3 pase power

[Steve Jenkins]

Well, we are getting started on the home remodel and the new shop. Most of my equip is 3 phase and I've been planning on getting a rotary phase convertor but I think it is possible for the power company to use two transformers to create three phase at the pole. Is this possible? I want be able to ask semi-intelligent questions when I contact them.
Thanks
I know, I know PICS. I'll get some I promise

[Mike Cutler]

Steve. I would just explain your needs to the power company. They will be able to look up the closest pole, and transformer to you and tell you if 3 phase is avaiable for you, and what any additional requirements/ costs would be involved. The customer service rep may not have an immediate answer, but the T&D ( transmission and distrubution) department will.

There sure have been a lot of electrical questions lately.

[Steve Clardy]

Not sure Steve. Normally they have to run lines to you. Maybe check to see if any are already close to you.
I run a rotary for my 3000# Hempel lathe, and a static box for my 7hp overhead pin router. Both work fine.

[Ian Barley]

I have just moved to a new shop (I know, pics will follow) which has native three phase power - previously I was running three phase machines off a rotary converter. Basically the machines ran but perform massively better with native three phase. I may have had a duff converter but I would do whatever I can to get real three phase if I was you.

[Norman Hitt]

Steve, have YOU physically looked at the "Power Lines", that your house is connected to?

A few years back, I was contemplating getting some 3 phase equipment and called the Electric co to find out costs, and was told they would have to set a transformer to hook me up and it would cost me $1,700. Needless to say, I decided to forego any 3 phase equipment.

About two years ago, we had to have a new Main box installed out by the meter to bring it up to the "current Code", before the city would allow any new wiring to be installed for the new shop. I was talking to the electrician as he was changing out the big box, and happened to notice that my neighbors power, (which comes off the same pole as mine, and the pole has a transformer of some kind on it), had one more wire going to his meter than mine, and I asked the electrician, "What's the Deal with That hookup"? He looked at it and said, Oh, they've got 3 phase going to your neighbor's house for some reason. I checked with the neighbor and he said, yes, our HVAC's, the pool pump, and something else was 3 phase.

To make a long story short, the 3 phase had been there since both of our houses were built, (some 32 yrs before), but I didn't know it, and "Apparently", even the Dept at the Electric co, that I had talked to didn't know it was there either, or they wouldn't have said they would have to set a transformer to give me 3 phase power.

Check it out, it may already be available..........you might get lucky.

PS: I don't really understand what all is available on the power lines in our back alley. They are only service lines, (not transmission lines), that end 3 houses past ours, Buuuut.....there are two smaller bare cables, (maybe 3/8" to 1/2" dia) close to the ends of the crossbeam at the top of the poles, (I think just to keep the poles in tension as I saw no hookup to them), then about 2 feet below that there are 4 larger aluminum power cables spaced about a foot apart, then down below that are the two large, (about 1" +) insulated cables attached to steel cables (for strength), for the telephone and Cable TV lines. I walked down our alley (it is a LONG block), and was surprised to find 65% had 3 phase connections, but mine was in the 35% with only single phase, buuuuut......My connection, however, is the ONLY ONE, where they used three aluminum cables that were about 3/4" or maybe even 7/8" in diameter for the drop to my meter, and I have NO IDEA why. All the rest of the house drops were using MUCH smaller cables to the meters.

I wonder why 4 power lines? Is it one line for each of the phases, plus one for the ground? If so, why are there three Or maybe four transformers scattered along the poles in this one long block?

[lou sansone]

first of all is there three phase on the road? it is easy to tell. There should be 3 parallel wires plus one neutral / ground about 10 feet below the 3 parallel wires. Most state highways have it, many secondary roads do not. If there is no three phase then you are out of luck from the power company. IRT the 2 transformer question, the power company usually uses 3 to form a Y system. You can use 2 transformers to form an open delta system, but I personally have not see this done with the primary power company's systems. I have created many open delta systems in the past using just 2 transformers. What you will probalby want is a 208 Y system. The big deciding factor is motor load. I think you want to show them that you plan on having a 15 to 20 hp motor and that should be sufficient. I have three phase in my shop and that is how I went about it.

best wishes
lou

[Steve Jenkins]

I've checked the poles and there are only two wires for as far as I care to see. I guess once I get a bit farther along I will try to talk with the utility co. and see if they can come up with somehting other than multi multi thousands to run 3 phase from wherever.
I imagine that a rpc (rotary phase converter) is going to be my best bet.

