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Rating plate of three phase transformer includes
Voltage
Current
Power
All of the above
All of the above
The rating plate (or nameplate) of a three-phase transformer provides essential specifications required for installation, operation, and maintenance. It includes values such as rated power (kVA), primary and secondary voltages, rated currents, frequency, connection type, and impedance voltage to ensure the device operates within safe limits.
The rating plate (or nameplate) of a three-phase transformer provides essential specifications required for installation, operation, and maintenance. It includes values such as rated power (kVA), primary and secondary voltages, rated currents, frequency, connection type, and impedance voltage to ensure the device operates within safe limits.
S=3тАЛVLтАЛILтАЛ тАФ Total apparent power in a three-phase system
IratedтАЛ=3тАЛVLтАЛSтАЛ тАФ Calculation of rated current from power and voltage
The nameplate acts as a technical passport for the equipment. The power rating (S) is defined by S=3тАЛVLтАЛILтАЛ for a three-phase system, where VLтАЛ and ILтАЛ are the line voltage and line current respectively. These parameters are factory-tested to guarantee the transformer meets thermal and electrical insulation standards during continuous operation at rated load.
Nameplate information is mandatory for preventing overloading and ensuring protective relay settings are correct.
The rating plate must be made of a non-corrosive material, typically fixed to the tank.
Apart from V, I, and P, the plate also mentions vector group, cooling method (e.g., ONAN), and impedance voltage (Z%тАЛ).
Enables safe selection of protection devices like circuit breakers and fuses.
Facilitates correct paralleling of transformers.
Incorrect information can lead to catastrophic insulation failure.
Plate weathering can make it difficult to identify specifications over time.
Power system grid synchronization.
Preventive maintenance and site audit protocols.
Standard Indian transformer ratings are governed by IS 2026.
Option A, B, and C are incomplete individually because a single parameter cannot define the transformer's operating envelope.
D is correct тАФ The rating plate includes all electrical parameters including voltage, current, and power ratings to define the operating limits of the transformer.
Always remember that transformer power is expressed in kVA or MVA, not kW, because the load power factor is unknown at the design stage.