I'm pretty sure it was here that I read a post where someone referred to having a two phase motor, and Scott T setup to power it, in the last few weeks. An elevator,maybe? Can anyone help me find the post? Was trying to explain to a co worker that 2 phases of a wye 208 system weren't 2 phase today, and can't find the post to show to him, that 100 years ago there where true two phase systems. I've shown him the vectoral diagrams, but he doesn't believe it was used anywhere. I've worked with it in paper mills in Maine, but don't have any reference. Just looking for something else to prove I'm not bat S crazy to him. Thanks!
My first post, been lurking for years. Know I'm not crazy
- Thread starter jmc679
- Start date
- Status
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
The Wikipedia article about two-phase is decent starting point, see if that helps.
Also, using google to search the forums is usually better than the built-in search-
http://forums.mikeholt.com/showthread.php?t=53674
(there are a bunch more)
Also, using google to search the forums is usually better than the built-in search-
http://forums.mikeholt.com/showthread.php?t=53674
(there are a bunch more)
Tony S
Senior Member
- Location
- Resting under the Major Oak UK
This may help or confuse.
Here's one of many threads you can search:
http://forums.mikeholt.com/showthread.php?t=174732&page=3&highlight=philadelphia
http://forums.mikeholt.com/showthread.php?t=174732&page=3&highlight=philadelphia
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Two phases of a wye was never "2 phase". If you connected a 208 two wire load to it there is only one possible phase angle - 180 degrees.
If you involve the neutral conductor then you get different possible phase angles involved, but you only have 120 volts to the neutral so that isn't going to work so well for powering two phase wound motor with that much variation in voltage between lines, though it probably will develop some torque just because there is some phase differential.
A true two phase generator has two windings that are 90 degrees from one another, There is a few possible ways to connect them which can give you two phase three wire, four wire or five wire system, but the two main windings are still 90 degrees from one another and the output voltage of one coil is 90 degrees out of phase with the other coil.
Three phase systems have 120 degree angle between each source coil, and 120 degree phase differential between output leads.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Just to clarify:
The term “two phase” has different meanings depending on where you are because of the history involved. Here in North America, the first AC distribution system installed from Niagara Falls to Buffalo by Nicola Tesla and George Westinghouse was in fact two phase power, so 4 wires providing two phases offset from each other by 180 degrees. This is “true” two phase power. It never was used anywhere else outside of North America, because very quickly it was determined that you could deliver more power with one less wire by using 3 phase.
But elsewhere in the world where this true two phase system never existed, the term “two phase” is commonly used to describe two-out-of-three phases, which we call “single phase” power here because we have to differentiate.
The term “two phase” has different meanings depending on where you are because of the history involved. Here in North America, the first AC distribution system installed from Niagara Falls to Buffalo by Nicola Tesla and George Westinghouse was in fact two phase power, so 4 wires providing two phases offset from each other by 180 degrees. This is “true” two phase power. It never was used anywhere else outside of North America, because very quickly it was determined that you could deliver more power with one less wire by using 3 phase.
But elsewhere in the world where this true two phase system never existed, the term “two phase” is commonly used to describe two-out-of-three phases, which we call “single phase” power here because we have to differentiate.
I thought I read the post here. May have been on a different site. I'm quite familiar with true 2 phase. I spent more time than I wanted to in a paper mill here that had the system uo and running. I believe it was 40hz too. It's been almost 15 years. Just remember the substation layout and the motors where HUGE. A 10hp was near the size of a common fifty. Spent better than a month in a substation that took 2300v delta, with the help of a scott T setup, two xfrmrs. The main and teaser bussed at 8' off the floor, to 440 bussed at 5'8 off the floor and multiple two pole breakers tied to those busses. I just thought it was here that I recently came across a post about it. The guys I work with consider two legs from a wye two phase even though it's nothing like the animal. I've showed them vectorals, and wiki articles. It's a vernacular thing where I work. Just trying to educate them. There take is yes it's possible. Wasn't something used. Often, if ever. Ironic as we still use 120v delta all over the boats we build.... No that wasn't a mistype. Wye systems are new technology here... 208Y/120 confuses the hell out of my coworkers. Thanks for the links and help!
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Two lines from a three phase system can and is (whether correct or not) called "two phases", but like I mentioned earlier, to connect a two wire load to this is still single phase usage of whatever is available. Connecting a two wire load to a real two phase supply is also only single phase usage as it relates to that load.
Frank DuVal
Senior Member
- Occupation
- Electrical Contractor, Electrical Engineer
I came across a Sq D QO panel with sharpie writing saying 120 V Delta in a lab. Hunh? :blink:
I measured and sure enough, 120 between phases. Turns out it was installed to test some ship equipment!
I thought the angle was 90 deg.
I can't say I've had any direct experience but tat's what it looks like in my J&P transformer book. Pages 173 to 200.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Correct. Picture a four-pole alternator.
Two phase 5 wire 90° phase angle was common(and is still present) with PECO energy in Pennsylvania, and southern New Jersey.
I know of some in Seattle WA as of 2010.
If you notice switch gear buckets 'handle tied' on 240V switch gear its probably two phase.
I believe the underground distribution in center city Philadelphia is still 115kV -> 13.5kV 5 wire two phase. Its all 60Hz. I have never herd of a different freq like 40hz (after 1930). I imagine it would be quite expensive to change that in Philly so two phase is is.. And its actually quite nice to work with. 240 all around to pack more punch than 208 and plenty of 120 to N all around.
They usually set transformers in basements of buildings to convert it to three phase 120°.
Siemens/ ITE is the best go to for 5 wire stuff when replacements are needed.
Size neutrals at 150% of phase.
See attached photos.
Cheers
I know of some in Seattle WA as of 2010.
If you notice switch gear buckets 'handle tied' on 240V switch gear its probably two phase.
I believe the underground distribution in center city Philadelphia is still 115kV -> 13.5kV 5 wire two phase. Its all 60Hz. I have never herd of a different freq like 40hz (after 1930). I imagine it would be quite expensive to change that in Philly so two phase is is.. And its actually quite nice to work with. 240 all around to pack more punch than 208 and plenty of 120 to N all around.
They usually set transformers in basements of buildings to convert it to three phase 120°.
Siemens/ ITE is the best go to for 5 wire stuff when replacements are needed.
Size neutrals at 150% of phase.
See attached photos.
Cheers
Attachments
cpinetree
Senior Member
- Location
- SW Florida
Here is an interesting article about 2 phase: https://hackaday.com/2018/03/15/a-tale-of-two-phases-and-tech-inertia/
This is linked in the above article: https://www.atlasobscura.com/articles/magnificent-photos-of-power-stations-in-the-early-1900s
Some pretty cool pictures of Philadelphia abandoned power stations.
This is linked in the above article: https://www.atlasobscura.com/articles/magnificent-photos-of-power-stations-in-the-early-1900s
Some pretty cool pictures of Philadelphia abandoned power stations.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Cool, another one for the "Oddball services" list.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I could be wrong but thought I read on this site one time that all the distribution is three phase, and any two phase service still in operation is connected via Scott-T transformer.
- Status