2, August 2015

Design of an Automatic Power Phase Selector

1
Uchechukwu Innocent Ezirim, 2 Uchenna Bright Oweziem, 3 Chinedu Cletus Obinwa, 4 Solomon
Okwuchukwu Ekwueme
1,2,3,4
National Engineering Design Development Institute, Nnewi, Anambra State.
 As such, a changeover switch or automatic changeover is
Abstract— Phase selector is a mechanism used in alternating required to change from one source (PHCN) to another
or switching between power phases with respect to the availability (Generator), which is needed to be automatic [10]. The
of power on any of the phases. Over the decades, there has been
human relief stand-by switch is designed simply to monitor,
frequent phase failure in the power phases resulting to manual
switching of the fuse from one phase to the other. However, this operate and maintain power, as its principle of operation is
paper focuses on the design of a phase selector using automatic based on combine operations of the relays, contactors and
switching mechanism. This during its operation, transfers the overload coil. In the whole, the duration of starting and
consumer’s loads to the available power source in the case of closing of the loads to the contactor should not be more than
power failure in the power supply from the national grid and 5 sec. Their complexity has increased as lots of features are
automatically detects when power is restored to the failed phase
added to its intelligence aimed at making it automated
and returns the loads to this source. In the course of this design,
several tests were carried out such as the continuity test of process, be it in industries, commercial complexes,
contactor and relay coils to ascertain low resistance, continuity hospitals, hotels or even modern residences. The need, as
test on the contacts of the materials used to ensure free flow of such, for independent standby power system has therefore
current, conductivity of the wires and the whole system was also increased manifold.
simulated using the Proteus electronics software. In the quest to get such a changeover switch, some
challenges are encountered.it was observed that single phase
Keywords: Conductivity, Power, Phase, Voltage, Proteus.
electricity customers having three (3) phases found it
difficult to automatically change from one phase to another
I. INTRODUCTION
when the need arises. It still renders or limits the changeover
Power failure or outage has been a major challenge to to a semi-automatic and a semi-manual device. Considering
national development as economic activities are at most a case scenario where the changeover is very far from the
times brought to standstill. user and the phase on which the consumer was, went off (as
In addition, there are processes that need not be experienced in most African countries like Nigeria) at an
interrupted because of their importance, such as surgery ungodly hour, hence the reason for this paper is to proffer
operation in hospitals, transfer of money between banks and remedy to such a case so as to make the changeover pure
lots more [1]. Most industrial and commercial processes are automated switch with less human stress. The incorporation
dependent on electrical power [3][7]. As industrial processes of a phase selector design to the changeover switch brings
and IT applications diversify, power consumers have the dream of such a design to a reality. It then makes the
adopted another means of power supply so as to compensate changeover sensitive enough to distinguish and select
for the inconsistence of the power supply from the power between poor phases and phase failure.
providers, thus the use of Generators since there is need to
alternatively supply power from another source as a result II. METHODOLOGY
the need to combine the use of power supplied by the
national Power Supply/Distribution Sector and Generator, A. Design Development and Considerations
leads to the introduction of change-over switch between During the design of the phase selector, a lot of
nation‟s power supply and Generator[13]. The introduction considerations, conditions and cases where considered
of change over switch proffer the means to change from which at the end give rise to the design of phase selector
national power supply to Generator or vice versa but it was control [6]. These considerations are guided by a truth table
manually done .hence this system often results in waste of of a three variable input of a digital system as shown below.
time and energy. It was faced with a lot of limitations which TRUTH TABLE
includes: S/N R Y B X
i. The stress of turning the metal gear to effect the 1 1 1 1 1
2 1 1 0 1
changeover manually.
3 1 0 1 1
ii. Inability to detect the level of the voltage and the 4 1 0 0 1
sequence of the three phases. 5 0 1 1 1
iii. Inability to select between the phases as in the 6 0 1 0 1
single phase consumers. 7 0 0 1 1
8 0 0 0 0

