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 Post subject: 400HZ
PostPosted: Mon Mar 04, 2013 9:06 am 
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I'm working on a project on a military base where there are some small (120V, 100A) 400HZ panels fed by a static inverter. Are there any standards that address the arc flash hazard at 400HZ?

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PostPosted: Mon Mar 04, 2013 3:43 pm 
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owassatpk wrote:
I'm working on a project on a military base where there are some small (120V, 100A) 400HZ panels fed by a static inverter. Are there any standards that address the arc flash hazard at 400HZ?

Thanks

owassatpk wrote:
I'm working on a project on a military base where there are some small (120V, 100A) 400HZ panels fed by a static inverter. Are there any standards that address the arc flash hazard at 400HZ?

Thanks

IEEE 1584 is for 50Hz. and 60 Hz. systems. The short circuit calculations would be different due to the change in the inductance i.e. Xl = jwl and w changes but I don't know of any 400 hz. arc flash equations. Perhaps someone has a lead on other information regarding 400 Hz. The other issue is being a small 120V 100A panel would be excluded from the general IEEE 1584 equations anyway which are for 3 phase systems.

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PostPosted: Tue Mar 05, 2013 8:24 am 
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400 Hz is used on aircraft. The higher frequency allows the generator or alternator to be physically small relative to 60 Hz or 50 Hz. Aircraft can tolerate the short transmission distance 400 Hz has.

I looked at SKM Power*Tools, it seems to allow selection of a 400 Hz system. Path is Project->Options->Application. Did not go beyond that.

As the esteemed administrator wrote, if the military base panels are a single phase system, IEEE 1584 does not apply.


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PostPosted: Tue Mar 05, 2013 8:42 am 
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Actually, it could be 3-phase. I know aircraft (like the F111 shown in my avatar) use 3-phase 120VAC, 400 Hz in the flight control systems.


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PostPosted: Tue Mar 05, 2013 11:02 am 
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Larry Stutts wrote:
Actually, it could be 3-phase. I know aircraft (like the F111 shown in my avatar) use 3-phase 120VAC, 400 Hz in the flight control systems.


owassatpk wrote:
I'm working on a project on a military base where there are some small (120V, 100A) 400HZ panels fed by a static inverter. Are there any standards that address the arc flash hazard at 400HZ?

Thanks


brainfiller wrote:
IEEE 1584 is for 50Hz. and 60 Hz. systems. The short circuit calculations would be different due to the change in the inductance i.e. Xl = jwl and w changes but I don't know of any 400 hz. arc flash equations. Perhaps someone has a lead on other information regarding 400 Hz. The other issue is being a small 120V 100A panel would be excluded from the general IEEE 1584 equations anyway which are for 3 phase systems.


Thanks for the reply. I went back to look at the system again and found my original post was incorrect. The panel in question is 450V, 400HZ, 800A 3 phase. The panel is fed by two (2) 180kW inverters connected in parallel (input voltage is 480V, 3 phase). The inverters are "self protected" against external faults which I assume means they will shut down automatically if they sense a fault or overload condition, like a self-protected DC power supply. SKM will do calculations at 400HZ, but the internal impedance of the solid state inverters is not available and the inverters will shutdown if faulted in any case. It would seem the system has the capacity to develop enough energy to create an arc hazard, but the fact that the invertes are self protected would suggest the time would be very short, limiting the total energy. With the lack of guidance from the IEEE I'm not sure where to go with this?


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