ou have been hired as an engineering consultant to diagnose an overheating and low output voltage problem with a three-phase transformer. The service technicians informed you that the transformer has a solid nickel core, insulated aluminum windings and a single phase of the transformer is rated at 50 kVA, 6900/400 V, 60 Hz. The transformer cannot be disconnected for open and short circuit testing and only the input lines and output outlets are accessible for current and voltage measurements. (a) The following measurements were taken after and during working hours when all the electrical devices were off and on,respectively. No load condition: Input Phase Current = 3∠−60°A, Output Voltage = 400∠0°V Load condition: Input Phase Current = 8.45∠−37.35°A, Output Voltage = 370∠−0.64°V Assuming the input voltage is maintained at its rated value, calculate the modelled internal parameters Ro, Xm, Reqand Xeq of the transformer referred to the high voltage side. (b) When the transformer is delivering the building’s load during working hours,calculate: i.The power factor of the building’s load ii.The regulation at this load iii.The efficiency at this load
Please only answer b part iii. Thank you.
You have been hired as an engineering consultant to diagnose an overheating and low output voltage problem with a three-phase transformer. The service technicians informed you that the transformer has a solid nickel core, insulated aluminum windings and a single phase of the transformer is rated at 50 kVA, 6900/400 V, 60 Hz. The transformer cannot be disconnected for open and short circuit testing and only the input lines and output outlets are accessible for current and voltage measurements.
(a) The following measurements were taken after and during working hours when all the electrical devices were off and on,respectively.
No load condition:
Input Phase Current = 3∠−60°A,
Output Voltage = 400∠0°V
Load condition:
Input Phase Current = 8.45∠−37.35°A,
Output Voltage = 370∠−0.64°V
Assuming the input voltage is maintained at its rated value, calculate the modelled internal parameters Ro, Xm, Reqand Xeq of the transformer referred to the high voltage side.
(b) When the transformer is delivering the building’s load during working hours,calculate:
i.The power factor of the building’s load
ii.The regulation at this load
iii.The efficiency at this load
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