Trying to clear a concept - if I want to get the equivalent DC VOLTAGE to AC 120V, I use the form factor of 1.11 i.e. 120VAC is equiv to 120/1.11 =108VDC?

 

Trying to clear a concept - if I want to get the equivalent DC VOLTAGE to AC 120V, I use the form factor of 1.11 i.e. 120VAC is equiv to 120/1.11 =108VDC?

There is no equivalent DC voltage to AC voltage.

If you mean what DC voltage has the same power as 120VAC, then the answer is 120VDC.
That is because 120VAC is measured in RMS = root mean square.

120VAC has a peak value = 120V x √2 = 120 x 1.414 = 170V

In other words, a 120VAC sine wave is 170sin(2πft) where f is the line frequency (60Hz in North America).

 

To perhaps further clarify, the AC RMS voltage value has the same power (resistive heating) value as the same value of DC voltage.

The peak values of the two are, of course, different.
For an AC sine-wave, the difference factor is the √2.

Where did you get the factor 1.11?

 

The Formulas, (rounded-off for ease of use ), are ............

AC-RMS-Volts = DC-Volts when used in Power calculations.

AC-RMS-Volts times 1.4. = AC-Peak-Volts
AC-Peak-Volts times 0.7 = AC-RMS-Volts.

AC-Volts through a Bridge-Rectifier and Bulk-Storage-Capacitors .............

AC-RMS-Volts times 1.4. = DC-Volts.
Under heavy Loads, the rectified DC-Voltage will easily "sag" down to the AC-RMS-Voltage.

To get maximum DC-Voltage, with minimum AC-Ripple,
requires a large Choke, ( Inductor ), and multiple large Bulk-Storage-Capacitors.
This is called a "Choke-Input-Filter".
SMPSs, ( Switch-Mode-Power-Supplies ),
have some tricks to get around this requirement, and reduce size and costs.
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1.11 is the ratio of the rms Voltage (or current) of a rectified sinewave to the average DC voltage of rectified sinewave.

rms being 1/√2 x peak, average DC being 2/π x peak.

I recently had a customer complain that the battery charge current meter on our product was 10% out, and had to explain that our meter was right and so was his, but he was measuring the rms value, and our meter was reading the average value. Not the easiest thing to explain to your average electrician.

 

1.11 is the ratio of the rms Voltage (or current) of a rectified sinewave to the average DC voltage of rectified sinewave.

Of course, that explains where the ratio came from, I knew it seemed familiar.
It's the ratio between the RMS (rectified or not) and the absolute value (rectified) average value of a sine-wave.

Not sure if that's what the TS is looking for, as that ratio does not normally a factor when comparing devices powered from AC or DC.

I recently had a customer complain that the battery charge current meter on our product was 10% out, and had to explain that our meter was right and so was his, but he was measuring the rms value, and our meter was reading the average value.

Well, they can't both be correct.
Interestingly, the average value, not the RMS, is the correct current to read at a battery charger's output.
The RMS current value is only correct for a resistive load where power is proportional to the square of the current, which a battery is essentially not.

 

beatsal,
if you want to heat up your electric stove, those AC and DC are equivalent. 120VAC=120VDC