efficiencies of appliance 3-phase brushless motors? - Page 2

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Re: window air conditioner, was: efficiencies of appliance 3-phase ...
On Friday, January 11, 2019 at 8:30:07 AM UTC-8, default wrote:
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Home Depot has a 5kbtu window AC unit for around $100 or $130; I forget exactly.

I went ahead and took apart my broken Sears/Kenmore front load washing machine (turns out it has broken shocks, among other problems) and pulled out the motor.  It's a J52AAC-0102 if anyone's curious.

I was about to ask if anyone knows of circuits to play with 3-phase motors but I found something already.

https://hackaday.com/2012/01/19/building-a-variable-frequency-drive-for-a-three-phase-motor/

http://blog.hardcore.lt/mic/driver-schematics.png

Unfortunately that MC3PHAC controller is at End Of Life due to low sales.  

Michael


Re: window air conditioner, was: efficiencies of appliance 3-phase ...
On Fri, 11 Jan 2019 10:34:01 -0800 (PST), snipped-for-privacy@gmail.com wrote:

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Ebay has some cheap VFD controllers starting at ~$50 (for 220VAC)
Single phase in, three phase out.  

Re: window air conditioner, was: efficiencies of appliance 3-phase ...
On Thu, 10 Jan 2019 22:04:29 -0800 (PST), snipped-for-privacy@gmail.com wrote:

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I installed my own inverter (VFD 3-ph) "mini-split" in 2002.  I saw
them in an episode of "This Old House" (or something like that) and
figured I could DIY the installation.  I did call an AC contractor but
back then they didn't want to touch it and denigrated the whole idea
and told me how inferior they were.  (the same guys are selling them
and promoting them today)

My 18,000 BTU cost me $1,300 with all the parts except for the
electrical disconnect and wiring, and I did need to buy some metric
wrenches and a flaring tool.  It is a heat-pump so I just disconnected
the base-board electrical heater and ran the line outside to a
disconnect and didn't run new wiring to the breaker panel.  (they say
it needs 20 amp service but I've never seen it go over 10 amps, and it
is soft-start)

I built a small deck out some scraps of treated lumber to keep it off
the ground, but they sell brackets so you can mount the compressor on
the side of the house or put in on a small slab.  I did not pump down
the system with a vacuum (the pump and gauges would have cost $350).
Instead I purged it with the pre-charged gas that was already in the
compressor unit - let it leak for a few seconds until the refrigerant
displaced the air in the lines.  (they claim you need a vacuum pump in
the ads, but had instructions for purging in the literature that
shipped with it)  It has been working like a champ for ~16 years now
so I guess purging works.

I did all the work myself and it took me a few days to finish the job
but I'm tickled with the results.  (it is running right now to warm
the room to 65 - outside is 30 current is down to 2 amps - it does
have to cycle on and off since the ambient and outside coils are below
freezing and it needs to defrost from time to time)

I did have trouble flaring the copper tubes.  I bought the flaring
tool at an auto parts store and had flared tubes before without
problems, but the tubing that shipped with the unit was not dead-soft
and tended to tear.  A little silicone grease on the point of the
flaring tool fixed that.  (1/4" copper for high pressure liquid
refrigerant and 1/2" gas return)

My wife has her own house and since she saw my installation she wanted
one too.  She got 2 completely independent units (one compressor can
serve multiple inside units) One of hers is 10,000 and the other
12,000 BTUh.  She paid $4,000 for the units with professional
installation including the electrical work and wiring.  Her
compressors are mounted on brackets on the brickwork of her house.
Her units are newer and when they are running they are quiet - can't
tell they are on.   Mine has a pretty aggressive fan and that makes
some noise, but then my system cools/heats the house faster than hers
does.

Now I want an LG inverter style for my bedroom window unit.

Re: window air conditioner, was: efficiencies of appliance 3-phase ...
snipped-for-privacy@defaulter.net says...
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It is not so much if purging works or not.  For around 20 or 30 years it  
has been illegal to dump any refrigerent into the atmosphere.  The claim  
by the government is that it depleats the ozone layer.  There is a big  
fine for doing that.


Re: window air conditioner, was: efficiencies of appliance 3-phase ...
On Fri, 11 Jan 2019 17:59:02 -0500, Ralph Mowery

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The R134a refrigerant can be bought by anyone and they  sell one pound
cans for recharging car AC's.  Or you can go on-line and order a 30 lb
cylinder without a license. (unlike R-30)

The info I found said it was a greenhouse gas, but not ozone
depleting.  The information that shipped with it gave the reason for
purging to be:  moisture freezing in the evaporator valve and blocking
it. (the "valve" is often just a length of copper capillary tubing)
The AC people said it is necessary to prevent acids from forming and
destroying the compressor.

I've no doubt that it is better to recycle it, and better to draw all
the moisture and air out with a pump.  But given the number of cars on
the road leaking it by the pound, I figure my one-time loss of an
ounce or two shouldn't matter.

AND if you still want to say it is wrong, read the label on a can of
computer "Dust-Off."  There are people on Utoobe who buy that stuff
because it is cheaper than the same stuff labeled as a refrigerant.

The units do have desiccant dryers in the compressors to eliminate
moisture.

Back in the day... the EPA forced AC contractors to buy some pretty
damn expensive refrigerant recovery equipment, to deal with the hassle
of sending it off to be recycled into fresh clean stuff, and to take
classes to learn the law and how to recycle to get a license.  That
same regulation is capitalized by AC contractors today that see
DIYer's cutting into profits that they think are rightfully theirs.
Now it is political, cans of "dust-off" not withstanding.  The other
faction with a vested interest are the thousands of auto-repair
businesses who don't want to spend the money on specialized equipment
or hire specialists to work on AC.  


Re: efficiencies of appliance 3-phase brushless motors?
snipped-for-privacy@defaulter.net says...
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At least 10 or more years ago the heat pumps and probably other  
heating/cooling systems moved to speed controlled motors.  There is a  
way where the motors start up slow to move the air that is sort of a way  
to cheat on the 'government efficency' numbers.



Re: efficiencies of appliance 3-phase brushless motors?
On Fri, 11 Jan 2019 17:51:42 -0500, Ralph Mowery

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Huh?  That doesn't sound believable.  An AC runs and uses power which
is easily measured in watts, can be used to cool water or air which
have known caloric absorption rates for measurable temperature
rise/fall... which, in turn, can be used to calculate power doing
useful work.

That is how microwave ovens are tested for efficacy.  How much
temperature rise in a known quantity of water is produced in a
specific amount of time.  An AC is playing the same game, and the same
measuring techniques can be used to test efficiency.  The testing
equipment would cost a little more.

Soft start is generally just easier on the mechanical components and
eliminates the large power spike starting induction motors create.
Eliminates the centrifugal switches, and is easier on the power source
(wiring and circuit breakers)  

Soft start can also provide feedback in AC systems to avoid
overloading compressors with a lot of back-pressure when starting.
(eliminating the pressure switches or thermal overloads AC's and
refrigerators currently use)

Are you sure you aren't confusing this with Auto computers programmed
to run lean in testing but richer in normal driving?

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