DOI:10.17605/OSF.IO/GFMTZ Page 43
 ISSN: 2277-3754
ISO 9001:2008 Certified
International Journal of Engineering and Innovative Technology (IJEIT)
Volume 5, Issue 2, August 2015
Having these conditions in mind and also knowing the fact sequence was adopted for checking the availability of any
that the coming up and going off of power supply from phase that can be allowed to supply the consumer. i.e. when
power providers (Nigeria), does not notify anyone before there is live in the Red phase, it will be supplied thereby
making their decision in this part of the world. As such the isolating other phases even if they have live, but
conditions and questions considered are as follows; immediately the Red phase is out, then the Yellow phase
i. The power supply of 240 volts single phase for the will be on check, if it has live, it will be selected for supply
three phases at a frequency of 50 HZ was even if there is live in the blue phase. Immediately the
assumed. Yellow and Red phase went off, the Blue phase will be
ii. The load of 10kilowatts (kW) was assumed. allowed to supply, which means, if the Red phase comes up,
iii. If the whole three phases comes at once, how do I then the Blue phase will be cut off and the Red phase will be
select a phase out of them? allowed to supply automatically. Thus the phases check and
iv. If two out of the three comes up, what happens? selection are in the order of preference with the Red phase,
Yellow phase and Blue phase respectively.
v. If one phase comes up, what happens?
vi. How does one communicate to a particular
contactor to close while others are open?
vii. How does one avoid the bridging of two or more
phases?

The above conditions and questions were considered

during the design of the phase selector control. Having cited
the truth table, the “X” is the output of all the conditions in a
particular row in the table, with “1”meaning on, up or high
while “0” means off, down, low or no output from the phase
selector.
B. Design Method
Having considered these conditions in the truth table,
several scenarios were then considered so as to achieve the
switching mechanism needed for the device and to control
and transfer the load easily, as such the device chosen is a Fig1. (a) Designed Circuit Diagram
single phase contactor with three poles operating at a
frequency of 50 Hz, since we are controlling single
phase[4][11].
With the targeted load at 10kw
Since power is P:
;
Where is the power factor (i.e. 0.8)
= 240v
P = 10kw

∴l= = = 52.08 53 amps.

Hence the current ratings of the contacts made by the
contactors will be 60 amps as a result of the load. Since the
three phases are involved we would be using three of the
Fig1. (b) Simulation of the Designed Circuit using Proteus
contactors with three poles,50 Hz,240 volts ratings each. It
was noted from contactor chart that the coil current of such C. Material Selection
contactor is rated 2 amps. Thus a relay with a contact of a The components used for this design are the relays and the
current carrying capacity of 5 amps and 240 volts at 50 Hz, contactors and are chosen based on the following;
with double pole is suitable for such design. The relay is i. They are readily available
selected and arranged in such a manner that it can cut off ii. Not expensive hence cost effective
some phases, if at least one phase came up, which means iii. Easily replaceable when faulty
that provided there is normal voltage at any phase, hence it iv. And having the same voltage rating as the supply
will have the enablement of isolating the other phases Contactors of three poles with rating 50Hz, 240volts each
pending when the situation changes to another way. It and relay with a contact of a current carrying capacity of
should also be noted that the Red, Yellow and Blue phase 5amps and 240volts at 50Hz, with double pole was suitable

