3 ms·

In-sync AC grids are an engineering marvel; high-voltage AC lines are comparatively lossy due to the skin effect among other things; a frequency of 50 or 60Hz y

In-sync AC grids are an engineering marvel; high-voltage AC lines are comparatively lossy due to the skin effect among other things; a frequency of 50 or 60Hz yields what are, by modern standards, comically huge step-down transformers; etc. It's worth considering whether the relative ease of running AC motors makes all the difficulties of AC supply worth it. (It's worth remembering that the "modern", i.e. 1930s, three-phase power grid is built primarily to power motors on factory floors. I don't know if these are the highest load these days, but wouldn't be surprised if not.)

VBprogrammer 3y ago
> It's worth remembering that the "modern", i.e. 1930s, three-phase power grid is built primarily to power motors on factory floors. Small nitpick, I don't believe 3 phase power was picked primarily because it was convenient for powering 3 phase motors - it was picked because it's convenient for generating and transmission. There is no need for a neutral conductor in a balanced AC transmission system for example and it can very efficiently be converted to high voltage and stepped down again. It also results in modest power pulses though the generator compared to single phase etc.
- tyingq 3y ago
  Feels like it's both to me. 3 phase, 3 wires is optimal for the amount of conductor material needed to distribute it. But it's also optimal for motors for a few reasons. Easy to reverse direction of the motor, self starting without a capacitor, and higher overall power and efficiency.
algo_trader 3y ago
If you are building a custom mini grid from scratch, how do you get from batteries/panels to distribution-level 11kv DC without going through AC ?
- 20after4 3y ago
  All of the DC/DC boost converters that I am aware of use inductors to transform low voltage to high voltage. It's technically pulse-width-modulated DC instead of AC but there isn't a lot of difference between the operation of a boost converter and the operation of a high frequency inverter.
quickthrowman 3y ago
Motors consume around half of the world’s electricity, and nearly all of the power consumed by motors connected to the grid is consumed by three-phase A/C induction motors. Motors aren’t just in factory equipment, HVAC systems have all sorts of motor driven equipment. VFDs have made A/C motors far more efficient than one driven by an across-the-line starter.
tuatoru 3y ago
The biggest point loads are aluminum smelters. Probably next are electric arc furnaces for steelmaking, the so-called mini-mills.
- bob1029 3y ago
  Semiconductor factories are not far down the list either. Texas will probably see quite a few come online within the next decade. When I was working at SAS in ATX circa 2013, the 2 manufacturing lines were responsible for something like 10% of the city's average power consumption. I can't imagine the bleeding edge will have improved much - EUV light sources aren't exactly Energy Star compliant.
Scoundreller 3y ago
> a frequency of 50 or 60Hz yields what are, by modern standards, comically huge step-down transformers Should switch to 400Hz like aircraft do. Not just comically huge transformers, but also motor/generator magnets. > A special generator was designed to create an output of 400 Hz. This allowed a motor which was the size of a watermelon to be replaced by one the size of a one-pound coffee can which could do the same work. > The saving of weight allowed increased cargo capacity and decreased fuel consumption. Power at 400 Hz for aviation was a success and became the standard of modern AC-powered aircraft. > Airports all around the world standardized on the same power system. This included the physical plug and cable as well as the 400 Hz power so that aircraft from anywhere in the world could land and be serviced wherever they landed. The aviation power system of 400 Hz became one of the first worldwide-adopted standards. https://fcxinc.com/why-the-aviation-industry-operates-on-400-hz-power/ https://fcxinc.com/why-the-aviation-industry-operates-on-400...
- teraflop 3y ago
  > Should switch to 400Hz like aircraft do. Higher frequency lets you get away with smaller transformers, but decreases the skin depth on transmission lines which increases losses.

VBprogrammer 3y ago

> It's worth remembering that the "modern", i.e. 1930s, three-phase power grid is built primarily to power motors on factory floors. Small nitpick, I don't believe 3 phase power was picked primarily because it was convenient for powering 3 phase motors - it was picked because it's convenient for generating and transmission. There is no need for a neutral conductor in a balanced AC transmission system for example and it can very efficiently be converted to high voltage and stepped down again. It also results in modest power pulses though the generator compared to single phase etc.

tyingq 3y ago
Feels like it's both to me. 3 phase, 3 wires is optimal for the amount of conductor material needed to distribute it. But it's also optimal for motors for a few reasons. Easy to reverse direction of the motor, self starting without a capacitor, and higher overall power and efficiency.

algo_trader 3y ago

If you are building a custom mini grid from scratch, how do you get from batteries/panels to distribution-level 11kv DC without going through AC ?

20after4 3y ago
All of the DC/DC boost converters that I am aware of use inductors to transform low voltage to high voltage. It's technically pulse-width-modulated DC instead of AC but there isn't a lot of difference between the operation of a boost converter and the operation of a high frequency inverter.

quickthrowman 3y ago

Motors consume around half of the world’s electricity, and nearly all of the power consumed by motors connected to the grid is consumed by three-phase A/C induction motors. Motors aren’t just in factory equipment, HVAC systems have all sorts of motor driven equipment. VFDs have made A/C motors far more efficient than one driven by an across-the-line starter.

tuatoru 3y ago

The biggest point loads are aluminum smelters. Probably next are electric arc furnaces for steelmaking, the so-called mini-mills.

bob1029 3y ago
Semiconductor factories are not far down the list either. Texas will probably see quite a few come online within the next decade. When I was working at SAS in ATX circa 2013, the 2 manufacturing lines were responsible for something like 10% of the city's average power consumption. I can't imagine the bleeding edge will have improved much - EUV light sources aren't exactly Energy Star compliant.

Scoundreller 3y ago

> a frequency of 50 or 60Hz yields what are, by modern standards, comically huge step-down transformers Should switch to 400Hz like aircraft do. Not just comically huge transformers, but also motor/generator magnets. > A special generator was designed to create an output of 400 Hz. This allowed a motor which was the size of a watermelon to be replaced by one the size of a one-pound coffee can which could do the same work. > The saving of weight allowed increased cargo capacity and decreased fuel consumption. Power at 400 Hz for aviation was a success and became the standard of modern AC-powered aircraft. > Airports all around the world standardized on the same power system. This included the physical plug and cable as well as the 400 Hz power so that aircraft from anywhere in the world could land and be serviced wherever they landed. The aviation power system of 400 Hz became one of the first worldwide-adopted standards. https://fcxinc.com/why-the-aviation-industry-operates-on-400-hz-power/ https://fcxinc.com/why-the-aviation-industry-operates-on-400...

teraflop 3y ago
> Should switch to 400Hz like aircraft do. Higher frequency lets you get away with smaller transformers, but decreases the skin depth on transmission lines which increases losses.