Powering tethered drones

Tethered drone technology provides insight into the evolving bills-of-materials for new generations of flying machines.

A Japanese engineering company, Fukaden Corporation, is enabling humanitarian efforts by providing power for mobile communication base stations designed into their tethered drones. These lightweight, portable drones can be deployed by first responders to deliver near-instant communication capabilities.

Fukaden has demonstrated its Power Control BOX II main power supply unit, which delivers power via a tether to the drone. It enables 1kW of power to be delivered up to 150m.

Also, power can be scaled by using units in parallel to triple the power to 3kW, providing cellular service to a 10km diameter.

Historically, the drawback of tethered drones was the thickness and weight of the power cable. Long, heavy cable adds weight creating more drag, which requires more power and limits the ability to add new drone features, such as sensors or high-resolution cameras.

Fukaden drones require 1kW to 5kW and increasing the supply from 24V to 370V reduces supply current by 15x. This allows thinner tether cable, which reduces the weight of the 1kW tether cable by more than 10x, from 125g to 11.1g per meter.
Running 370V requires a high density, lighter DCDC converter module in the drone to step the power down to 24V for the drive motor. The initial converter design was heavy and required too much space. So, the company replaced the converter with a Vicor DCM power module.

The Vicor DCM is an isolated DCDC converter module that uses high-frequency, zero-voltage switching (ZVS) technology and is characterized by high conversion efficiency and high output-power density. The DCM reduced the volume by 75 per cent and weight by more than 50 per cent.