George's Power Supplies

[N4LTA]

You have to have been licensed for 20 years or so to understand where Carl is coming from.

It has little or nothing to do with CW operating.

Last time I went to a local Ham club meeting (5-6 years ago to upgrade to Extra - I had been an advance for 20 years and was too lazy to take the 20 wpm test). The new no code licensee applicants who were taking the Tech test,  went on and on about getting a free yellow jumpsuit if they "passed" the test and went absolutely ape sh$%t over me only missing one question on the Extra exam ( I was dissapointed in missing one  - since you can memorize all the answers by repeatedly taking practice exams on the net.)  About 1/2 of the appplicants failed the Tech test.

I enjoy CW but don't often operate it. I am a life member of the club, but I don't participate, because most of the activity is emergency prepardness and that is not what I want to do. Ham radio was once an area where you had to be a technical minded person to participate (to get licensed even).

The ham world is different today  - who can say worse or better.

Pat
N4LTA

[KM1H]

At least 630M wont be open to voice modes but there will likely be a battle between CW and the digi chirpers

[Opcom]

Ok in that case no offense taken. I am 51. Not many generations to go. I've had the FCC general phone since '86 but not the ham ticket, that was only '95 or so.

This whole amateur radio thing got started on a bet. A friend kept goading me to get a tech license and he would also test at the same time but I did not want to bother with it.

Finally he bet me $100 that we could not get a certain habitual alcohol abuser, with whom we were well acquainted, to cram all night and pass the tech license the next morning. I had no choice in the matter but to cram the drunk all night and take the test with them the next morning.

[k4kyv]

This is my story of a lost-neutral scare.  My house was wired in the 30s, and the old wiring is two-wire no ground.  They  didn't even have 240v available until  they got an electric stove, and the third  wire was added between the house and the pole transformer.  Since then, circuits have been added, and those do have the 3rd wire ground.  Probably typical of old houses, where wiring has been added piecemeal over the years since electricity was first installed. Rewiring the entire house would require too much ripping up floors and ripping open ceilings and walls.

Shortly after we moved here, we had a new breaker panel installed, rated for 200 amp service.  The work was done by a licensed electrician, and the job was inspected and passed by the county inspector before power was applied.  The breaker panel was supposed to be a good one, made by a reputable manufacturer, Square D.

At the time, my ham station was still in the house, in an upstairs bedroom. I run the filaments and low power stuff off one  side of the line, and the 120v plate transformers run off the other.  That actually gives the tube filaments a slight boost when the plates are pulling current, since with a common neutral, a voltage sag on one side of the line causes about a 50% of-the-sag boost on the other.  There was a proper ground, tied to the house wiring ground, plus the rf/lightning ground I added for the station equipment.

I had used this for several years with no problem, until one evening when I hit the transmit switch, the lights in the room got so bright they startled me. Luckily, nothing was damaged; a lot of appliances and other stuff could have been wiped out.  I cut the mains switch at the panel and investigated.  What I found was, the panel had two separate neutral bus bars, held together with rivets, and only one of the bars was tied to the main neutral wire.  Over several  years, the riveted connection had corroded, and contact became intermittent or non-existent.  It hadn't caused any obvious problems as long as both sides of the line were loaded pretty close to the same.  But when I hit the transmit switch and the 1 kw plate transformer for the rf final plus the one for the modulator began to pull  current, the voltage on that side of the line sagged to almost zero, whilst the voltage on the other side of the line soared to close to 240 volts.  Luckily I immediately  noticed something wrong, and this condition existed only for a few seconds.

Instead of replacing the entire panel, or even hiring an electrician, I looked inside the panel and the cause of the problem was immediately obvious.  The bus bars were still hot to the touch, and there were black spots on the metal surrounding the rivets. I noticed several unused holes in each of the bus bars, so I took a piece of #10 scrap copper wire from the junkbox, cut it up into several short pieces  a few inches long, and used the spare holes in the bus bars to bond the two together with a half-dozen or so separate strands of #10.  That cured the problem, the electricity in the house was back in service within an hour, and that panel is still in service to this day, with no further problems. I'm sure a professional electrician would have insisted that the power be cut immediately, the panel be replaced with a new one at a cost of hundreds of dollars, and we would have been without power for at  least a couple of days. What really surprised me was that the manufacturer of the breaker panel would have bonded two neutral bus bars together at the factory with nothing but rivets instead of a securely connected heavy gauge strap.

