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Author Topic: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19  (Read 545 times)

KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #15 on: March 08, 2023, 04:02:08 AM »

Presumably the pole transformer takes any 2 hot lines from the HV 3 phase (120 degrees off phase with the other two pairs } and converts to balanced 240 (180 degrees out of phase). Then feed each property with a 240: 120-0-120 transformation with a CT?

No, just one single phase and neutral. The separate 120's are reverse windings in the transformer in your yard or at the street. My sister across the creek can have power just fine in a storm when mine is out.  All three phases come by here. Most neighborhoods geographically not necessarily population wise have only a single phase service provided.

Do your xfmrs have 2 x separate  120 vac windings..... or is it one 240 vac winding...with one CT ?

It has two 120 volt windings with one center tap or neutral. I can't see how you could get your single pole 120 volt circuits any other way. Or, how you could get them 180 degrees out of phase. The potential difference between the two is 240 volts.
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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #16 on: March 08, 2023, 04:08:07 AM »

Unfortunately my EE PE retired NASA engineer friend K5AL  passed away on me a week short of 90 years old.  He would have been a good person to ask. 

I have found over the years that I am wrong about how I think things work a lot.
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #17 on: March 08, 2023, 07:56:55 AM »

If the sec of the pole pig has 2 x separate 120 vac windings, they would have to be connected in the middle to make the CT.
That was what was on my small, ancient pole pig.  Dual primaries is what u typ see on a ham plate xfmr, so it can be used on 120 or 240..... but that's a totally different aapplication.

The other method is just one 240 vac winding, with a single CT dead center, in the middle of the winding..then only one winding, with a CT..... similar to a fil xfmr with a CT. 
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VR2AX

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #18 on: March 08, 2023, 10:30:51 AM »

What's the view on the single phase plate transformer choice for this power level? How much is the 240 going to dip at key down? (did he connect to the 250?)
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #19 on: March 08, 2023, 01:47:02 PM »

What's the view on the single phase plate transformer choice for this power level? How much is the 240 going to dip at key down? (did he connect to the 250?)

The new plate xfmr is fine.  The main issue with this power level is the V drop, from the pole pig in the street...to the primary of the plate xfmr.   It's one big loop.   It's typ 3-000  CU  wire from main 200 amp panel to the meter base, then  more 3-000
 CU up to the pothead, where it's crimp spliced into just 2-00  aluminum drop line. The other end of the aluminum drop line connects to more aluminum..that runs between utility poles.   In my case, my drop line terminates across the street, dead center between 2 x poles.....(mid span drop) then  down 1.5 poles to the rinky dink 50 kva xfmr..... that feeds 9 x homes...and we all have...'200 amp' service.

On buddy's HF 3x6 amp, his dropped 8 vac under a 90 amp load.  6 vac from street xfmr to his main 200 amp panel, then another 2 vac, from main 200 amp panel...over 20' to the HV supply.  He used 2 ga from main panel to HV supply.  In his case, he had 240 vac coming in, unloaded..... so we used the 230 vac tap on the xfmr.  That's normal to use a tap that's a full 10 vac lower than the no load incoming vac.

Mine used to be 247.2 vac in spring + summer.... and 239.9 vac in fall / winter.   I could set a clock by it.  These days, it's all over the map, varying by the time of day, hr, week,  never know what's it's gonna be from one day to the next.   I check once or twice a week, and lately it's sitting around 234 vac... and once in a blue moon, as high as 236 vac. 

My plate xfmr primary has taps for 198-208-218-230-240-250.  Only options are the 230 tap..or the 218 tap.   I don't like the idea of using the 218 tap...in case the incoming vac shoots back up to 240 +.

On SSB, it's really a non issue.   When Rich Measures pulse tuned his 4x10, with 30 wpm dots... the old bitty next door left
 her porch light on all night long.  Her porch light would pulsate like a machine gun.  You  can see lights blink on CW with just a 3 vac drop.   On SSB,  you never get that effect.  Rich used  150' of just 4 ga wire from his HV supply, to his main panel.  His plate xfmr was puny at just 68 lbs (later switched to a slightly bigger 86 lb xfmr, still way too small).  His no load B+ was 9900..which dropped down to 9 kv...sucking 500 ma of idle current ( which then maxed out the CCS rating of his 4.5 kv xfmr).... then while talking on SSB, it dropped a bunch more.  With a cxr it dropped even more.  This is what happens when stuff is not sized correctly.

On high C filters, you get this massive current spike every 8.3 msecs, when on 60 hz  single phase power.   W8JI measured  60 amps on peaks, every 8.3 msecs, just on an AL-1200, running 1.5 kw out.  Scale that up to 10-15 kw out, and you can see that the peak currents on high C filters is just wicked.   Issue then is, you also get wicked V drops everywhere, from Cu wire, AL wire, all connections and splices, breakers / fuses / cross connects, relay contacts, contactor contacts, etc, etc.

