0
the short answer: to distinguish as an AC transformer, as opposed to a DC transformer.
The long answer:
A Kva stands for Kilo-Volt-Amps. The Transformers mounted on telephone poles work with hundreds of thousands of volts so rather than 750,000 V, we use the abbreviation kilo, being the metric prefix for thousand and write 750 kV. As for 'VA' some high school physics tells us Voltage*Current=Power. voltage being measured in volts (V), current in amperes or amps for short (A), and power being Watts (W). However alternating current is a very fickle beast and the voltage and current vary in a wave like fashion causing the power to reverse direction. Other factors come into play such as power sag, types of electrical loads, and wasted energy, the equation soon becomes very messy. at times the power is actually negative and is flowing away from your house! so to simplify things they use Volt-Amps to represent the maximum amount of power as an absolute value that the electricity can deliver. as opposed to the USEFUL amount of power which is lower due to resistances in the wires and other loses. Engineers have to worry about the KVA when designing a system so it can handle everything thrown at it, keeping the wires from melting and that transformer from blowing up!
Wiki User
∙ 12y ago
Wiki User
∙ 14y agoTransformers are rated in KVA because voltage refers to iron loss or core loss and ampere
refers to copper loss.
iron loss or core loss are of two type
1) Hysteresis losses
2) Eddy current losses
Wiki User
∙ 13y agoKVA rating indicates the transformers maximum power output capacity. Power is power to a transformer, it does not matter if it is reactive or real, the transformer rating is based on the amount of current that is flowing through it. If it was rated in Watts you would have to factor in Power Factor which would only lower this capacity. Since this will be load dependant it is not as convenient as a rating.
Wiki User
∙ 9y agoThe watt is a measure of true power, which is the product of the supply voltage, load current, and load power factor. The volt ampere is a measure of apparent power, which is the product of the supply voltage and the load current.
A transformer manufacturer has no means of knowing the power factor of the load its transformer will supply. Accordingly, transformers are rated in volt amperes -the product of their rated secondary voltage and their rated secondary current.
Wiki User
∙ 11y agoPower rating of any equipment depends on power consumed by that equipment,
in other wordspower depend on Voltage, Current & Phase angle between Voltage & Current vactor.
P = V * I * cosØ
In case of transformer, there are two types of losses occure in transformer one is iron loss & other is copper loss.
Iron loss occcure in core of the transformer and its value depends on supply voltage, whereas copper loss occures in winding of the transformer and its value depends on load current.
there is not any relation with supply voltage & load current in case of transformer, so power rating isdepends onSupply voltage & Load current
P = V * I
There is not any role of power factor in calculation of power of transformer so, its rating is defines as VA (Volt-amp, or KVA).
Wiki User
∙ 11y agoPower is voltage times current times power factor. The power factor is determined by the load. As the transformer manufacturer has no idea of the power factor of the load the transformer is to supply, he can only specify the transformer's rated current and rated voltage, the product of which is apparent power, expressed in volt amperes.
Wiki User
∙ 13y agoin transformer the losses never depends on power factor depends only on voltage (constant losses) and current (variable losses) so...
Add your answer:
Earn +20 pts
Transformer rating is expressed in?
VA or KVA or MVA
Why transformer is measured in kva?
The rating of the machine (kva or kw) depends upon the power factor, since the load power factor to which the transformer is supplying power is not known, it may be capacitive, inductive, or resistive that is why its rating is in kva not in kw.
Can you operate a transformer below kva rating?
What limits the use of a transformer is its operating temperature, as excessively-high temperature will act to break down its insulation. The temperature reached by a transformer is a function of its rating (expressed in volt amperes), so operating a transformer below its rating is perfectly okay.
What is mean KVA Rating of transformer?
copper loss is directly propostional to I (AMPERE) and iron loss directly propostional to V (VOLTAGE) then total losses is equal to volt ampere hence the rating of transformer in KVA. SULTAN
Why transformer rating is called kva not kw?
Transformers are rated in KVA because that is a more accurate way to measure their capacity requirements. KWH is apparent power, while KVA is true power, and the ratio between them is power factor. The power factor is a function of the load, and not the transformer, so a poor power factor would make KWA look less to the transformer while, in fact, the true power, if not met by the transformer, could overload the transformer.
What is the KVA rating required of the testing transformer?
Depends on the kva rating of the devices to be tested using a transformer.
Do the load carried by a transformer is affected by KVA rating?
yah! definately affects, the kva of transformer is suitable for the certain load according to the rating.
Why you are indicating capacity of transformer in KVA?
transformer action doesn't depend on power factor that is why we indicate its rating in KVA
Transformer rating is expressed in?
VA or KVA or MVA
Can you use a step up transformer 110220 with output of 16 kva?
Yes, but your input current is going to be high at 133 amps. The output of the transformer is not going to be 16 KVA, that is the rating of the transformer.
What is kva rating of single phase transformer?
This is the rated output of the transformer, obtained by multiplying the rated secondary voltage by the rated secondary current. And it's 'kV.A', not 'kva'.
How the ka rating of mccb is calculated?
ka of mccb=transformer(KVA)x100/1.732xsecondary voltagex%impedence of transformer
480 transformer to 120 ac current what is the kva on transfomer?
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.
What is the result when 3 kva power requirement is being supplied by 250 kva transformer?
The result is that the transformer runs cool and contented. The '250 KVA' rating on the transformer is its maximum ability to transfer power from its input to its output without overheating, NOT an amount of power always running through it. If the 3 KVA load happens to be the only thing connected to the transformer at the time, then only 3 KVA flows into the transformer from the primary line, and only 3 KVA leaves the transformer secondary.
Why the rating of transformer in kva?
because we dont know power factor of the secondary laod
What is the minimum load have to go for a new transformer?
All transformers have a power rating given in kVA which determine the maximum load that can be connected to that transformer.
Why transformer is measured in kva?
The rating of the machine (kva or kw) depends upon the power factor, since the load power factor to which the transformer is supplying power is not known, it may be capacitive, inductive, or resistive that is why its rating is in kva not in kw.
