This paper presents two series-connected motor drive system topologies. These configurations have been designed for applications in which it is necessary to control two motors independently by using a standard three-leg inverter. The systems will be called in this work as a monolithic systems, since both machines and the three legs inverter have been considered as the same product. The monolithic systems are seen as a potentially viable industrial solution for applications requiring one highpower (three-phase machine) and one low-power machine (singlephase machine). Furthermore, the paper presents: i) relevant characteristics of the systems, ii) pulse-width modulation techniques; iii) control strategies; iv) voltage and current analysis; v) unconventional induction machine design to improve the performance of the monolithic system; and vi) simulated and experimental results.