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3 phase to single phase larger transmitters




 
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Author Topic: 3 phase to single phase larger transmitters  (Read 4924 times)
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fg5fc
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« Reply #25 on: March 26, 2019, 07:54:44 AM »

Many thanks Opcom and W2PFY for your very useful inputs, for the moment i'm a little busy, i while make a try later.
Regards
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W2PFY
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« Reply #26 on: March 26, 2019, 08:34:21 PM »

I changed this post as it was not relevant? I don't even remember writing the post? I don't drink or drug...anymore.....Too old!

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WB3JOK
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« Reply #27 on: March 26, 2019, 10:56:22 PM »

In the past I had a Nobatron power supply with a 3-winding saturable reactor. A 6L6 on 300VDC fed into a high-turns winding on the middle leg regulated 28VDC/50A output. The two other windings, on the outer legs, were connected to oppose AC current. As the 6L6 magnetized the core in response to the output going lower under load, more AC mains juice was allowed through this reactor into the power transformer to bring it back up to 28VDC.

Speaking of interesting regulation methods:

I got the transformer and filter choke from a Motorola MSR2000 (14VDC/30A power supply designed to charge/float batteries to run repeaters or cell phone equipment) which used a ferroresonant transformer to a pair of big rectifiers and a pi-section filter (large caps and the hefty choke). But the regulation came from an (unfortunately missing) 65 mH choke switched across the ferroresonant winding and its 20 uf cap, through a triac triggered by an SCR and bridge rectifier (to conduct on both half cycles)! With no pulses to the SCR gate, the inductor is out-of-circuit and the available voltage at maximum... connecting the inductor across the resonant tank must detune it so the voltage drops. More on-time, less output. Never seen anything like it Wink I smoked a couple of smaller fractional-henry chokes experimenting with it, so there must be quite a circulating current.

If anyone's interested I have the manual, but it's a 7 MB PDF which is above the allowable attachment size.
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KL7OF
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« Reply #28 on: March 26, 2019, 11:42:44 PM »

On Hass-Kamp, I opine that the 'created' phase's voltage will change with the amp load, and phase will change with inductor and or transformer tap changes. It might not be too critical for welding because they use a narrowly selected current range and can adjust the current with the control to get it there. After reading all of the articles it looks like they might be better served by adding a switch to cut in or out banks of capacitors and adding some kind of 'phase-o-meter' to see when the created phase is 'closest to the middle' once the arc is struck.

It would be a wild experiment to try it on an AM transmitter. Whatever effect it may have would probably not improve the modulation quality. For once I am glad to have a valid excuse not to try a wild experiment. spitzensparken und poppencorken.
I want to try the haas kemp on my frt39...the IPA and PA stages that run off the Plate supply are linear.   
  I have run this transmitter with the stock 3phase plate iron wired with all 3 coils hooked to single phase ..It worked to about 75% of its rated output..With the same transformer cut down to 2 coils , the transmitter works to about 60% of its rated output.  I am trying to acquire another suitable complete 3 phase transformer so I can experiment with the Haas-Kemp and I also have a homebrew 3phase converter made from a 15 hp 3 phase electric motor that I would like to try.. 
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fg5fc
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« Reply #29 on: March 27, 2019, 09:22:56 AM »

Hello KL7OF

Could you explain exactly how you made the wiring" I have run this transmitter with the stock 3 phase plate iron wired with all 3
 coils hooked to single phase"
Regards
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fg5fc
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« Reply #30 on: March 27, 2019, 09:34:38 AM »

By reflecting well, putting the 3 primary windings in parallel and in phase and the three secondary windings in series
is this the truth?
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KL7OF
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« Reply #31 on: March 27, 2019, 10:10:09 AM »

By reflecting well, putting the 3 primary windings in parallel and in phase and the three secondary windings in series
is this the truth?
Yes...   once you get the phase(s) figured out for maximum output it works at about 75% of rated output.
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fg5fc
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« Reply #32 on: March 27, 2019, 10:25:00 AM »

Thanks KL7OF

I guess with a low voltage in the primary for instance 24 vac , i got the job!
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kc4mne
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« Reply #33 on: October 29, 2019, 12:58:42 AM »

