Control of Cabin and Cargo Heaters in Aerospace Applications

The comparison between a proposed aircraft cabin and cargo heater control system and conventional control schemes is presented together with the key performance figures of the systems. An active AC/DC converter comprising a Phase-Locked Loop (PLL) is proposed to control the energy supplied by the AC Variable Frequency (VF) source to the heater loads instead of controlling the energy by means of a Pulse-Width Modulated (PWM) AC power flow. The proposed system eliminates problems associated with interharmonics generated in the AC VF PWM case - a material advantage. It draws a close to sinusoidal current from the VF source, features a near unity power factor, and operates within the VF range due to the use of PLL.