[TowerTalk] Power Distribution

[Larry McDavid]

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>>> 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. :)

I suppose I'm "the guy from Anaheim." have no household appliances that 
operate on 3-phase power. If I lived in Europe, I surely would! My 
friend in The Netherlands operates even his garage door opener motor on 
3-phase power.

But, I wish I did have 3-phase mains power available. Surely no one will 
challenge that induction motors are more efficient when operated on 
3-phase power. In my case, I have a 5 HP, a 3 Hp and a 1 Hp motor on 
equipment in my home shop; all are 3-phase motors and I use solid state 
VFDs to both control their speed and to generate the 3-phase power from 
single phase 220 vac.

Air conditioner Freon pumps use induction motors. If there were demand 
(supported by the power infrastructure, or perhaps the other way 
'round), these air conditioning systems would be more efficient and have 
a higher SEER rating when operated on 3-phase power. With no 
infrastructure here, there is no demand for the improved design and I 
agree it is entirely possible that what 3-phase air conditioning systems 
there are will be for commercial use and may have a lower SEER rating. 
In time, those systems will have higher efficiency as regulatory demand 
forces it.

There is huge demand enforced to use high-efficiency air conditioning 
systems. I have just replaced one (of two) 3-ton AC systems in my 
two-story home. I was offered a higher efficiency (that is, SEER rating 
or the new AHRI EER term that seems to have replaced SEER) at higher 
purchase cost BUT with the assurance of receiving $2700 in rebates and 
credits for agreeing to purchase that higher efficiency system. "System" 
means the furnace (yes, I have two!), the evaporator coil, the Freon 
lines, the condensing unit and even the enhanced thermostat capable of 
controlling a multi-stage Freon pump and variable-speed fans. But, to my 
regret, all that operates on single-phase power.

Some folks here seem opposed to 3-phase power just because they don't 
have it and see change, any change, as a bad thing. Having worked in 
industry, I've been around 3-phase power all my life and I don't see it 
as strange at all.

I am astonished at some of the KWHr rates mentioned here. Even other 
cities nearby Anaheim in Southern California have KWHr rates that 
astonish me. I have a local friend in a nearby city, perhaps 12 miles 
away from my home in Anaheim, who pays up to $0.38 per KWHr in the 
summer when he is using air conditioning; in fact, that was two years 
ago when I compared rates and his rate today may be higher. But, here in 
Anaheim, my baseline rate is about $0.07 per KWHr and my one-and-only 
step above the baseline is to $0.12 or so per KWHr.

When using two independent 3-ton central air conditioner systems, my 
city utility bill is about $450 for TWO months, not one month. And, that 
utility bill includes water, sewage, trash collection, street sweeping 
and a nominal donation to our city paramedics. Again, I must point out 
that Anaheim benefits from the huge tax base generated by Disneyland, 
our vast convention center and all the hotels that support visitors to 
these attractions. But, I believe the greatest factor is that many years 
ago Anaheim decided to provide its own power distribution system and 
bought into part ownership of a nuclear generating station and the Four 
Corners coal fired generating station; the city thus gets a discount on 
the wholesale price of electrical power it then distributes and sells to 
city residents.

The two underground transformers that supply homes on my short 
cul-de-sac street are fed 3-phase power. The cost differential to supply 
3-phase power to the homes would have been minimal if done when the 
track homes were built 35 years ago and the underground drop cables 
first placed. I don't understand the logic of objecting to 3-phase power 
if it were available to our homes.

Finally, someone here pointed out that SCR motor speed controllers often 
generate electrical noise. Noise is tough to avoid when chopping off 
power in the middle of a sine wave! But, today (gosh--see eBay!) low 
cost VFD controllers are available, both with single-phase and 3-phase 
input. While these can possibly produce noise for other reasons, they 
don't suffer from chopping off power under high current loads 120 times 
a second. And, they provide nearly full motor torque even at low speed. 
Hard to complain about that!

Larry W6FUB


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Best wishes,

Larry McDavid W6FUB
Anaheim, CA  (20 miles southeast of Los Angeles, near Disneyland)