270 VDC in the avionics

The aviation industry is also seeing a trend toward using more and more electrical energy (power). And that’s not even mentioning fully electric flight! For this reason, there is a need to make improvements to both new and existing designs without increasing weight.

One solution to rising electrical consumption is to increase the voltage level of the aircraft’s electrical system. In recent years, we have therefore seen an increasing use of a third system based on 270 VDC, in addition to the 115 V/400 Hz AC and 28 VDC onboard electrical systems. This 270 VDC system for aviation was first defined in MIL-STD-704B on November 17. Battery systems in this voltage range have been in use much longer in the maritime sector, primarily due to their relatively high power density and capacity. The renewed interest in using the 270 Vdc network in avionics is also partly a result of the development of new electromechanical equipment capable of replacing traditional pneumatic and hydraulic systems.

Higher operating voltage improves electrical efficiency, contributes to weight reduction in aircraft, enhances aircraft safety and reliability, and has positive environmental impacts.

The 270 VDC is generated, among other methods, by rectifying the traditional 3-phase 115 VAC 400 Hz line-to-line voltages. In the event that the 3-phase generators are not running, parallel energy storage solutions (batteries, etc.) provide a permanent and redundant 270 VDC power supply. The aircraft’s 115V/400Hz AC network consists of three wires (phases A, B, and C, with N being the aircraft’s metal structure), while the 270VDC network is designed with only one wire (since the negative terminal can be formed by the aircraft’s metal structure):

As mentioned earlier, increasing the operating voltage makes it possible to reduce the weight and size of the wiring harness. Replacing the traditional electromechanical switch (which is heavy and bulky) with solid-state power controllers also contributes to this.

It is therefore important for developers and manufacturers of all equipment connected to the 270 Vdc grid to conduct testing in accordance with the applicable standards and regulations. Programmable DC power supplies, DC grid emulators, or even battery emulators are indispensable in such applications. Today, bidirectional power supplies can also be successfully deployed. With such a power supply system, both a DC source and a DC load profile can be realized. TT&MS BV supplies 270 Vdc power supply systems ranging from 100 W to 1 MW+, as well as 3-phase 400 Hz (800 Hz) AC generators and power analysis test equipment.

For more information, please visit the following pages:

1. Aerospace and aviation, electrical testing solutions
2. Commercial and military standards
3. Key electrical tests in the aviation industry
4. AC power supplies for avionics applications
5. 270 VDC in the avionics
6. APS4000 Simulation Software for Power System of Aerospace
7. Electrical Safety & Compliance Testing