Motor life becomes very short when the core reaches saturation - about 15 seconds in some cases. We will look at this and some of the causes later. Some energy is consumed by simply magnetizing the iron core. Different materials consume different amounts of energy. This is usually considered an energy loss.
Some energy is converted into heat within the iron core.
Different materials convert different amounts of energy. This is also usually considered an energy loss. Once a core is magnetized, demagnetization and reverse polarity re-magnetization consumes more energy and takes quite a long time, relatively speaking. The amount of this loss is proportional to the frequency of polarization reversals. This happens 120 times per second when operating an AC motor at 60 hertz.