Post by Legis on Nov 17, 2010 19:52:43 GMT -5
If this has been clarified long ago in some god forsaken thread, forgive me, because I just registered to the forum.
Legis says hi to everybody!
I have been reading some post regarding the parallel/series wiring of the capasitors of the XPA-1 and XPA-2 amplifiers.
First of all, it is true that both amps use this wiring technique to boost caps' voltage rating. If the voltage rails were only 63V, would that mean that the maximum output to 8 ohms would be ~480-490W. Parallel series wiring doubles the voltage rating, which is why it has been necessary (and beneficial...) to implement.
Second of all, it is also true that this wiring technique lowers to total capacitance to one fourth of the filter caps' total value, meaning the secondary capacitance of XPA-1 is 30,000µF and XPA-2 45,000µF.
Thirdly (I think this fact has been overloooked) the fact I want to emphasize is that parallel/series wiring tehnique actually lowers the total charge of the capacitor only by half while it keeps the total amount of energy, that the capacitors can store, the same as is in all-parallel wiring of the caps.
The total amount of charge (Q) of the capacitor(s) can store, is calculted: Q = C*V (capacitance in fards times the voltage rating of the capacitor in volts)
Now when we calculate the total charge of XPA-1's 12pcs 10,000µF capacitors wired in all-parallel-style and in series/parallel-style we see that the charge only drops to half when wiring the caps in parallel/series:
all-parallel-style: 12*10^-2 F x 63V = 7,56 coulombs
series/parallel-style: 3*10^-2 F x 126V = 3,780 coulombs
However the charge is always about the total energy (E) that is stored, so let's calculate it in both wiring techniques. The total energy is calculated with formula E = ½CV²
all-parallel-style: 0,5 *12*10^-2 F * 63^2 = 238,14 joules
series/parallel-style: 0,5 * 3*10^-2 F * 126^2 = 238,14 joules
(Little perspective how much power this amount energy can produce: The transformer charges the capacitor bank every 20 milliseconds in alternating current mains network of 50hz. If the whole energy of the capacitor bank is dissipated in 20 milliseconds the generated power is: P = (238,14 Joules) / (5*10-3 s) = 47628W = 47,6kW. If we let the capacitor bank's current fluctuate only by 10% between the cycles, the generated power would be 4,76kW.)
The point: This shows that the parallel/series wiring does not affect the total energy storage of the capacitor bank, nor it does not hinder the performance in any way. Actually the raised voltage rating does drop the distortion generated by the caps, so wiring capasitors in parallel/series is actually beneficial compared to all-series wiring with the same capacitors.
References:
1) www.kpsec.freeuk.com/capacit.htm
2) hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng.html
3) www.engineeringtoolbox.com/capacitors-energy-power-d_1389.html
Legis says hi to everybody!
I have been reading some post regarding the parallel/series wiring of the capasitors of the XPA-1 and XPA-2 amplifiers.
First of all, it is true that both amps use this wiring technique to boost caps' voltage rating. If the voltage rails were only 63V, would that mean that the maximum output to 8 ohms would be ~480-490W. Parallel series wiring doubles the voltage rating, which is why it has been necessary (and beneficial...) to implement.
Second of all, it is also true that this wiring technique lowers to total capacitance to one fourth of the filter caps' total value, meaning the secondary capacitance of XPA-1 is 30,000µF and XPA-2 45,000µF.
Thirdly (I think this fact has been overloooked) the fact I want to emphasize is that parallel/series wiring tehnique actually lowers the total charge of the capacitor only by half while it keeps the total amount of energy, that the capacitors can store, the same as is in all-parallel wiring of the caps.
The total amount of charge (Q) of the capacitor(s) can store, is calculted: Q = C*V (capacitance in fards times the voltage rating of the capacitor
Now when we calculate the total charge of XPA-1's 12pcs 10,000µF capacitors wired in all-parallel-style and in series/parallel-style we see that the charge only drops to half when wiring the caps in parallel/series:
all-parallel-style: 12*10^-2 F x 63V = 7,56 coulombs
series/parallel-style: 3*10^-2 F x 126V = 3,780 coulombs
However the charge is always about the total energy (E) that is stored, so let's calculate it in both wiring techniques. The total energy is calculated with formula E = ½CV²
all-parallel-style: 0,5 *12*10^-2 F * 63^2 = 238,14 joules
series/parallel-style: 0,5 * 3*10^-2 F * 126^2 = 238,14 joules
(Little perspective how much power this amount energy can produce: The transformer charges the capacitor bank every 20 milliseconds in alternating current mains network of 50hz. If the whole energy of the capacitor bank is dissipated in 20 milliseconds the generated power is: P = (238,14 Joules) / (5*10-3 s) = 47628W = 47,6kW. If we let the capacitor bank's current fluctuate only by 10% between the cycles, the generated power would be 4,76kW.)
The point: This shows that the parallel/series wiring does not affect the total energy storage of the capacitor bank, nor it does not hinder the performance in any way. Actually the raised voltage rating does drop the distortion generated by the caps, so wiring capasitors in parallel/series is actually beneficial compared to all-series wiring with the same capacitors.
References:
1) www.kpsec.freeuk.com/capacit.htm
2) hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng.html
3) www.engineeringtoolbox.com/capacitors-energy-power-d_1389.html