ABSTRACT
I1 in calculations on transformers
• construct a transformer no-load phasor diagram and calculate magnetizing and core loss components of the no-load current
• state the e.m.f. equation for a transformer E = 4.44 f m N and use it in calculations • construct a transformer on-load phasor diagram for an inductive circuit assuming the volt drop in the windings
is negligible • describe transformer construction • derive the equivalent resistance, reactance and impedance referred to the primary of a transformer • understand voltage regulation • describe losses in transformers and calculate efficiency • appreciate the concept of resistance matching and how it may be achieved • perform calculations using R1 =
( N1 N2
• describe an auto transformer, its advantages/disadvantages and uses • describe an isolating transformer, stating uses • describe a three-phase transformer • describe current and voltage transformers
A transformer is a device which uses the phenomenon of mutual induction (see Chapter 9) to change the values of alternating voltages and currents. In fact, one of the main advantages of a.c. transmission and distribution is the ease with which an alternating voltage can be increased or decreased by transformers.
