Basic Electricity 2, WASSCE (PC 2ND), 2019

Question 4

 

  1. State
    1. two types of transformer construction;
    2. two methods of cooling a transformer.
  2. The copper and iron losses of a 50 kVA transformer are 800 W and 650 W respectively. If the transformer operates at 0.8 power factor lagging, calculate its efficiency at full load.

Observation

The expected response was:

 

    1. Types of transformer construction
      • Shell type
      • Core type
    2. Methods of cooling transformers
      • Air
      • Oil
      • Water
  1.  


  2. Many of the candidates did the first part well but could not determine the output from KVA and pf as such could not compute the efficiency.