Synchronous Reactance Controller for Energy Reduction 8

[ibkenb]

I am an electric utility power engineer and have been asked to evaluate a "Synchronous Reactance Controller" that promises our customer up to 10 % energy savings. Personnally, I think it is snake oil, but in fairness I would like to know if anyone has evaluated such a system and would share their results.

The device promises VAR correction which lowers the KVA demand and our associated charges. However, it also promises to filter the harmonics out of the supply voltage and to balance the three phase voltages. I am sure there are some efficiency savings with the harmonic improvements, but I do not know how to quantify them.

I cannot obtain information on the internals of the device and since it is connected in a shunt (parallel) I am at a loss as to how it may balance loads/voltage.

 

[ScottyUK]

jraef,

A tank circuit is a parallel resonant circuit comprising a series R-L element in parallel with a C element. It is a damped circuit because of the R, and is a reasonable representation of a real world parallel inductor - capacitor arrangement. It has a maximum impedance at resonance, resonance being detuned slightly from the 1/(sqrtLC) of a pure L-C circuit.

I can't quite figure out how they have connected the tank circuit into the system, other than to use it to trap harmonics while presenting a high impedance at system frequency. How they achieve PF correction on top of that I'm not sure.

I share your scepticism, mainly because they cloak it all behind smoke and mirrors. Good engineering, on the whole, sells itself.



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If we learn from our mistakes,
I'm getting a great education!

 

[jraef]

ScottyUK,
Sorry for not making myself clear. I know what a tank circuit is, but what I was questioning was how are they using it in this application. My "nebulous" comment was aimed at the fact that the term "tank circuit" has been used to define many things, and in and of itself is open to further explanation. I have even seen it used to describe ferroresonant transformers, which would do something for power quality but nothing for energy savings. My point was that flippantly throwing terminology regarding (somewhat) complex systems into marketing pieces aimed at the general public serves to obfuscate rather than educate, and obfuscation leads me to believe they are hiding something.

"Venditori de oleum-vipera non vigere excordis populi"

 

[ScottyUK]

Jraef,

I think we're on very similar wavelengths. It's just that your receiver runs on 60Hz power, and mine runs on 50Hz...



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If we learn from our mistakes,
I'm getting a great education!

 

[MarkAthay]

Scotty,

A common way to filter out the most egregious harmonics (5th harmonic) while at the same time improve the power factor is to install a filter at the 4.7th harmonic. You size the capacitor to provide the desired PF correction and then install a reactor in series with it to resonate at the 4.7th harmonic. While I can't mathematically crunch out why it works, intuitively I can see why it does, and experience shows that it indeed does work.

Because they're using the term "tank circuit" to describe the inner workings of their black box, I have to wonder how much of it is actually electronic, and how much of it is simply an old fashioned (but still good) synchronous condensor. I strongly feel that both static VARS and synchronous condensors are good for the system, and each has it's place.

Mark

 

[ScottyUK]

Hi Mark,

The thing I'm trying to puzzle out in my mind is what they are doing with the tank circuit to produce a filtering action, if indeed that is what they've done with it. The blurb suggests that they are using it as an energy store, which indeed it is, but quite how they are using it to suppress harmonics has me curious. the circuit must be quite different in topology from the more normal resonant trap that you describe.



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If we learn from our mistakes,
I'm getting a great education!