Transformers, like inductors can only handle a specific amount of voltage and current before overheating, with AC or DC input. AC 'real' power delivery from a transformer is measured in kilowatts (kW) which is identical to KVA when "Power factor = 1". In the extreme, with "Power factor =0", a transformer could be fully loaded in terms of KVA, while supply zero 'real' power (kW).
A transformer's capacity is rated in volt amperes(V.A). This is the product of the secondary winding's current rating and voltage rating.
Transformers are rated in KVA or VA (volt-amps). They transform voltages from one value to another. The current in a transformer is inverse to the voltage. This is why transformers are rated in KVA and smaller ones in VA.
Transformers are rated in VA or kVA. That is because the voltage is limited by the power loss in the magnetic core, and the current is limited by the power loss in the resistance of the windings. The rated voltage times the rated current gives the transformer's rating in kVA.
the capacity of a transformer is defined as a product of voltage and current flowing through it.AS THE CURRENT IS MEASURED IN AMPERES AND VOLTAGE IN VOLTS, Hence transformers are measured/rated in KVA
Rated voltage is the voltage at primary side. Rated current can be found from the equation, Rated Current= Output KVA / Output rated voltage
A 132 kV substation is normally called a grid substation. It would normally use two or more 132/33 kV transformers rated at 90 MVA, or two or more 132/11 kV transformers rated at 30 MVA.
You can't determine the output voltage of a transformer by knowing kva. Transformers will be marked as to input and output voltages. Some will have multiple input and output voltages. The output voltage depends on the ratio of coil turns between input and output.
Because it is the current rating of the windings that determine the maxium load current, and the product of rated current and rated voltage, in a.c., is apparent power (in volt amperes), nottrue power (in watts).And, incidentally, the correct symbols are kV.A and kW, not kva and kw.
The kVA rating will be listed on the transformer's nameplate, which is usually on the front of the transformer. The 480v to 120v is irrelevant, because many transformers with different kVA ratings convert 480 volts to 120 volts. The kVA ratings can be different and thus affect the rated current through the transformer.
Transformers are rated in KVA, both the primary and secondary windings have the same KVA rating. (KVA is the voltage multiplied by the amperage then divided by 1000). If you have a 10 KVA step up transformer with 120V on the primary: A = 10k / 120 = 83.33A and if the secondary produces 240V: A = 10k / 240 = 41.667A
Transmission transformers are rated in mva. Distribution transformers are rated in kva. Power transformers are measured in va. There are, of course, exceptions, but this is the normal nomenclature.Answer (for UK terminology)In the electricity supply industry, the name 'power transformer' is used to describe those transformers used in the transmission system (400/275/132-kV levels), while 'distribution transformers' are those used in the distribution system (33 & 11-kV and 400-230-V levels). Power transformers and primary-distribution transformers are rated in megavolt amperes (MV.A), while secondary-distribution transformers are rated in kilovolt amperes(kV.A).Note that 'mva', 'kva', and 'va' are incorrect symbols for 'megavolt ampere', 'kilovolt ampere', and 'volt ampere'. The correct symbols are shown in the above paragraph (except that the period, or full stop, should be placed above the line).However, I suspect your question is really asking why are transformers rated in (mega) volt amperes rather than in (mega) watts? The answer is simply that the load that a transformer can supply is determined by the product of the transformer's rated secondary voltage and rated secondary current -the product of which (for alternating current) is the volt ampere, not the watt.
A big one - one that can supply thousands (k) of V.A (not kva, but kV.A).AnswerA volt ampere is used to measure apparent power (the vector sum of true power and reactive power. Transformers are rated in volt amperes, rather than in watts because to rate transformers in watts, it's necessary to know the power factor of the load, and transformer manufacturers have no way of knowing that. A kilovolt ampere (kV.A) is one-thousand volt amperes. Distribution transformers are typically rated in kilovolt amperes. For example, pole-mounted distribution transformers are typically 5 kV.A, 50 kV.A, etc., and are used to reduce high-voltages to residential low voltages.Power transformers, used on transmission systems, are usually rated in megavolt amperes.