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Old 08-27-14, 06:50 PM   #11
NiHaoMike
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You forgot the "L" part of the LC filter. A shunt capacitor by itself does reduce harmonics, but adding series inductance makes it far more effective. And then there are tuned LC filters that specifically block or shunt a harmonic.

LC filters don't make sense at low power levels, but do make sense at high power levels. They are sometimes used in commercial and industrial settings. Presumably, they could be used for residential if there was a real need.

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Old 08-28-14, 03:00 AM   #12
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Quote:
You forgot the "L" part of the LC filter.
Actually, I did not. You failed to realize what I was talking about.

The PFC that gets the bad rap is the capacitors in a box sold as "power factor corrector for home". Such a device connects parallel to the line. There's practically no low power factor inductive devices of significance. This type of device corrects inductive DISPLACEMENT, but there's hardly any device at home that has displacement reactive current.

The problem in residential/light commercial are the HARMONICS caused by POWER ELECTRONICS, which is why these aftermarket devices are practically ineffective at doing anything at home.

Quote:
LC filters don't make sense at low power levels, but do make sense at high power levels.
Low and high are completely arbitrary. Please define them and perhaps include a few credible sources.

The 380v DC you mentioned that you call "HVDC" for example is considered LVDC in the context of this thread. In the context of this thread, anything under 1,000v is LOW VOLTAGE, per ANSI C84.1 even though in the lingo of people who wire LAN cords, stereo wires and such calls any utility sourced power "high voltage".
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Old 08-28-14, 07:13 PM   #13
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LC filters are not the same as PFC capacitors. A parallel LC network connected in series with the load can be tuned to appear as a high impedance at the harmonic you're trying to get rid of.

380V is called "HVDC" in a data center because traditionally, just "DC" referred to 48V. The high copper cost (in order to get a reasonable efficiency) has prevented 48V from getting widespread use, but 380V DC fixes that. (Not to mention that calling 380V "low voltage" is misleading at best!)
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Old 08-28-14, 10:12 PM   #14
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Quote:
LC filters are not the same as PFC capacitors. A parallel LC network connected in series with the load can be tuned to appear as a high impedance at the harmonic you're trying to get rid of.
I'm aware of that and nowhere did I say they're the same. I'm contrasting legitimate use vs marketing and application as snake oil product.

What you mentioned is categorized as passive filter and often called passive PFC. Passive harmonic filters have been used for decades in all kind of products including computer power supplies sold in European market to comply with IEC 61000-3-2. It has also been been integrated into a lot of lighting ballasts in US market.


Quote:
380V is called "HVDC" in a data center because traditionally, just "DC" referred to 48V.
We're not talking about data center specific matters so I am sticking with general definition as it relates to power. Not telecom, aviation, naval, data centre, etc.

Quote:
(Not to mention that calling 380V "low voltage" is misleading at best!)
In your opinion.

Under generally accepted standards, If it's 1,000v or less, it is low voltage, per IEEE 241-1990 and IEC 60071. We use arbitrary, but generally accepted standards and guidelines so we can have somewhat of a consistency and not have everyone jumping around with their own definition of terms creating confusions.
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Old 08-28-14, 11:06 PM   #15
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So what would you call 380V DC (or 180V) if it was used to distribute power in an off grid house? "Low voltage" normally refers to 48V or less.

In general electronics work, it is accepted that anything above 30V AC or 50V DC should be treated as high voltage as far as safety goes.
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Old 08-29-14, 06:03 AM   #16
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My power coming down from the panels is up to 600Vdc in North America and 1000Vdc in Europe but has its own set of regulations. For inspection purposes, a sub 50Vdc circuit in a house does not require an inspection the same way typical AC wiring does.
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Old 09-01-14, 04:10 AM   #17
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Quote:
Originally Posted by mejunkhound View Post
Do you REALLY believe that big, heavy, costly to produce (both in $$ and environmental first costs), and lossy passive components (LRC) are more effective than power electronics? If you REALLY believe that, maybe the earth IS flat?
....
I have designed power electronics for a living ever since FETs were invented and still consult in that area. Have chaired sessions of Applied Power Electronics Conference and Power Electronics Specialist Conference (some specifically dealing with harmonics) and authored a few dozen papers on the subject.
Big, heavy and lossy in some applications, but I believe these words are used to discredit passive components as outdated to present power electronics as being all around better no compromise solution when the real justification is lower production, shipping cost and gravitation towards irreparable and proprietary engineered product.

In my opinion, it has led to use of power electronics in applications where they offer very little functional advantage while their serious disadvantages are not presented rationally and the cost to eliminate these disadvantages no longer give them competitive advantage over traditional design.

