400 hz

rmgill · Sep 20, 2007

Hmm, i'll have to find out if DC rectifiers can work on 400 Htz. If they can then I can see running a whole house UPS system on it. Charge the batteries with the rectified DC and then use an inverter for the 60htz AC. Hmm, gonna have to call some vendors tomorrow.

OPCOM · Sep 20, 2007

Common rectifiers will work fine on 400Hz. There are also solid state converters to make 60Hz from 400Hz. Any large converter should be able to sync up it sphase to the normal power grid 60Hz and make for no glitches at time of transfer.

StrykerPerry · Jan 23, 2016

I would like to know how to convert mine also or if they are worth something to someone to sell or trade mine runs great and is in like new condition

papakb · Jan 23, 2016

There are a couple of ways to make 60 cycle power from 400 cycle sources but they're expensive and not very practical. Early methods were with "rotary converters" which are all that dynamotors really are. The electronic converters come in 2 flavors, modified sine wave and pure sine wave. Modified sine wave generators are basically square wave generators that product harmonics out the ying yang and therefore shouldn't be used around radios or devices that have transformers in their input circuitry because all of the hash generates lots of useless heat in inductive loads. Pure sine wave converters are much better but are going to cost you if you need much power.

Aircraft love 400 cycle power because transformers, motors, synchros and servos can all be made much smaller and lighter. The Air Force was never concerned with power consumption as much as with weight. The Navy on the other hand didn't care what it weighed as long as you could keep the power consumption down. Onboard ship we had 400 cycle synchros and servos in our radars and after living around them for years I have a dead spot at 400 cycles and no longer hear it.

Kurt
KG6KMJ

Wdr · Mar 30, 2016

I was just thinking after reading this thread, if you were wanting to run 3ph motors couldn't you use standard Variable Frequency Drives and supply them off a 400hz gen set? I'm not sure if any of the monitoring circuitry would be affected by 400 vs 60 hz in, I wouldn't think so though, the incoming line is rectified to dc so I would think the 400hz would actually be better? But I know it's recommended to oversize generators feeding VFDs by a large amount because of the harmonics the drive creats, not sure if the 400hz would reduce that.

papakb · Apr 11, 2016

400 hz was used in aircraft because transformers took less steel in their cores and therefore were lighter. The same held true of synchros, servos, and motors in general. The flyboys didn't care about how much power things drew since they had all then needed as opposed to the sailors who didn't care what it weighed as long and it didn't eat up too much power. The rule of thumb was never try to run 400hz stuff on 60hz and vice versa. The transformers and inductive loads will heat up and die and ugly death. Light bulbs and resisitive loads don't care what you feed them.

We had a radar with a 22 ton antenna (AN/SPG-49B) that used 400hz stuff because when it was originally designed in the 1950's it was a USAF project. The Navy added gyroscopic stabilization and stuck it on a ship as a part of a missile system so we inherited a lot of 400hz components.
.
rmgill, What radar unit do you have?

There's a lot of very nice Collins radio gear out there that runs on 400hz.

Kurt
KG6KMJ

patracy · Apr 11, 2016

Wdr said:
I was just thinking after reading this thread, if you were wanting to run 3ph motors couldn't you use standard Variable Frequency Drives and supply them off a 400hz gen set? I'm not sure if any of the monitoring circuitry would be affected by 400 vs 60 hz in, I wouldn't think so though, the incoming line is rectified to dc so I would think the 400hz would actually be better? But I know it's recommended to oversize generators feeding VFDs by a large amount because of the harmonics the drive creats, not sure if the 400hz would reduce that.

Interesting point you bring up. I'm playing with VFD's for a lathe I have. It will take up to 400hz input and output. Stands to reason you could dial it down to 60hz. The problem though is that you're presented with 220v outputs across all 3 legs. Not sure how you'd put that to use.

400 hz

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