Effects of 400HZ on power supplies.

[Crazeey2]

I know that certain aircraft run at 120Vac/400HZ and I understand the reasons behind. My problem is that I am using a standard 120Vac/60HZ ATX power supply. We were able to test that it does indead work at 400hz and higher. My question is, what effects will this have on the power supply? Shorter Life span etc.....

Thank you for your time,

Sincerely,

Josh Noonan

 

[nx4me]

Hello,

I can only offer information based on my experience. I fly 747's and have been using my laptop on ships power (400hz) for over 4 years with no ill effects to date.

Hope this helps,

Marshall

 

[tfhastie]

Transformers are optimized to work at a specific frequency, and I bet that your ATX powersupply probably has a transformer inside that steps the 120VAC down to whatever the output voltage is supposed to be (~12VAC if it outputs 12VDC...etc)...

If you change the frequency that you pump into the transformer, you run the risk of overheating it. The core of the transformer is designed to be most efficient at one frequency (i.e. 60Hz), so if you change the frequency, the core may heat up and wear out sooner. This is why some hair-dryers burn out if you take them from North America (60Hz) to Europe (50Hz... I think)...

Anyways... I'd keep a close eye on the temperature of your powersupply if you're gonna be using it on a 400Hz system... I'm not an electrical guy, , but I know that there are some issues with changing input frequencies of AC equipment.

 

[dpc]

I believe that some aircraft are equipped to provide 120V at 400 Hz, since it is readily available. I would be surprised if a standard NEMA receptacle was used, but I don't really know.

I do know that United Airlines has information on their website regarding need for special laptop power supplies to allow use of 400Hz power.

I doubt that your battery problems are related to the 400Hz issue. Heck, I've lost three batteries on my laptop, and it's hardly even left the office.

As for airplane use of 60Hz fluorescent lighting, I believe most still use special 400 Hz ballasts.

I think some newer aircraft are providing 60 Hz power, but keep in mind that the added weight of additional inverters is not something airlines take lightly (no pun intended).

400 Hz is used to save weight and weight is still money when you have to lift it in the air.

 

[BrianR]

The power supply adaptor for a laptop uses a switching power supply which is much more tolerant of higher frequency power than a regular transformer based power supply, (like found in a plug-pack). Plug-packs will get hotter on 400Hz because they have an iron cored transformer and the amount and grade of iron is calculated for 60Hz (unless the product label specifies otherwise). A 60Hz design gives more iron of a lower grade than a 400Hz design, and the increased iron losses cause a temperature rise.

 

[Iwe007]

Crazeey2,
How did you test, that your power supply was running directly on 400 Hz supply? and more (up to what frequency?)
I worked on Aircraft Electrical Power Generation and Distribution System (EPGDS)design, and I know the following:
1. After the generator produces the constant frequency alternating current power rated on average at (115 Volts, 400 Hz) this power is conditioned (i.e. changed / transformed / rectified (changed from ac to dc)) before it is distributed to the specific equipment users based on their specific power supply specifications. For example, in the Regional Jet design I worked on there is a 120VAC,60 Hz outlet in the cockpit. True, there is frequency tranformer action (conditioning) happening upstream between this outlet and the 400 Hz generator.
2. Most Aircrafts use 400 Hz Constant Frequency power.
3. Hamilton Sundstrand, a division of United Technologies has a monopoly on this generator system. This company has comfortably hiked prices on this generator and forced customers to pay through the nose!(feels like another Microsoft case?)Those who hate monopoly are doing something about it.
Think about this: Boeing wants to start using Variable Frequency power on their jets! This means, that the upstream equipment is no longer 'seeing' 400 Hz constant frequency but depending on the speed of the turbine engine the equipment will see anywhere from 360 Hz to 720 Hz !
The effects: Change in frequency affects rotating equipment, including electric motors to hair (blowers) dryers!etc. Frequency is a function of rotating machine speed, torque and current draw. Simple fact to remember regarding changing the frequency: At lower frequencies than the rated design spec, the motor will draw a lot more current, at higher frequencies the motor will run with much less torque to the extent that it might fail to rotate the load connected to it (it is called stall doode!)

 

[guzzizoomr]

I would concur with what Iwe007 offered. We manufacture aircraft lighting systems where I work, the vast majority of which are 400 Hz. We have been asked to manufacture a "wild frequency" ballast for fluorescent lighting on one of our customer's ships, from 50 to 480 Hz. We were able to do it, but they never did tell us why they wanted to accept such variable frequencies. Getting back to your question, I'd watch how hot your transformer gets, because they are optimized for a certain frequency. Considering how little they cost, I wouldn't want to have to put out a fire at 35,000 feet because I was too cheap to use the proper equipment for the proper job. "Adapting" general purpose equipment for aircraft use is not something to be taken lightly (I did just that for 12 years).
Good luck.

 

[ssp3194]

Typical ATX power supplies rectify the incoming ac power to generate a dc voltage which in turn is converted to low voltage power supplies for the motherboard, drives etc. The effect of 60Hz or 400Hz is pretty much lost after rectification. If the rectified dc filter capacitor is not rated for the higher ripple frequency, you could get overheating and failure but in general this will work because of higher quality of parts (capacitors in this case).

 

[andrewg85]

The basic functioning of a switchmode power supply:

The input power is rectified from AC into DC. So if you input 240Volts AC you get 240 Volts DC (minus 0.6 volts in the rectifier diodes)
The DC is then switched on and off at a high frequency to go through a transformer (as transformers do not convert DC and work off mutual inductance, when each time the power is switched off, the magnetic field is induced into the other coil producing a secondary voltage).
The transformer puts out the voltage it was wound for and then again, the voltage is rectified and filtered.

So running a swichmode power supply at 400Hz shouldnt be much of a problem.
Andrew.