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Steve Conner

Fri Apr 02 2010, 09:42PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Here's Steve's ferrite cored CCPS:

wrote ...
a smart pig is developed that can run unattended for 60 years of abuse by lightning and temperature swings.

That's the difficult part. The old-fashioned copper and iron transformer is pretty bulletproof, simple, and cheap to produce. And the efficiency isn't such an issue: SMPS waste power at low loads too.

The weight isn't really a problem either, the power company have trucks and cranes to install the poles anyway.

Arcstarter

Fri Apr 02 2010, 11:51PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Steve McConner wrote ...

Here's Steve's ferrite cored CCPS:

wrote ...
a smart pig is developed that can run unattended for 60 years of abuse by lightning and temperature swings.

Not to mention, high freq AC can cause loads of problems, such as insulation breakdown, resonance with the parasitics, and then you would have to rectify it because most household items do not like such frequencies. Then, for induction motors and transformers and other things that must have 60hz AC would need an inverter, which would make any gain in efficiency due to using an inverter distribution transformer pointless. Of course, they could start manufacturing things that run on the HF AC, but how well do you think that'd go?

klugesmith

Sat Apr 03 2010, 02:31AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

If ferrite could be used in pole transformers a good percentage of the global electrical energy waste would be solved.
The average pole pig loafs at low loads heating the iron and copper.

Very large conventional transformers are spectacularly efficient, just as very small ones are lossy. It's just the way the physics of copper/aluminum and iron scale. When you double the linear dimensions, you get 16x the VA rating with 8x the volume, weight, and losses (assuming equal flux and current densities).

Here is a table of efficiency standards, reproduced from

(a M$ PowerPoint document ). The doc -might- call out the standard test method. Clearly the efficiency drops to zero at no load (just as with SMPS).

Liquid-Filled Efficiency Levels (DOE vs NEMA)
Single Phase
KVA DOE NEMA TP-1
10 98.62 98.4
15 98.76 98.6
25 98.91 98.7
50 99.08 98.9
100 99.23 99.0
250 99.32 99.2
500 99.42 99.3
833 99.49 99.4

The pole pig which serves my household and about 7 neighbors is a 50.

On closer inspection of the document, it's a story about design changes to -meet- the DOE requirement by 1/1/2010, with a cost increase of about 30% over the company's older products. The cost/efficiency physics and economics have been well understood for decades.

radiotech

Sat Apr 03 2010, 08:50AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The old term was day/night effeciency. Because of the technology the losses are accepted. But the watts/kilogram factor cannot be reduced for iron alloy cores. The core size is determined by the space needed by the windings, which increases as more copper is added to reduce resistance loss. They still need power at no load.
to magnetize the core, amps are needed in the primary. There is also another issue. The reactive power from the cores circulates
in the network, often requiring large reactors on distrubution secondary feeders to improve regulation. Low power factor results in high wattage loss in the overhead lines. Utilities charge penalties for this.

Regenerative drives are used already in large drives > 500 Hp. These use smps design.

Inverter technology could also allow increasing the frequency to values used on aircraft (400 0r 800 Hz). 60/50 Hz belongs to the era of magnetic motors. Nothing in the home or industry couldn't
be operated on 400/800 Hz. Laundry motors are already being converted to DC for ease of speed control for best effeciency.

Large industrial motors are already vfd, for same reasons.

A 400 Hz pole pig would weigh less per watt than a 60 Hz one.

Kyle

Sat Apr 03 2010, 07:11PM

Registered Member #2325 Joined: Sat Aug 29 2009, 10:08PM
Location: Southern California
Posts: 11

Klugesmith wrote ...

The pole pig which serves my household and about 7 neighbors is a 50.

How specifically do you find the kVA rating on a pole transformer? I know that a good portion of manufacturers place the kVA rating on the actual canister, but the one closest to me just has "100" labeled on the side of it. I doubt it's a 100kVA, it's quite a bit too small for that. Is there a size reference to go by to determine the rating?

On subject of the OP's question - I've been searching for the same thing for quite a lengthy amount of time now. (I'm in SoCal as well.) There is a substation near me that Edison seems to be partially using the property as storage. There's about twenty distribution transformers just laying around. I'd love to shoot up there and question one of the workers one day if it's somehow possible to get a hold of one. I still don't have the guts to do it, though. ;P But, you never know, it might work just asking the power company.

radiotech

Sat Apr 03 2010, 07:52PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

The large numer 50 would denote 50kVA.

A 50 with all the houses main breakers off will consume about 600 Watts.

As energy sytems get more smart, ie closed loop distribution, the load can request energy quantitatively. A smart pig will then configure enough cells to power up leaving the others ready to come on line. Some cell based systems are arrays of smps units commanded by a fibre optic link. and are connected so that the load
can be driven with some cells off. They are used on remote compressor stations on a pipeline and allow starting very large motors that previously needed large inrush currents with
large feeders.

Ken Herrick

Sat Apr 03 2010, 08:46PM

Registered Member #2489 Joined: Mon Nov 30 2009, 06:23PM
Location: Oakland, CA USA
Posts: 17

Kyle & all-

There's a nameplate riveted onto mine near the bottom. Gives all the particulars.

KCH

Ken Herrick

Sat Apr 03 2010, 08:49PM

Registered Member #2489 Joined: Mon Nov 30 2009, 06:23PM
Location: Oakland, CA USA
Posts: 17

--and I should have specified: mine that's for sale is10 KVA & is also marked 7200/12470Y.

KCH

HazzWold 1993

Sun Apr 04 2010, 03:26AM

Registered Member #2563 Joined: Mon Dec 21 2009, 10:17AM
Location: Australia
Posts: 280

is the 7200 on yours the primary or the secondary?

klugesmith

Sun Apr 04 2010, 03:47AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

radiotech wrote ...
Nothing in the home or industry couldn't
be operated on 400/800 Hz. Laundry motors are already being converted to DC for ease of speed control for best effeciency.

Agreed. Here's a company that makes 400 Hz 3-phase generators and motors for construction machinery. Also some equipment (like concrete saws) that uses them. For example, a 400 Hz 7.5 horsepower 12,000 RPM induction motor that weighs only 16 pounds, and no semiconductors in the power path. (except maybe to regulate the generator field current)

[edit] also they make 400 Hz inverters running off mains.

>> A 50 with all the houses main breakers off will consume about 600 Watts.

Radiotech, I'm sure you can teach me a lot. I'm no pro when it comes to utility electrical engineering. [edit] Through the wonders of the Internet I've learned that the figures I gave above are relatively recent "energy star" type standards -- so there are probably plenty of decades-old pigs in service that were made when cheapness counted more than efficiency.

As for the potential of mains-frequency transformers when Green policies are in effect:
This environmental-impact paper compares three different 100 kVA distribution transformers.

These are for applications where average load is only 25% of rating, so probably the design is slanted to minimize core losses. And it's for 50 Hz, good for core loss, though of course everything is bigger than we're used to in USA.
The class AA, CC, and C-with-amorphous-iron are progressively bigger, heavier, and more expensive. No-load losses (kW) are given as 0.32, 0.21, and 0.06!
[edit] They talk about how many tonnes of CO2 are saved. Not clear if they figured the tonnes of CO2 from producing the extra iron and copper. (I bet it would only slightly affect the balance.)

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