The AM Forum

Does anyone have three phase power in their residence?

Will power companies supply it if you live in a residential zoned area if you ask?

The home I grew up in in Phoenix had three phase power. My father was an electrical contractor and, back in the 1950's put an AC unit in the house -- back when most people had swamp coolers.

It was a small commercial unit, water cooled with a water tower, and ran on three phase current.

I remember as a teenager helping him upgrade the service on the house to 200 amp three phase (the main power service disconnect had three ganged breakers).

My parents have passed on, but my sister and I still own the house, but I don't know if he ever downgraded to single phase after I moved out. I'll check next time I get there.

I know the original AC unit is long gone, in fact the house is on it's third AC system.

I'm wondering if this is common or rare in residences. None of the houses I've owned or any of my friends have owned had three phase power.

Wow!     3 phase residential.   MY house was built in 1958 and when I moved in, it had the original Carrier A/C.  It hardly worked and ran on 240....Needless to say, I had it replaced with a new carrier unit.  The compressor unit was in the back of the garage and it was about 5' long X 2 1/2' high X 2 1/2' deep........I think 40A

Tom - AB3FL

Three Phase
Your making me all fuzzy feeling.
No more problems running 1.2 Gigawatts
Time for a BC Rig!!!

PHIL K2PG has three phase power at his residence for his Coillins AM transmitter. It is running at legal limit, he didn't want to convert anything to single phase.
IF you really need 3 phase for that special transmitter project, you can buy motor converters to make three phase from single phase. A real light dimmer when it starts up.

Fred

If the motor-generator was connected to power only the plate section, it would have the property of "kerchunkery" (tm).

I suspect many residential areas don't have 3 phase going down the street so that would be a deal breaker right there.  Moreover, I believe our 3 phase service at work has 3 transformers.  Pretty expensive to provide for one residence.

Mopman Fred said:
That's because a lot of farms utilize 3Ø to run heaters and blowers in their grain silos. Of course, it helps that the power plant is about 3 miles from Phil's QTH.

I have a 200 A 3 phase service --only because I live in an old building that used to be a blacksmith/welding shop. It sure makes HV filtering easier if you run 3 phase generated B+. Uses a lot of rectifiers though.
Skip

Right on the three phase complexity remarks.

I think for new three phase service, at least around here, you have to sign up for commercial Demand service, i.e. in order for the power company to go to the expense of installing such service your power bill will be higher reflecting the ultimate demand of the service.

I'd look up the rates and rate structure before planning.  Most times three phase contracts are handled by a pwr. co'.s engineering dept, not the 'sales' dept.

"... Uh, Mon Power?..   
 "Ok, yeah, I'll hold.. " 
 "damn touch tone.. "
 "<6, ,3, 1,>.."
" uh hi,"  "yeah, well I gotta 50kw vapour phase cooled reactor here... "

"Say What!"   
 "you say minimum $300/mo,? .. "   " AND 50 Cents/Kwh?...  " 
 "Click."

If you only have one wire on the pole then there is no way to get 3 phase from the power company.

One does not need a "motor generator" (actually motor alternator) set up to run 3 phase stuff off single phase.

You can check the web and find that you can make a good 3 phase power using a 3 phase motor of greater HP than the thing you want to run via what is basically some switches and a few well placed oil caps.

If the power requirement is low enough you don't even need the switches, just the caps.

I do this trick all the time to run my milling machine. Works fine.

My neighbor used to run his on single phase (reduced torque) by using the cap start trick on his three phase motor...

Works like a charm. Makes some noise though.

            _-_-bear

If you have poles & wires feeding your place, you may be in luck.  There need to be three wires up on the high tension side, and make sure you get a wye hookup as an open delta (two pig service) does not give true 3ph.

We have 480V 3PH here at the Arizona acreage. It is within the bounds of a small co-op (Electrical District 3), and I inquired how to go about it.  They subsidized $5K of it, I had to pay $2K towards the upgrade.

There are three 50 kVa pigs outside now.  I worked commercial power in my broadcast job for years, so the hookup after the meter was old hat.

Our KWH cost is just a plain residential rate, so it doesn't hurt too badly.  I hope to recoup the investment by using 3ph in most motor areas.

Now that 1940 water-cooled WECo 405B in storage has a reason to live on 160.... 8)

Ive been using a 7.5 HP 3 phase motor and a phasing cap for a few decades to run machine tools and a 5 HP 2 stage compressor in the garage.

I havent reached the level yet to need similar in the basement but this latest acquisition just might force it 8)

Carl
KM1H

carl,

LUV teh 1920's breadboard construction!  8)  ....qth to send flowers and card pse?

(assuming thats just a picture pose)

I shouldnt joke, my hb rig had full B+ on the tank coil and no shielding or safety features at all.  :P It was death personified.

