efficiencies of appliance 3-phase brushless motors?

The efficiency only depends on the motor, 1 or 3 phases.

The only difference is the power consumption on each phase.

...

How does the efficiency compare with brushless permanent magnet motors?

Michael

Ours in the UK are 220/240V but get my underpants clean in 1 wash so I'd say 100%

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terminal_crazy@sand-hill.uk

You have electricity in the UK?! No way! :o

100% efficiency doesn't exist. A standard motor (not professional model) can barely be above 80-90%.

Standard motor? What's that?

Looks like 3-ph motors run from 70% @ 1/4hp to around 88% at 3hp. I'd forgotten I had this in my notes.

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I was curious how it compared with brushless motors but I guess this will do.

Universal motors with brushes run around 30-60% efficient.

The "infinitely inefficient" shaded pole motor runs around 10-20% efficient.

Michael

The ones you have at home.

A typical American home may have:

- Shaded pole motors on desk fans and circulating air for the refrigerator. (I was really upset when I found the old broken dishwasher in my parents' home had a giant shaded pole motor for the water pump.)

- Universal motors for dough mixers, blenders, drills and circular saws

- 3-phase motors driven by control electronics for washing machines

- brushless motors for remote-controlled model aircraft, and possibly for modern appliances

Michael

The reason for the big shaded pole pump motor is because they draw pretty much the same current when stalled as when running. So if the design allows sufficient cooling without a fan then if the pump motor is stalled with food debris or a fork or something it won't burn up. Granted, there are other ways to deal with stalled motors but the shaded pole solution is simple and cheap. Except that you pay more for the power to run the motor. This can be a wash though, so to speak. Just save all your dirty dishes until the weather gets cold when the extra heat from the pump motor will warm your house. Actually, I supose a clever design would use the heat from the pump motor to help warm the washing water. Eric

I wonder how a fork can finish in the pump !

Lots of air conditioners are moving to speed controlled three phase compressor motors these days. They've been in use for large commercial AC's for awhile now, and plenty of the newer heat pumps use them. There's at least one window unit that uses a VFD and three phase motor.

Oh that's a surprise! Are they fairly close in efficiency to the electronically commutated / brushless motors then?

Are the 3-phase motors run in open-loop, or do they require precise feedback control like the brushless motors need?

Window A/C unit?! Which???

Thanks,

Michael

Dunno about it being three phase, but here you go:

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		     dannyb@panix.com  
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Oh neato! Even better; it's Brushless DC (BLDC)!

"... thanks to LG's unique BLDC motor and dual inverter compressor..."

Annoyingly, though, Lucky Goldstar is only offering a couple of models in the US, with ratings in the 14,000 BTU range.

I wrote to them asking if they'd please consider selling smaller, like 5 to 10,000 ones. Not at this time...

--
_____________________________________________________ 
Knowledge may be power, but communications is the key 
		     dannyb@panix.com  
[to foil spammers, my address has been double rot-13 encoded]

I doubt the motors are any more efficient than a standard 3 phase doing the same amount of work. BUT... they throttle back when you don't need cooling instead of cycling on and off.

I put in a "mini-split" with an inverter (what the AC folks call their VFD type products) My power bill was lower than no AC and relying on fans for cooling. (I suspect some of that savings was due to the refer running much less due to the lower humidity in the house)

They have feedback of course. Dependent on temperature. I have a volt/ammeter on my mini-split. Hot summer day with a hot house I turn on the 18,000 BTU AC and the current will hit 8-9 amps (250 volts single phase). After it runs for a time the current drops as it approaches the set-point until it is chugging along with only ~2 amps or less and on really hot days it runs continuously at 2 amps, and begins cycling on and off if it has more capacity than it needs to satisfy the set-point.

LG makes them:

LW1517IVSM

14,000 BTU

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.

Since they do run the compressor slower as cooling needs are met, you probably shouldn't look at an inverter AC the same as you would a standard AC. If you need 10,000 BTU a 14,000 btu will throttle back to around 20% of the power a 14K would require and that would still be less than the 10K would use.

Of course if 5K (does anyone make one that small?) does the trick, 14K would be way over-kill.

With standard AC units the best savings meant using the smallest AC that would do the job. Presumably you could live with the longer time to cool-down... and maybe there'd be a couple of days each year when the temp/humidity was so high that it might not keep up with your needs. These inverter type units are a game-changer in that respect. And they soft-start, so you aren't pulling 40 amps to get the compressor turning over from a dead stop.

Some dishwashers have the pump impeller under a screen that can come loose which then allows foreign objects to contact the inpeller. Eric