08-05-2012, 04:34 PM
OPEN CIRCUIT TEST AND SHORT CIRCUIT TEST ON SINGLE PHASE TRANSFORMER
51355420-LAB-MANUAL-FOR-E-E-CS.pdf (Size: 523.09 KB / Downloads: 62)
FORMULAE
EQUIVALENT CIRCUIT
Open Circuit Test
1. No Load Power Factor (Cosfo) =
Where, Woc – Open Circuit Power in Watts
Voc – Open Circuit Voltage in Volts
Ioc – Open Circuit Current in Amps
2.No Load Working Component Resistance (Ro) = in Ohms
Where Voc – Open Circuit Voltage in Volts.
Ioc – Open Circuit current in Amps.
3. No Load Magnetizing Component Reactance( Xo) = in Ohms
Where Voc – Open Circuit Voltage in Volts.
Ioc – Open Circuit current in Amps.
Short Circuit Test
4. Equivalent impedance referred to HV side ( Z02 ) = in Ohms
Where, Vsc – Short circuit Voltage in Volts
Isc – Short circuit current in Amps
5. Equivalent resistance referred to HV side (R02 ) = in Ohms
Where, Wsc – Short circuit Power in Watts
6. Equivalent reactance referred to HV side (X02) = Z02
2 - R02
2 in Ohms
7. Transformation ratio (K) =
Where, V1 – Primary voltage in Volts
V2 – Secondary Voltage in Volts
8. Equivalent resistance referred to LV side (R01) = in Ohms
9. Equivalent reactance referred to LV side (X01) = in Ohms
Efficiency and Regulation
10. Output Power = X ×KVA × cosf in Watts.
Where, X-Fraction of load
KVA - power rating of Transformer and Cosf - Power factor
EC2259 Electrical Engineering And Control System Lab Manual
Prepared by G.Panneerselvam, Vel Tech Multi Tech
11. Copper loss = X2 × Wsc in Watts
Where, Wsc- Copper Loss in Short Circuit condition
12. Total Loss = (Cu Loss + Iron Loss) in Watts
13. Efficiency = x 100 in %
14. Regulation = × 100 in %
Where, V2o – Open Circuit Voltage on HV side.
PRECAUTION
• No Load Condition should be observed at the time of starting
• Meters are checked for proper Type and rating.
PROCEDURE
OPEN CIRCUIT TEST
• Connections are given as per the circuit diagram.
• The SPST Switch on the Primary side is closed.
• The Autotransformer is adjusted to Energize the transformer with rated Primary Voltage
on the LV side
• The Volt meter, Watt meter and Ammeter Readings are noted at No load condition
• The Autotransformer is brought to its initial position
• The Supply is switched off.
SHORT CIRCUIT TEST
• Connections are given as per the circuit diagram.
• The SPST Switch on the Primary side is closed
• The Autotransformer is adjusted to energize the transformer with rated Primary Current on
the HV side.
• The Voltmeter, Wattmeter and Ammeter Readings are noted down at short circuit
condition.
• The Autotransformer is brought to its initial position
• The Supply is switched off.
GRAPH
The graph are drawn as
• Output power Vs Efficiency
• Output power Vs Regulation