I have a separate sub-panel out in the shack.  It is fed from an old 40-amp electric kitchen range circuit no longer in use. The electric range used two hots and combined ground/neutral.  I ran the cable out to the shack, using some 3-wire direct-burial cable given to me, that I put in plastic conduit anyway. The ground wire on that cable is insulated, so I use it for the neutral, carefully kept away from contact with ground.  The safety/RF/lightning ground uses a separate #4 solid bare copper wire, which is connected to an 8' ground rod at the shack, plus a run to the house where it is bonded to the main entrance ground.  I did not  run it inside the plastic conduit, but direct-buried it about 6" below the surface, like a ground radial, plus I connected several ground radials each about 20-30' long to the ground rod at the shack.

I notice there usually is a volt or so difference between the neutral and ground, as measured at the shack.  I tried temporarily shorting the two together with a clip lead, and there was enough current to make a visible spark.  I also noticed that with the neutral shorted to ground at the shack, it makes enough of a ground loop that audible hum appears in the receiver and transmitter audio equipment.

Now, all the audio equipment and low power station equipment is fed through a 120v isolation transformer with a balanced midtap. The midtap is grounded, so that each side of the 120v line runs at 60 volts above ground.  This has eliminated several pesky ground loop problems that had previously baffled me.

The problems and confusion involving grounds, neutral and associated safety issues would never occur if the US had adopted a standard from the outset to run everything off a single voltage (240v) balanced to ground, with a midtapped transformer at the pole and everything in the house bonded to a safety ground running to that midtap, so that the maximum voltage above ground anywhere in the system would have been 120v, but nothing pulling current at 120v, and there would be no need for a separate neutral and ground. But the national electrical system, like my house wiring, was assembled piecemeal over the years, so we have what we have, and it would be impractical to replace everything from scratch.

[KE6DF]

The problems and confusion involving grounds, neutral and associated safety issues would never occur if the US had adopted a standard from the outset to run everything off a single voltage (240v) balanced to ground, with a midtapped transformer at the pole and everything in the house bonded to a safety ground running to that midtap, so that the maximum voltage above ground anywhere in the system would have been 120v, but nothing pulling current at 120v, and there would be no need for a separate neutral and ground.

In the UK, do they do this? Or do they use one side at ground potential and the other at 220?

I'm guessing they have a center ground as the standard plug has three prongs.

[W7TFO]

The usual Euro power scheme is 220 V (not 240) single phase for residential service.  Hot & neutral + ground.   

Most of the service to the houses is done with big coaxial cable from what I've seen.  Very little metallic conduit, but a lot of that fat coax running everywhere.

The next step up is three-phase 380V, not sure about it being delta or wye.

Everything there is 50 Hz as well. 

There are several 'standard' outlet types in use throughout, so taking gear from country to country means adapters or changing the plugs on your cords.

73DG

[K5UJ]

We are talking about running both 120 and 240 volt loads on a single 240 volt circuit with no neutral.
Using the green grounding conductor as the return for 120 volt current

Pat
N4LTA

You run a rig corded with two hots and ground without neutral return.  Even if there is a 120 v. load in the cabinet (but it is better if there isn't one) you run that paralleled to 1/2 of a 240 v. primary transformer that has a center tap (usually a big load like the plate supply).   You do not need, and in fact you should not have, a neutral return under these circumstances.

However, everything inside a rig powered by 240 v. service should be designed to operate off 240 v.   A very light load such as a few hundred ma. might not be a problem at 120 v.  The ground conductor regardless of its color is bonded to the cabinet and only that and is safety only.

