03-11-12: Jea48
Norm has the transformer configured for balanced power. That cuts the KVA rating of the xfmr in half. The xfmr maximum continuous FLA rating is 5 KVA.
Good point, Jim. Agreed.
03-11-12: Jea48
Just wonder if the poor PF, caused by too much capacitance on the AC line, is doing anything to the power xfmrs and switching power supplies of his audio equipment. You are the EE here.... What say you?
Good question, which I had been wondering myself. I don't know the answer.
03-11-12: Norm
Would you please elaborate how increasing the capacitance to the secondary side of the transformer may cause voltage to "lag"?
The voltage across a capacitor cannot change instantly. It changes in response to the accumulation or depletion of the charge it is storing, which in turn is proportional to the integral of current, over time. As a consequence of that, for a sinusoidal AC waveform of a given frequency, and assuming an idealized capacitor model, and since the integral of a sine wave is an inverted cosine wave, the voltage across a capacitor will lag the current by 90 degrees, or 1/4 cycle.
03-11-12: Norm
Also, how much additional current is the transformer "pulling" by adding 220uf.
10 amps, based on the assumption that 120 volts is placed across the 12 ohm impedance which the capacitor has at 60 Hz.
03-11-12: Norm
Jim, are you saying that by adding 220uf to the circuit I have effectively lowered my 10kVA xfmr rating to 5kVA?
No, the capacitor has nothing to do with that, although the capacitor significantly increases the amount of current the transformer has to supply, and significantly increases how much of the 5 kVA capability is being utilized. Referring to the
data sheet for the transformer, each of the two secondary windings is rated to handle 41 amps. Presumably you have them connected in series, with nominally 60 volts appearing across each winding, and 120 volts across the series combination. 120 x 41 = 4920 VA, or a little under 5 kVA.
Also, to make sure I'm envisioning your setup correctly, I'm assuming that the two primary windings are connected in series, and are fed by a single-phase 120V line and breaker rated at 40 amps or more. Is that correct?
Best regards,
-- Al