Here come the EVs

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ABMax24

Minister of Fire
Three times as much power for only 1.5 times as many conductors.

The big thing is phase balancing, 3 phase loads are usually balanced and typically pull power evenly from all 3 phases. Large single phase loads need to be balanced across all 3 phases.
 

semipro

Minister of Fire
Jan 12, 2009
4,027
SW Virginia
Three times as much power for only 1.5 times as many conductors.

The big thing is phase balancing, 3 phase loads are usually balanced and typically pull power evenly from all 3 phases. Large single phase loads need to be balanced across all 3 phases.
Ok, interesting. I read up a bit here and it looks like somehow the net effect of using 3 phase is that each conductor can effectively carry more current because of the simultaneous opposing direction of flow in the conductor from the other phases. I don't fully understand but it does explain how adding 50% more conductors can result in even greater overall power transfer. I love learning new stuff.

When traveling in rural areas I've always noticed many farms served by 3-phase and wondered why. I suspected cow milking equipment. Anyone know why else?
 

SpaceBus

Minister of Fire
Nov 18, 2018
5,957
Downeast Maine
Ok, interesting. I read up a bit here and it looks like somehow the net effect of using 3 phase is that each conductor can effectively carry more current because of the simultaneous opposing direction of flow in the conductor from the other phases. I don't fully understand but it does explain how adding 50% more conductors can result in even greater overall power transfer. I love learning new stuff.

When traveling in rural areas I've always noticed many farms served by 3-phase and wondered why. I suspected cow milking equipment. Anyone know why else?
They probably have electrical machinery that calls for 3-phase power, probably beyond milking equipment. When I worked for a company that built media blasting cabinets many of the blower and conveyor motors were 3-p. The professional grade wood working machinery is also usually 3-p, which is what Bholler was getting at in an earlier post. Once you get above homeowner grade tools and equipment it is usually 3-p.
 
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ABMax24

Minister of Fire
Ok, interesting. I read up a bit here and it looks like somehow the net effect of using 3 phase is that each conductor can effectively carry more current because of the simultaneous opposing direction of flow in the conductor from the other phases. I don't fully understand but it does explain how adding 50% more conductors can result in even greater overall power transfer. I love learning new stuff.

When traveling in rural areas I've always noticed many farms served by 3-phase and wondered why. I suspected cow milking equipment. Anyone know why else?
There's also some other advantages when dealing with the rectification of the AC power to DC, which is of particular importance to EV's. Single phase AC has a point 120 times per second where the voltage is zero and so is the useable power output, this requires capacitors to store energy to produce a smooth DC output. 3 phase by nature doesn't have this problem, if you look at the chart below the sum of the power output at any time is always the same, this produces a smooth DC output.

3 phase when wired in the delta configuration also doesn't require a ground as the 3 phases cancel each other perfectly. Our welders at work operate this way, 3 power wires and a safety earth ground, they also produce an extremely smooth DC output.

1623503528653.png


To answer your question, 3 phase is often supplied to farms for a couple reasons. Farms often pull significantly more power than a standard house, well pumps, septic, grain dryers, milking equipment, pumps, etc. 3 phases systems simply supply more energy to power all these loads. The other is many loads require 3 phase power to operate, particularly motors.

For small lower output electric motors single phase works fine, although it does require a start winding in the motor and a starting circuit to get the motor spinning. (think bicycle with one pedal up and the other down, how do get moving if you can only push down on the pedals?). The starter circuit acts 90 degrees to this to get the rotor moving and inertia takes care of the rest. 3 phase motors don't have this problem, they are self starting. The other is vibration, as talked about before single phase goes to zero power 120 times per second, which requires inertia in the motor and whatever it's turning to absorb the rotational vibration. 3 phase doesn't have this issue either, its a smooth output, (think single cylinder engine vs 3 or 4 cylinder).
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
24,479
central pa
Amish use 3-p electrical stuff, but they also use generators and refuse to be grid connected.
We have lots of Amish here connected to the grid. Some just for barns others for the house as well.
 

begreen

Mooderator
Staff member
Nov 18, 2005
88,261
South Puget Sound, WA
Sounds like I could get into the charging business. We have delta 3-phase running right by our house. It feeds the water system down the street.
 

