Design and Construction of an Automatic Three Phase Selector
Chapter One
Aim and Objectives
The aim of this work is to design a device that will overcome the challenge of switching over manually during phase interruption or power fluctuation by automatically selecting the next healthiest available phase to feed the equipment. In the implementation of this, the following objectives were achieved:-
- To develop a simple low cost device aimed at easing the prevalent burden faced by delicate industries and institutions electrical equipment’s. Since supply is always on along the distribution lines that supply such sites, what pesters on the progress of work thereof is always the unwarranted trip of phases due to power usage from neighbouring The automatic phase selector therefore, erases this setback from the face of progress of work in such offices.
- To enhance a greater sharing load balance and a better three phase power distribution and monitoring for industrial and domestic
- To provide lasting solutions to the heavy losses incurred by commercial institution, industries, hospitals, airport etc. Caused by poor manual selector means and inefficient switching
- To reduce the damages caused to our household equipment’s example electronics like television, radio, video-player And electrical appliances like refrigerator, air condition fans which is usually a result of poor selector of phase manually.
- It is also aimed at eliminating the loss of human life due to electric shock from the manual selection of the three phases, during supply of high voltage.
CHAPTER TWO
LITERATURE REWIEW
Basic Concept
As the growing population of human race widens the gap between energy supply and energy demand, the imbalance in energy availability sent researchers into excavating for a way of settling this age long squabble. Hence, the continuation of the unsettled yearns for sufficient power. Consequently, the power lines are frequently over loaded resulting to a trip of power by the action of switch gears or by the load shading process undertaken by the distribution authorities.
Effect of Power Failure
For the past 100 years, the utility’s job has been to keep the’ lights on.’ For today’s highly automated factories and processes, that is no longer sufficient. Even ¼ second voltage sag is sufficient to bring our modern machines to a screeching halt, resulting in hours of interrupted production and irrecoverable scrap. Yet it is interesting to note that most utilities are only required to record outages that last more than 1-5 minutes. So if factory is experiencing 10-12 momentary interruptions every year, costing millions of dollars in lost productivity, it is likely that the utility would represent that it was providing perfect power. This demonstrates a significant disconnect between the two positions, one that is unfortunately very commonly found. Thousands of facility-years of power monitoring at large industrial plants clearly demonstrates that, almost without exception, these plants experience anywhere from 8 to 24 power quality disturbances every year that are significant enough to impact plant operations. Most of the events are of short duration (1-6 cycles), corresponding to the clearing time of upstream utility protective equipment such as fuses, sectionalizes, breakers and recloses (Brumsickle et al., (2003),Conaster et al., (2002). It is important to understand the impact of such power disturbances on a plant’s equipment and processes.
A process interruption caused by voltage sag may require a complete restart of the process, with hours of interrupted production. This can clearly cause substantial economic loss to the plant. However, most plants operate with contingencies built in for unscheduled downtime, and these inefficiencies are typically absorbed within this allowance. For plants with a substantial cost of downtime, voltage sag ride-through solutions can protect against process interruption. The market has been conditioned to correlate equipment failure, especially catastrophic failure, with voltage surges (Guasch, L et al., 2000). The use of multiple layers of surge suppressors provides clear evidence that the fear of equipment damage drives users to this ‘apply and pray’ strategy. Yet, voltage sags occur thousands of times more frequently than damaging voltage surges. In fact, even lightning strikes on the power grid, thought to be a main culprit for voltage surges, have rarely been correlated with actually measured voltage surges, but have frequently been correlated with voltage sags (Greenfield, J. D., 2006). The impact of voltage sags on equipment has not been studied in detail, and the interactions are poorly understood. The very equipment at the heart of industrial automation—industrial drives, PLC’s, robots, and motors— are also possibly most susceptible to damage from short duration voltage sags. This is a very counterintuitive result as one expects equipment to be robust under lower voltage conditions. In fact, some of the practices being followed to allow equipment controllers to ride-through voltage sags may exacerbate the potential for damage to equipment.
CHAPTER THREE
METHODOLOGY
Material Selection
The components used for this design are the transformer, comparator, relays and the contactors. These components were chosen based on the following:
- They are readily available,
- Not expensive hence cost effective,
- Easily replaceable when faulty
- And having the same voltage rating as the supply contactor of three phases with rating 50Hz, 220-18volt each.
Principle of Operation
This work was achieved using many design approach, which include the approach of sectioning the system into various units as illustrated in the block diagram of Figure 2.1 The device has three transformers which receive the inputs voltages. The transformers step-down the 220 V AC to 18 V AC. Full wave bridge rectifiers were used to convert 18 V AC voltage to 12 V DC voltage.
