notes/uni/mmme/2051_electromechanical_devices/transformers.md

author	date	title	tags	uuid	lecture_slides	exercise_sheets
Akbar Rahman	\today	MMME2051 // Transformers	transformers alternating_current ac	486f441f-14ec-41e5-94f9-06f25c534086	./lecture_slides/MMME2051EMD_Lecture8.pdf	./exercise_sheets/Exercise Sheet 11 - Transformers.pdf

Transformers are used to convert between AC voltages.

Transmission is always done at very high voltage to reduce copper losses (heat loss, E = i^2R).

A current carrying coil induces a magnet inside the core. Another coil is wrapped around the core. This coil has a current induced in it by induced magnetic field.

\frac{i_s}{i_p} = \frac{v_p}{v_s} = \frac{n_p}{n_s} = \text{turns ratio}

Note that the current fraction is s over p, not p over s like the others. Transformers have very high efficiency so will not be considered for this module and has been left out of the equation above. Derivation in lecture slides (pp. 12-15).

Transformers are usually described as having a ratio p:s, where p is the number of primary coils and s the number of secondary coils.

Referred Impedance

\frac{Z_P}{Z_S} = \left(\frac{n_p}{n_s}\right)^2

Derivation in in lecture slides (pp. 19-21).