[time-nuts] Power glitch - Sat morning

[jimlux]

On 4/1/20 8:13 AM, Didier Juges wrote:
> When you feed an electrical moteur with that, it sounds like a Harley
> Davidson :)
> It's a feature!


Only if the motor is 2 phase, also.

208 delta/120 star(wye) is a very common distribution scheme in "light 
industrial/office" applications.  Most of the loads are 120V, but you 
have a higher voltage available as 3 phase for things like air 
conditioning and compressors, pumps, machine tools and the like.

It's also really common with large portable generators - you get 3 legs 
of 120V which is what most loads are looking for, but you also get a 3 
phase output if needed. In general, for large "rotating machines" 3 
phase units are smoother running and less expensive than single phase.

There are a lot of 240V appliances/lighting fixtures that will run off 
208 too (at increased current or reduced output).

In more "heavy industrial" you'll see 480/277 wired the same way - 480 
three phase for the big motors, heaters and the like, but a single phase 
to neutral for lower voltage applications (lots of HID and fluorescent 
light fixtures for 277). In such facilities, 240 and 120V loads are done 
with local "dry transformers" fed with 480 from two of the phases. 
That's why surplus places have a lot of those transformers (typically 
1-10kVA) with a 2:1 winding, both center tapped.  You can do 240:240, 
240:120, 480:120, or all the other combinations.

I did work in a place that had 240 delta supplied (for 3 phase motors), 
but one of the phases had a grounded center tap (so there was a 120V 
line/ground/neutral available). This is moderately common as well. There 
was no 3 phase return in this one. (which would have been 139 V 
phase:neutral).


In EU, where 240V is the default line voltage, I wonder what the 3 phase 
distribution is?  Is it 415 delta / 240 star
> 
> On Tue, Mar 31, 2020, 10:58 AM Mark Spencer <mark at alignedsolutions.com>
> wrote:
> 
>> A few decades ago I was chatting with an electrical engineer during some
>> down time during a long project in Canada.  We started talking about
>> residential AC power.
>>
>> Reportedly in some multi tenant buildings in Canada the individual suites
>> may be supplied with two phases from a 208 / 120 volt three phase system.
>> I never got around to measuring the voltage from my dryer or range plugs in
>> my condo before I moved into a single family home that has a 240 / 120 two
>> pole / single phase supply.
>>
>>