A Choice of Acceptable Sections of Electric Wires and Cables in on-Board Circuits of Aircraft Electrical Equipment

Abstract

Purpose. Implementation of choice of maximum permissible sections S il of the uninsulated wires and insulated wires (cables) with copper (aluminum) cores (shells) in the on-board power circuits of electrical equipment of different aircrafts with AC current of frequency f>50 Hz. Methodology. Theoretical bases of the electrical engineering, electrophysics bases of technique of high voltage and high pulsed currents, applied thermal physics. Results. The engineering approach is developed for a calculation choice on the condition of thermal resistibility of aircraft cable-conductor products (CCP) of maximum permissible sections S il of the uninsulated wires, insulated wires and cables with copper (aluminum) cores (shells), polyvinyl chloride (PVC), rubber (R) and polyethylene (PET) insulation, on which in malfunction of operation of on-board aircraft network with AC frequency of f>50 Hz flows of i k (t) current at single phase short circuit (SC) with given amplitude-temporal parameters. It is determined that in the onboard power circuits of electrical equipment of aircrafts (f=400 Hz; for permanent time of slump of T a =3 ms of аperiodic constituent of current of SC) maximum permissible amplitudes of current density of δ ilm ≈I mk /S il of single phase SC at time of its disconnecting t kC =5 ms in the on-board network of aircraft without dependence on the numerical value of amplitude I mk of the given current of SC for the uninsulated wires with copper (aluminum) cores is accordingly about 2.48 (1.40) kA/mm 2 , for wires (cables) with copper (aluminum) cores (shells) and PVC (R) with insulation-1.85 (1.18) kA/mm 2 , and for wires (cables) with copper (aluminum) cores (shells) and PET insulation-1.53 (0.99) kA/mm 2. The influence on a choice in the on-board network of aircrafts of maximum permissible sections S il of its CCP and accordingly maximum permissible amplitudes of current density δ ilm of current copper (aluminum) parts of its wires and cables of frequency f of AC in the on-board network of aircraft is determined, but duration of flow t kC (time of disconnecting) renders in the on-board network of aircrafts of emergency current of SC i k (t. For diminishing in the on-board power circuits of electrical equipment of aircrafts of maximum permissible sections S il of the electric wires (cables) applied in them and accordingly providing of decline for different aircrafts of mass and overall indicators of their on-board CCP is needed in the on-boar networks of aircrafts along with the use of enhance frequency of f=400 Hz of AC to apply the fast-acting devices of their protecting from SC in course of time wearing-outs of t a <<100 ms. It isshown that application of enhance frequency of f=400 Hz of AC in the on-board networks of aircrafts as compared to its frequency of f=50 Hz results in the considerable increase (in four times) of fast-acting of devices of their protection from SC, operation of which is based on the air electric explosion of metallic wire. Originality. First for the on-board network of aircrafts wi...

A Refined Mathematical Model of Physical Processes in a Conductor at a High-Current Pulse Discharge

“…Physical phenomena associated with the study of multiphysics processes occurring in conductors when pulse currents flow through them are relevant. This is confirmed by both International Standards [1,2] and a number of publications [3][4][5][6][7][8][9][10][11][12]. To the greatest extent, this concerns the study of the processes occurring in conductors during high-current short-term electrical discharges, which are accompanied by a number of complex and interrelated physical phenomena [9][10][11][12][13].…”

“…In a number of cases, the calculations are based on the introduction of "normalizing coefficients", which are introduced when determining the Joule integral ("action integral" in these works). This approach is justified, which is confirmed experimentally, if the frequency of the processes is low: 50-400 Hz [6,7] (the penetration depth of the electromagnetic wave is greater than the transverse dimensions of the conductor). If we consider short-term pulse processes [3][4][5], then before using approximate formulas, it is necessary in each specific case to estimate the penetration depth of an electromagnetic wave, at least in a steady-state mode [10,14], comparing it with the dimensions of the conductor.…”

“…The processes considered in [3][4][5][6][7][8] concern "the execution of an approximate calculation of the critical and maximum permissible cross-sections and current densities in wires and cables". In a number of cases, the calculations are based on the introduction of "normalizing coefficients", which are introduced when determining the Joule integral ("action integral" in these works).…”