What about lightly loaded transformers.

[Elecme]

What do you think about loading a 11/ 415 V transformer by a light load (25 - 30 %) of its rated capacity.
Are there any problems with harmonica ?!What about the effect on the other loads. Elecme

 

[Batu]

Hi,
The capacity of the transformer is generally it's power. For the voltage the general rule is U1xN1=U2xN2 (U stands for voltage and N stands for the wiring) so the voltage you will get from the transformer is according to the voltage you supply it. The thing you should also consider is the current. If the power stays the same but the voltage drops then it means current rises which is not good for the transformers windings and insulation. The transformer may get too hot by the current and cause a trip or high noise level as well..

Regards,
Batu

 

[Elecme]

I am talking about light load, which means lesser current. Elecme

 

[jwerthman]

There is no problem with lightly loading a transformer.

 

[jghrist]

Transformer magnetizing current, which is independent of load, will introduce a small amount of harmonic distortion. Serving the same load with a larger transformer will produce more harmonic distortion. The harmonic distortion from transformers is small enough that it is unlikely to be a problem, however.

The main reasons for not lightly loading transformers is that no-load losses are higher as a percent of the load and the transformer capital cost is higher for the same load. Load (copper) losses increase with the square of the load, however, so you have to balance all of the factors.

 

[cuky2000]

Transformer could operate OK at light load conditions even though is not the optimal scenario.

There are negative effect associated with light-loaded conditions:
a- Efficiency at light load is less than at full load.
b- Ferroresonance is more likely to happen at light load than at full load.
c- Short and long term negatives economic impacts

Negative economic impact in the short term are associated with extra initial investment to purchase the transformer and additional Installation costs in foundation, oil, auxiliary power, etc. Long term (typical 20 to 30 years) may be associated with extra power losses, the interest of the increment on capital investment compared with smaller unit that satisfy the needs of electrical system and additional O&M costs.