Voltage divider

[Mike. Watterson]

Originally Posted by merlinmaxwell

most of them had an isolated chassis anyway.

But not capacitors and distances between the 0V bus bar and chassis or case metal parts that meet any 250V standard. I have I think five USA sets that are battery mains, and not one meets safety criteria even with isolation RF earthing capacitors replaced even with 2KV parts, though they might all be safe in practice.
I'd only use modern 115V gear that's plastic cased on an autotransformer, nothing vintage and especially if it didn't have an internal isolating transformer.
Of course if it's for yourself and you are qualified to decide, then an autotransformer is fine.

[Herald1360]

VAPhi? Reference to power factor perhaps? For sinewaves at any rate, power factor is cosΦ where Φ is phase angle between voltage and current. VA*cosΦ is actual watts.

[Al (astral highway)]

Originally Posted by Herald1360

VAPhi? Reference to power factor perhaps? For sinewaves at any rate, power factor is cosΦ where Φ is phase angle between voltage and current.

Neat explanation, Chris. I wouldn't have spotted that the phi was an anglicisation of Φ, as I've never heard the symbol pronounced! Thanks!

I found this resource for those less expert than you on the forum, who'd like some more insight. Here's an extract...

Power factor calculations

For sinusuidal current, the power factor PF is equal to the absolute value of the cosine of the apparent power phase angle φ (which is also is impedance phase angle):

PF = |cos φ|

PF is power factor.

φ is the apparent power phase angle.


The real power P in watts (W) is equal to the apparent power |S| in volt-ampere (VA) times the power factor PF:

P(W) = |S(VA)| × PF = |S(VA)| × |cos φ|


When the circuit has a resistive impedance load, the real power P is equal to the apparent power |S| and the power factor PF is equal to 1:

PF(resistive load) = P / |S| = 1

The reactive power Q in volt-amps reactive (VAR) is equal to the apparent power |S| in volt-ampere (VA) times the sine of the phase angle φ:

Q(VAR) = |S(VA)| × |sin φ|

Single phase circuit calculation from real power meter reading P in kilowatts (kW), voltage V in volts (V) and current I in amps (A):

PF = |cos φ| = 1000 × P(kW) / (V(V) × I(A))