two phase or three phase

Hi Ralph,

Yikes! Hit the books for sure!

The schematic in the link

Next step is to look at the wiring manual for the Kohler and see if their "single phase" naming convention is actually 0 and 180 deg center tap.

Thank you for the links!

-T

Ah Ha!!!! I get it now!

Hi Ralph,

Ah Ha! I get it now. I was looking at in from the prospective of an electronic circuit designer not a utility supplier.

In the following

Thank you for the education!

:-)

-T

Hi Snag,

Figured it out with Ralph's help.

I was looking at in from the prospective of an electronic circuit designer not a utility supplier.

In the following

And you were correct. it just did not sink in.

-T

Follow up:

I misunderstood the meaning of two phase, three phase, and split phase. It is what the utility delivers to the primary of the transformer, not what is delivered to the house.

I was taking a secondary center tap transformer as two phase. It is two phase (0 deg and 180 deg), but that is not what the utility refers to on the primary of their transformer. The utility calls two phase zero degree and 90 degree.

I also did not realize until digging into Kohler's specifications that their wording of single phase and three phase were not for the SAME unit. They have four sub units. The single phase and the three phase use different alternators.

And indeed the single phase alternator unit does provide zero degree, neutral, and 180 degree split phase, which will indeed make my dryer and my stove happy.

Thank you all for the education!

-T

The 2 phase and the common home split phase has tripped up many people. Dom't feel bad about that. Unless in certain rare parts of the country true 2 phase is seldom heard of. Probably not used enough for most college courses to mention.

I am scratching my head trying to figure out where that would even be useful.

College boys with ties sure make things complicated.

Motors for one thing. Simplified version.. The larger motors need something like a starting capacitor to get them running on single phase. That is not needed for 2 and 3 phase motors.

On those giant motors in college, they had us do some mechanic phase shifting until the got up to speed. I do not remember if what phase they were, but I think the were three phase

Why would they? And even if they did, it would be a very expensive complication.

It really looks, behaves and for all purposes is two phases that are 180 deg out of phase, regardless of what it's called, which is split-phase. You can have two phases of any difference. The ancient two phase you're referring two was implemented as 90 deg, but the general case is it can be 1 to 360 deg phase difference.

No, Kohler made their generator as 0 and 47 deg, to make sure it wouldn't work for any application and no one would buy it. Good grief.

Wrong. Split-phase is what is delivered to almost all homes. Some that have special needs, eg a shop in a garage that has

Wrong again, no utility supplies 90 deg two phase power, it existed briefly 100 years ago.

The Adams hydroelectric power plant an Niagra Falls was the first large scale hydroelectric plant, made possible by generating AC, which could use high voltage for transmission.. The Adams Plant was the final win in the "war of the currents" between DC - Edison and AC - Westinghouse (Tesla). The first couple (2?) generators were 2-phase, but for transmission to Buffalo that was changed to 3-phase with 2 transformers connected in a Scott/T connection.

The system voltage for our houses is 240/120V, which hopefully has been established for at least 3 months as being single-phase.

In 2- and 3-phase motors the magnetic field in the "stator" can be thought of as rotating, which drags the "rotor" around. It was this vision by Tesla that added to the usefulness of multi-phase systems. Also tricks don't have to be used to create a starting torque as in single-phase motors. Three-phase uses less copper than 2-phase.

System voltages for 3-phase are commonly 208/120V and 480/277V, both with wye connected transformers.

A large building may have 480/277V distribution with small transformers to 208/120 in electrical rooms. These transformers may have 3 transformer cores, but could have 2 and be connected Scott/T. The transformers are true 2-phase with 3-phase primary and secondary. This connection screws up the power factor and the cores have to be derated, but it may be cheaper.

A large apartment building may have 208/120V 3-phase service with 2 of the phases going to each apartment (Clare talked about it).

If you had a lot of single-phase plus a little 3-phase stuff, maybe a machine shop, you could have a 240/120V single-phase transformer and add

In corner grounded 240V 3-phase one of the connections between transformers is grounded. This is a grounded conductor, not a neutral. May be used, I think on center pivot irrigation.

There are ungrounded system, like 240V 3-phase ungrounded. A single ground fault won't shut down critical equipment. Requires an alarm if there is a ground.

All these have been "System Voltages" - what you get from the utility. There are also "utilization voltages" - voltage at the operating equipment. In the NEC motor tables voltages are 115, 200, 230 and 460. If you look at motor manufacturer literature and motor nameplates it will be lower than system voltages.

I always called system voltage - power transmission system - like this :

One utility supplied it for everything I hooked up over the years but at 460 volts. The largest well motor was 100 hp. The other nearby utility supplied a center tap delta supply. Some farmers could get just wheels only power to move the pivots. The utility power supply there was single phase. The utility would supply 460 vac single phase. We added a rotary phase converter to make the pivots move. Other farmers had internal combustion engines to power the actual well. They added belt driven 3 phase generators to power the pivots. The most common one by far was manufactured by Lima.