Then add in the 'normal drop' from the plate xfmr,  + glitch resistor...and you further compound the issue.   This is why you don't want a plate xfmr with a high secondary DC resistance, cuz it will kill V regulation every time.

In my case, I opted at the last minute, to locate the HV supply (HV supply is just the xfmr + FWB / contactors etc, no filter caps) very close to the main panel.... then ran Teflon 393 coax, to carry the B+  over 20', then down 5', to the HV filter box, then to both RF decks.  Then used 1-0 cu wire from main panel to plate xfmr box.   I can't do anything abt the drop from the street, except use more C filtering, which works good.... esp on dynamic loads, like SSB.  On data  modes, you get max static load drop, but nothing u can do about it...and for static loads, everything is in steady state anyway.
« Last Edit: March 08, 2023, 01:54:08 PM by VE7RF »
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #20 on: March 08, 2023, 01:57:37 PM »

I know several folks in the US, that have 250-252 vac coming in.   Typ, the 240 vac tap is used.  If the B+ is a tad high, the 250 tap can be used.   You can only do so much.   Again,  SSB is a non issue, lights don't blink or anything.  On CW they will, but that depends on cw speed, and filter C used.
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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #21 on: March 08, 2023, 02:21:00 PM »

Here everything coming from the pole pig or pad mount to your residential meter base is 4/0 4/0 2/0 aluminum and has been for decades. I must have sold a million feet of it.

The utility transformer with a neutral and your plate transformer with or without one are two different stories.
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #22 on: March 08, 2023, 03:42:29 PM »

Here everything coming from the pole pig or pad mount to your residential meter base is 4/0 4/0 2/0 aluminum and has been for decades. I must have sold a million feet of it.

The utility transformer with a neutral and your plate transformer with or without one are two different stories.

Dunno what gauge Al is used between poles, I think it is 4-0, just looking where the 2-0 alum drop line splices into the line between poles.  It all sounds wonderful, but we are being sold a bill of goods imo.  9 x homes hanging off the same 4/0 alum , and also hanging off the same rinky dink 50 kva xfmr...and we all have...'200 amp' service.  I already have 2 x neighbours sucking 7 kw all night long with their stupid EV cars.   2 x cars per home around here.  Imagine 18 x EV cars sucking 7 kw all night long.  Then toss in thes silly heat pumps, and the load is gonna skyrocket.

I talked to the local power co.  They said, just let it blow up / burn up..and they will install a bigger one.  They make em in 75/100/125 kva.   125 kv is the biggest single phase 240/120 pole xfmr they can use.  ( A 75 kva weighs 900 lbs).

If they are gonna use aluminum, it really should be 2 x sizes up from 3/0 cu, like 250 mcm.   Alum only conducts 60% as good as cu.

Local ham buddy, who is also an electrical contractor, tells me the power company uses a 9-11 amp slow blow  HV  fuse, in the feed to the 14.4 kv top line.   Around here, everybody has natural gas.  Now the push is on to electric everything.  That's ok, I can always use my 218 tap, and suck even more current.

To handle the fil current on the big tubes, I had to use a Sola constant V xfmr....that feeds the small Variac..that feeds the fil xfmr..that feeds the cathode.  It's the only way to keep the cathode V constant.
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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #23 on: March 08, 2023, 04:35:51 PM »

Fortunately, I don't have any neighbors. So, I have my very own pole pig. The power company put capacitors in for power factor correction in back in the summer and they were going to put it in my front yard. Of course, you have the contractor who decides where to place them, the contractor that places them ,and the utility. I explained to the gentlemen that I owned everything for 2000 feet up the road, why not move it up a couple of poles. They did.  The next will be regulators I'm sure. And, I'll have that battle which is the disadvantage of owning property.
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VR2AX

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #24 on: March 09, 2023, 11:24:34 AM »

What's the view on the single phase plate transformer choice for this power level? How much is the 240 going to dip at key down? (did he connect to the 250?)

The new plate xfmr is fine.  The main issue with this power level is the V drop, from the pole pig in the street...to the primary of the plate xfmr.   

Right, as long as the utility suppliers (usually not the energy producers) can still supply the power at the reduced voltage, which is likely de minimise in their books. We as hams, whether you are talking about 10 w ccs or 10 kw ccs, are in the same boat. Just like one or two more ev in the chain.
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VR2AX

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #25 on: March 09, 2023, 12:26:34 PM »

Fortunately, I don't have any neighbors. So, I have my very own pole pig. The power company put capacitors in for power factor correction in back in the summer and they were going to put it in my front yard. Of course, you have the contractor who decides where to place them, the contractor that places them ,and the utility. I explained to the gentlemen that I owned everything for 2000 feet up the road, why not move it up a couple of poles. They did.  The next will be regulators I'm sure. And, I'll have that battle which is the disadvantage of owning property.

Certiorari will be your sword in battle
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