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capacitor across an AC line

I know that a capacitor does not consume any power if connected across an AC line except for a small ammount , but lets just say a pure capacitance.

I was playing around with a meter similar to the Killowatt meter and with a hair dryer the voltage and current multiplied together came to the same as the displayed watt on the meter within a few percent. Then I hooked up an amplifier that has a transformer in it and the displayed power was about 80% of the volts times amps.

I then hooked a 50 uF capacitor across the line, only the capacitor. Just rough numbers calculate the capacitance reactance as 53 ohms at 60 hz. Sure enough the meter shows about 2.3 amps just about what a 50 ohm resistor would show. However the wattage display was about 2 watts which still seems normal due to a slight leakage and such. I understand the meter showing this due to the lead or lag of reactance and wattless power.

Finally getting to the question is that if I bring up the AC up slow with a variac to keep the main surge down would a 1 amp fuse blow at around 50 volts when the current got past 1 amp or could I keep going to the full 120 volts AC ?

Reply to
Ralph Mowery
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** That is rather high, normally is it closer to 65%.

IOW transformer fed PSUs have a PF of 0.65.

** Strange question.

The fuse will blow when its current rating is exceeded by a sufficient ratio - about 50% or so.

That the load is a capacitor ( with current and voltage not in phase) has no effect.

... Phil

Reply to
Phil Allison

I looked over the numbers and the amplifier without drive was about .66 and when loaded heavy was .75.

I though the fuse would blow when the amp meter was showing enough current for it to blow with just a capacitor across the line. As we all know a fuse does not blow at the exect time the current is slightly exceeded.

I had never looked into the effect of inductive and capacitive loads on an AC line. Just knew there was a power factor due to the lead and lag of current and voltage. My main item of interist is at Radio Frequency and only look at the AC power was to make sure it was enough to power the equipment. I just hapen to see some numbers come up on the meter I had gotten a few weeks ago and got courious as if it was a cheep meter from China and giving false readings or if they were reasonable close. I do have a good multimeter to check the actual voltage and a clamp on meter for the current. For most work if it is from 5 ot 10 percent from those it is close enough for me. With the first calculated and displayed values were way off I started to see why. Such as the meter showed 100 watts and the volt amp multiplying was showing 150 watts and under load it was 1200 on the meter and 1500 calculated with the V and I . Checking with a hair dryer for a mostly resistive load the V and I calculated the same as the meter.

Reply to
Ralph Mowery

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