3CW20000A7-1-1.jpg


right out of Better Homes and Gardens ... a great center piece !  ...73 ....John

You could use it as combination transmitter and tankless water heater for your house.

The Bear is right on!!!
I also know a fella who has a machine shop with a motor generator to make three-phase and it is definitley a light dimmer when first turned on.

It's strange that Allan Weiner didn't try a "Commercial Demand" with his electric company to get three-phase for WBCQ. It's an electrical nighmare $$ over there sucking on single phase power for several 50KW transmitters.

Fred

All fine & well, but all a 'phase trick' does is run a motor.  Not much for the power supply in a transmitter there. ::)

Thats just the way I picked that Eimac Steamer up a few weeks ago at the local surplus place. The tube looks brand new, or at least it hasnt had any serious dissipation. It has a 1995 date code.

Filament transformer and filament seal blower are Italian. It also came with a lab quality conductivity meter and several liquid conductivity standards. Im wondering if it wasnt some some of university lab demo for heat transfer.

Anyway the price was too good to pass up, they had no idea what it was. It could sure make a loafing linear to keep 3885 clear 8). Ill bet even Patrick could hear it.

Carl
KM1H

Why not?  It runs my welder just fine.

Carl

Hey Carl,

N1HCI and I saw that at ESS too.  I decided I couldn't afford to run that 100 Amp filament, let alone the plate transformer for that thing.  Will you be drilling a geothermal well to dump the heat?  Man, let me know when you fire up so I can disconnect my antennas.  Frankly, I'd love to play with that thing too.
73,
Mark
Concord, NH

I drop in there once a week and I think he got tired of me fondling it and dropped the price in half. The filament is ony 700W and the xfmr is included. Thats not much on the electric bill as long as its only on when needed ;D

I doubt if I'll ever use it but its a great conversation piece. Its in the kitchen eating area window for now. 8)

Carl
KM1H

Well, I finally got back to our Phoenix house, and it does still have three phase power.

There are four lines coming in from the pole-pig up on the pole in the alley.

Three insulated hot wires and a very thick uninsulated common wire.

The house has three sub panels. Two are fed off two of the hot lines with two ganged breakers from the main panel on the back of the house near the meter. I assume these panels are only for 240 volts and the 120 volt curcuits between one of the hot lines and ground.

The third sub panel, which goes to the utility, furnace, and AC room is fed by three phase with a tripple ganged 50 amp set of breakers. I'm pretty sure nothing in the house needs three phase power any more since that original three phase AC unit was replaced years ago.

The service is 200 amp three phase.

I wonder if the current AC unit runs off 208V. I'll have to check that before I leave Phoenix.

The whole thing seems like overkill for a ordinary 2000 sq ft 1955 tract home.

I wonder if we are paying more per KWH than the neighbors. Probably not, since knowing my dad he never would have put up with that.

Sounds like 208 wye 4 wire.

Lots of people think you need three transformers to make three phase. If you power company says that, tell them you want a Scott T configuration. It uses two transformers but I don't know if it would work in a Y configuration to give you 208/120 volts. You may need a separate indoor step down transformer for your 120 volts. Can anyone enlighten me here?   

Three phase is tough in new residential areas. If you have underground service with pad mounted transformer you are probably out of luck. If you have overhead lines you may have a chance, but many residential areas are fed with single phase overhead lines.

Some older house have three phase lines because when air conditioning was a new thing, many system required three phase power. This dates to the 50's and earlier.

Most power companies have discontinued the old three phase open delta  services that used two high voltage phase wire and two transformers. The services has a "high leg" that caused lots of problems. One of the transformers was a 240 /120 volt secondary. From two points in the delta, you got 120 volts but from the other you got 190 volts. That burned lots of things up when someone used the high leg  breaker space.

Almost all three phase is now delivered using three phase transformers and delivered at 208/120 wye and 480/277 wye except speciality industrial services that sign a long term contract.

If you don't have a three phase primary in your area, you are out of luck on getting three phase from the power company. The three phase converters will work with motors but are not much use when trying to deliver power to a non motor load. The whole purpose in three phase power delivery is to get more power with less conductor.

The rotary converter are less efficient than just designing a single phase solution They work fine when you have a three phase motor and only have a single phase power source, but the power transfer is not efficient.

