I need help understanding AC electricity and generators (1/3 phase)

[fatjay]

I have googled and googled over the years and have come to a limited understanding on how things work. I will go down the list of my current assumptions, if I'm wrong please correct me.

I currently have a generator that is 10kw 110/220v. In 220v mode i have a ground, neutral, and 2x 110v's 180 degree's out of phase. These 2x 110v's go to the 2 busses in my breaker box by way of a 50a 2 pole breaker. When the power goes out, I switch off my main, switch on my generator, and I can use electricity, both 110v and 220v devices.

There's many generators on craiglist that are 3 phase. From my understanding, it's 3x 110v's 120 degree's out of phase. Being that my breaker box is only 2 phase(i know hte terminology is wrong, but i don't know the right way to say it), I would only be able to utilize 2 of the 3 phases available from the generator. So 15kw becomes 10kw. However does putting those 2 phases together create a usable 220v? I'm guessing no. Which means I wouldn't be able to utilize any 220v appliances in my home.

Why is a 110v/220v generator called single phasea nd not 2 phase? It provides 2 phases of electricity capable of generating 220v? They're definitely distinct from generators that only provide single phase 110v.

I realize that some of this I am not even asking the right questions, so please be patient.

 

[Industrial Toys]

The 110 and 220 are not out of phase. They are just different windings either from a stator or transformer. Three phase legs ARE 120 degrees out of phase.

There has been much writeen here about using three phase generators for single phase. It gets very complicated.

My take on it. You can use many three phase generators for single phase at a reduction in capacity, some better than others. I would say, that's ok in a pinch, but I personally would opt for a single phase unit when requiring single phase.

 

[fatjay]

So the 220v is 2x110v of single phase?

The reason I want to learn more is because at 10kw I’m generating just under what I want, I’d like to go 20kw, but I’m having a hard time finding anything that big that isn’t 3 phase or propane, and I’d prefer diesel since I have diesel tanks but no propane.

 

[Industrial Toys]

I am a fanatic. Have three slow running Diesel sets 7.5KW X2, (one inverter, one conventional) a 12.5KW and 3.7KW Air cooled Yanmar Screemer.

I'm always amazed at what people THINK they need. The smaller set I can operate, the better in my opinion. I run all these little guys into a 200 amp ASCO auto switch. No one says you can't do that.

AND YES, people often refer to the two phases in a single phase panel. Wrong! Leg might be the better term.

 

[Roadworthy]

To further muddy the waters, if you have three phase 208 you can go phase to neutral to get 120 volts. There is really no way to get single phase 240 out of it though - other than to use more equipment. Your best bet is to just get the equipment you need.

 

[Grumpycat]

25 years ago I ran a computer center which had a 50kW Liebert 3-phase UPS. However the electricians wired the output as 3 zones of 208 with neutral so 120V devices would operate.

It was a beast with something like (109) 12V group-27 sized lead acid batteries.

 

[Topzide]

Check out Generator Accessories – Gas Generators | Central Georgia Generators
They have pto kits for use with tractors and stand alone units. 21kW - 25kW units with 3 - 4 week lead time

 

[Carl_NH]

So the 220v is 2x110v of single phase?

The reason I want to learn more is because at 10kw I’m generating just under what I want, I’d like to go 20kw, but I’m having a hard time finding anything that big that isn’t 3 phase or propane, and I’d prefer diesel since I have diesel tanks but no propane.

Why do you need more than 10KW @ 240VAC? Its easier to reduce load and only power what you need in an outage. I understand if you want to run AC, and hot water, a well pump and the rest of the house at the same time you will need 12-15KW to meet peak demand, but if you can manage/reduce the load to what is needed that's preferable.

As Topzide suggested there are PTO driven generators that one of your tractors can run that generate 12-15KW and you will need 20-25 PTO HP roughly to run these. Your B8200 is a bit light at 15PTO HP.

