A novel multilevel converter that is especially suited for high speed multi-megawatt switched reluctance motor drives operating at the medium voltage level is presented. The drive is capable of variable speed, four-quadrant operation. Each phase leg of the converter contains an arbitrary number of cascaded cells connected in series with the phase winding. Each cell contains a half-bridge chopper connected to a capacitor. The converter is named the cascaded chopper cell converter. The modular nature of the converter with the ability to add redundant cells makes it very reliable, which is a key requirement for medium voltage drive applications. A comprehensive control algorithm that overcomes the challenges of balancing and controlling cell capacitor voltages is also proposed. A suitable startup algorithm to limit startup current and switching losses, as well as ensure that cell capacitor voltages remain controlled at startup, is suggested. Details of the drive design such as component sizing and control parameter selection are also discussed. A detailed simulation model is developed and explained, and simulation results are provided for primary validation. Operation with standard current and speed control is first simulated. Then a scheme that gives way to a controller that operates the drive in single-pulse mode is developed and presented. This single-pulse control scheme controls the turn-on and turn-off angles, as well as the energization voltage level, in order to obtain high efficiency. Practical considerations related to the drive such as reliability, efficiency, and cost considerations are also discussed. Finally, a detailed comparison of the proposed converter to another competing converter is performed. Besides its scalability to high voltages and powers, the reliability and efficiency of the proposed converter makes it also a candidate for sub-megawatt applications requiring minimum downtime, or any application where high efficiency or improved performance is required. A small part of this work is also dedicated to brushless dc machines. Control methods for a new converter for brushless dc machines are proposed and verified via simulation. The main advantage of this converter with the proposed control is that it allows exact control of torque or speed up to twice the rated speed, without resorting to current phase advancing or other flux-weakening techniques. / Ph. D. / Electric motors are used in a very wide range of applications. They are found in power tools, in household appliances like washers and dryers, in compressors for HVAC, in fans, blowers and pumps in industry, and in electric vehicles and electric transit systems, only to name a few. An electric motor that is combined with an electronic circuit that allows precise control of the motor speed and torque is referred to as an electric drive. Very large electric drives – reaching multi-megawatt powers – are used in several applications such as in ship propulsion, in large pumps for moving water and sewage, and others. Very few electric motor drive options currently exist at that power level, and so multi-megawatt electric motor drives present an interesting research opportunity. This work proposes a novel drive system that is best suited for high speed multi-megawatt electric drives employing the switched reluctance motor. The switched reluctance motor was chosen due to its robustness, high efficiency, and high speed capability. A novel electronic converter that is scalable to high power and voltage levels is proposed. It features high reliability which is essential in multi-megawatt applications that typically require very high uptime. It has a modular structure, thereby allowing for simple construction. A comprehensive control algorithm for the drive system consisting of the converter and motor is proposed. Also a suitable algorithm that keeps the electrical and thermal variables within the allowed limits during the startup stage is proposed. A detailed simulation model is developed and explained, and simulation results are provided for primary validation. Next, a control scheme that results in high efficiency through appropriate control of the drive’s various parameters is proposed. Practical considerations related to the drive such as reliability, efficiency, and cost considerations are also discussed. Finally, a detailed comparison of the proposed converter with another competing converter is performed. Besides its scalability to high voltages and powers, the reliability and efficiency of the proposed converter makes it also a candidate for sub-megawatt applications requiring minimum downtime, or any application where high efficiency or improved performance is required. A small part of this work is also dedicated to drives using another type of machine called the brushless dc motor. Control methods for a new converter for brushless dc machines are proposed and verified via simulation. The main advantage of this converter with the proposed control is that it allows exact control of torque or speed up to twice the rated speed, which makes it useful in traction applications.