However, the rectified voltages are fed into the inverting and non-inverting inputs of the two comparators through the voltage dividers. The voltage dividers were used to reduce each of the rectifier voltages to half so that the comparators will not sink. The comparators compare the input voltages and takes logical decisions. These logical decisions are in two ways, for instance (I) the output of the comparator becomes high (1) when the voltage in the non-inverting is greater than the inverting input. (II) When the voltage in the inverting is greater than or equals to the non-inverting, the comparator output remains low (0).
Accordingly, Transistors were connected across the comparator outputs so as to swing and drive a sufficient current to operate the relay coils.
CHAPTER FOUR
RESULT AND DISCUSSION
Testing and Result
The Automatic three phase selector process was tested with the three phases power supply required and alternated between the three phases which is available. In other to test the performance of the system, the operation of the system is literally guided by the truth table as in table. 4.1. With eight possible conditions, based on these possible conditions. Switch
𝑠1 is the switch controlling the phase1, switch 𝑠2 is the switch controlling the phase 2, switch 𝑠3 controlling the phase 3, switch, 𝑠0 is the reset or neutral switch.
CHAPTER FIVE
SUMMARY, CONCLUSION AND RECOMMENDATION
Summary
This work was achieved using many design approach, which include the approach of sectioning the system into various units as illustrated in the block diagram of Figure 2.1 The device has three transformers which receive the inputs voltages. The transformers step-down the 220 V AC to 18 V AC. Full wave bridge rectifiers were used to convert 18 V AC voltage to 12 V DC voltage.
However, the rectified voltages are fed into the inverting and non-inverting inputs of the two comparators through the voltage dividers. The voltage dividers were used to reduce each of the rectifier voltages to half so that the comparators will not sink. The comparators compare the input voltages and takes logical decisions. These logical decisions are in two ways, for instance
- The output of the comparator becomes high (1) when the voltage in the non-inverting is greater than the inverting input.
- When the voltage in the inverting is greater than or equals to the non-inverting, the comparator output remains low (0).
Accordingly, Transistors were connected across the comparator outputs so as to swing and drive a sufficient current to operate the relay coils.
But since the system include contactors because of handling big loads; the small relays are used to actuate the contactors. The break down operation and design of each unit is as power supply unit, voltage sensing unit, logic control unit and switching output unit.
Conclusion
The automatic phase selector was designed and constructed to automatically select any phase that has current without affecting the load. The device reduces the possibility of power being off completely in case of power failure in any particular phase if users connect their electronic gadget to it and reduces the response time needed to switch from one phase to another. The completed project work has been tested having met all the requirements for safely and reliability, and the outcome has turned out to be successful. Based on the experience gained, it is concluded that the performance test carried on the completed project was satisfactory.
Recommendation
I would recommend that further work be done on the following areas:
- On the voltage-sensing network, putting into close consideration the use of peripheral interface
- A software model of the design should be done and simulated to enable further research and improve the performance of the
- The department should acquire more research-oriented equipment’s in the departmental laboratory, to make enough materials available for students.
REFERENCES
- Adebayo, A. A and Yusuf, B. M. (2013). Ameliorating Power Supply Problem in Nigeria Trough Small Hydropwer. Journal of Research and Development, 1, 56-60.
- Adedokun, G. and Osunpidan, I.B. (2010). Panacea to Epileptic Power Supply in Nigeria. The Pacific Journal of Science and Technology. 11, 164-170
- Brumsickle, W. E., Divan, D. M., Luckjiff, G. A., Freeborg, J. W., & Hayes, R. L. (2003). Operational Experience with a Nationwide Power Quality and Reliability Monitoring System, IEEE-IAS Annual Meeting Conf. Record, Vol 2, pp. 1063 – 1067.
- Conaster, B., Nastasi, D., & Phipps, K. (2002). Following the Trail of Destruction, Power Quality Magazine, pp 62-66.
- Curtis, A. C. (2000). A Handbook on Electronics Design. U.S.A: Mc-Graw Hill.
- Guasch, L., Corcoles, F and Pedra, J. (2000). Effects of unsymmetrical voltage sag types E, F and G on induction motors, Proceedings of the Conference on Harmonics and Quality of Power, Volume: 3, Pages:796 – 803 vol.3.
- Greenfield, J. D. (2006). Practical Digital Design Using Integrated Circuits. New York: John Willey and Sons Incorporation.
- Khairul A. and Husnain-Al-Bustam (2011). Power Crisis & Its Solution through Renewable Energy in Bangladesh. Journal of Sel ected Areas in Renewable and Sustainable Energy. 1-15.
- LM139/LM239/LM339/LM2901/LM3302 datasheet. Texas Instruments. August 2012.
- LMH7322 datasheet. Texas Instruments. March 2013. Retrieved 2014-07-02.