[N4LTA]

In Europe the standard 3 phase voltage is 380/220  which is incidentially the same volts/hz as the USA. That means that a magnetic device is more or less interchangable ( athough this is terribly misunderstood and mis used)

You can run a 380 volt three phase motor on 460 volt three phase and it work just fine except at a higher speed. In fact - if you hook up a 480 volt motor on an inverter drive and run it at 50 hz speed it will have 380 volts on the terminal.

I often see European companies spending lots of money getting special transformers to run 380 volt motors in the USA - and they have problems  -  The proper terminal voltage for a 50 Hz 380 volt motor is 460 volts at 60 Hz. Same with transformers - the /Hz is important.

Also - I think most 220 volt single phase residential distribution is ungrounded - but I am not sure about that. I think the distribution voltage is 2 hots and no neutral - I'd have to check on that though.

Pat
N4LTA

[k4kyv]

I remember back in the 60s, in both UK and on the Continent, the outlet plugs were round, with two round prongs.  They all looked similar, but the spacing and prong diameter varied from country to country,  so they weren't necessarily interchangeable.  I suspect the ones in UK used standard English measurement (based on inches) while the ones on the Continent were metric.  Last time I visited UK, they had changed over to those gawd-awful things that looked like something you would use with a KW-1 or Johnson Desk KW.  They were heavy and bulky, with prongs that looked like they would handle 30 amps with ease; they used those things on EVERYTHING, even small desk lamps and electronic devices that might draw no more than 5 or 10 watts.  Don't know who the genius was who managed to come up with that idea.

I know they use 220 volts (or 240 or whatever), but not sure if it is grounded on one side, balanced to ground or simply left floating, and that might also vary from country to country.  If they had put me in charge in every country back when electricity was first being distributed, I would have decreed 220/240 volts balanced to ground, using two-conductor shielded wiring, with the shielding grounded and strapped to the midtap of the mains transformer. That would cut way back on ground loops and a.c. power noise, and would be less of a safety hazard.

I believe the standard here used to be 110/220v, but now it's 120/240.  I notice a lot of older stuff is marked "110".  I also see "115/230".  I think it's whatever the local power company decides.  Here, it varies anywhere from 105 to 125 volts, depending on the time of day and weather condx.  When we have abnormally hot or cold wx, with all the air condx or heaters running throughout the region, it is not unusual for the line voltage to the meter to drop below 110, but at other times it may soar above 125. I'm also aware that a lot of older radios were never designed to run off the higher line voltages that prevail to-day.

I have one of those little "Kill-a-Watt" meters, and it amazes me how poor the power factor is with almost any appliance I plug in, large or small. 0.60 is not at all unusual.

[KE6DF]

 Here, it varies anywhere from 105 to 125 volts, depending on the time of day and weather condx.  When we have abnormally hot or cold wx, with all the air condx or heaters running throughout the region, it is not unusual for the line voltage to the meter to drop below 110, but at other times it may soar above 125.  is not at all unusual.

Here we have consistently high voltage. I've never seen it outside the range from 120 to 122 summer or winter.

But I live in the fastest growing city over 10,000 population in the US over the last decade, so most everything is new.

There are no above ground powerlines within 3 miles of my house, and 15 years ago the whole area was cow pastures.

Also, the distrubution transformer for several houses is in our front yard, so no voltage drop in the feed lines.

Those Kill-a-watts are cool. Fun to monitor things.

Dave

[N4LTA]

"Green ground" is a term used by electrical contractors and engineers used to describe what the NEC calls the "grounding conductor". The National Electric Code NEVER allows current to be carried in this conductor except under fault conditions. NEC and NEMA require this conductor to be green in color or bare copper inside equipment and identified with green tape in a raceway. The so called neutral conductor is called the "grounded conductor" by the NEC and must be white or natural gray in color or identified with white tape. To meet NEC requirements  - you must have a grounded conductor  - if you have phase to neutral loads (120 Volt loads) tied to the power system. If you have a 240 volt transformer with a 120 volt secondary winding  - that does not apply. The whole idea is that no current be carried in the grounding conductor (the green ground)

The standard in the USA is 120/240 volt single phase as the line voltage. Motors are rated 115/230 volts to account for voltage drop

The 3 phase standard is rapidly becoming 208/120 volts replacing the old obsolete 240/120 high leg delta where one leg of the delta had a center tapped secondary resulting in 120 phase to ground from 2 legs and a 190 volt high leg. The high leg burned out lots of equipment when it got hooked up incorrectely to a 120 volt load.