Hello, know that is is an old post but will take a swing at it. Picked up a Collins 21E. Like to run it on single phase. Three phase is not an option since it is not even available on my street. Did anybody ever try the Hass-Kamp method from the welder guys? One plus is that I have 3 separate plate transformers for the 21E. So putting two or three in parallel is an easy cheap option. Ordered the ER back issue with the 3 phase to single transformer wiring but still have not received it. I know the primary is wired as Delta and the output is wired as Wye, each leg going to a rectifier. The center of the wye being B-. Don't really want to use a rotary converter since the size required would be big $$$$. Any ideas? Thanks
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KL7OF
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« Reply #34 on: October 29, 2019, 09:28:00 AM »

I have built a "3 phase generator" out of a 3 phase motor..A 15 HP 3PH motor has 3 legs...2 of those legs are attached to 220V single phase with a capacitor start and the motor will run...the 3rd leg on the motor "generates" the missing third leg..  I use it to run my lathe and mill..I tried it on the 3 phase transmitter and it works well enough...The "generated leg" draws a  more current than the other 2 legs so the 3 phase power is not completely balanced but no heating of components and no flamage...I got the plans for the generator from LINDSAY BOOKS...It  was cheap to build...
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kc4mne
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« Reply #35 on: October 29, 2019, 11:04:26 PM »

I have a rotary phase converter for my bridgeport milling machine. I bought it several years ago on ebay from American Rotary, think the idler motor is like a 5 HP on mine, works fine for the milling machine. But to do a 5KW AM Transmitter that way properly it would require about a 50 HP idler motor, or combination of to get to 50 HP.  If I only had one plate transformer or other 3 phase equipment the big rotary converter either homemade or store bought makes sense. But since I happen to have 3 identical 3phase plate transformers the idea of running two or three in parallel to make the B+ would be easier and less expensive. Adding some capacitance to the B+ with a string of electrolytic caps that I already have a box of is also pretty easy as well. That is why I am asking about the transformer ideas to run the 3 phase on single. If not, being a plumbing contractor, I know several air conditioning and fire sprinkler contractors that deal with large HP pumps all the time, and probably have an old motor lying around that I can use as an idler and acquire for free. So I would just have to get some run capacitors and some start caps on a timer relay to get the beast rolling. The starting amps are also going to be insane. A a pair of 25hp may be better since i only need to single phase start one, and the second should start off the 3 phase generated by the first one. But still a ton of work, space, wiring, and effort to run a transmitter every once in a while. But then we are all insane if not I wouldn't be trying to do this to begin with and you would not be reading it having been there already before me. LOL Wink
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W7TFO
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« Reply #36 on: October 30, 2019, 12:58:28 AM »

Some of those ideas will work OK, others not.  You will have to decide what does OK, just watch out for harmonics in the AC pre-rectifier waveforms.  Break out yer scope, connect with caution around that HV.

A real Phasemaster is the most elegant solution, and they do show up from time to time on broadcast used-gear websites, i.e. https://www.thebdr.net/  eTc.

A word of advice:  Key the drive, not the plate supply.  Have the B+ on a timer, say 15 minutes on from first key up so it isn't constantly on-offing in PTT mode.  Your contactors will thank you.

73DG
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Todd, KA1KAQ
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« Reply #37 on: October 30, 2019, 09:56:59 AM »

I've got a 21E here that has been converted by W2INR, but I think by the looks he basically had a special transformer built by Dahl and just redesigned the power circuit.

Probably not much help as far as tweaking the original 3 phase circuit, but something to consider...
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W2PFY
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« Reply #38 on: October 30, 2019, 05:51:00 PM »

Quote
A word of advice:  Key the drive, not the plate supply.  Have the B+ on a timer, say 15 minutes on from first key up so it isn't constantly on-offing in PTT mode.  Your contactors will thank you.

Yup, on me big Westinghouse MW-2 they always keyed the drive.The B+ was always on with HV contactor to key the desired transmitter and modulator.

If I were to key the plate transformer I would be keying a massive 100 amp contactor and the clunk it would make could be heard for about 100 feet. I think that sound would get old and the contactor would probably need to be repaired every once in awhile if you could find parts to repair it? When I UN-key the transmitter dumps -400 volts on all the big tubes preventing a melt down.
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KD6VXI
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« Reply #39 on: October 30, 2019, 10:03:35 PM »

Dahl made a lot of single phase xformers to convert 3 phase boxes to single.

I bought an fm station a couple years ago, came with a 20kw phasemaster converter and a monster plate xformer!

No more worries about 3 phase, and cheap transformers are abundant in 3 phase!  Nobody wants em.....

