B747 Electrical System
 

Hi,
Hoping to get confirmation on the average steady-state current requirements for powering a B747 during turnaround is?

Cheers,
G.

From the Airport Planning Manual for the 747-400:

Two co-located connectors, each rated at: 90 KVA, 200/115 Volts AC, 400 HZ, 3 Phase.

Thanks QA1, really helpful information. I'm looking at a theoretical situation where batteries could be used to provide power to this system during a 1 hour turnaround, as such the approximate capacity is of interest.

I assumed a 0.9 Power Factor which would suggest that the average power draw will be 81kW, and therefore 81kWh for a 1 hour turnaround. I'm from a mechanical background and am concerned with the logic I have used as this value seems quite large.

Wondering if I could get some feedback on this logic.
Cheers,
G.

Did I understand that you deduct that if the batteries are certified (=theoretically good for) 1h in emergency situation, that you can expect to perform a 1h turnaround on batteries only? If so, the I see a logic mistake here. I'm flying the 747 and without going into too much detail (in other words, I forgot))), there is a nice load-shedding logic build into the electrical system, and almost all ancillary power consumers (including most of the cabin lights, baggage door operation etc) are load shredded on batteries only.

What SSD says. Plus, the better designed and built Ground Power systems base their performance PF on 0.8.

I would also add, due load shedding, power consumption will vary a lot on the ground especially if you operated high current draw equipment. So an accurate steady state current draw will be difficult to determine unless you can get access the the Boeing Electrical Load Analysis information for the 747-400.

This is from Boeing in 2012, referring to standard 90kVA receptacles.

The 787 airplane utilizes two (2) forward ground power receptacles and one (1) mid-aft ground power receptacle. Each receptacle is rated at 90 kVA, as is standard on all Boeing current production widebody airplanes.

By design each receptacle can support continuous 90 kVA and a peak power consumption of 112 kVA for up to five (5) minutes regardless of the output capacity of the Ground Power Unit (GPU). For continuous supply, the airplane will draw less than 90 kVA from any receptacle.

Although the 787 is designed to perform a normal gate turn with two 90 kVA GPUs, Boeing recommends that a third 90 kVA GPU be available for non-normal engine start due to an inoperative Auxiliary Power Unit (APU).

Solid-state GPUs used for powering the 787 aircraft should meet or exceed the following inrush current levels:
Worst Case Max Current: 1100 Amps peak
Average Max Current: 730 Amps peak
Decay to less than 500 Amps within 10 msec
Decay to steady-state Amps within 130 msec.
Solid-state GPUs should be adjusted to the above specifications.

From your comments, it appears you want to power a 747 using external batteries for a one-hour turnaround. For a 747, this would be a very short stop, typically it would be closer to 2 hours
To establish the capacity required, you would need to look at the input spec for the inverter you intend to use that would provide the required two 90kVA outputs. The quality of the output of the GPU inverter would need to meet specs, such as DFS 400 / MIL-STD-704E / ARP5015A.

The above info was obtained from the internet, as I am only familiar with and have experience of the aircraft side of things. If the aircraft does not like the quality of the ground power, it will kick it off.

Looking at the energy required and the cost of batteries, I’m not sure if this is a feasible possibility.

Just what I was thinking, there is likely a very significant difference between peak demand and average.

One analogy: although your house has a 100 amp service (USA 120/240 2 phase) it would be very rare to see the meter on the side of the house spinning at anywhere that rate, even with all burners and the oven going on the electric stove.

Both peak and average values would be needed to size the inverter and batteries. My (non aviation specific) gut feeling is that you would be looking at a 'lot' of battery.

If you can add a trailer hitch to a 747 maybe a Tesla electric car would be about the right size :E


A GPU likely has ammeters that could give you a rough idea by logging peak current for each 5 (or even 1) minute interval during a 'typical' turnaround and then summing the 'amp/minutes'.

This would provide the battery capacity (amp/hours) after efficiency and voltages are factored in.

Of course this would not be worst case but at least one data point beyond assuming maximum draw the whole time.