Construction Of Automatic Phase Changer

Project and Seminar Material for Science Laboratory Technology SLT

Construction Of Automatic Phase Changer

Chapter One


Raw power instability in developing countries creates a need for automation of electrical power generation or alternative sources of power to back up the utility supply.

This automation is required as the rate of power outage becomes predominantly high. Most industrial and commercial processes are dependent on power supply and if it processes of change-over are manual, serious time is not only wasted but also creates devices or machine damages from human error during the change-over connections, which could bring massive losses. The starting of the generator is done by a relay which switches the battery voltage to ignition coil of the generator while the main power relay switches the load to either public supply or generator. Fig 1 shows the generalized block diagram of the system. The approach used in this work is the moduler approach where the overall design was first broken into functional block diagrams, where each block in the diagram represents a section of the circuit that carries out a specific function. The functional block diagram fig 1 also shows the interconnection between these blocks. Each section of the block is analyzed below. A manual change-over switch consists of a manual change over switch box, switch gear box and cut out fuse or the connected fuse as describe by the by rocks and Mazur{1993}.This change-over switch box separate the sources between the generator and public supply when there is power supply outage from public supply, someone has t go and change the line to generator. Thus when power supply is restored, someone has to put off the generator and then change the source line from generator to public supply.

In view of the above manual change-over switch system that involves man power in starting the generator and switching over from public supply to generator and vice-versa when the supply is restored.

The important attached to cases of operation in hospitals and airport in order to save life from generator as fast as possible makes it important for the design construction of automatic change-over switch which would solve the problem of manpower and the danger likely to been countered changeover.

The electronic control monitors the incoming public supply voltage and detects when the voltage drops below a level that electrical or electronics gadgets can function depending on the utility.

Fig 1 Block diagram of an automatic change over switch

Component List

Component Name, Quality

  • Step down transformer 3
    (Files 22ov – 12v 300mA)
  • Fuse (F1 – F3 = 5A) 3
  • IC (IC1 – Ic3 =741) 3
  • Transistor (T1, T2, T3 = BC 557) 3
  • Relay (RL1 – RL3 = 12v LC/o Relay) 3
  • Zener diode CZD1 = ZD3 = 5, 1v 3
  • Variable resistance (VR4 – VR3 = 10K) 3
  • Resistance (R1, R2, R4, R5, R7,R8 = 3,3k 9
    R3, R6, R9 = 10K)
  • Diode 9
  • Capacitor (C1 – C4 = 1000uf 25V 7
    C5 – C7 = 470uf 35V)
  • Wires ACC, TO
  • Requirement

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Construction Of Automatic Phase Changer

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Construction Of Automatic Phase Changer


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