I'm studying "Micro-" Electronic Engineering, and as such, I'm fairly ignorant of power electronics in general, save for design concepts found in switch-mode/linear power supplies you might find in puny domestic (mains) powered stuff. And even then anything >100W is considered "high power" for us!
My question regards commercial jetliners, and electrical power generation/distribution. I've been reading through the fascinating stuff over at b737.org.uk. From the (surely) over-simplified schematic here I can see that the B737 has five main power sources for its various AC 115V 400Hz (and other) buses.
1) Ground power
2) APU
3) No. 1 engine
4) No. 2 engine
5) Batteries: "static inverter". Granted, this one probably can't even power hydraulics/pumps/etc...
Question: How on earth are all these alternating-current sources kept in-phase?
... or perhaps I should first ask this question: is there, in fact, any time when there is more than one source at a time connected to a single bus? I'm assuming that this must occur at least sometimes, at least momentarily - such as when switching between APU/ground/engines.
If the answer to the above is "no, one source at a time", then how do all the different systems cope having their power cut in and out to a source that could suddenly be completely out of phase? I see from the schematic that the APU can power "No. 1" and "No. 2" gen. busses during take-off. At some point, the APU has to hand things over to the engine-powered generators in-flight, right? How "smooth" is this transition of power sources?
As for DC power, are the batteries running in parallel the whole time helping "filter" the spikes? Or do sensitive systems have to assume "dirty", discontinuous power here as well and do their own filtering/conditioning?
Obviously I have no idea about aircraft systems, just curious!
My question regards commercial jetliners, and electrical power generation/distribution. I've been reading through the fascinating stuff over at b737.org.uk. From the (surely) over-simplified schematic here I can see that the B737 has five main power sources for its various AC 115V 400Hz (and other) buses.
1) Ground power
2) APU
3) No. 1 engine
4) No. 2 engine
5) Batteries: "static inverter". Granted, this one probably can't even power hydraulics/pumps/etc...
Question: How on earth are all these alternating-current sources kept in-phase?
... or perhaps I should first ask this question: is there, in fact, any time when there is more than one source at a time connected to a single bus? I'm assuming that this must occur at least sometimes, at least momentarily - such as when switching between APU/ground/engines.
If the answer to the above is "no, one source at a time", then how do all the different systems cope having their power cut in and out to a source that could suddenly be completely out of phase? I see from the schematic that the APU can power "No. 1" and "No. 2" gen. busses during take-off. At some point, the APU has to hand things over to the engine-powered generators in-flight, right? How "smooth" is this transition of power sources?
As for DC power, are the batteries running in parallel the whole time helping "filter" the spikes? Or do sensitive systems have to assume "dirty", discontinuous power here as well and do their own filtering/conditioning?
Obviously I have no idea about aircraft systems, just curious!