POWER SUPPLIES - Power Supply Rack (PSR)
At the beginning of the B737 project, the simulator was powered by two multi-voltage computer power supplies. The power supply had been adapted, by adding a bench mark card that converted the input power to an output of 5, 12 and 24 Volts. Whilst this power supply was adequate for a very basic set-up, there were inherent problems; least of all fuses continually blowing due to overloading of the 5 volt circuit.
Learning from this experience, the simulator now has power supplies that are dedicated to a specific voltage and to a specific purpose (aircraft system).
For the most part, these units are centrally located within the Power Supply Rack (PSR). This said, the throttle system does not utilise power from the PSR but has dedicated power supplies mounted within the Throttle Interface Module (TIM).
LEFT: Power Supply Rack (PSR). The units are attached to an open- air L-shaped frame with a removable plastic cover (attached using velcro). The units are not totally enclosed as they become quite warm during use and operate optimally with good air circulation. The cardboard upper cover minimises dust settling on the upper unit. The frame sits forward of the MIP in the corner of the room, or can be located directly in front of the CDU bay (behind the MIP). The warning tape is to remind me to turn off the mains power before adjusting any unit - 240 Volts will kill you! The smoke detector will 'alarm' if smoke is detected.
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.
The power supplies have a tripping mechanism that protects each unit from overheating or an over supply of current, they are parallel mounted with each supply linked together and requiring only one main 240 volt power lead. The power supplies are placed in a partly enclosed case; the case minimizes the chance of accidently touching a live 240 Volt wire and places all the units in one area.
Depending on the voltage and power requirements of various components, power from the units is directed to either 5, 12 or 28 volt busbar(s) located behind the MIP or located within the center pedestal.
There are many different power supplies available. I have selected S150 models produced by Meanwell. These power supplies provide protection from short circuit, overload and over voltage in addition to other features such as fixed switching at 25 kilo hertz. They also have replacement 2 year warranty.
The PSR philosophy allows for additional power supplies to be easily added to the rack as the project expands.
The following power supplies are currently mounted in the PSR.
- One 12 volt 12.5 amp units
- One 5 volt 30 amp units
- One 28 volt 5.6 amp unit
- One 16.5 volt XX amp unit
- One computer power supply (5 & 12 volts) mounted in MIP (legacy from Flight Deck Solutions)
The computer power supply was part of the Main Instrument Panel that was purchased from Flight Deck Solutions (FDS). Rather than waste this power supply, I have used it to supply the power requirements to illuminate the MIP backlighting and to power the FDS System card.
Additional power supplies will be required to operate the forward and aft overhead panels which includes the two map lights.