480/277 volts is the standard three phase voltage for large loads - the motors are rated at 460 volts -  again for voltage drop.

277 volt is used for lighting and some small single phase HVAC units. Generally in a large industrial facility the neutral is reduced as the 277 volt load is usualy small compared to the 480 volt load.

For even larger loads - 12470/7200 volts or 13,200 or 13800 volts is the standard although 2,000/14400 is becoming popular.

The old 4160/2400 volt medium voltage is obsolete but still in use on older systems.

Motors are common up to 13,800 volts three phase. Most large power plants use medium voltage generators - 13,800 is common and then stepped up to 230KV or 500 KV or even higher.


Common transmission voltages are 44KV, 66KV 115 KV, 230 KV 500KV and 750 KV.

Different power companied have different standards but most are pretty close to the above.

Pat
N4LTA

[k4kyv]

In the 50s, 7200v was pretty much the standard voltage for rural distribution systems. Most houses had a 3 kva pole transformer.  By the late 50s and early 60s the proliferation of electric appliances had overloaded those 3 kva pole pigs, and the power companies began replacing them en masse with something more like 10 kva's.  The old 3 kva jobs were usually sent to metal scrap yards.  Some power companies would sell them to hams, priced at their weight in scrap metal, just a few bucks each. This was back when copper was cheap. A 3 kva transformer, taken out of the oil and big can, made an excellent plate transformer for a 1 kw transmitter.  Many of them already had a midtap from the factory, so they worked great for full wave rectifier type supplies as-is. With others, you had to dig into the winding and try to find as closely as possible the mid-point of the HV coil, and bring out a tap.  Even after years of use, the stink from the transformer oil never quite went away.  Some hams would take them to a motor re-winding shop and have them dip the whole thing in varnish to kill the smell.  The power rating of a 3 kva transformer out of the oil was probably degraded to just about 1 kw power rating as a plate transformer.  Usually, some kind of variac or autotransformer was needed on the primary (formerly secondary) winding to reduce the HV to about 6200vct, enough not to arc over the 866As or 872As.

[N4LTA]

In the south it is interesting in how the distribution system developed. The first "high voltage" 3 phase sysem was a 2400 volt phase  to phase system. The distibution transformer was a 2400 volt to 240/120 volt transformer with two high voltage bushings. As loads grew the lines were soon loaded and the idea was to convert to a 4160 volt phase to phase system and use the existing single phase transformers connected phase to neutral  - many areas underwent a "conversion" in the late 60s to 4160 volts.

The loads continued to grow and now there is very little 4160 left - most lines converted to 12,470 phase to phase and used single phase 7200 volt transformer phase to neutral. Right after I graduated from college in 1973, you could buy 2400  and 4160 volt transformers for near nothing as systems went to 12470/7200. The city of Spartanburg, SC is still an underground 4160 volt system but it is heavily loaded and obsolete.

About 25-30 years ago 22000/14400 became the standard for new lines and now 12470  is getting old and dated. Voltages much higher than 22000 are hard to deal with for distribution especially underground cables although I worked on a 44KV cable system in 1974 but it was a transmisson line for a large factory.


Pat
N4LTA

[KA3EKH]

