capacitors

[Anonymous]

i want to knw more about this topic i didnit understand it well.

FROM IVAN

[Spir Georges GHALI]

@guest said:
i want to knw more about this topic i didnit understand it well.

FROM IVAN

Dear Ivan

 

to be able to reply, please let me know what information you want to know about capacitors.

[saipurushotham]

sir , I need the different types of capacitors ,and where we are using that different types of capacitors (their ranges)

[Spir Georges GHALI]

@saipurushotham said:
sir , I need the different types of capacitors ,and where we are using that different types of capacitors (their ranges)

Dear ;

As you know, in principal, each capacitor is composed of 2 conductive parts with isolator between them, and the type & kind of components are different of each manufacture depending on his design to achieve the needed capacitance that drives to the Capacitor’s Reactive Power in “ kVAR ”, and to have 3 Phases Capacitor, the manufactures connect 3 elements in “ Star  or  Delta ” connection way. Noting that :

• – That most of used connection way is “ Delta ”.
• – Most of Capacitors used on LV networks are “ 3 Phases ”.
• – There are resistances connected between phases to discharge the capacitors to “ < 50V  during 1 min ” as defined by IEC 60831

 

Most of manufactures have many ranges of LV Capacitors depending on :

– Network Frequency that’s : 50  or  60Hz

– Nominal Network Voltage value that’s : 3 Phases, “ 230,  400,  415,  525,  690V ”

– The Capacitors Reactive Powers’ values in “ kVAR ” are in general : 2.5,  5,  6.25,  7.5,  10,  12.5,  15,  20kVAR, and some manufactures produce also “ 25,  30kVAR ”

– To have more than these Reactive Powers’ values, we assemble in Parallel “ 2 or more ” of those Capacitors, noting that the IEC 60831 advise to assemble up to 60 to 65 kVAR

– The Pollution’s Percentage “ Gh/Sn ” that the Capacitors can withstand, where : Gh : the Total Powers of Non-linear Loads in kVA, Sn : the apparent Power of the Transformer ( kVA ), noting that there’s 3 ranges as follow :

1- Standard  or  Classic range, for which “ Gh/Sn ≤  15% ”

2- Overrated  or  H  or  Confort range, for which “ 15%  <  Gh/Sn ≤  25% ”

3- Detuned  or  DR  or  Harmony range, for which “ 25%  <  Gh/Sn ≤  50% ”  

Rem. 1 : the same Capacitors can be used on “ 50Hz  or  60Hz ”, but as the Capacitor’s Impedance value is not the same ( Zc with 50Hz is bigger than with 60Hz ), the Reactive Power ( kVAR ) is also different ( Qc relative to 50Hz is smaller than Qc relative to 60Hz ).

 

Rem. 2 : we should be attention of the Rated Voltage value for which the manufacture defined the Capacitors Reactive Powers’ values, and if the network voltage’s value is smaller than that Rated Voltage value, the Capacitors Reactive Powers’ values should be modified ( Qc relative to 380V is smaller than Qc relative to 400V ).

 

Rem. 3 : depending on the “ Gh/Sn ” value, the above ranges are using as follow :

– Standard  or  Classic range is used for “ Slightly Polluted Networks ”.

– Overrated  or  H  or  Confort range is used for “ Polluted Networks ”.

– Detuned  or  DR  or  Harmony range is used for “ Highly Polluted Networks ”.

 

Rem. 4 : each unit of “ Detuned  or  DR  or  Harmony range ” is composed of “ Detuned Reactor with Capacitor ” connected in Serial way, and the supplying should be done first to the Detuned Reactor then to the Capacitor.

 

Rem. 5 : the “ Detuned  or  DR  or  Harmony range ” are produced in “ 3 types ” depending on the “ Tuning Order ” that are “ 2.5,  3.8,  4.3 ”.

 

Rem. 6 : if “ Gh/Sn > 50% ”, a special and deep study of network should be done to know all Harmonics and their amplitudes, then decide the suitable solution in which we use the Passive or Active Filters or both, but an economical study also should be done to choose the best solution.

 

So, depending on : the Network Frequency & Voltage Values, the Pollution’s Percentage, we choose the suitable range, then, from the available Capacitors Reactive Powers of that range, we can choose the capacitors’ units, and we assemble them to have the units we need.

 

Exp. : Network’s information : 400V,  50Hz,  Gh/Sn = 21%, and to correct the Power Factor value by Automatic Capacitors Bank we need the units : 10, 20, 30, 3×40 kVAR   

For that :

– The suitable range is : 3 Phases, 400V,  50Hz, from “ Overrated  or  H  or  Confort range ”.

– To have the needed unites, we have the following possibilities :

A- For “ 10 kVAR ” : 1×10 kVAR  or  2×5 kVAR  or  2.5+7.5 kVAR

B- For “ 20 kVAR ” : 1×20 kVAR  or  2×10 kVAR  or  5+15 kVAR

C- For “ 30 kVAR ” : 2×15 kVAR  or  3×10 kVAR  or  10+20 kVAR

D- For “ 40 kVAR ” : 2×20 kVAR  or  10+2×15 kVAR  or  4×10 kVAR

Noting that the final choosing should be done depending on the costs value of each combination.

[Author]

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