Question

A transformer has a core load of 64 w and copper loss of 144 w, when it is carrying 20% overload current. The load at which this transformer will operate at the maximum efficiency

Answer 1

Answer:

80%

Explanation:

Given A transformer has a core load of 64 w and copper loss of 144 w, when it is carrying 20% overload current. The load at which this transformer will operate at the maximum efficiency

Given copper loss is equal to core loss

So c^2 x Wcu = Wi

So x = √Wi / Wcu

x = √64 / 144

  = 8 / 12

x = 2/3

So it is carrying 20 % overload current.

Now we get  

= 120 x 2/3

= 80%

Answer 2

Answer:

The load at which this transformer will operate at the maximum efficiency is 80%

Explanation:

The transformer is overloaded by 20%,  

Cu loss at 1.2 rated current = 144 w

for the full load current the copper losses(Full load Cu loss)

= 144\(1.2)^{2} = 100 watts.

Maximum efficiency occurs at = sqrt {Iron-loss\Full-load Copper loss}

x = sqrt{64\100} =0.8*100% = 80%