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Posted by Solar Flare on January 16, 2007, 5:42 pm
Notch filters are always good selective units. Our problem is
filtering 10MW ++ loads full of harmonics. That is a lot of heat to
disapate. hmmmmmm... building heat in the winter and hot water? Why
bother when tons of heat is thrown away in the main transformers via
cooling fans and pumps. Trouble is the utility buldings run metered in
with the big bulk of the consumers and is not apparent to anybody in
the utility. **SIGH**
>
>>Capacitive reactance is lower to higher frequencies...
>
>>> How does that work? I thought they could only reduce IV phase
>>> angles.
>>>
>>>>Power Factor correction capacitors can help absorb some of the
>>>>harmonics.
>
> Interesting. I wonder how to calculate the power factor improvement
> for,
> say, a 4.7 uF cap in parallel with a 150 watt 277 V load with a 10%
> 3rd
> harmonic distortion.
>
> The first step might be to calculate the original power factor, with
> no cap.
>
> This seems different and more promising:
>
> https://www.galco.com/circuit/PFCC_har.htm
>
> Harmonic currents can be significantly reduced in an electrical
> system
> by using a harmonic filter.
>
> In its basic form, a filter consists of a capacitor connected in
> series
> with a reactor tuned to a specific harmonic frequency. In theory,
> the impedance of the filter is zero at the tuning frequency;
> therefore,
> the harmonic current is absorbed by the filter. This, together with
> the natural resistance of the circuit, means that only a small
> level
> of harmonic current will flow in the network.
>
> A 600 Hz filter might help a power supply that clips 10% of an 60 Hz
> peak.
>
> Nick
>
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