This paper provides the fundamentals of integrated motor-drive system design knowledge which could be used as a basis to change the existing machine design approach from being a separate machine design tool to a more advanced engineering package. Various user's preferences including motor performances at transient, rated and flux weakening operations along with the inverter quality are studied by means of a competent co-simulation process which utilizes FEM, MATIAB and SIMULINK packages to build the framework based on which magnetic, electric and electronic devices and quantities are modeled, simulated and post processed. A case study of an interior permanent magnet motor connected to a field oriented controlled drive is investigated and the design process concepts are developed by means of a comprehensive statistical analysis. The initial goal is to reduce the search space of the optimal region. It is shown that incorporating the inverter effects into the design process changes the idea of an optimum motor design and not only the design parameters but also the expectations from motor performance have to be revised. In fact, an integrated motor drive system design process regarding the best motor operations in the transient, rated and flux weakening modes is targeted as the ultimate goal. A set of practical solutions are proposed to fulfill any motor operations requirement while keeping the inverter efficiency at the highest possible level.