Thomas Schulz wrote:
> In article <4852a4fe@212.67.96.135>, Dave <foo@coo.com> wrote:
>> I'm looking to use a Sun Netra T1 onboard an aircraft where the supply
>> is 120 V 400 Hz
>>
>> The specs on the Netra T1 are:
>>
>> 100 - 240 VAC, 47 - 63 Hz, 2 A (max)
>>
>> Has anyone ever tried running one at 400 Hz? My guess is that it is
>> unlikely to be an issue, as the input voltage will soon be converted to
>> DC in the switch mode power supply by a bridge and capacitors. A higher
>> frequency should have not be an issue there, and if anything gives the
>> capacitors an easier time.
>
> Actually the most likely problem would be the bridge. High power diodes
> can be quite slow (have a high stored charge) and can overheat if they
> are run at a high frequency. There are fast diodes available, but they
> cost more and are usually not used if not needed. This is definitely
> a problem in the part of the supply where the switching is done as the
> frequency there is usually over 20000 HZ. I am not sure if 400 HZ is
> high enough to cause problems, but it might be.
> If you try it and blow the bridge, most likely the only other thing that
> will be killed would be a fuse (I assume it does have a fuse). In that
> case the cost of the parts to fix it would not be very high.


I would have thought 400 Hz was pretty slow by semiconductor diode
standards, since the diodes are not going to be very large.

We believe we have solved the problem. We have a 400 -> 50 Hz converter,
but its too small to handle the power we need (it's not just the T1, but
other bits too, totalling about 1 kW). However, we will use that to
power some of the equipment (including the T1) and some other bits,
which we know are speced for 400 Hz will be run from the 400 Hz supply.