Use 3 Phase Iron on the Single Phase Rig - No Converter

[WA1HZK]

I know this is old information to a lot of the "Big Guns" but say you have a KW BC Rig or a 2KW amplifer or something stupid and you blow up the power transformer due to the fact it's older than dirt. Consider the three phase transformers pulled out of the 5KW class & up transmitters. I had let the smoke out of my 833 rigs plate iron last week and had to send it to it's next life in Dipsy Dumpster land. Bummer, no good iron laying around the shop. I had stripped a 5KW FM rig last fall and sold the pieces on E-Bay. That made me some money and gave me a nice radio cabinet which was what I was looking for anyway. The 3 phase iron in the rig could not find a home with any of the locals. It was stashed in a container & on it's way to a tower base project. Would have made a nice anchor. Anyway, I figured that I should take that iron over to the shop and hook it to my 220 VAC variac and see what I could do with it. The thing had three primaries wired for 208 or 240 volts and a plus or minus 10% tap also. The secondaries were "Y" connected and used to make 3000/3800 VAC at several amps. I connected up the center primary and cranked up the power. I got about 2500 volts out of the center secondary and no hum. I then connected another primary in parallel and cranked up the power. Massive hummage & no volts. I then cross connected the two primaries and tried it again. No hummage and lotsa equal AC volts on two of the three secondaries. I also tried powering up the third primary in both phases but you know that was not going to work. The good news was that I had 2/3's of a 5KW-CCS Thansformer working! In "Ham Use" That's still a lotta snot! I series connected the two hot secondaries and was able to get 5 KV plus! I moved the taps down on the primaries to max windings to get minimum voltage on the secondaries and used the lower voltage tap on the secondaries to get the RMS AC plate volts I needed for the 833 rig. Works perfect and now I have a dozen possibilities on selecting taps to raise or lower the voltage to the rig. Don't throw those 3 phase transformers away! They work pissa for the old tube rigs. I just stuffed mine into my console and ran the promary & secondary power remotely to the transmitter. PS, high winds may take the first floor off of the house but the rig will still be there due to the force of gravity on that old iron.
Keith
WA1HZK

[flintstone mop]

It definitely pays to experiment!!! Put Peter Dahl on notice!!!

Fred

[fg5fc]

Dear OM,
I'am new on the forum and i just read your post about using a three phase transformer connected to be used as a mono phase transformer. I agree with you about the connection's diagram, but i wonder if the size of the wire( primary and secondary) of the transformer should not be too small to give the 2/3 of the power even if the iron is OK!

Best 73's from John FG5FC
Guadeloupe,FWI

I know this is old information to a lot of the "Big Guns" but say you have a KW BC Rig or a 2KW amplifer or something stupid and you blow up the power transformer due to the fact it's older than dirt. Consider the three phase transformers pulled out of the 5KW class & up transmitters. I had let the smoke out of my 833 rigs plate iron last week and had to send it to it's next life in Dipsy Dumpster land. Bummer, no good iron laying around the shop. I had stripped a 5KW FM rig last fall and sold the pieces on E-Bay. That made me some money and gave me a nice radio cabinet which was what I was looking for anyway. The 3 phase iron in the rig could not find a home with any of the locals. It was stashed in a container & on it's way to a tower base project. Would have made a nice anchor. Anyway, I figured that I should take that iron over to the shop and hook it to my 220 VAC variac and see what I could do with it. The thing had three primaries wired for 208 or 240 volts and a plus or minus 10% tap also. The secondaries were "Y" connected and used to make 3000/3800 VAC at several amps. I connected up the center primary and cranked up the power. I got about 2500 volts out of the center secondary and no hum. I then connected another primary in parallel and cranked up the power. Massive hummage & no volts. I then cross connected the two primaries and tried it again. No hummage and lotsa equal AC volts on two of the three secondaries. I also tried powering up the third primary in both phases but you know that was not going to work. The good news was that I had 2/3's of a 5KW-CCS Thansformer working! In "Ham Use" That's still a lotta snot! I series connected the two hot secondaries and was able to get 5 KV plus! I moved the taps down on the primaries to max windings to get minimum voltage on the secondaries and used the lower voltage tap on the secondaries to get the RMS AC plate volts I needed for the 833 rig. Works perfect and now I have a dozen possibilities on selecting taps to raise or lower the voltage to the rig. Don't throw those 3 phase transformers away! They work pissa for the old tube rigs. I just stuffed mine into my console and ran the promary & secondary power remotely to the transmitter. PS, high winds may take the first floor off of the house but the rig will still be there due to the force of gravity on that old iron.
Keith
WA1HZK

[WA1GFZ]

why didn't you rewind it?

[fg5fc]

Indeed, i have a three phased transformer some body built for me 8 years ago to feed my homemade linear (3cx3000f7) unfortunately since i'm retired i haven't three phase power line in my new QTH, that the reason i asked you some info about your experience...I remember when the "guy" has built the transformer i was so surprised about the smalll size of the wire! the transformer i have : 3x 240v primary "y"and 3x 2400v "y" DC OUTPUT 5KV 2AMP a big gun! may be i could get 5kv 1AMP?

Best regards, John FG5FC 

why didn't you rewind it?

[WD8BIL]

but i wonder if the size of the wire( primary and secondary) of the transformer should not be too small to give the 2/3 of the power even if the iron is OK!

Power is power..... amperage is amperage !!!

IN GENERAL; the core is determined by the the power
                   wire size  is determined by the amperage
Both will determine temp rise but 5KW iron will will have no problem in the config Keith has described.

As long as the input voltage is near design value, in Amateur service, it should work just fine.

[fg5fc]

Thanks to WD8BIL for the comments! i guess when you have a big transfomer putting several amps on three phased you should get that you need for ham use...

JOHN FG5FC

[W1ATR]

The next good news is you can grab 3 phase transformers for pennies on the pound off of epay. The tesla lunitics don't shoot the price thru the roof due to the fact they don't think they can use them.(neither did I until right now )

Harold, any suggestions on the test setup, or do I test this thing like a single phase?(variac+I&E metering on the primary, and a fluke 40K probe, and DVM on the secondary is the setup I use with 1ph tests.) The tranny I would like to test out is a unit i pulled out of a henry 3000D plama gen. that's been keeping the door open for 10 years. It would be interesting to see if this 200 lb chunk is usable for something. It's supposed to be 4800V-2A.

SK