Somebody please double check my homework.
I got four 2400 MFD electrolytic caps and just selected a 10 ohm 200 watt power resistor from the scrap bin. I get 0.48 seconds to charge these caps through the resistor using a very simple formula I found:
CHARGE TIME = 5*R*C
I'm setting a time delay relay to .5 seconds before shorting out the resistor.
Karl
You get an A. If you happen to have a smaller wattage resistor, it would work. It is only in the circuit for half a second. But certainly no problem using what was in your scrap pile.
Dan
=A0 =A0 =A0 =A0 =A0 =A0 =A0 Dan
Don't forget that once you remove that resistor, the rectifiers are only conducting for a very short part of the cycle. Once the capacitors are charged up the incoming power has to go to nearly full voltage before they start to re-charge the capacitors. So, the current Spikes can be quite high for a very short period of time, 120 times a second. Since all the power is being consumed over a very short period of time, and at high amperage, a higher percentage of the electricity you are paying for is used to heat the wires.
You can reduce that, and the inrush current, and reduce you output ripple with a choke between the rectifiers and the capacitors.
According to the servo amp manufacturer, a choke is not necessary and this is on the high end of recommended capacitance. Now, I have no clue on wire size needed to prevent the insulation from melting. I'm going with four #12, one to each cap, and will check for excessive heating after startup.
Karl
The higher the capacitance, the higher the peak current through the diodes. The servo amp manufacturer doesn't care about your 'power factor', either.
The cap will charge to 99.3% of applied voltage in 5 time constants.
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