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View Full Version : OT.. AN/TRC-27 genset output?



J Tiers
09-23-2005, 10:55 PM
As part of a related "iron problem"... got a couple engines recently.

One is the genset from an AN/TRC-27 microwave radio. No radio, just the genset. May be known as a PU-278.

Anyhow, the thing has a small 1.5 HP Briggs. Alternator is direct connected, 400Hz, 115V. Made in 1958, apparently the system was used through the 60's.

I don't have a handle on the genset electrical output power, but I'd like to know approximately.

The 400Hz generator, naturally, is physically much smaller than an equal 60Hz would be, and so size is a poor guide in this case. One can guess, but then there is de-rating for environment, etc, etc.

From the 1.5HP input, one could guess maybe 300-500W, given losses and military de-rating.

So far, google has not been helpful. I found places to get the complete system manual, or a complete ex-mil TRC-27 system, neither of which I want.

It's a long shot, but does anyone happen to know the actual electrical output rating of the genset?

CCWKen
09-23-2005, 11:19 PM
I can't help you specifically but the 500W range seems about right. An auto alternator draws about 1.5hp from the engine. Given the period, 32-55A was a common design. A few simple mods could easily produce 115vac.

J Tiers
09-24-2005, 09:23 AM
<font face="Verdana, Arial" size="2">Originally posted by CCWKen:
Given the period, 32-55A was a common design. A few simple mods could easily produce 115vac.</font>

I doubt if it is anything close to 55A, 5.5A is more like it. Already produces 115V... at 400Hz....

The variables here vs that usual calculation, (which would be right for a 12V automotive unit), include:
Military derating for all climates
direct 115V out
the 400Hz, which reduces sizes, may change efficiency
direct connection vs a lossy belt
Military demands for efficiency and light weight



[This message has been edited by J Tiers (edited 09-24-2005).]

CCWKen
09-25-2005, 09:59 PM
You missed the most important part of the quote.

<font face="Verdana, Arial" size="2">An auto alternator draws about 1.5hp from the engine. Given the period, 32-55A was a common design. A few simple mods could easily produce 115vac.</font>

To clarify, an automotive 12vdc alternator of that period would put out 32-55A. Also, the auto alternator could be modified to output 115vac. I did not mean to say that the mod would retain the 32-55A output. As you say, it would be closer to 5A.

J Tiers
09-25-2005, 10:14 PM
Didn't miss it, wasn't sure how it applied.

Actually I thought maybe you were under the impression this was a 12V, but it's already 115V by original design.

I guess we just didn't quite connect. No problem, thanks anyhow.