 

[fatjay]

10kw @110vac, 5kw @220vac, 50a 220v breaker. I run a server rack with many computers and servers in the basement for work, wife likes ac and hot water. The goal is minimal interruption during power outages. Working from home, kids are attending virtual school this year. We lose power regularly.

I'd rather not tie up a tractor, I'd like a dedicated machine. I'll buy/build whatever i need within reason, just want to learn what I need to do it right.

 

[Industrial Toys]

My first genny was a pto 15KW Onan. Great machine, but un-nerving having your tractor run full tilt unattended. And at night, for what? to run the fridge?

I run my hot water heater at half power. Less lime deposited on the element and half the load to worry about in an outage. I have never un out of hot water, but I mostly live alone except for weekends.

I kind of WISH, with all my resources, that I lost power regularly. Also have a 3000 watt telecom style inverter. 48 volt input that I "intend" to plug into my E-Gator one of these days.

REALLY, the trouble is not so much loss of power, as never knowing how long it will be out. The modern IT systems to keep you informed are worth nothing and getting worse as they get more complicated.

 

[CalG]

May I suggest that a study of 3 phase Wye (Y) vs 3 phase Delta would put you in a better understanding.

Wye configuration allows easily balanced loads for both 220 (208) a and 110 single phase needs, as well as full 3 phase output.

Delta configurations allow options as well, (vis "corner ground" etc.

It would be a requirement to KNOW the nature of the generated source to determine if the single phase power draw would be right for you.

"Computer grade" power may require an inverter as a buffer between any engine driven source and the electronics. Your freezer won't care at all. ;-)...

 

[Industrial Toys]

Most modern switching supples are pretty forgiving. Until they fail! DC to light frequency input, very wide voltage range. Many servers have redundant PSUs.

But yes, you need something between power loss and generator power. Unless you don't care about uninterupted service.

NOTE: My Telecom Inverter will not accept the power of my Kubota/Onan 7.5 KW Generator, so I can't recharge my batteries using that. The frquency isn't bang on. Something to keep in mind.

 

[Mat4644]

This sites does a good job explaining.

In the United States, utility companies are required to provide a split-phase 240V feed to your house. This consists of two legs of 120VAC that are 180 degrees out of phase with one another.

 

[fatjay]

This sites does a good job explaining.

In the United States, utility companies are required to provide a split-phase 240V feed to your house. This consists of two legs of 120VAC that are 180 degrees out of phase with one another.

View attachment 666934

I knew got that from somewhere, but I'm ready to believe anything.

I wish i still had my oscope. I should shop for another some day.

My computer systems all have pure sine wave UPS's that clean/condition the power before passing it into the servers.

 

[strantor]

I knew got that from somewhere, but I'm ready to believe anything.

I wish i still had my oscope. I should shop for another some day.

My computer systems all have pure sine wave UPS's that clean/condition the power before passing it into the servers.

You should. If you really want to understand this stuff. Playing with a scope is how I finally wrapped my head around single phase, 3 phase, and "how many degrees out of phase."

(Assuming an isolated scope) put one probe across L1 and L2 of of a 3phase supply, observe sine wave. Put 2nd probe across L2 & L3, observe 2nd sine wave, 120 degrees out of phase from the first. Put 3rd probe across L3 & L1, observe 3rd sine wave, 120 degrees ahead of L2-L3 and 120 degrees behind L1-L2. 3 phases. 120 degrees out of phase from each other.

Now approach a single phase supply. Place probe across L1-L2, observe sine wave. Now take second probe and put it... where? Across L2-L1? That's silly. It's obviously the same thing as L1-L2, but reversed! There's only one phase. And it isn't any amount of degrees from anything, because there's no other phases to reference it against. Sure, you can reference to ground/neutral, but that's not a phase, it's a center tap of the one (single) phase of supply. It's a mind trap. Ground/neutral doesn't count.

