Industrial problems in design, selection and installation of an adjustable speed drives (ASD) for asynchronous motor

Adjustable speed drives (ASD) is replacing rapidly the conventional electromechanical contactors. Earlier engineers has shown hesitation to except the change of conventional starting method to soft starting using solid state switches as the cost relatively high. But now, industrialist prefers this power electronics based inverters for both soft starting and speed control, this in fact getting more attention as price of solid states semiconductors has gradually reduced and eventually the ASD is cost effective as compare to electromechanical switches especially when the questions of efficiency, energy saving and reliability arise. Since ASD is not a stand-alone device, hence, there are many practical problems and failures faced by design engineers, project engineers as well as the maintenance engineers. Hence, this paper is an industrial based paper which includes practical failures or problems faced by engineers during design, selection and installation of ASD for asynchronous motor in particular.