Pat
N4LTA

I wish I had three phase power here. There is only single phase up here on Henry Nyellar mountain. Three phase is about two miles from here. I have had the use of 3 phase power at my work station when I worked for Armstron transmitter. I used it to run Big Mac a pair of 4-1000s modulated by a pair. Originally this transmitter had a single phase 4Kv supply. Dale(VE3AAM and I worked together for a while. We spent a number of evenings removing the single phase power components from the McMartin BA 2.5K and sliding in the iron from a Gates 5P . More power!!!. At full strap the plate voltage was about 4800 voltys the way I configured the iron. The high power/low power switching was easy. The primaries of the plate transformer were in Delta for full strap mode and Wye for Cruizin' mode. Very smooth transition from one to the other. In closing: If you are lucky enough to have 3 phaze power in your residence make use of it. Time to put that big maul on the channel cawwmmmn ownnn
DeTim WA1HnyLR

Back in the 1970s a friend moved his wood shop from an industrial building with 3 phase into his garage. His table saw was a 5 hp Rockwell Unisaw, the radial arm saw and air compressor were both 3 phase as well.

I bought a small, $40 box from Northern Hydraulics, which at the time was one small shop in Burnsville, MN. It ran the table saw and radial arm just fine but wouldn't start the compressor on cold mornings. I finally wired the box to one 240 volt breaker and added a 1 HP spare motor that ran as long as the breaker was on, which improved starting. The usual drill was to come out in the morning, fire up the wood stove, switch on the breaker for the three phase, fire up the radial arm to provide more power for starting the air compressor, start the air compressor and shut off the radial arm saw. The compressor started fine by itself after the first run to warm up. We ran that way for several years until he moved back into a building that had three phase.

I don't know what was in the box but I'm sure it was just a few oil caps.

Two-transformer distribution or open-delta is an approximation of three phase power.  One transformer is giving two legs & neutral, at 180 degrees phase.  The other transformer is tied across the leftover leg to give the remaining 120 degrees.  This is akin to the Scott connection.  It is easily identified by the presence of a 'wild leg', with a higher leg-to-neutral than the other two.  It cannot give equal voltages to neutral like real three-pig service.

This is widely used for motor loads, where the rotary inertia carries the deal OK.  Don't buy it for eventual use in power supplies, as it will not easily power a single-core transformer (such as a plate transformer) down the line due to the screwy phase relationship.  I will generate a host of unfriendly harmonics in the ripple, usually leading to rectifier and filter failure.

This discussion has now gotten me wondering which type of system I have.

We may have the wye configuration, but then, if I'm understanding this correctly, the single phase systems must run on 208 (for those that don't run on 120).

In that house, there is an electric range and a 5 ton AC.

It's possible the range might be running on 208 even though if it is a 240 volt model. The burners would not get as hot, but the oven would probably work because it's thermostatically controlled -- even if it's only getting 208. It would heat up slower though.

The AC, however, must either be a 208 volt single phase unit, or perhaps 3 phase. I assume it wouldn't work properly if it's desinged for 240 and only getting 208.

Looks like I need to do a little more checking.

I wish I had brought my DVM on this trip.

Or perhaps I've got one of those unbalanced systems, but I can't see my dad ordering that back in the '50's when he put in the three phase AC conpressor.

Have to disagree on the open delta bank being an approximation of three phase. It is true three phase just like any other three phase delta delivery. I am a power system engineer - been doing it for nearly 40 years.

If you have two solid voltage sources spaced 120 degrees apart delta connected - then the other point on the delta must be 120 degrees from the other two - there is nothing approximate about it - it looks like and is the exact thing as if you used three transformers - except in the capacity that is available from the two transformer rather than three.

The high leg is due to the nature of the tapped winging - not due to any phantom principal.

Draw a triangle to scale  - side 1 is a center tapped 240 volt winding going from a to b

From b to c is another leg - a 240 volts winding

The vector voltage from a to center tap or from B to center tap is 120 volts.

The vector voltage from C to a is 240 volts even though there is no winding -

the vector voltage from c to the center tap of the tapped winding is about 190 volts or the high leg.

All of these voltages are real and usable.

The open delta bank was a standard for many power companies for years. It was the standardization of the wye system at 208/120 and 480/277 volts that has slowly phased it out.

If you do have Wye it's simple to figure out. You will have four wires to your breaker box. The voltage from leg to leg will be 208 volts. The voltage from any leg or phase to neutral will be 120 volts. It could be slightly higher or lower depending on the load. I have seen lows of 198 volts in the same configuration in factories. That was not good because our industrial battery chargers would not properly charge the fork lift batteries in their given time.  

With a wye system - 208/120  you will have approx 208 from any two phase wires and 120 volts from any phase wire to neutral. 208 volts was selected to give the standard 120 volts from phase to ground.'

In any grounded wye connected system the phase to neutral voltage is the phase to phase voltage divided by the square root of three. So 208 volts was selected as the standard phase to phase voltage.

Before the 208/120 system was common, the most often used system was the delta connected 240 volt system.