DOI:10.17605/OSF.IO/GFMTZ Page 44
 ISSN: 2277-3754
ISO 9001:2008 Certified
International Journal of Engineering and Innovative Technology (IJEIT)
Volume 5, Issue 2, August 2015
and was selected for such design. However, with these powering the contactor CT1 and at the same time the
components carefully selected and arranged in such a Yellow phase will be disconnected by virtue of energizing
manner that it can cut off some phases, when at least one the relay one (R1), thereby stopping the yellow phase from
phase comes up makes it unique and innovative. Hence the energizing contactor CT2.Also at the same time having
system is a combination of relays and contactors energizing contactor CT1,Y2 from CT1 will then energized
assembling. relay two (R2),thereby disconnecting the Blue phase and
stopping it from energizing contactor CT3. At the end CT1
D. Relay and Contactors Considerations
will be energized and send as an output phase to the
The relays and the contactors were selected based on the changeover system not minding the fact that other phases
calculated power and current input in section B above. are available. The same scenario is applicable to conditions
1 to 4 as in the truth table, provided the RED phase has live.
Scenario 2:
When there is no live in the RED phase, the case changes.
Now the yellow phase through the normally closed (NC)
contacts of the Relay one (R1) energizes the CT2 and at the
same time Y2 through the normally open (NO) contact of
contactor CT2 energizes the relay two (R2) and that result to
disengaging the Blue phase and as such allowing only the
yellow phase to be supplied as an output to the changeover
system. The same scenario is applicable to condition 6,
provided the Red phase is out and the yellow phase is
present.
Scenario 3:
At this situation when other phases are off with only the
Blue phase present, the case changes. The Blue phase
through the normally close (NC) contacts of Relay two (R2)
then supplies the CT3,but it will only went off if the Red
phase or the Yellow phase comes up, if such case happened
then the previous scenario will be repeated.
Scenario 4:
At this condition no output will be seen at the contactors
outputs terminal, hence no supply from the output
terminal.in this case the automatic changeover then triggers
the Generator set to start.

III. CONCLUSION
Automatic phase Changeover is highly of great
importance in Africa, to aid the automatic switching over
from Generator to public power source. Changeover of this
kind makes it easy for such switching to take place, and with
the added advantage of being able to select between phases,
Coupled to its flexibility it can be adopted in any automatic
changeover circuit with ease, it is also less expensive and
easily available. The most important feature of this design
is that, electricity consumers in the developing countries,
Source: www.wikipedia.com [14] who suffer the challenges of power supply. especially in
Nigeria where the power phase are often incomplete have
E. Operational Description of the Circuit
the advantage of selecting between phases for their power
As stated, the operation of the system is literally guided consumption without really doing the changing manually, as
by the Truth Table as in fig.1 with eight possible conditions, have been the normal practice.it saves the stress and time ,it
based on these possible conditions ,the operations of the also provides better protection as compared to the manual
system are summarized into four (4) major scenarios[12]. practice because of the use of overload is the changeover
Scenario 1: system. However, this design can for future work be
From the diagram, when there is voltage and power in the improved on by incorporating Programmable Logic Circuit
three phases, the power will standby at the line side of the (PLC).
contactors, through the connections of the design system,
the Red phase will energized the relay one (R1),thereby

DOI:10.17605/OSF.IO/GFMTZ Page 45
 ISSN: 2277-3754
ISO 9001:2008 Certified
International Journal of Engineering and Innovative Technology (IJEIT)
Volume 5, Issue 2, August 2015
ACKNOWLEDGMENT diploma in electrical engineering. He has the following publications to his

