DC Machine Equivalent CSI Drive System

Electric motors are a hidden backbone of modern life. They are found almost everywhere: in household appliances, elevators, electric vehicles, industrial robots, satellites, medical devices, and even humanoid robots. In short, they keep our society moving. Electric motors are never used alone. They convert electrical energy into mechanical motion, but to do so, their electrical currents must be precisely adjusted. This task is performed by power converters, so- called inverters, which convert DC voltage and current into the AC ones required by most modern electric motors. While the basic operating principles of electric motors have remained largely unchanged since their invention, still relying mainly on copper and iron, the technology used in power converters has evolved rapidly. This is driven by continuous innovation in power semiconductor devices. A recent breakthrough is the development of gallium nitride (GaN) monolithic bidirectional switches, which enable efficient realization of current source inverters (CSIs) without the high losses that previously limited their use. CSIs offer important advantages: they enable efficient motor operation, eliminate the need for current sensors, and apply smooth voltage waveforms to motor windings. Despite these benefits, CSIs are rarely used in practice and are often not taught in university drive courses, making engineers hesitant to adopt them. The uniDCm (universal DC machine) project addresses this challenge by functionally and physically integrating a CSI directly into the motor. In this concept, the inverter directly modulates the motor phase currents, so that the complete drive system can be viewed and supplied from the DC side. As a result, the combined system behaves like a classic DC machine from the users perspective. This approach fully decouples the internal motor type and control complexity from the user. Regardless of whether the motor is a permanent-magnet synchronous machine or a reluctance machine, the drive system behaves externally like a universal DC machine. The user is presented with simple plus and minus terminals, enabling true plug-and-play operation without requiring detailed knowledge of the motor or inverter technology. At the same time, the concept improves efficiency by reducing motor losses and allows the use of more cost-effective materials. In particular, it promotes reluctance motors, which require no permanent magnets and rely only on iron and copper, making them more sustainable and less dependent on critical raw materials. Overall, the uniDCm project enables any AC motor to behave like a DC machine, paving the way for more efficient, more sustainable, and easier-to-use electric drive systems.