System architecture for real time power management.
A major characteristic of aircraft evolution is the rapid growth in the electrical and
electronic content of each subsequenat ircraft generation.T he dominant technology used
in an aircraft electrical power distribution network to switch power and to protect the
aircraft wiring from hazardous electrical faults is the electro-mechanical relay switch
and the electro-thermal circuit breaker. Despite the maturity of these devices they do
however suffer from a number of problems relating to reliability, accuracy, and limited
The design, fabrication and testing of a novel Solid State Power Controller (SSPC) is
described. The design uses power MOSFET's to provide both the power switching
operation of a relay, and the power interruption capability of a circuit breaker. The
majority of the control functions required by this device are performed digitally by
virtue of a real time program executed on an embedded microcontroller.
A number of methods are derived for characterising existing I2t wire protection trip
response curves. Reproduction of a true 1 2t trip response in real time using iterative
computational methods is described.
An examination of the semiconductor thermal characteristics was undertaken. The
methods adopted for extracting the power semiconductor thermal response involved
direct measurement using infrared thermal imaging techniques and simulation using a
computer based modelling tool. Knowledge of the semiconductor die temperature is of
vital importance in the context of the overall protection strategy. A finite difference
calculation performed in real time has been demonstrated as a viable method to predict
the operational temperature of the MOSFET power switching devices used in the