[Mike Cutler]

[QUOTE=lou sansone] "I have created many open delta systems in the past"

That's a lot of power Lou, it would be kinda interesting to hear what you set up the Delta's for. . If we start talking about Toroidal Saturation Core Reactor transformers and power supplies though, I'm outta here.

[Dev Emch]

Steve...
The short answer is nope. If you check your feeder line, you will see either two wires or three wires which are hung from insulators. This incomming line is called a feeder and is usually a 7200 volt line. The three phase line can then be used to provide three distinct feeder lines from which numerous homes can be hung.

You will need three transformers to drop this voltage down. There is a unique way to do this with only two transformers which is called an "auto transformer". This is often done when you loose one of your transformers and you quickly reconfigure the remaining two as an auto transformer.

The problems that most folks have with phase converters is that they are using to small a converter or they have a soft service condition.

Right now I can see the females causing lots of trouble so I gotta go. Wil try to get back on line later when they are not preoccupied in hassling me.

[lou sansone]

[QUOTE=Mike Cutler]

"I have created many open delta systems in the past"

That's a lot of power Lou, it would be kinda interesting to hear what you set up the Delta's for. . If we start talking about Toroidal Saturation Core Reactor transformers and power supplies though, I'm outta here.

hi mike
open deltas are used quite often in factories that are trying to save a few bucks. I have configured many machines and process lines using them ( in the range of 100 to 200 amps only ). I would have perfered to spend the extra money and close the delta, but it was not my call at the time.


here is some info on open delta connections

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).




<CENTER><!--mstheme--><TABLE borderColorDark=#333333 cellPadding=0 width="50%" borderColorLight=#666666 border=5><TBODY><TR><TD align=middle width="100%"><!--mstheme-->Figure 1-8: Open Delta Connection<!--mstheme--></TD></TR></TBODY></TABLE><!--mstheme--></CENTER>



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.

more info can be found at this link

http://www.elec-toolbox.com/usefulinfo/xfmr-3ph.htm

lou

[lou sansone]

just another follow up on the 3 phase utility info. I have to believe that if there is no 3 phase on the street then there is really no way for the power company to transform it down and deliver it to you. You will be stuck using a rotary phase converter.


lou

[Kelly C. Hanna]

Congrats on the new house and shop Steve! It was great hearing about the move yesterday and I'll bet you're both excited!

[Tom McDermott]

Hi Steve,

You may also want to look at VFD - Variable Frequency Drive. It's an electronic 3-phase generator (like a rotary converter), but gives you soft-start capability and ability to change the motor speed electronically. Available with 230V 1-phase input power. They are in about the same price range as rotary converters of similar HP.

By the way - your 2-part program on spray finishing at the NTWA was teriffic!

-- Tom

[Jim Becker]

Lou...thanks for your piece up above--very interesting. I actually think I saw a two-transformer setup earlier today not far from here. Conductors led into a small business building along a local highway.

[Charlie Plesums]

One of the good things about a rotary converter is that the modern ones are very efficient... 98% or better. You have to start them before you start anything in your shop, and they have to be big enough to handle the starting load of the biggest machine, plus whatever else is running (e.g. starting load of the saw, with the dust collector already running).

One of the bad things about a rotary converter is that they normally run all the time, and are not silent.

Variable frequency converters allow your machines to run at other speeds, but they do so by changing the frequency of the power - not just 60 hz. I know many machines can handle it without a problem, but I don't know if all machines can. I would love to make my shaper run faster when I use small bits, but would it be happy with 120 or 150 hz power?

Some of the inexpensive static converters use one phase for starting, but primarily drive the 3 phase motor with single phase. This means max of 70.7% power from your machines.

Some power companies assume that 3 phase power is for industrial use only, and thus require a demand meter. You pay less per kwh for the power used, but pay a big surcharge for the peak demand in a month. I have heard horror stories of the demand charge being several times the power charge in an electric bill, so it is worth checking into. If you tell the power company that you are going to have a big motor (like a 15 hp vacuum pump for a CNC machine) they have to bring wiring and transformers big enough to handle that load, so may make that your minimum demand charge.

I thought you had a neat shop when I saw it... what are the new plans?

Charlie