King air 200 blown current limiters

[seriousflyer]

Hello,

I am hoping for some responses on the cause and result of a blown 325A current limiter in the king air electrical system.

I know it is there to protect the isolation bus from receiving to much current. But I am wondering how this current limiter would break sometimes ? And what does that mean for the generator bus ? All gen fed buses are u/s ?

Any discussion would assist me.

Thx,
Seriousflyer

[toelessjoe]

A current limiter is more like a slow blown fuse. eventually over time they can simply wear out. If it blows continuously it's obviously a sign of something wrong however they do eventually "fade to black" as it were. As long as both generators are online it's a non event (inflight). At least that's my understanding (and I'm freakin' brilliant).

Cheers,

- Toeless.

[Tim]

The 4 main buses are all dual fed, so if you happen to blow a current limiter it will have no noticeable effect because the other side is still getting power. If the opposite gen is offline too then you'll be running on batt only.

A good way to blow a current limiter is a cross-gen start instead of the proper gen assisted start.

[seriousflyer]

Why would the systems be running on BAT only if the one current limiter is "blown" and the opposite side GEN is offline ? Wouldnt the gen that is online run all the systems since all the buses are dual fed ?

[cdnpilot77]

Not all the busses are dual fed. The landing gear and windshield heat among other items are on the GEN busses that are not dual fed.

[Tim]

Why would the systems be running on BAT only if the one current limiter is "blown" and the opposite side GEN is offline ? Wouldnt the gen that is online run all the systems since all the buses are dual fed ?

i might be wrong, ill dig out my be20 book tomorrow and have a look.

[cdnpilot77]

Why would the systems be running on BAT only if the one current limiter is "blown" and the opposite side GEN is offline ? Wouldnt the gen that is online run all the systems since all the buses are dual fed ?

i might be wrong, ill dig out my be20 book tomorrow and have a look.

For the Dual fed busses you would still get your 28v to those main busses, as they are just that, dual fed from both generators. As I stated above, you would only have battery (24v) power to the GEN bus if you lost a Generator and the opposite current limiter.

[seriousflyer]

Thanks for the discussion, I understand the flow now.

[longestboat]

Hi. How old Is the 200? When starting the
The second engine in the older generation 200s
You must turn the generator on the already
Running engine off (after the gen load has come down a bit)
before you attempt to start
The other engine or it can blow the current
Limiter.
The newer aircraft have cross start protection
Built into the GCU which allows you to leave the geni online
Whilst starting the 2nd engine.

Just something worth checking with who ever
Flys / runs the engines.

[seriousflyer]

We have 7 BE20 and 6 of them have the GCU which I understand regulates the current flow from the different engine speeds.

SOPs are to start #2, once stabilized at 50%, turn on GEN to charge baterry, wait for load to drop below .3, GEN off.

Start #1, through 20% GEN #2 on, and assist #1, through 50% and stablized, check Current limiters, GEN #1 on.

These SOPS apply to all in order to blanket all the BE20 in the fleet.

We have a range of serial #s in the fleet which makes learning/teaching all the systems ...interesting.
#42 right up to #1342. We also have a HDC, which is a high density commuter, designed to have 11 pax, only 20 or so BE20 (HDC) made.

[CID]

They all have GCUs. The later ones have GCUs with cross start protection.