A year or so ago I converted a old RCA BTA-1MX for operation on 160, although I don’t operate as much as I would like I do run the thing up at least once a week. Being that I thought I would not need 1 kW I decided to remove one of the PA tubes and also decided to run the plate transformer on 120 volts instead of the 240 volt design. The original design of the transmitter is 220/240 volts operation, all transformers, contactors and the blower are 220/240 operation. There are lots of tap on the transformers. Having a sub feed panel out in the shop providing a 220 volt feed and isolated breaker was no issue but the problem was that there was no provision for a neutral for the transmitter, just two hot leads and a service ground. I have a 240 volt 15A rated plug that connects the transmitter to the sub panel, that panel a square D QO load center has a isolated neutral from the frame ground that are all fed by an 8-4 cable back to the main panel where the neutral and ground are connected together. Being that I did not want to run the transmitter at full plate voltage I decided that I would remove the 220 volt feed from one side of the plate transformer and run the transformer on 120 volts. This gives me around 1.25 kV and an output of around 375 w from the transmitter. The problem is what to do with the low side of the plate transformer? There is no neutral brought to the transmitter except to the auxiliary lighting circuit and that’s just a little 18 gage circuit that supplies cabinet lights  so what I did was install a # 6 ground wire from the low side of the plate transformer to transmitter ground. There was already a heavy #6 ground to the station ground and # 12 grounds as part of the power cable to the sub panel. This has worked for some months without any issues and surprises me that I have no problems dumping lots of current back on the safety ground with any of the GFI outlets or anything else around the house. BUT because of this thread and because it never felt right returning current on the safety ground last weekend I changed the input to the transmitter. I got a 240 volt autotransformer and installed that on a panel above the plate transformer so now the 220 volt feed from the contactor connects to the autotransformer and that in turn feeds the primary of the plate transformer. No current flows on the ground circuit and everything again is 220 volt only in the transmitter. The only question now is there any reason that I would not want to run the plate transformer at its rated primary voltage?  I am assuming that a power transformer don’t care what its primary voltage is as long as it’s less then what would cause a insulation failure. Maybe there is some efficiency issue but so what if it’s not at optimal efficiency. Having a autotransformer or powerstat (what’s the difference?) on the input to the power supply is great because you can run power up or down with no issues and I have seen this done before in broadcast transmitters where they use a autotransformer to control the input to the screen supply for controlling power but on all the old AM broadcast transmitters have always seen the stupid system of inserting resistors in series with the plate supply output to drop voltage and reduce power that way. At least now my transmitter is not dumping current on the ground and NEC may be happy, next I will have to fix the back door interlock!

[Opcom]

The usual Euro power scheme is 220 V (not 240) single phase for residential service.  Hot & neutral + ground.   

Most of the service to the houses is done with big coaxial cable from what I've seen.  Very little metallic conduit, but a lot of that fat coax running everywhere.

The next step up is three-phase 380V, not sure about it being delta or wye.

Everything there is 50 Hz as well. 

There are several 'standard' outlet types in use throughout, so taking gear from country to country means adapters or changing the plugs on your cords.

73DG

Hmm -  what impedance is that coaxial mains cable?

[KM1H]

My first rememberance of a pole pig in ham use was a friend of my fathers who was an OT in the early 50's.
He worked 20 CW only with a SX-28 and chased DX with a 3el HB yagi just above the roof.The TX was HB to PP VT-127A's and they ran white at key down. Ive no idea of the voltage but it must have been a bit more than 1KW input .

In the 70's and 80's when I was custom building single or dual 4X1 amps the 4160 pigs were the choice. I left the details to the buyers and gave them the pig in a can with schematic and parts list if wanted after demoing the amp on my PS.

[Opcom]

Electrical safety may be a moot point when the utility meter explodes and burns the house down. Problem solved!
I don't know what kind these are that are exploding, hopefully not same as used here.
https://www.youtube.com/watch?feature=endscreen&NR=1&v=LXfIY6mfWWc
https://www.youtube.com/watch?v=ri-1nFkr5Ks

[W9ZSL]

Well!  The 240 outlet has 2 hots and a neutral which is grounded with a 6 foot #8 directly to the incoming water main immediately below the fuse box.  The station itself is grounded directly to a cold-water copper pipe in the laundry room and to ground rods.  Everything is in the basement so the rods are driven immediately adjacent to the pipe inside.  The 120 outlets for the gear (which I wired and it was inspected) has hot, neutral and safety so they are standard 3-wire sockets on a separate 15 amp circuit.  

Since I have a recording studio, years ago I decided to add a sub-breaker box directly off the 240 mains.  That box has two breakers, both 15 amp.  One 120 volt side is designated "Control Room" and feeds all my recording gear.  The other is designated "studio" for artists to plug in amps.  Right now the only thing on that branch is the station.

