# Re: PFC for neons

```Mike:
Here is something plaigerized from Richard Quick:
Neons typically have an efficiency of about 50%, in that they
draw twice as much RMS power as they put out. This problem can be
resolved with the use of power factor correction (pfc) capaci-
tance across the line. The pfc capacitors used are the same as
for alternating current motors. The voltage rating should be at
least twice the line current used, and I like a 4x voltage margin
for long life. The formula used to determine ballpark pfc is as
follows:
9
10^
C = Corrected kVA  ------ 2
2(pi)fe^

This should read C = Corrected kVA times (10 to the ninth power)
over, (2 pi times f times e squared)

C = required capacitance in microfarads
f = frequency of applied voltage
e = applied voltage

CORRECTED kVA is determined by dividing the corrected power
factor output of the neon sign xfrmr (Volt-Amps below) by 1000

Corrected Power Factor

Secondary Rating         Volt-Amps
kV,mA

15,120                 900
15,60                  450
15,30                  250
12,120                 775
12,60                  400
12,30                  200
9,120                 600
9,60                  300
9,30                  150
7.5,120                 500
7.5,60                  250
7.5,30                  125
6,60                  200
6,30                  100

Not sure what you mean by "the typical motor start capacitor".
Oil with rating over 250 volts AC yes, electrolytic of any
rating absolutely no!
Ed Phillips
```