electrical question, quickly! first correct answer becomes the best answer?

Question

what are the common eficiencies fro transformers?

Answer 1

Standard Ratings and Overload Capacity

Dry-type transformers are available in three standard temperature rises: 80°C, 115°C, or 150°C. Liquid-filled transformers come in standard rises of 55°C and 65°C. These values are based on a maximum ambient temperature of 40°C. That means, for example, that an 80°C rise dry transformer will operate at an average winding temperature of 120°C when at full-rated load, in a 40°C ambient environment. (So-called “hot spots” within the transformer may be at a higher temperature than average.) Since most dry transformers use the same insulation on their windings (typically rated at 220°C), irrespective of the design temperature rise, the 80°C rise unit has more room for an occasional overload than a 150°C rise unit, without damaging the insulation or affecting transformer life.

Properly engineered you can get efficiency over 90%, but at a cost.

Effiency = output/ input
output = Input - Losses [ Core loss(iron loss ) ( Hysteresis loss )etc

Answer 2

A distribution transformer efficiency is in the range of 98% or higher.

The US DOE is actually mandating higher efficiency transformers to reduce losses and the greenhouse emissions needed to generate the kWh for those losses.

Click on the link below for details.

Answer 3

why are Arcing tips are used on circuit breakers?