Answer in official key is “mechanical loss & iron loss ”. Many times stray loss is also considered as total loss actually accured minus calculatable loss. This means loss that can be calculated is known as stray loss.
In hopkinson test known as regenerative test two identical machine coupled D.C shunt motor D.C shunt generator temperature rise can be check under rated condition large machine can be tested without drawing much power.
three types of electric breaking: Regenerative breaking( leads to economic and energy consevation) pugging (more efficient method of breaking) rheostatic breaking
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