It consisted of three 240 volt transformer connected in a delta configuration. For motors and three phase loads only the voltage was 240 between any two phase wires. There was no voltage from phase to ground and there was no neutral. When 120 volts was needed , it was easy to center tap one of the three transformers and ground it which would give 120 volts from two of the phases to ground - BUT the other phase had the "high leg"  which caused problems.

The high leg was there no matter whether you used three transformers in a full delta or two in an open delta.
This configuration usually used a standard three phase panel and every third breaker space was blanked out.

Now , it is most common when only motor loads or balanced three phase loads are to be served, that a 3 wire 208 wye or 3 wire 480 volt wye system is used rather than a delta connection. The center of the wye is ungrounded and unconnecetd and no neutral is used. Since the center of the wye is not connected to ground  - thre is no voltage from line to ground.

I still stand by the transmitter companies' statement:  Open Delta does not rectify to DC without problems.  If you used it anyway, it was at your own risk and you could expect to replace expensive parts soon and on your own.  RCA, Continental Electronics, Collins, Harris/Gates eTc.
 
                                      ...AND...

My neighbor has a two-pig open delta 240V service in his machine shop.  It will not play into a single-core 3 ph transformer, pops all the 200A fuses when connected.  I put a scope on it, and found the waveforms were just as I said:  180 degrees on the 120/240, and 120 degrees on the wild leg.  Not that I care, but that is the way Arizona Public Service set it up.  It is a moot point, as the local Co-op has taken over the entire grid out here and will be rebuilding all of it. 

I am already on with them, 480/277 Wye.  8.6c/kWh

No need arguing with you. You are obviously talking about something other than a two transformer wye connected primary, delta connected secondary bank.

The output is three phase - 120 degrees  - it would be impossible for it to be anything else -

And as I said  - the high leg is there in a two or three transformer bank - it is not phantom. - It's not to hard to prove - draw the triangle.



From a standard engineering text:

Open Delta Connection:

    The open delta transformer connection can be made with only two transformers instead of three (figure 1-8). This connection is often used when the amount of three phase power needed is not excessive, such as a small business. It should be noted that the output power of an open delta connection is only 87% of the rated power of the two transformers. For example, assume two transformers, each having a capacity of 25 kVA, are connected in an open delta connection. The total output power of this connection is 43.5 kVA (50 kVA x 0.87 = 43.5 kVA).
   
    Another figure given for this calculation is 58%. This percentage assumes a closed delta bank containing 3 transformers. If three 25 kVA transformers were connected to form a closed delta connection, the total output would be 75 kVA (3 x 25 = 75 kVA). If one of these transformers were removed and the transformer bank operated as an open delta connection, the output power would be reduced to 58% of its original capacity of 75 kVA. The output capacity of the open delta bank is 43.5 kVA (75 kVA x .58% = 43.5 kVA).

    The voltage and current values of an open delta connection are computed in the same manner as a standard delta-delta connection when three transformers are employed. The voltage and current rules for a delta connection must be used when determining line and phase values of voltage current.



You and your scope are not looking at an open delta connection - or ..............your wrong?

This is pretty basic stuff - I'd would have no problem putting my stamp on it.



Hugh P. Bunn, PE, SC #9801

NC, SC, GA, VA,
Unlimited electrical contractor SC, NC, GA, TN

Hi Hugh,

Obviously I am not looking at a correct setup for this guy.  That is why he called me over in the first place.  His service is wacky, and is already being re-engineered correctly by the growing electrical co-op.

My points were-

1:  If & when you ask for a 3-phase service, be sure what you are getting .  Just because the 'power company' sets it up and it works after a fashion, doesn't make it right.  If you know a P.E. have them look at the work order.

2:  Hams like us would most likely jump into the polyphase camp to run a vintage broadcast transmitter.  Hence my relation of the warning about power supplies.

There can be no argument with your statements, the physics of electricity is what is is.  The caveats contained in both your texts and mine relative to the various power distribution schemes are what I relate to as an 'approximation' in my previous post.

What I distilled out of it years ago was open delta setups are a cheap way to go, and Murphy's law finds them more often.

dg

I hope I didn't irritate you because I did not mean to.

There are a bunch of connection that generate a phase shift but not a true 120 degree shift and not true 3 phase. There are hundreds of stories of things worse than fuses blowing with them. There is no way you could run a three phase transmitter with one of these rigs effectively.

The best three phase system is the modern 208 or 480 wye system - as you said - but there are lots of old delta services still on the grid. They cause a lot of grief with the high leg and the confusion about motor voltage. Most 3 phase motors are still rated 230 volts  - they work fine on a 208 volt system but they cause lots of confusion - people ask for 230 volt three phase - and it usually isn't available - or needed.

I could tell you a lot of horror stories.

Pat
N4LTA