This is express our gratitude to the management of credit; A Remedy To The Electricity Crisis In Nigeria . Paper presented at
National Engineering Design Development Institute Nnewi, the Technical Vocations Education and Training (TVET) held at umunze
Nigeria for the opportunity given to us to achieve this 2011. Current Issues And Options in Power Transmission And Distribution
innovative project. In Nigeria held At The Nigerian Society Of Engineers Annual General
Meeting, “Canaan 2011” and Member, Nigerian Association of
REFERENCES
[1] Ahmed, M.S., Mohammed, A.S., Agusiobo, O.B. 2006. Technologist in Engineers. (NATE).
Development of a Single Phase Automatic Change-Over
Switch, AU J.T. 10(1): 68-74).
[2] Boyletad, L., Robert, Q., Nashelsky, L., 1999. Electronics
Device and Circuit Theory, (7th Ed), Prentice Hallo, New
Jersey.
[3] Deshpande, M. V., 1984. Electrical Power Systems, (4TH
Ed), TATA McGraw – HILL Inc, New Delhi.
[4] Donald, G. Fink, H. Wayne, B. 1978. Standard Handbook for
Uchenna Bright Oweziem, holds bachelor degree in Electromechanical
the Electrical Engineers, Eleventh Edition, McGraw-Hill,
New York, Engineering Technology, postgraduate Diploma in Industrial and
Production engineering and currently carrying out a research work in
[5] Ezema, L.S., Peter, B.U., Harris, O.O., 2012. Design of
automatic change over switch with generator control electric discharge machine for his master degree programme. He has the
mechanism, ISSN-l: 2223 9553, INNS 2223 9944, vol. 3. NO. following publications to his credit; “Design, Fabrication and
3.
Characterisation of an Electrically Powered Yam Pounding Machine”,
[6] Hughes, I., McKenzie, S., John, H., Keith, B., 2002. Electrical “Evaluation of Optimization of Tensile Strength Response of Coir Fibres
and Electronics Technology, (8th Ed), Prentice Hallo, New
Jersey. Reinforced Polyester Matrix Composites (CFRP) Using Taguchi Robust
Design”. He also has several conference papers such as Nanotechnology:
[7] Oweziem Bright Uchenna, Chinwuko Emmanuel Chuka,
Ezeliora Chukwuemeka Daniel, Obaseki Efosa. Design, Nanomaterials processing for a sustainable Environment and National
Fabrication and Characterisation of an Electric Powered Yam Development; Rail Transport Sector Financing In Nigeria: Issues and
Pounding Machine. American Journal of Mechanical Challenges. Paper presented at the Nigerian Society of Engineering
Engineering and Automation. Vol. 2, No. 2, 2015, pp. 26-35.
International Conference/AGM and member of Material Science and
[8] Theraja, B.L, A.K, Theraja. 1999. A Textbook of Electrical
Technology Society of Nigeria, Nigeria Association of Technologists in
Technology (23rd Ed), S. Chand & Company Ltd, New Delhi.
engineering also member of International Association of Engineers.
[9] Thomas, B., 2006. History on a novel but Short-lived Power
Distributed System, IEEE Power Engineering Society.
[10] William, D., Stevenson, Jr., 1982. Elements of Power Systems
Analysis, (4th Ed), McGraw- Hill Inc. USA.
[11] www.journal.au.edu//vol10 no1_a10.pdf, Retrieved on
28/11/12 at 10.28am.
[12] www.uk.ask.com/Automatic, changeover switch, retrieved on
02/04/13 at 12.45pm.
Chinedu Cletus Obinwa is a graduate of Mechanical Engineering from
[13] PERKINS (2002) Manual On Load Transfer.
the University of Benin in Nigeria. Presently undergoing his post-graduate
[14] www.wikipedia.com, Retrieved on 13/5/13 at 1.30am. 394-
410. studies in the field of Engineering Design, he also works as a Senior
Research & Development Engineer. He co-authored a research article in an
AUTHOR BIOGRAPHY
International Journal titled „Design of a Mechanical Water level
Controller‟. Others include, „A design of an egg incubator‟ submitted as a
requirement for Council for the Regulation of Engineering in Nigeria
qualification, Abuja, Nigeria. He is a member of the Nigerian Society of
Engineers Nnewi Branch, Nigeria.

Uchechukwu Innocent Ezirim is an electrical research engineering

technologist, a holder of higher National diploma and Postgragraduate

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 ISSN: 2277-3754
ISO 9001:2008 Certified
International Journal of Engineering and Innovative Technology (IJEIT)
Volume 5, Issue 2, August 2015

Solomon Okwuchukwu Ekwueme holds a Bachelor Degree in

Mechanical Engineering with specialization in Design and Manufacturing.
He is currently carrying out a research on “Thermal Characterization and
Analysis of Asbestos-free Palm Kernel Based Friction Lining Material for
his Master Degree Programme. He has the following publication to his
credit: Thermal Stability of Pulverized Palm Kernel Shell (PKS) Based
Friction Lining Material Locally Developed from Spent Waste, Waste to
Wealth Management: A Pathway to Economic and Sustainable
Development; A paper presented at the 13 th Annual Nigeria Materials
Congress/AGM held at Yaba College of Technology, Yaba Lagos State,
Nigeria on the 24th November 2014. He has done a research on “Behavior
of Steel when heated and on Thermal Design with Specification of 5ton
Capacity Refrigeration Plant. He is currently a member of Material Science
and Technology Society of Nigeria.

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