Calculating Lithium-Ion Battery Size for 90KVA 200/115V 400Hz 3-Phase AC System

Hi,

Interested in sizing some DC lithium-ion batteries (through a controller) to power the following system: 90KVA, 200/115 Volts AC, 400 Hz, 3-phase. 

The current approaches I've taken have been drastically oversized so I'm clearly missing something. 

Cheers,
Gaz.

You present a 450 A load demand and that is without considering any conversion losses -- it is not going to fit in your pocket. Why 400 Hz - are you dealing with an avionics system?

Show us your computations.

Hi James Ruggieri,

Yes it is an avionics system.

Currently I am assuming a 0.9 PF indicating an average 81kW consumption. Even operating this for an hour would require considerable battery capacity.

Well - if you are addressing an emergency backup situation - for your power needs the usual route is a diesel-generator feeding a 400 Hz motor generator. The battery approach is just too messy, too large and too complicated.

If your power requirement is 90KVA, 200/115 Volts AC, 400 Hz, 3-phase, then I assume the battery is for backup. You can go the generator route as JR says, but its not going to be an UPS. The system you are powering will take a hit during the generator transfer. A straight UPS, would need a battery that would probably be way to big for your wants. A generator and UPS would allow a smaller battery, since it would only be needed to carry the load for the time it takes for generator transfer, plus it would be uninterrupted switching.

Thanks for the feedback guys, you pose some interesting alternatives to explore. I have limited specs for the system, and was wondering from your experience although the system is defined as 90KVA, what would the expected KVA during steady state actually be, or is this very variable to the specific system?

Hi Garry,

The 90 KVA is the capacity of the system at full load. When you size your battery, to be cost effective, you want to determine what your system (load) is actually drawing. Say its only 45 KVA, or approximately 225 A, then you would size your battery on several factors. One, how long realistically do you need the system to run, before commercial power is restored? 10 min...20min...8hrs? Based on the battery specs in Amp/hr will determine how long the system can expect to run on battery. There are other factors, such as temperature, but you get the idea.

I do not know if your system is addressed by the FAA, but you may want to persuse the FAA database of Advisory Circulars that govern avionics systems, such as Visual Landing Aids, etc. in which case, they invoke certain requirements and architectures, including emergency power.