400 hertz

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muskrat

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St. Louis, MO
Do any of you have any experience/suggestions/code references for hooking up a transformer that's 480v-225a-60hz input and 400 hz on the output side?:confused:
 
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petersonra

Senior Member
Location
Northern illinois
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engineer
muskrat said:
Do any of you have any experience/suggestions/code references for hooking up a transformer that's 480v-225a-60hz input and 400 hz on the output side?:confused:
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A transformer cannot change the frequency.

Perhaps a motor-generator or inverter of some sort.

I have a fair amount of experience with 400 Hz systems. It's not a lot different than 60 Hz. You will have to apply some derating to larger conductors, like > 1/0.

If you used (2) 1/0 in parallel, it would probably be adequate for 225A. I would have to find my derating chart. I use 900 Hz, and it is worse there. The ampacity of a 1/0 conductor is reduced by about 25% at 900 Hz versus 60 Hz. However, with larger conductors the effect gets worse, so a 4/0 conductor loses about 40% of its ampacity at 900 Hz. I pulled these numbers from spreadsheets used for designing at 900 Hz. I don't have easy numbers to grab for 400 Hz, but the effect is much less there.

Fuses and circuit breakers will work a little different and their interrupting rating will be less at 400 Hz versus 60 Hz. Most of the manufacturers have pretty good data about this effect.

Here is a summary based on information from Square D. It's probably not much different for others.

The interrupting capacity of most Square D circuit breakers at 400 Hz is only about 10% of what it is at 60 Hz.

The thermal rating is reduced. I.e. - a 100 A nominal breaker might end up being a 90 A breaker. There is no formula for this. It is different for each family of breakers and for each load. They have charts that shows what it is.

The magnetic rating goes up by about 2.6 X. So a breaker that would magnetically trip at 100A at 60 Hz, will take 260A to trip at 400 Hz.

Use aluminum or plastic conduit or cable tray, if at all possible.
 
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jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
petersonra said:
A transformer cannot change the frequency.

Perhaps a motor-generator or inverter of some sort.

I have a fair amount of experience with 400 Hz systems. It's not a lot different than 60 Hz. You will have to apply some derating to larger conductors, like > 1/0.

If you used (2) 1/0 in parallel, it would probably be adequate for 225A. I would have to find my derating chart. I use 900 Hz, and it is worse there. The ampacity of a 1/0 conductor is reduced by about 25% at 900 Hz versus 60 Hz. However, with larger conductors the effect gets worse, so a 4/0 conductor loses about 40% of its ampacity at 900 Hz. I pulled these numbers from spreadsheets used for designing at 900 Hz. I don't have easy numbers to grab for 400 Hz, but the effect is much less there.

Fuses and circuit breakers will work a little different and their interrupting rating will be less at 400 Hz versus 60 Hz. Most of the manufacturers have pretty good data about this effect.

Here is a summary based on information from Square D. It's probably not much different for others.

The interrupting capacity of most Square D circuit breakers at 400 Hz is only about 10% of what it is at 60 Hz.

The thermal rating is reduced. I.e. - a 100 A nominal breaker might end up being a 90 A breaker. There is no formula for this. It is different for each family of breakers and for each load. They have charts that shows what it is.

The magnetic rating goes up by about 2.6 X. So a breaker that would magnetically trip at 100A at 60 Hz, will take 260A to trip at 400 Hz.

Use aluminum or plastic conduit or cable tray, if at all possible.
Click to expand...

Aw phooey, doesn't it ever get easier?
 
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muskrat

Member
Location
St. Louis, MO
So I called it wrong-Inverter (EPU). Feeding a radar for Air Nat. Guard. 480v 225 a feed on the primary side of 2 EPU. Coming off secondary 120/208 at 400 hz to a transfer switch so either one can feed another transfer switch to have stand-by power for the radar.
 
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