Power Supplies and Distribution

POWER SUPPLIES & DISTRIBUTION

Power Supply Rack (PSR)

At the beginning of the project (in 2011), the simulator was powered by two multi-voltage computer power supplies.  The power supply had been adapted by adding a benchmark card that converted the input power to an output of 5, 12 and 24 Volts.  This power supply was adequate for a very basic set-up, however, there were inherent problems - least of all fuses continually blowing due to overloading of the 5 and 12 volt circuit.

Learning from this experience, the simulator now has several separate power supplies that are dedicated to a specific voltage and to a specific purpose or aircraft system. 

For the most part, these units are centrally located within the Power Supply Rack (PSR).  An additional 5 volt and two 12 volt power supplies, that direct power for the operation of the autothrottle, rotation of the trim wheels and Belkin hub, have been mounted within the Throttle Interface Module (TIM).

The power supplies are attached to an open frame L-shaped bracket with a removable plastic cover (attached using velcro). 

The reason for not using a totally enclosed structure is that the power supplies with use can become quite warm.  An open frame structure enables good ventilation and airflow.

The upper cover minimises dust settling on the upper power supply. The frame sits forward and to the right of the Main Instrument Panel (MIP).

Dedicated Power Supply to Specific Aircraft Systems

The advantage of using a dedicated power supply to a particular aircraft system is that if a catastrophic failure should occur, the issue will only be within that system and any power leakage/spike will not be able to travel to other systems (located on a separate power supply).  Further protection is provided as each of the power supplies has a tripping mechanism that protects the unit from overheating and/or an over supply of current. 

Each of the power supplies are parallel mounted with each supply linked together and requiring only one mains 240 volt power lead. 

Depending on the voltage and power requirements of various OEM components, power from the units is directed to either 5, 12 or 28 volt busbar(s) located behind the MIP, in the Throttle Communication Module (TCM) or located within the center pedestal.

Amperage

Operating OEM components requires a relatively high amperage draw, and whilst it's feasible to 'piggy back' two power supplies of the same amperage to effectively double your amperage, I have chosen not to do this.  I prefer to use separate power supplies. 

This ensures that the power components receive is 'clean power'.

L-bracket and Safety

The power supplies are mounted in a partly enclosed case (L-bracket) that, in addition to enabling fresh air to circulate, provides adequate protection to ensure that nobody accidentally touches the power supplies when they are turned on (240 volts is debilitating).  As a further electrical safeguard, each of the 240 volt terminals on the rear of the units has been covered in clear silicon.  The black and yellow tape provides a further visual warning.

A further safeguard is the smoke detector that will 'alarm' if smoke is detected (for whatever reason).  Additionally, there's an audible alarm that will sound if any single power supply reaches a predetermined temperature.

When the simulator is complete, the Power Supply Rack will be replaced with a more elegant option based along the same design.

Maintenance

Although the power supplies do not require maintenance, removal of dust, especially from those power supplies that have an internal cooling fan is necessary.  The cooling fan sucks in fine dust particles which accumulate on the components.  Over time, this dust lay can become quite thick and theoretically can cause the power supply to operate at a warmer than optimal temperature.  It's an easy matter to remove the casing from the power supply, and using a small vacuum, remove any accumulated dust.

Power Supply Type

There are many different power supplies available.  I have selected power supplies manufactured by MeanWell (MW) as these units will provide a constant source of clean power rated at 20% above the certification provided.  What this means is that if you run the power supply at 100% it has a further 20% before the unit will be damaged.

When the simulator was built, a simple maths equation was done to determine the amperage that each aircraft system required.  When the aircraft system was married to the power supply, the rating of the power supply was no more than 80%.  Therefore, each of the power supplies will not be operated at maximum output.

Mean Well power supplies provide protection from short circuit, overload and over voltage, in addition to other features such as fixed switching at 25 kilo hertz.  Furthermore, the voltage on each unit can be manually adjusted to ensure it's output matches the voltage required.  They also have replacement 2 year warranty.  Depending upon the power supply purchased, an internal cooling fan may or may not be included.  The power supplies can be operated in ambient conditions between -25 Celcius and 70 Celcius.  MeanWell power supplies are manufactured in Taiwan, not China.

The PSR philosophy enables for additional power supplies to be easily added to the L-bracket as they are needed.

The following power supplies are currently mounted in the PSR.

• LRS 350-24 volt 14.6 amp (set to 28 volts (2)

• 5 volt 30 amp (3)

• 12 volt 12.5 amp (1)

• 15 volt 5.6 amp (1)

Interface Module Power Supplies

The three interface modules operate directly from power in the PSR with the exception of the Throttle Interface Module (TIM).

TIM has three internal standalone power supplies. Two 12 volt power supplies provide the power to operate the autothrottle and main DC TIM system, and a 5 volt power supply provides power to a commercial USB hubs.

To have wired everything in TIM directly to the Power Supply Rack would have resulted in too many wiring looms and an excessive length of wire.

Legacy Power Supply Unit

Another computer power supply (5 & 12 volts) is mounted under and behind the MIP.  This legacy power supply is from Flight Deck Solutions.

The computer power supply was part of the MIP purchased from Flight Deck Solutions (FDS).  As the power supply is mounted out of the way under the MIP shelf, I couldn't see benefit in removing it.  Therefore, I use this power supply to power the backlighting for the MIP and the FDS System card.  If and when this power supply fails, I will direct this system to an appropriate power supply in the PSR.

Power Distribution

The flight simulator requires various voltages to function.  For example, backlighting requires 5 volts DC while OEM annunciators (Korrys) require 28 volts DC.  Power is distributed to the simulator from a rated power supply located either in the Throttle Interface Module (TIM) or the Power Supply Rack (PSR) via a several busbars and terminal blocks.

Busbars and Terminal Blocks

Installed behind the Main Instrument Panel (MIP) is a small shelf on which three heavy duty high amperage busbars are mounted (5, 12 and 28 volts respectively).  Each busbar connects directly to various components.  A further 5 and 12 volt busbar has been installed to the inside of the center pedestal, and these busbars provide 5 and 12 volt power for OEM panels, Belkin hub and an Ethernet switch.  Additional 5 and 12 volt busbars are located within the Throttle Communication Module (TCM) which is a small box position on the forward firewall of the throttle quadrant.

Every simulator will require several bus and terminal blocks.  Busbars are used to transfer power from a common voltage to an outlying source, whilst terminal blocks are used to segregate positive and negative wires from a device to a local power source.

it's relatively straight forward to convert an inexpensive terminal bar into a busbar by routing the power wire between each terminal.

For the most part, I have used marine-grade busbars manufactured by Blue Seas (an American company).  Although the clear acrylic covers are not necessary, I find they are convenient in minimising dust and reducing the chance that something may fall onto the busbar shorting out the terminals.

•  Updated 15 February 2024