There is such thing as "two phase" but it's very rare and consists of 4 wires. Unless you live in a 100+ y/o industrial facility in some isolated part of Michigan, youve never seen it and probably never will. It's two separate single phase supplies, 90 degrees out of phase from each other.

So why all these phases and degrees? Imagine riding a bicycle with only one leg. You tape your one foot to the pedal, and as long as someone gives you a push to get started, you can can keep going. That's single phase, and that's why single phase motors (mostly) require starting capacitors - the push from behind to get them started. Now imagine you have 3 legs and 3 pedals. Never mind the absurdity or the breach of physics, you could take off from any position of the pedals or the legs any time of day or night, covid or not. That's why 3 phase motors are better. One of the reasons. The 197 machines in Michigan using 2-phase power can do the same. They're a dude with 2 legs on a bike with 2 pedals, but their pedals are 90 degrees apart. So they can ride, but it's goofy and unnatural looking, and that's why the idea didn't spread outside of a few little isolated pockets of early industry.

Know that you do not have 2 phase.
Know that you have single phase with 2 legs and a neutral. For the bike analogy you can consider the neutral a crotch or a knee i suppose. Maybe an ankle.
Know that your single phase is not any amount of degrees out of phase with anything, and speaking of degrees is a waste of breath.
Know that your best bet is a single phase generator, but if you can't find that, look into a 12-wire 3 phase generator. Most of the time with those you can wire them for single phase with a derating factor.

Most importantly, Know that your method of turning off your main supply breaker and turning on your generator is almost assuredly against local ordinance, national electrical code, and safe practice. You need a transfer switch, manual or automatic, which 100% eliminates any possibility whatsoever of sending power back up into the grid during an outage.

 

[Industrial Toys]

I have been in electronics on and off since the mid 70s. I bought a scope about twenty years ago. I have never plugged it in! lol

 

[RoyKing]

For average home you buy a 4 wire dedicated single phase alternator with digital voltage regulator. Mecc-Alte site will explain the different types available. You can get any size diesel gensets. The one I spec'ed for friend was small turbo charge perkins engine, 36kva mecc-alte 4 wire full size alternator, in a level 2 aluminum sound enclosure on a 60 gallon tank, run by deep sea 7200 line monitor with 200 generac ATS. There is no reason these days to buy a 12 wire head if you will never need 3 phase. Just more cost for more windings.

 

[Mat4644]

I didn't know about 2 phase until a couple years ago. Met someone from Philly that informed me older parts of the city especially Gov buildings were still wired for 2 phase. New installations are usually modern conventional. Since 2 phase public power generation no longer exists transformers are used to produce.

 

[mikester]

10kw @110vac, 5kw @220vac, 50a 220v breaker. I run a server rack with many computers and servers in the basement for work, wife likes ac and hot water. The goal is minimal interruption during power outages. Working from home, kids are attending virtual school this year. We lose power regularly.

I'd rather not tie up a tractor, I'd like a dedicated machine. I'll buy/build whatever i need within reason, just want to learn what I need to do it right.

Id suggest buying two 10kW generators and splitting your circuit and have the ability to cross feed. Put your well pump, fridge, basic lighting one one generator as the need to have. Put the energy hog electric water heater, AC on the second genny. When the primary genny blows up you now have a backup. AC and hot water is nice to have, intermittent use, and low priority.

If hot water is critical to you then get an LPG on demand water heater and power it up only when you need it. Put the computers on battery BU.

 

[3Ts]

The best way I can think of to explain this is that power distributed throughout the country is 3 phase. To deliver the power to a house one of these phases is tapped to run a line to the house (hence the term single phase). The transformer the house is connected to puts out 240v. However, it is a center tapped transformer, so between the center tap and either end is 120v. You have both ends and the center tap (plus ground) being run to your main breaker panel. Generators will have to emulate this.

Grounding electrical systems is a whole course by itself.