I.A. Ivanov1, R.M. Uvaysov2

1, 2 MIREA – Russian Technological University (Moscow, Russia)

In the framework of this work, the source of secondary power supply is investigated. The object of study belongs to the class of on-board devices and is intended for use as part of the power supply system for manned aircraft.

In the course of testing the layout of the switchgear at the manufacturer, a number of significant shortcomings were identified related to the cooling of heat-loaded elements, as well as to ensuring the stability of the structure during harmonic vibrations. The operation of the device in extreme conditions, both thermal and mechanical, leads to overheating and further burnout of individual electrical radio elements, as well as to the destruction of the printed circuit board structure.

The solution to existing problems can be found by modeling thermal and vibrational processes using specialized software.

The initial data for solving modeling problems are the electrical circuit diagram and maps of operating modes.

The analysis of the initial data showed the presence of excesses of the permissible values of the load factor on a number of electroradioelements. Therefore, in order to achieve reliable and efficient operation of the power module, we will need to use additional cooling.

As elements of the system, the cooling will use the perforation of the device case for natural ventilation, as well as the placement of heat sinks. This decision is justified primarily by the fact that the use of forced cooling would require a change in the design of the device, a partial circuit change, an increase in dimensions, and also an increase in the noise of our product.

When arranging the power supply unit in the equipment, it is necessary to pay attention to the correct location of its heat-removing system in space. Natural or forced convection air flow must freely “wash” the heat-removing surface of the case or heat sink fins.

Modeling in the SolidWorks software package showed the efficiency of a ribbed heat sink, thanks to which it was possible to reduce the temperature on the most heated electrical radio elements from 120 °C to 77 °C.

Due to the peculiarities of operation of the device under study, the region of possible harmonic oscillations lies in the range from 5 to 2000 Hz. The key task in the design is the exclusion of resonant frequencies from the permissible range.

The original version of the design did not meet the required characteristics.

The following possible options for shifting the resonant frequency to the right were considered in the work: rearrangement, adding fasteners, adding stiffeners, thickening the board.

The layout of the printed circuit assembly was made in accordance with existing requirements and ensured a uniform distribution of electrical radio elements on the printed circuit board. The most massive elements were located near the rigid attachment points, which minimized their impact on mechanical characteristics. At the same time, it should be noted that the implemented layout, after adding the appropriate heat sink, provides acceptable thermal conditions.

An analysis of the remaining options under consideration demonstrated the need for a comprehensive technological solution in the form of additional stiffeners and fasteners.

Ivanov I.A., Uvaysov R.M. Research of thermal and mechanical characteristics of the on-board device of the secondary power supply. Science Intensive Technologies. 2022. V. 23. № 6. P. 21−30. DOI: https://doi.org/10.18127/j19998465-202206-03 (in Russian)

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