I have a question can someone explain why transformers get hot in use and why must they not be allowed to get too hot
They get hot because like pretty much everything, they are not 100% efficient. When a transformer is powered on, even if there is no load on it there is something called iron losses - this is the amount of energy which is used to magentise the iron core of the transformer. These losses end up as heat. When the transformer has to start delivering power to the load, there are also copper losses to consider, this is because as more power flows through the windings, because the wire is not a perfect conductor, some heating of the copper winding occurs ( these losses are sometimes known as I squared R - meaning current x current x resistance) Iron losses are fixed, copper losses increase as the amount of power taken from the transformer increases. As for why you must not let them get to hot, from a functional point of view, above a certain temperature (varies according to insulation used) the enamel and other insulativbe properties will break down and you then get a shorted transfomer. Not helpful A second reason is for safety, some transformers will reach temperatures EXCEEDING the ignition temperature of flammable material - so in simple terms, a fire risk. Usually a transfomer has a thermal fuse fitted so that under overload conditions, it will rupture the fuse rather than get dangerously hot. Mark
Transformers are two separate coils of wire wrapped together around a core. The wires are not connected to each other Electricity flowing through one coil induces a currant in the other. When you are using a device connected to the transformer electricity has to pass from one coil to the other. This action does create heat. If the transformer gets too hot the insulation between the coils of wire will melt and short the circut. Some times they do catch fire. just a simplified explanation.
Of course a transformer must use AC voltage and current. Power consumed is calculated as P EI (volts x current). Even if the transformer is not connected to a load current must pass through the coils of wire. Although the resistance of the wire coils is minimized (where thick copper wire has less resistance) to obtain the needed effect many turns are required and thick wire may not be practical. The transformer will exhibit a heating effect equal to its I2R (current squared x resistance) losses.
Simple explanation: a transformer can actually be modeled as an LRC circuit where the L is in series with the R and are both in parallel with the C. L is the inductance R represents the lossyness of the inductor and C represents the capcaitance between the turns. The heat comes from the loss of power through the resistance of the coil. and this lossyness can be described by the Q (quality factor) of the inductor. Q can be described as w(Total Stored Energy/Avg power dissipated) here w is the operating frequency.