SpaceBus

Minister of Fire
Nov 18, 2018
5,957
Downeast Maine
We have lots of Amish here connected to the grid. Some just for barns others for the house as well.
Times are changing I suppose. I have only met Amish that have hook ups for their businesses.
 

SpaceBus

Minister of Fire
Nov 18, 2018
5,957
Downeast Maine
There's also some other advantages when dealing with the rectification of the AC power to DC, which is of particular importance to EV's. Single phase AC has a point 120 times per second where the voltage is zero and so is the useable power output, this requires capacitors to store energy to produce a smooth DC output. 3 phase by nature doesn't have this problem, if you look at the chart below the sum of the power output at any time is always the same, this produces a smooth DC output.

3 phase when wired in the delta configuration also doesn't require a ground as the 3 phases cancel each other perfectly. Our welders at work operate this way, 3 power wires and a safety earth ground, they also produce an extremely smooth DC output.

View attachment 279514

To answer your question, 3 phase is often supplied to farms for a couple reasons. Farms often pull significantly more power than a standard house, well pumps, septic, grain dryers, milking equipment, pumps, etc. 3 phases systems simply supply more energy to power all these loads. The other is many loads require 3 phase power to operate, particularly motors.

For small lower output electric motors single phase works fine, although it does require a start winding in the motor and a starting circuit to get the motor spinning. (think bicycle with one pedal up and the other down, how do get moving if you can only push down on the pedals?). The starter circuit acts 90 degrees to this to get the rotor moving and inertia takes care of the rest. 3 phase motors don't have this problem, they are self starting. The other is vibration, as talked about before single phase goes to zero power 120 times per second, which requires inertia in the motor and whatever it's turning to absorb the rotational vibration. 3 phase doesn't have this issue either, its a smooth output, (think single cylinder engine vs 3 or 4 cylinder).
More like single cylinder compared to inline six or v12. Inline sixes are inherently balanced with no dead spots in the crank rotation and the piston movement, much like three phase power, cancels out the vibration of the opposed piston. It's a shame they aren't in more cars.
 

gggvan

Member
Dec 6, 2012
117
I suspect in the future, there will be wireless trickle/full charging emitted from roads/smart lights/signals along sides of streets. Sort of like the wireless phone chargers you set your phone on/near. Also, in the chinese ev, can't remember the name now, you only rent the battery, they have drive in stations that physically swap out the battery for a fully charged one in a few minutes.
 

semipro

Minister of Fire
Jan 12, 2009
4,027
SW Virginia
I suspect in the future, there will be wireless trickle/full charging emitted from roads/smart lights/signals along sides of streets. Sort of like the wireless phone chargers you set your phone on/near. Also, in the chinese ev, can't remember the name now, you only rent the battery, they have drive in stations that physically swap out the battery for a fully charged one in a few minutes.
Nio is the Chinese swappable system I believe you're referring to. Better Place tried it more than 10 years ago but the world wasn't ready for it then. Getting manufacturers to cooperate on a standard is tough. (Think about getting in a rental car and trying to find the windshield wiper switch at night).
Wireless charging is tricky for a variety of reasons. I agree it's the future but it's out there a bit.
I keep thinking that maybe using light, as in lasers, might be a better way to transfer energy to moving vehicles. That's obviously out there too though.
For now, nothing comes close to the connection of electrical conductors. I keep thinking back to the slot cars I had as a kid and maybe conductive tires, etc.
 

SpaceBus

Minister of Fire
Nov 18, 2018
5,957
Downeast Maine
The Japanese big three in bikes have agreed on a standardized swappable battery for motorcycles, anything is possible.
 

begreen

Mooderator
Staff member
Nov 18, 2005
88,261
South Puget Sound, WA
The new GM Ultium battery pack looks like it is better designed for swap-outs and upgradeability.