DC to AC conversion and motor control
The system architecture
An electric propulsion powertrain, whether in electric road cars, Formula E race cars, emerging eVTOL aircraft, or marine propulsion systems, relies on three critical components:
The high‑voltage battery, the inverter, and the electric motor.
The high‑voltage battery, typically lithium‑ion and commonly operating at 400 V or 800 V, stores energy in chemical form that can be rapidly released as DC electrical power.
The electric motor is coupled to the drivetrain, wheels, or propeller and is responsible for converting electrical energy into mechanical power for propulsion and absorbing mechanical power during regenerative braking. Modern powertrains typically use a three‑phase, permanent‑magnet motors because they offer high torque density, excellent efficiency and compact packaging across a wide speed range. These characteristics make them ideal for automotive, aerospace, and marine applications where performance, efficiency and weight matter.
Located between the battery and the electric motor is the most intelligent and arguably complex part of the system, the inverter.
The inverter at the heart of DC to AC and motor control
The inverter sits between the battery and the motor and performs bi‑directional conversion between DC and AC power. The inverter consists of six high‑power semiconductor switches arranged in a three‑phase bridge, controlled by a complex control unit. By switching these devices in a carefully timed sequence, running complex control algorithms in micro-second intervals, the inverter produces a three‑phase AC waveform from the battery’s DC supply.
The amplitude and frequency of the AC voltage determine the motor’s torque and speed. The inverter constantly adjusts the amplitude and frequency of the output voltage based on driver demand, vehicle conditions, and safety limits, becoming the true “heart” of the electrified powertrain.
What makes a powerful inverter
A high performance inverter must deliver exceptional capability across electrical, thermal, mechanical, and software domains. Key attributes include:
- Compact and lightweight: Allows for the unit to, fit within the tight packaging and weight constraints of a vehicle.
- High efficiency: Maximise EV driving range, reduces thermal losses, and limits cooling-system size. Modern silicon carbide power modules can switch at >20kHz for maximum inverter efficiency, however balancing inverter and overall system efficiency often relies in delicate trades offs and overall system efficiency conditions.
- Ability to handle high DC-link voltages:, To match the demands of today’s 400 V and 800 V battery systems, the inverter must operate reliably at high DClink voltages. Doing so unlocks higher performance, reduced current for a given power level, and lower conductive losses.
- Advanced software control: The control platform must be, able to respond instantly to changing power demands, such as rapid acceleration or braking events, or reacting safely in crash events.
- High currents and high frequency capability:, Inverters deliver the currents and switching frequencies to support the delivery of the high torque, speed and power levels required for high‑performance electric powertrains.
- Low harmonic distortion and precise control: Minimising harmonics and nonlinearities ensures smooth, quiet, and accurate motor operation across the full torque–speed envelope.
In essence, the inverter must combine power electronics, thermal management, software engineering, and control theory into one compact platform.
Why our MCU Product Family hits the mark.
The Motion Applied MCU-600 inverter and MCU-X platform are engineered specifically to excel in demanding electrification applications. They deliver world‑class power density, compact size, and low mass, making them ideal for high‑performance automotive, aerospace, and marine propulsion systems.
At their heart are 800 V silicon‑carbide (SiC) power modules, enabling high switching frequencies, fast dV/dt transitions, and exceptional efficiency. Silicon carbide not only reduces losses but also allows for smaller cooling systems, pushing system power density to new levels.
MCU-600 and MCU-X incorporate novel and patented motor-control algorithms, providing precise torque delivery, fast transient responses, exceptionally smooth operation, and have developed to ASIL-D ISO26262 functional safety standards. Combined with their thermal robustness and mechanical packaging optimised for demanding environments, the MCU Product Family represents a new benchmark in inverter technology.
Article by Mark Tatlow, Head of Engineering, Electrification