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Re: [TowerTalk] Power Distribution

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Power Distribution
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Date: Sun, 08 Aug 2010 14:54:49 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>

On 8/8/2010 2:35 PM, jimlux wrote:
> Jim Brown wrote:
>    
>> On Sun, 8 Aug 2010 10:17:39 +0200, Milan DlabaŠ wrote:
>>
>>      
>>> most of family houses in Europe (even in Czech
>>> rep.) - probably more than 90% of family houses have 3 - phase  power
>>>        
>> system
>>      
>>> as normal way.Peak input power of my house is around 20 kW - including heat
>>> pump, washer, dryier, el.stove, ham radio  and etc. and still we have input
>>> circuit breaker 3x32A.I thing, that this is normal modern way how to do
>>>        
>> it.I
>>      
>>> can not imagine 200A input circuit breaker .
>>>        
>> Question. How much equipment actually RUNS on 3-phase power? Does your
>> refigerator connect to a 3-phase outlet?  Your washer, dryer, heat pump?
>> Stove? Or do they connect to ONE PHASE of the 3-phase system that comes into
>> your home? Same question for the guy from Anaheim. :)
>>      
> Electric heat and hot water is often done with 3 phase elements (even
> here in the US) because a 3 pole lower current switch is comparable in
> cost to a 2 pole higher current one (more current means bigger contacts,
> bigger springs, bigger electromagnet on the contactor, etc.)
>
>
>    
>> I'm asking this because I've never SEEN a 3-phase home appliance. Maybe they
>> exist, and I live a sheltered existence. :) Remember, I said that except for
>> running big motors, there was no good reason for 3-phase. Several suggested
>> big DC power supplies are easier to filter, and that's certainly true, and I
>> would do it for a broadcast transmitter, but not for ham power levels (at
>> least not legal ones). Remember that what you might save in filter caps you
>> might pay back with buying three smaller power transformers rather than one
>> larger one. :)  And, for that matter, there are switching power supplies,
>> and they don't have to be noisy if they're done right.
>>      
> I agree.. *today* it's probably a wash, because power semiconductors and
>    ASIC controllers make life easier.  My washing machine has a 3 phase
> inverter built into it (running off single phase feed, of course), but
> I'm pretty sure it's a fairly high rate switcher.
>
>
>    
>> As to big air conditioners -- I can't even dream of owning or using one. I
>> live in California, where my monthly bill for power averages $180, WITHOUT
>> air conditioning, thanks to a billing rate of $0.42/kWh if our monthly draw
>> exceeds a rather low limit.
>>      
> Yow..
> Our bills in SoCal run in that range, but we DO run A/C.  Our peak rate
> is 0.34/kWh (4th tier), bottom tier is 0.11/kWh.
>    
I don't pay that much for the house and shop combined and they both have 
airconditioning although the one in the shop is the largest window unit 
I could find and it runs off  240 AC. The shop is heavily insulated, 
including the floor. It's the healthy, high fiber, high strength 
concrete poured over Styrofoam(TM). Unfortunately the contractor talked 
me into using a "rat wall" type of foundation, instead of a regular 
poured foundation. This means the floor, foundation/outside wall base 
are all one pour.  Had I gone with a separate foundation, I could have 
isolated the floor from the foundation with 1/2" bead board between the 
foundation and floor. The current construction is quite a heat loss in 
winter, plus each corner has at least 5 or 6 diagonal hairline cracks 
due to temperature differential.  A few feet from the outside wall and 
you can walk barefoot on that floor as it's the same temp as the air in 
there. OTOH that might not be advisable due to metal splinters<:-))
> If one lived in, a hot humid climate, say, Houston, a $300/month tab to
> run the AC may seem cheap at the price (according to my aunt who lives
>    
I think we pay something like 7 cents per KWH, BUT there are a whole 
bunch of surcharges, renewable energy charges, delivery charges, (bout 
12 different items) and they bring the total to a tad over 10 cents per 
KWH.  The commercial rate on the shop is a tiny bit cheaper but we are 
talking hundredths of a penny with the surcharges being about the same 
and both are flat rates.

Electric heating up here is just not economical but heat pumps are.

73

Roger (K8RI)
> there anyway)..
>
> Keeping this moderately ham radio related..  Solar Panels are still not
> worth it economically.. Commercial power is just too cheap, unless you
> manage to qualify for subsidies, etc.  However, solar panels, if you
> have battery storage, do provide a handy emergency backup, if sized
> right. Most of the subsidies are for battery-less grid-tie systems these
> days (which makes more sense in a bigger picture... reduces peak load on
> the infrastructure, don't have waste/emissions issues from battery
> manufacture, etc.)
>
>
>
>
>
>
>
>
> That rate increases again if I add air
>    
>> conditioning. My major cost is pumping water from the well. And yes, three-
>> phase motors would be more efficient -- IF they were available in sizes that
>> matched the uses of a single family home. :)
>>      
> More than a decade ago, we were looking for a 3 phase motor that was
> less than 4" in diameter for a specific application, and that's very
> similar to what well pumps need.  Franklin Electric (a big maker of
> smallish electric motors.. say<5HP) was developing a PWM inverter to
> drive well pumps to eliminate the need for the accumulator. The idea was
> that a variable speed drive would make for a smaller, more reliable pump
> that would automatically adjust the speed to keep constant line pressure.
>
> However, even there, I suspect that they were running off single phase.
>
>
>
>
>
>    
>>      
>>> Your system is older and I
>>> understand, that rebuilding could be quite expansive.
>>>        
>> Yes, the infrastructure cost is the killer. As Jim Lux noted, it's far
>> easier to do it right when you're forced by history to start from scratch,
>> as was the case in much of EU after WWII (and in other countries much later
>> in time). Heck, when I was a child, I learned that there was still a lot of
>> DC wiring around NYC!
>>
>>      
> Not too many years ago, I was involved in a project to see if there is a
> way to detect excessive leakage current in the wiring plant in NYC (e.g.
> the stories of dogs being electrocuted when urinating on a metal cover
> plate that happens to be live)..
>
> Not only is the physical distribution plant mostly undocumented, a lot
> of it dates from the days of Edison, and in some cases uses single wire
> feeders with ground returns via the lead pipe conduit.  Working for
> ConEd is apparently an interesting job.
>
> ---
>
>
> Keeping it more towerish... How big are the motors used on a telescoping
> tower?  Those might benefit from 3 phase, if only for the simpler
> switching to reverse them. OTOH, in comparison to the $10k cost of a new
> tower and installation, saving $100 in switches, etc, might not be worth it.
>
>
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>    
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