As for the dryer, it has a separate fused line from the mains.  "George" the transmitter will have it's own fuses for each hot with the neutral going to the chassis/rack ground.  My main concern is dividing the various 120 volt supplies.  The only thing operating from 240 will be the PA plate supply which should run at about 1500VDC at 200 ma under load.  The modulator B+, both filament transformers, screen supply for the PA and its bias supply are all 120.

As far as the rectifiers, I'm sure using something from RF Parts Company or Silicon Alley would save space, but I already have the rectifiers on hand and space really isn't a consideration.  Thanks!  Mike-W9ZSL  

[W3GMS]

Mike,
Your Neutral should not go to the chassis.  Connect 120V devices between neutral and one side of the 240V circuit.  The only AC related wire going to the chassis should be the safety ground wire.  That safety wire then goes back to the ground bar in your electrical panel.  That in turn, back in the panel, connects to the neutral only at one point, hence no current will flow in the safety ground unless you have a voltage breakdown between a primary component and chassis.  In that case you will have "fault current" in the safety ground wire but only during the fault! 
Joe, W3GMS 

[n1ps]

ALL residential receptacles must be tamperproof

Pat could you further explain what is a tamperproof receptacle?  Are we talking special tools to "unlock" a receptacle?  Or a seal?

Is this really an insurance issue?  Joe the house owner replaces a "tamperproof" receptacle...the house burns down (for other reasons) but the insurance investigator notices the tamperproof receptacle was tampered with and...no pay!

TNX

Peter

[N4LTA]

This is a website that shows the Leviton tamper resistant receptacle and explains a little about them. It also states that UL had withdrawn its listing of the cover plate (cheap) type


[url][http://www.onestopbuy.com/Leviton-Product-Focus/Tamper-Resistant-Receptacles-36583.asp/url]


I really don't think that the insurance company can refuse to pay for code violations found after the fact.  - the mortgage companies would never put up with that.

 
Pat
N4LTA

[n1ps]

OK TNX.  I had not heard of these type receptacles and was concerned that a homeowner could not "tamper" with a bad receptacle that had this rating.  Seems like a good idea to use them where kids are present.  For this kid, I'll have to resort to another method when sticking meter leads in a TR socket to see if it is live or what the voltage is

p

[Opcom]

OK TNX.  I had not heard of these type receptacles and was concerned that a homeowner could not "tamper" with a bad receptacle that had this rating.  Seems like a good idea to use them where kids are present.  For this kid, I'll have to resort to another method when sticking meter leads in a TR socket to see if it is live or what the voltage is

p

the stupid things cost more too - $5, not 89 cents. $7 if it is a combo light switch and outlet. If we are talking about the same thing, with the little blockage plates inside the prong-holes that keep only one object from being inserted at a time. Supposed to keep a child from inserting a fork tine in one side only. He now has to get two forks and stick them into both slots at the same time or they won't go in. Educational - forces the kid to do it right.

[W9ZSL]

Here's the problem as far as I can determine.  My service panel is 3 wire with 120 on each side and wire #3 going directly to ground through the incoming water main.  The outlet for the dryer is 240 with 3 wires period.  Granted there will be a few ohms difference between the service entrance ground and the "neutral" at the dryer outlet and the station ground.  Unless the station was located at the service panel there will always be the possibility of ground loops because of the difference in resistances. That would be more important if and when I try to interface this transmitter with my recording studio.  At that point ground loops and RF feedback could become a nightmare.

For now though, balancing the current draw on either side of the 240 volt incoming power source is the key here...remembering that there are two HV supplies with 240 for the PA plate.  That can be ignored because it uses both sides of the mains.  I suggest that I can probably get away with putting the plate and filament supply for the modulator on one side and the filament, bias and screen supply for the final on the other.

[Opcom]

The breaker boxes are the only places where the neutral is supposed to be bonded/grounded to earth, right? or not even there?

I would take it off that water pipe and drive a ground rod in order to avoid eating up the pipe from electrolysis.