DIY 115V AC 400Hz Power source

[kyndal]

Hi guys.  

I'm considering taking on a  project.  where I need to power some aircraft equipment 
that runs  110 / 115 VAC  at 400 Hz 
preferably build a fairly beefy source.  maby 500w

I'm considering attempting to modify an automotive 12V DC - 110V AC 60hz  inverter 

I'm hoping to just "bump up"  the output frequency..  so to speak
I am of course also aware that it's not that simple.  hoping for some input

my understanding is that Topology wise, the 12V DC is switched at much higher frequency..  in the khz range  as a boost converter?   then rectified. and re-switched at 60hz ? 
square or sine  for the output

Would it be feasible to modify the output part for the higher 400hz frequency if I found a suitable victim ?
(wind up the imaginary NE555 in there)

or is this approach not the way to go? 
thoughts?  previous attempts ?

[Circlotron]

If you need a sine wave I'd try a 400Hz sine oscillator -> eBay class D amplifier -> step up transformer. Those amplifiers cost next to nothing nowadays.

[moffy]

If trying to hack a 12V to 110V inverter you will most likely come across this board or similar: https://www.ebay.com.au/itm/191994422854
that is what you would need to hack to change the frequency, not sure it's doable easily.

[BrianHG]

Get a mono class D car audio amplifier which can do 1000 watts continuous into a 4 ohm load.
Add a 60v to 120v 750 watt toroid transformer which can do 400hz.

Supply 13.8v DC to the amp and a 400hz sine wave at 1v rms to the audio input and you will clear 500 watts at 120v output.

You can also look at variable frequency high voltage pure sine-wave BLDC motor controllers.

[IanB]

or is this approach not the way to go?
thoughts?  previous attempts ?

It really depends on your budget and reliability/quality constraints. You can buy an "aircraft ground power supply" that will provide a clean, reliable, pure sinewave 400 Hz AC output at various power levels for somewhere around $1500. You may be able to find such a power supply used/surplus for less than the new purchase price?

[Stray Electron]

  Go to Ebay and look up the Elgar AC Power Sources.  They're made specifically for what you want to do.  They're heavy and expensive to ship so there's practically no market for used ones so if you can drive to the seller's location and pick them up in person, they can be had very cheaply IF the seller really wants to sell it and not to set on it and hoping for a pot of gold!  I've bought several for less than $1 per pound weight.

   The frequency is set by the plug in module so either buy one with a 400 Hz module or a variable frequency module, or buy the module separately.

    One of the GOOD things about the Elgars is that they are rock solid and all their documentation is online somewhere, but you'll have to figure out what docs you need and the correct name so that you can search for it.

    Other companies make similar devices but Elgar is by far the largest seller and has a wide selection of power, frequencies, number of phases,  etc etc,

[jonpaul]

We used motor generators from Surplus

The Elgar, Kikusui are VERY heavy and costly

What's exactly is the load, Avionics equipment? Synchros?

j

[IanB]

This one is not that heavy (about 10 lb / 5 kg):

https://www.powerstream.com/frequency-converter-60hz-400hz-500w.htm

Probably worth looking on the used market for this or other manufacturers.

[kyndal]

thanks guys,  a lot of good input already. 

some suggestions to buying existing one.   unfortunately the USD 1500$  cost is a bit more than hoped for.
I like the idea of an Audio (sine generator)  class D amplifier. 

I wonder what would happen, if I managed to find the 60hz generating circuit in an off the shelf 30$ inverter. 
and injected a 400hz  square or tone instead..

[IanB]

some suggestions to buying existing one.   unfortunately the USD 1500$  cost is a bit more than hoped for.

Have you looked around on eBay or other such sources for used/surplus equipment?

[kyndal]

I have been keeping an eye out..
I'm hoping to make a couple.  if I can figure out a nifty hack

[BrianHG]

Find a car amp or home audio amp which can do a true 2000 watt into 8 ohm and it will have enough voltage headroom to deliver 120v ac, up to 2000 watts.

Note that some home or pro stereo 500 watts/channel amps (for 8 ohm speakers) run in 'bridged' mono mode  will also deliver 120v ac directly at speaker terminals up to 1000 watts max. (True 500watts RMS, not peak 500watts, otherwise you will need a 800watts peak per channel amp...)

However, remember you need to feed the left channel a true 400hz 1vrms while feeding the right channel an inverted version of the same 400hz unless your amp has a built in bridge function for 2x/4x the power output.

Also remember that there is no longer a true GND as one channel goes up 79v while the opposite channel goes down to -79v.  The amp GND and chassis will be stuck in the center at 0v.