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Author Topic: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19  (Read 546 times)

VE7RF

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10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« on: March 01, 2023, 05:09:13 AM »

Here, 3 x paralleled 8 ga Teflon wires (silver plated, and stranded)  are used to wire each side of the incoming 240 vac mains...to the pair of paralleled  3 pole contactors.  A 3rd contactor (double pole) will be later installed for the HV step start. Right angle drive to be installed on the small 240 vac variac, through the rear panel, so fil V can be dialed in.

Incoming line cord is 3 ga....and is 10' long. Other end can be trimmed off as required, and will be hardwired into a small 125 amp sub panel, then off to main panel.

https://www.youtube.com/watch?v=OokpV9aEG9A
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VR2AX

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #1 on: March 02, 2023, 09:56:28 AM »

Is the COM terminal on the transformer (neutral?) at ground potential? That would be the UK approach however I gather that US/NA is different.
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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #2 on: March 02, 2023, 04:58:54 PM »

If he finds his  primary at his particular location to be 240 volts then common will be 120 and and 120 on the 240 tap. Added.  If his primary happens to be 250 then it will be 125 and 125 added.  Measure it with a meter to get the desired secondary. The two primaries are equal more or less depending on the single pole loads at his location at the time.
There are only two wires feeding the transformer and they are equal and hot.
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #3 on: March 02, 2023, 09:45:03 PM »

If he finds his  primary at his particular location to be 240 volts then common will be 120 and and 120 on the 240 tap. Added.  If his primary happens to be 250 then it will be 125 and 125 added.  Measure it with a meter to get the desired secondary. The two primaries are equal more or less depending on the single pole loads at his location at the time.
There are only two wires feeding the transformer and they are equal and hot.

There is NO neutral coming into the amp.  Everything runs of 240 vac.  There is only ONE primary on the plate xfmr.  It can only be wired for 240 vac.   It does NOT have dual 120 vac primaries.
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #4 on: March 02, 2023, 10:19:03 PM »

Is the COM terminal on the transformer (neutral?) at ground potential? That would be the UK approach however I gather that US/NA is different.
Nope. Here is NA, the 230 vac, both are hot leads.   In NA, the  pole pig in street has an UN-balanced 12.5 kv / 14.4 kv input ( one side grnded)..... and a BALANCED  240 vac output.  In NA, the secondary of the pole pig has a grounded  CT. That grounded CT is also looped back to the grounded side of the 12.5 / 14.4 kv.   That's done for safety...in case of a 12.5 / 14.4 kv primary to secondary short.

There is 120 vac from either hot leg to the  grounded CT.   The CT is the neutral.  In the main panel in the home, the Neutral buss and the ground buss are bonded inside the main panel.   On any sub panel hanging off the main panel, the neutral and grnd buss are NOT bonded together.  Reason for that is.... all fault current must flow through the ground wire.

In NA, BOTH sides of the 240 vac are hot, both must be fused  (or a dual breaker, with tie-bar between em....  and both require a switch, like a DPST.

In the UK, and elsewhere, the pole pigs are UN balanced on BOTH the input HV side...AND the low 230 vac  output side. In the UK, there is NO CT on the low V side.    BUT, one side of the 230 vac is grounded / neutral.  That grnded side of the 230 vac is also fed back to the grounded side of the  HV input of the pole pig.  Same deal, done for safety...if  the HV side arced to the low V sec, inside the pole pig.   

In the UK, only ONE side of the 230 vac requires a breaker / fuse / SPST switch.

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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #5 on: March 03, 2023, 03:28:41 AM »

If he finds his  primary at his particular location to be 240 volts then common will be 120 and and 120 on the 240 tap. Added.  If his primary happens to be 250 then it will be 125 and 125 added.  Measure it with a meter to get the desired secondary. The two primaries are equal more or less depending on the single pole loads at his location at the time.
There are only two wires feeding the transformer and they are equal and hot.

There is NO neutral coming into the amp.  Everything runs of 240 vac.  There is only ONE primary on the plate xfmr.  It can only be wired for 240 vac.   It does NOT have dual 120 vac primaries.


Not familiar with Canada. But, in the U.S. 240 volts is two 120 volt legs added. Period.
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VR2AX

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #6 on: March 03, 2023, 03:48:23 AM »

There is 120 vac from either hot leg to the  grounded CT.   The CT is the neutral. 

Thanks to both for your explanations. Presumably, even though outside the amp the grounded CT is the AC primary current return (and guessing the two 120 vac hot legs are 180 degrees out of phase)..