--Shane
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kc4mne
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« Reply #40 on: October 30, 2019, 11:54:15 PM »

Thanks for the Key The Drive idea. I like it. On the bauer I key the contactor that feeds the b+. but your idea is way more elegant especially at 100 amps on that contactor, just have to make sure the big tubes are happy with no drive. But i still have some time to get there. I am going to start experimenting with the hass kamp idea and go from there. will report my findings.  i even have a nice hv probe for the scope that i have never used. sure i finally will now.
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w8khk
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« Reply #41 on: October 31, 2019, 01:42:28 AM »

I have a 5 KW continuous, 8 KW surge, military generator which provides 120 or 240 volts single phase, or 208 volt Wye three phase power.  Two cylinder overhead Onan engine.   New carburetor.  Available for any lowball offer.  It powered my home during hurricanes in Florida in the 70s and 80s, and during snow and ice outages in GA since 1990.  Needs 24 volts for starting, a couple lawnmower batteries are sufficient.  No longer needed at this QTH.
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« Reply #42 on: November 02, 2019, 12:22:17 AM »

It might be possible to use a 3-phase motor driver that runs off the single phase power. variable speed drive - just using it for the conversion. Might need some filters on it. It might be hard on the plate iron. I don't know, just thought I'd throw it on the table.
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kc4mne
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« Reply #43 on: November 11, 2019, 11:46:11 PM »

I am reporting the findings of me experiments. The attached picture is the output of the Haas Kamp method. Maybe not a perfect implementation since I am feeding a plate xformer with single phase on the two outer coils, inverting the polarity on one of them. The center coil was fed in series with 400mf worth of capacitance from each of the 240 legs.  The three phase out delta (5kv) was fed into a second identical transformer to step down the 5kv back to 240 V so i can connect the scope to that. Needless to say the "fake" phase is a mess. I would even go as far as saying that with the amount of capacitance the welder guys say they are using, which is way less than the 400mfd that i used that their fake phase has voltage that is no low that it is not doing anything, but since in that process they inverted the connections to the second coil, they get 70% of the welders capacity, and the cap fed coil is doing more harm than good. That being said the transformers work great on single phase by feeding the outer coils (one with polarity inverted) and I did some restive loading up to a 10KW load on what was a 16KW spec on three phase spec xformer and it did not even blink. So with two of them in parallel I will feed the monster with no issues. Adding a second filter choke to the b+ and three times the filter caps as the original to get rid of the added ripple from the single phase supply. I also feed the primary's using the 208V terminals  with the 240V that my qth service has, which is bumping up the secondary voltage to very near the 3 phase level.  HAAS KAMP DOES NOT WORK!


* haas kamp.jpg (109.52 KB, 1024x467 - viewed 52 times.)
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KL7OF
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« Reply #44 on: November 12, 2019, 09:47:18 AM »

This is very interesting...On your scope, I assume the light blue line is the "fake" phase...And you used AC capacitors...Thanks for the report...It will take me a while to digest this....Steve
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KL7OF
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« Reply #45 on: November 25, 2019, 10:18:59 AM »

Haas-Kamp as it was explained to me...
   The transformer is based on a 3 phase core having 3 sections and built so that the magnetic flow circulates thru the core in a figure 8 pattern.  Wire the far left and the far right cores so that they are operating opposite of each other.  (criss cross one)  wire the center coil in either orientationbut pass each leg thru a motor start capacitor of sufficent size to create a 90 deg phase shift AT FULL LOAD CURRENT.    This forces the core to function as it was originally designed and get the flux spinning in a figure 8.

This sounds almost exactly like what kc4mne did with perhaps more capacitance than the welder guys use....I can't help but think that there is still  more experimenting to be done and that this can be made to work...  I am trying to acquire some 3 phase transformers to work with..I appreciate the thought and time others have put into this....  Steve KL7OF
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kc4mne
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« Reply #46 on: November 25, 2019, 10:29:48 PM »

Yep that's the theory, but not what I saw. However my "load" was also inductive since I was not loading the 4+kv out directly, I was feeding it into another of the same transformer and stepping it back down to 240V and loading each coil with 5KW using electric range burners as a load. Loading the 4+kv directly would be more challenging and would require a much more elaborate "range burner in series" setup that i did not want to get into, especially at those voltages! One mistake and I could be a dead piece of bacon on the floor, getting an additional broiling from all the range burners as well! What I did learn is that firing the two outer coils in reverse polarity, completely cancels out the magnetic flux in the center coil like if it were not even there. Zero volts output on both primary and secondary. In my case I have three identical transformers, so with two in parallel running single phase I have more than enough current capacity. Adding a second choke and three times the filter caps to make up for the single phase ripple.
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