Look around online and the very issues I expressed is happening everywhere.
I am not talking about how well your vehicle holds up after you run into a bridge pillar at 60 mph.

Rather, I am seeing what I would describe as "ran over a boot, drive train obliterated and the whole car was beyond economic repair"

Search the web for fried inverter. I am seeing things like so called 1800W such inverter getting fried from tools that are UL listed and considered as appropriate to use on 120v 15A circuit and I've experienced a few myself too.

If you think I am a "misinformation" why do the typical power electronic full-conversion technology tend to follow a certain fault pattern?

While it can be made more resilient like a jar being less breakable than a wine glass, power electronics tend to ultimately fail like glass and fail like this:


While passive components degrade like this:


Things like glass viewing platforms have an incredible factor of safety built into it and have a layer or two of redundancy. Power electronics based converter stations use multiple elements in series/parallel to make up for their failure proneness and these facilities stock replacement power electronics like they're light bulbs.

Electronic fluorescent ballast is of the "power electronics" design. They're normally used with adequate level of redundancy where enough of them are in use and a failure of any single one of them don't cause issues. They have always enjoyed higher failure rates than the traditional coil design.

In applications where a single failure will result in an immediate functional issues such as high wattage HID street and sports lighting where one outage will cause an objection, the highly resilient and durable electromagnetic coil and core ballast technology continues to be used. Heat rises and the higher areas tend to be a lot hotter. There are some type HID light bulb driving devices of the " power electronics " type, but again they enjoy high failure rates, so they're generally not used where replacement labor cost is high. As the wattage gets higher, the advantage of solid state type fades as well.

The only reason fluorescent lighting sees a wide use of the lower reliability driver power electronics technology is that driving them at higher frequency on an inverter improves the efficiency of the bulb themselves and they're usually used in quantity to provide mutual redundancy so the failed power electronics driver swap out can wait until next routine maintenance.

When I say poorer reliability, I mean that when every bulb in the fixture is out, it's almost always the POWER ELECTRONICS control gear that failed. It's much less common to see an electromagnetic ballast go out like that.

I also routinely hear of "load accidentally shorted and fried my 3000 watt inverter" but not once have i heard "I accidentally shorted the bus bar and fried the power company's transformer". Passive devices are durable enough that fuses protect them very effectively with very minimal nuisance trip.

With POWER ELECTRONICS, it's a constant battle between nuisance trip vs failure. Larger units require the use of very expensive LIMITRON type fuses with a half-cycle clearing current that's less than power chip thingies in a unit. When the fault current isn't quite enough to clear the fuse in half a cycle, sometimes the power chip thingies let out the smoke.

Not once have I heard of a shorting in even a 50A circuit frying a utility transformer, yet even those 3,000 watt inverters give away from motor starting surge.

The older DC side commutation static inverter that produces AC output through a line frequency transformer and much heavier, but do not have the same failure proneness of the modern high frequency double conversion design that is desirable for portable or weight restricted applications like aerospace and aviation use where fragileness in exchange for weight is a given.

Sadly, this failure prone design is the dominant design today even for stationary use and is the cause of "my inverter fried" stories where lbs/kW is entirely unimportant.

Last edited by ICanHas; 09-01-14 at 04:13 AM..
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Old 09-01-14, 08:34 AM   #18
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So why do you like to support the use of "failure prone" active PFC rather than tuned LC filters?
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Old 09-01-14, 06:47 PM   #19
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Quote:
So why do you like to support the use of "failure prone" active PFC rather than tuned LC filters?
It's a line pollution control to clean up the pollution caused by highly polluting power electronics loads. LC filters are good. It would be the most effective combined with facility level electromechanical power conditioner.

I support NOT using full conversion POWER ELECTRONICS in the first place or a drive method using the integrated EMBEDDED SYSTEM design using locked-up away from tear-down firmware. Power electronics cause things to be fragile an unreliable especially when used for full conversion and try to run the show, but they're useful as a side show parts.

Many power electronics based solid state double conversion UPS have abysmal efficiency.

Here's one of the most resilient, durable and dependable design of line conditioner, power factor correction and harmonic mitigation and can be made to surpass the efficiency of power electronics based double conversion at larger sizes.

No adverse interaction with fuel driven generator. The power factor can be smoothly adjusted to leading or lagging by changing the field excitation level using limited amounts of power electronics or entirely analog embedded system free motorized variable auto transformer free design. NO HARMONICS.

http://www.emersonindustrial.com/en-...L_KE000021.pdf


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