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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #7 on: March 03, 2023, 05:45:10 AM »

Yeah, each leg will have opposite voltage relative to neutral at a point in time.  That is the neutral in the utility service transformer. A typical 240 volt U.S. plate transformer only needs two wires in and two wires out to work.
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #8 on: March 06, 2023, 09:34:57 PM »

If he finds his  primary at his particular location to be 240 volts then common will be 120 and and 120 on the 240 tap. Added.  If his primary happens to be 250 then it will be 125 and 125 added.  Measure it with a meter to get the desired secondary. The two primaries are equal more or less depending on the single pole loads at his location at the time.
There are only two wires feeding the transformer and they are equal and hot.

There is NO neutral coming into the amp.  Everything runs of 240 vac.  There is only ONE primary on the plate xfmr.  It can only be wired for 240 vac.   It does NOT have dual 120 vac primaries.


Not familiar with Canada. But, in the U.S. 240 volts is two 120 volt legs added. Period.

No, there is NO  two  120 volts added .   It's a straight 240 vac across the entire sec winding of the pole pig.   For  240 vac applications, the CT doesn't enter into the equation, and not required.  (not required in the actual HV supply, nor any other device that operates on 240 vac).
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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #9 on: March 07, 2023, 03:04:51 AM »

If he finds his  primary at his particular location to be 240 volts then common will be 120 and and 120 on the 240 tap. Added.  If his primary happens to be 250 then it will be 125 and 125 added.  Measure it with a meter to get the desired secondary. The two primaries are equal more or less depending on the single pole loads at his location at the time.
There are only two wires feeding the transformer and they are equal and hot.

There is NO neutral coming into the amp.  Everything runs of 240 vac.  There is only ONE primary on the plate xfmr.  It can only be wired for 240 vac.   It does NOT have dual 120 vac primaries.


Not familiar with Canada. But, in the U.S. 240 volts is two 120 volt legs added. Period.

No, there is NO  two  120 volts added .   It's a straight 240 vac across the entire sec winding of the pole pig.   For  240 vac applications, the CT doesn't enter into the equation, and not required.  (not required in the actual HV supply, nor any other device that operates on 240 vac).


Good Lord. What do you think every 120 volt appliance in the house runs on. It is one leg of it. The 240 volt appliances use both legs. They don't even break but one leg on a range. Take the rear cover off the back with the oven turned off put still plugged in and poke your finger on the bake or broil elements. There is 120 volts on one side as long as it's plugged in.
As soon as I turn my amp on there is 120 volts on one leg. The other 120 volts is not turned on until the timer turns the step start relays on.
You want to poke your finger on that leg of my transformer and see what's on it when there is nothing coming out the secondary ?
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VR2AX

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #10 on: March 07, 2023, 11:06:03 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?
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KM4AH

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #11 on: March 07, 2023, 02:18:54 PM »

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.
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #12 on: March 07, 2023, 10:40:51 PM »

single phase and grnd coming down each residential street...which feeds a pole pig  every few poles.

Only main streets have  all 3 phases of the HV  3 phase.  Apartment flats  and condominiums have all 3  HV phases, since they are on main streets, or have had 3 phases installed.  In those cases, the 3 phase  xfmr outputs  208/120 vac .  Each floor gets just 208 vac single phase, ( like legs  A+B) and also 120 vac, also single phase.  1st floor gets legs A+B. 2nd floor gets legs B+C.  3rd floor gets legs A +C.   Then the process just repeats as you go to floors 4 and higher.

The reason for the 208/120 is..... the 120 is just the sq root of 3 ( =1.732) .  208 / 1.732 =  120 vac.

Commercial buildings typ get 208/120 as well.   In some cases, it's 360 / 208.   In some cases it's 480/277  or  470/ 271.  Some cases it's 600 / 346.  The higher voltages are typ for light industry or heavier capacity.

99% of the telco offices I looked after were 208/120.    Main office down town was  470/277   In those cases, we brought the 14.4 kv 3 phase right into the building, and used our own step down xfmr.  We got a lot cheaper rate.  Flip side is, the step down xfmr's cost money, and are big and heavy.  Small sites like cell sites are just 240/120..same as residential.

Across the water, In the city of Vancouver, it's all 12.5 kv.  Here in town, a lot of the 14.4 kv has been upgraded to 25 kv.
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VE7RF

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #13 on: March 07, 2023, 10:43:33 PM »

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 ?
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VR2AX

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Re: 10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 19
« Reply #14 on: March 08, 2023, 02:39:17 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.

UK has 11 kV three phase (divided by 1.732 single phase), which is stepped down to commercial/domestic 415v three phase/240 single phase, carried on wooden poles along the streets in rural areas and suburbs. Houses usually take in just single phase, rare to have three phase supplied to a house (they assume you want to run a business from home, which can cause some interesting issues..). In built up areas the domestic supply cables are buried under the roads and also run underground to houses.

Hong Kong and Macau have 380v three phase/220v single phase. It is common to find three phase as well as single phase supplied in apartment buildings, lifts and other machinery in the main buildings, also domestic users may fit large air-conditioning units which use three phase.
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