Re: Ballasting a Pole Pig (Revisited)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi D C.

I just ran your ballast design (7.5x4.5x4.5 inches with 125 turns and 
0.1 inch gap) thru my ballast program assuming the 7.5 inch and 4.5 
inch numbers were first the radii and then assumed they were the 
diameters.  Following are the results:

Assuming radius specification:

******************** BALLAST DATA ********************

Ballast Voltage                =  240 Volts rms
Ballast Current                = 11.0 Amps  rms
Line Frequency               =   60 Hz
Outside Toroid Diameter = 15.0 inches
Inside  Toroid Diameter   =  9.0 inches
Toroid Core Area           = 13.5 square inches
Relative Permeability       = 2100

GAP Size  = 0.10 inches

********************** RESULTS **********************

Inductance                         =  57.9 mh
Required Number of Turns =   126
Volts per Turn                    =   1.9 volts
Peak Flux Density              =  8213 gauss

Note, program is currently written with the ballast current as the 
independent variable so I have to keep adjusting it until the number 
of turns comes close to your 125 turn specification


Assuming diameter specification:

******************** BALLAST DATA ********************

Ballast Voltage                =  240 Volts rms
Ballast Current                = 21.0 Amps  rms
Line Frequency               =   60 Hz
Outside Toroid Diameter =  7.5 inches
Inside  Toroid Diameter   =  4.5 inches
Toroid Core Area           =  6.8 square inches
Relative Permeability       = 2100

GAP Size  = 0.10 inches

********************** RESULTS **********************

Inductance                         =  30.3 mh
Required Number of Turns =   124
Volts per Turn                    =   1.9 volts
Peak Flux Density              = 16697 gauss

I bet this is the design you are using, but the inductance is 30 mh 
(XL = 11.3 ohms) instead of 125 mh.  If you are using 200 nf of 
capacitance for CP, this would be the equivalent of 720 uf on the 
primary (assuming a turns ratio of 60) which is 3.7 ohms of 
XC.  Therefore, (XL - XC) = 7.6 ohms which would limit the current to 
31.6 amps.  Seems like a CP smaller than 200nf would result in larger 
current and a CP larger than 200nf would result in smaller current limiting.

Gerry R


> > > Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
> > >
> > >
> > > No.  120 mH provides control with 30 Amps as the max amount that 
> > > may be drawn.
> > >
> > > Dr. Resonance
> > >
> > >
> > > > Hi Dr R,
> > > >
> > > > 120mh is 45 ohms at 60Hz.  At 240Vac, this would limit the 
> > > > current to 5.3amps or ~1.2KVA.  Is this in error or Im I missing something??
> > > >
> > > > Gerry R