The power
frequency transformer has a laminaed core and generally at least
two windings referred to as a primary and secondary. For small single
phase transformers ashell type core is used.This consists of a central
iron sectioncarrying the windings and two outer section which provide
the return path for the flux.The laminations are either formed from
'T' and 'U'
shapes or from 'E' and 'I' shapes.The
laminations must beinterleaved so that the air gap in one lamination
is covered by the next lamination in the stack.The Transformer is
highly efficient so that for practical purposes ,input equals output,ie.,V1L1-V2L2.
The equation E = 4.44BmAiN eneables
the number of turns to be determined.Bm is the maximum flux density,say
1`.35wb./m2.AiN is the net area in square metresof the centre iron
section,usually 90%of the gross area to follow for the lamination
insulation.f is the frequency .
The turns ratio N1/N2 - V1/V2.
the voltage ratio
The primary ampere turns N1I1-N2I2
the secondary ampere turns |
