LOAD TEST ON SINGLE PHASE TRANSFORMER
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1. Input Power =Wattmeter reading × Multiplication factor in Watts
Multiplication factor =
2.Output power = VSY × ISY × cosf in Watts.
Where VSY - Secondary Voltage in Volts.
ISY- Secondary current in Amps.
3.Percentage of Efficiency = × 100 %
4.Percentage of Regulation = × 100 %
Where, VO – No Load Voltage in Volts
VL – Load Voltage in Volts
• No Load Condition should be observed at the time of starting
• Meters are checked for proper Type and rating.
• Connections are given as per the circuit diagram.
• The SPST Switch on the Primary side is closed and the DPST Switch on the Secondary side is
• The Autotransformer is adjusted to Energize the transformer with rated Primary Voltage
• The Volt meters and Ammeters Readings are noted and tabulated at No load condition
• The DPST switch on the secondary side is closed.
• The transformer is loaded upto 130% of the Rated Load, corresponding Ammeters, Voltmeters
and Wattmeters readings are noted and tabulated.
• After the observation of all the readings the load is released gradually to its initial position.
• The Autotransformer is brought to its initial position
• The Supply is switched off.
The graph drawn as
• Output power Vs Efficiency
• Output power Vs Regulation