Integrated electrical machine-compressor

1. Electrical machines with silent rotor In the recent decades, substantial developments on the electrical machines with silent rotors resulted in increase their performance, reliability and ease their manufacturability as well as reduce their cost. Silent rotor machines include magnet-less topology (switched reluctance) [1], flux reversal permanent magnet topologies (flux switching/switched flux, doubly silent and flux reversal) [2] and variable flux topologies also known as hybrid AC/DC machines [3]. All the above-mentioned electrical machines have the same rotor structure shown in Figure 1. The rotor is gear-shaped made of one solid piece of ferromagnetic material. The rotor does not consist of any magnets or winding. Therefore, it is simple, easy to manufacture and these topologies are characterised by easy heat removal since all the active parts (magnets and winding) are located in the stato