help needs a practical reason why transformers are rated in kva???? 2

[kelvesfans]

help needs a practical reason why transformers are rated in kva????

 

[rcw retired EE]

Because horsepower or calories would be too cumbersome?

Simple but not technically rigorous explanation:

The transformer rating is based on the thermal capability of the windings to dissipate the heat generated by current flowing in the windings. The current is directly proportional to the KVA, not the kW.

A transformer carrying 1 kW at 0.001 power factor will have the same current and heating as one delivering 1000 kW at 1.0 power factor since they are both delivering 1000 KVA.

In designing a transformer, the desired voltage ratio determines the number of winding turns, the KVA determines the windings' conductor sizes based on current ratings.

 

[cuky2000]

In a simplistic way:

Transformer rating(kVA)= real power(kW) + reactive power(kVar).
Transformer power rating in kVA, indicates its capable to provide real power such as heat, torque x rpm, force x radial distance in combination with reactive power to provide magnetization to circuits load elements such as reactances and capacitances.
A good characterization unit for the power rating of a transformer is in kVA because represent either 100% real power, 100% reactive power or a combination of kW and kVar.

 

[dpc]

As opposed to rating them how?

 

[cranky108]

I like rating them in MVA. Our cival engineer rates them in KIPS, our mechinical engineer rates them in FEET. Our accountant rates them in dollars. Our public relations people rate them in decibels.

How would you like to rate them?

 

[dpc]

The environmental guys rate them in ppm, and maybe gallons.

 

[rcw retired EE]

..and environmental and fire protection engineers rate them in gallons of oil. Client's architects only want to know the color.