Transformers
A step up Transformer
Transformers
- Transformers are devices that make use of electromagnetic induction to change the size of the voltage for an alternating current
- An alternating current in the primary coil / input coil causes the core to magnetise, demagnetise and remagnetise continuously in opposite directions.
- This produces a rapidly changing magnetic flux across the coil. This flux passes through the secondary / output coil where it induces an alternating voltage of the same frequency but different voltage, assuming the number of turns is different.
Equations
\[V_{p}=N_{p}\frac{\Delta \Phi}{\Delta t}$$
$$V_{s}=N_{s}\frac{\Delta \Phi}{\Delta t}$$
$$\frac{N_{s}}{N_{p}}=\frac{V_{s}}{V_{p}}\]
Inefficiencies
- The rapidly changing magnetic flux produces "eddy currents".
- Due to the magnetic core being cut by the flux, an e.m.f. is produced which produces eddy currents.
- These are looping currents that create a magnetic field against the field that induced them. (lenz law)
- The effects of eddy currents can be reduced by laminating the core, which makes it harder for eddy currents to flow.