Column: Airspace
Figure 1: VoloCity by Volocopter
High-voltage isolation in electric urban air mobility
By Mark Patrick, Director of Technical Content, Mouser Electronics O
ne type of urban air mobility (UAM) vehicle will be air taxis, typically envisioned as multicopters designed for electric vertical take-off
and landing (eVTOL). Tey are expected to be compact and quiet and yet equipped with the right systems to successfully deal with the constraints of densely-populated urban areas. Te propulsion system is required to liſt the vehicle, including the pilot, passengers and luggage – and batteries – directly into the air. Tis places a heavy demand on the power system. Aviation industry practice suggests this requires liſting power of 1.2-2.0 times the vehicle’s weight. Te Volocopter VoloCity (Figure 1) is
an example of the type that may be used in commercial taxi services. With a stated take-off weight of up to 900kg, assuming take-off power is 1.5 times vehicle weight, this requires some 1350kW. Since the VoloCity is an eight-rotor design, each motor will need batteries to supply it with 200kW. Since power delivery is limited by the maximum discharge rate, and to
14 March 2024
www.electronicsworld.com
mitigate the peak current demand and hence keep cable thickness and weight to a minimum, a high battery voltage is required. Although not stated in the manufacturer’s datasheet, if the voltage is 800V – which is comparable to some of today’s high-end roadgoing electric vehicles (EVs) – the current demand would be 250A.
High-voltage isolation Te high-power electrical systems involved in UAM can be dangerous if mishandled, so they must be safe. Additionally, systems working at a potential of hundreds of volts pose a threat to nearby devices operating in the same airframe. Tis means that high- and low-voltage elements must be kept separate to ensure functional safety. Isolating high-power components and
cables helps prevent electrical shock and protects against faults such as short circuits or insulation failures. Isolation is, therefore, essential to reduce the risk of injury to people and the vehicle’s electrical system. Isolation can also prevent disturbances such as high-voltage transients and voltage spikes from influencing low-voltage
electronics like sensors and signal- conditioning ICs, embedded controllers and communication systems. Isolation can also reduce electromagnetic interference, ensuring accurate data measurements and proper functioning of the vehicle’s electronic systems. For cables, thicker insulation supports
higher voltages; on the other hand, every cubic millimetre and gram saved can extend flying time. Choosing highly- integrated components with built-in isolation can save a lot of space. Tese can include isolated voltage sensors that combine signal conditioning, analogue- to-digital conversion (ADC), power and isolation in a single device. Tis will simplify designs, save weight and make onboard systems simpler, easier to integrate and lighter. One example of an integrated component
featuring isolation are digital sensors with built-in high-voltage isolation, like Texas Instrument’s TMCS1101/TMCS110-Q1 isolated current sensor shown in Figure 2. Tese are crucial for ensuring safety and reliable data acquisition, measuring various parameters without compromising the
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