Aircraft Primary Power Distribution OverviewJan 27, 2022
Hello friends, my name is Andrew and welcome to the
powerlabs of Ametek Power and Data Systems. In a typical midsize commercial airplane or helicopter for a main system, there are actually three main system components: generation,
distribution, and storage. I would like to start this video by showing you the system and introducing you to the basic components of the system. Storage batteries are an essential part of the
aircraft's electrical system to provide safe backup
powerin case the
primarypower source fails. They can also benefit the system by acting like a large capacitor and providing a filtering effect on power lines.
The other major use of the battery is to provide starting power for the engine when no shore power is available because batteries only have limited storage, it is important to get the engines running On-board generators and power supply continuous electricity needed for
aircraftflight batteries come in various chemistries lead acid NiCad lithium ion each of the three has advantages and disadvantages for this lab setup we took the economical route by purchasing two 12 volt automotive batteries and connecting them in series to provide the necessary 24 volts that the electric aircraft electrical system expects to see, the key to a successful motor start is to have a source that can supply enough power to get the motor moving and this can require such high momentary currents like 1200 to 1500 amps for the first moments of the sequence the second part of the system is the power
distributiongrid electricity needs to flow to power the generators charge the batteries on the grid and most importantly provide power to essential flight electronics as well as the coffee pot and toilet waste pump necessary for those longer flights in this configuration that we have stripped down remove any enclosures that contain the distribution network and we can really get a good look at the various buses and interconnections in the aircraft system copper bus bars and heavy gauge wires are used to deliver currents with minimal voltage drop and various sensors are implemented to monitor the basic voltage-current parameters and all health shunts and hall effect sensors can be used for current measurement and current transformers are used for ensure that all current produced by the generating device is taken into account for c Each power source is connected to the grid and its usually isolated from each other by heavy duty switches called contactors, of which we have six here in this system, since these switches are closed electricity can flow to and from the various buses, contactors also play a key role in system safety by providing isolation. of electrical failures and the ability to establish bus architectures with different levels of criticality and required availability rates in the event of a system failure it may be necessary to remove non-essential loads and isolate the failure by opening the respective contactors depending on the complexity and automation of the electrical system the logic to handle these failures can be more pilot intensive complex systems have greater automation to reduce the pilot workload during these events and as systems continue to move more and more towards state switching solid and microprocessor controlled control, the whole notion of individual high current contactors will disappear and what we will start to see is virtual buses becoming a reality in aircraft systems, but that's a topic for another video.
On a twin-engine aircraft, these contactors can only close when the generators are producing healthy power. Here are also two other contactors in this system that may be less obvious, they appear to be in parallel with the generator contactors and that's because they are actually in this architecture. These contactors are specifically dedicated for the engine starting function when using the generator. as a motor to make the motor rotate during the first 20 seconds of the starting sequence these contactors handle the large starting current supplied by the battery or external power board once the motor starts and power is generated these contactors are open and the generator line.
The contactors now take control of the distribution of power from the generator. There are two remaining contactors in this system: the battery contactor and the bus link contactor, while the battery contactor is pretty obvious, it is used to connect and disconnect the batteries from the bus. The bus link contactor is really unique to a multi engine aircraft, often this contactor is left open during normal operation to provide g Good separation between the two generating sources and the two main buses, this bus link becomes useful for provide a redundant source of power to the loads and perform specific functions such as crossover engine starting assist where the active generator helps the battery wind up the second engine, the third piece to a
primaryelectrical power system is generation the generator is a rotating machine that creates electricity and relies on a powered motor to provide the rotational motion to produce voltage and current running we can basically produce up to 800 amps and that's with a cruising rotational speed of say 10 to 12,000rpm , this equates to approximately 22 kilowatts or approximately 30 mechanical horsepower to provide provide power to the entire aircraft to regulate the generator voltage a generator control unit is used to tightly adjust the field current within the generator to ensure that we have a solid and stable 28.5 volt output, the GCU is a one of the most important parts of the electrical system, as well as being the key component to control the motor starting logic.
A loss of voltage regulation can cause widespread electrical damage to aircraft loads. redundant testing and regulation functions exist in this unit so it's a quick introduction to our main electrical system in later videos we'll go into more detail of system architecture and performance and also demonstrate some boot generation sequences aircraft using this setup for more videos like this feel free to subscribe to our channel or visit us at AmetekPDS.com Thank you
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