Transformer power is given by P=V*I which takes the unit of KVA while that of KW has energy term which is not produced by the transformer.It only steps up or down the voltage.
Answer:
In a pure D.C. circuit, KW = KVA. However, in any A.C. circuit, there is real power {KW} and apparent power {KVA}, due to the voltage and current being out of phase. Power Factor is the ratio of KW to KVA. Transformers are rated in both KVA and PF. Multiplying the transformer KVA rating times the PF will yield KW.
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A transformer has separate ratings for maximum voltage and maximum current. Multiply the two together and that is called the VA rating, or kVA for larger transformers. So the transformer rating is independent of the power factor of the load.
VA is just volts x amps. Watts takes into account Power factor such that watts = volts x amps x Power Factor. Since the Power Factor is one for a pure resistive load and decreases with inductance. Therefore a transformer rated in VA indicates maximum power rating. The K is just a multiplier of 1000.
the unit of generators power is KVA becoze the kva is the power that contain the active power (KW) and the reactive power mean that the name plate of any generator must contain the rated kva of it (like the transformer P (KW) = P (kva) * cos fi P (KW) = V I cos fi for single phase P (KVA) = V I when cos fi closed to 1 this will increase the useful power that exit from the generator or transformer with my pleasure
Transformer rating is based on the maximum temperature a transformer can run at. This temperature is dictated by the amount of current flowing through the transformer windings. This is why transformers are rated in KVA (voltage * current), not kW - it doesn't matter what the phase relationship is between voltage and current, just the magnitude of the current.
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.
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.
kvar can be calculated as follows the a product KVA andt the sine of the angle between the KVA and KW.
12HP is approximately 10.8 KVA. You would want to use a 15KVA transformer to supply this motor. KW = HP * .75 KVA = KW * 1.2 (These formulas are approximate)
the unit of generators power is KVA becoze the kva is the power that contain the active power (KW) and the reactive power mean that the name plate of any generator must contain the rated kva of it (like the transformer P (KW) = P (kva) * cos fi P (KW) = V I cos fi for single phase P (KVA) = V I when cos fi closed to 1 this will increase the useful power that exit from the generator or transformer with my pleasure
Transformers are rated in KVA which is equivelant to "apparent power". Loads, {such as heaters, lamps, etc.} are rated in KW which is equivelant to "real power". Things such as power factor and transformer efficiency account for the diifference between the two values. KW's are what the load requires and KVA's are the values of the input power required in order to serve a given KW load. Unfortunately the utilities charge for KVA not KW. It's not too unlike a glass of beer. The enjoyable part is the beer itself. However, you pay for both the beer and the foam at the top of the glass.
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.
Transformer rating is based on the maximum temperature a transformer can run at. This temperature is dictated by the amount of current flowing through the transformer windings. This is why transformers are rated in KVA (voltage * current), not kW - it doesn't matter what the phase relationship is between voltage and current, just the magnitude of the current.
kVA = kW divided by (power factor). The power factor is the cosine of the angle between voltage and current.
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.
KW is multiplication of KVA and power factor. Power factor is load dependent and varies as per the type of load. Hence the rating or capacity is mentioned in KVA not in KW
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.
For normal power factors (pf=80%), you have 0.8 kW for every kva. In general however, kW = pf x kVA. Where pf is the power factor, it is the cosine of the angular difference between the voltage and the current of a circuit in alternating current circuits.
kva and kw are related as KVA = (KW/PF) pf:power factor
kvar can be calculated as follows the a product KVA andt the sine of the angle between the KVA and KW.