Simulation Results of Four Level Convertor for High Speed Switched Reluctance Motor

The aim of this paper is to present that four level converters are most suitable for excitation of high speed switched reluctance motor drives. Switched reluctance motor drives are preferred for high speed industrial applications because they offer a wide speed range and that their are torque/inertia ratio is very high . Conventional asymmetric convertors are not suitable for excitation of high speed switched reluctance motor drives because the excitation time is very short. While exciting switched reluctance motors the excitation current in a phase should be switched on at the time inductance begins to rise and it must build up sufficiently during the raising period of the inductance to produce required positive torque output. Further the excitation current must be reduced to zero before the inductance begins to fall. During its fall time of excitation current it should not extend to the decreasing period of inductance to avoid production of negative torque. Four level convertor is recommended to achieve the above mentioned facts in excitation of high speed switched reluctance motor drives. The Four level convertor has an additional capacitor and an active power switch. The high voltage in the charged capacitor is applied to the phase winding in the fast excitation mode and the phase current gets rapidly decreased without extending to the negative region during demagnetisation mode. The simulation results of such a four level convertor used for operation of high speed switched reluctance motor drives show that current stress is less than the voltage stress during excitation conditions.