N
[email protected]
- Jan 1, 1970
- 0
A 12 uF recycled motor run cap on the same extension cord as a 61 W fan
raised its power factor from 0.69 to 0.98, with an audible spark. A series
choke with 18/2 lamp cord ($31 for 250' at Home Depot) wound on a square
varnished steel coathanger core might limit the switch inrush current.
R. Clarke's nice web page on magnetism
http://www.ee.surrey.ac.uk/Workshop/advice/coils/terms.html#efarea
says magnetic flux Phi = IL/N = 0.04/N webers, and the max flux density
B = Phi/Ae = 1.6 teslas, to avoid saturating steel, so NAe = 0.04/1.6
= 0.025 = NPir^2, for a core cross section of radius r, and L = 0.004
= Mu0MurN^2r^2/Le henrys, where Le is the core perimeter in meters...
10 PI=4*ATN(1)'powfac
20 V=120'load voltage (rms)
30 P=61'load power (watts)
40 PF=.69'uncorrected power factor
50 XC=V^2*PF/(P*SQR(1-PF^2))'reactance (ohms)
60 C=1/(377*XC)'ideal PF correction capacitor (farads)
70 PRINT V,P,PF,1000000!*C
80 CS=12'standard cap value (microfarads)
90 C=CS/1000000!'standard cap value (farads)
100 IC=V*377*C'cap current (amps)
110 IMAX=20*P/V'peak cap current (amps)
120 DT=V*SQR(2)*C/IMAX'charging time (seconds)
130 L=V*SQR(2)*DT/IMAX'series inductance (henrys)
140 FRES=1/(2*PI*SQR(L*C))'resonant frequency (hertz)
150 PRINT CS,IMAX,L,FRES/60
170 MU0=PI*.0000004'free-space permeability
180 MUR=200'relative steel permeability
190 MU=MU0*MUR'absolute steel permeability
200 B=1.6'allowable max flux density (teslas)
210 NR2=IMAX*L/B/PI'Nr^2 constant
220 N2R2=4*L/MU/PI'n^2r^2 constant
230 WA=.1*.1/(39.37^2)'wire area (m^2)
240 NL=50'initial number of turns
250 R=SQR(NR2/NL)'core radius (m)
260 E=2*R+SQR(NL*WA)'square core edge (m)
270 N=N2R2/NR2*E'iterate
280 IF ABS(N-NL)>.1 THEN NL=N:GOTO 250
290 N=2*INT(N/2+.5)'round to even number
300 WIRELENGTH=3.281*PI*N*R'bifilar wirelength (feet)
310 PRINT N/2,WIRELENGTH
320 ECORE=39.37*E'core edge (inches)
330 RCORE=39.37*R'core radius (inches)
340 PRINT ECORE,RCORE
350 VCORE=4*ECORE*PI*RCORE^2'core volume (in^3)
360 LCOAT=36'coathanger length (inches)
370 DCOAT=.07'coathanger diameter (inches)
380 VCOAT=LCOAT*PI*DCOAT^2/4'coathanger volume (in^3)
390 NCOAT=INT(VCORE/VCOAT+.5)'number of coathangers
400 PRINT LCOAT,DCOAT,NCOAT
volts watts Power factor ideal PF cap (uF)
120 61 .69 11.78694
standard peak current inductance 60 Hz
PF cap (uF) (A) (H) harmonic
12 10.16667 3.343618E-03 13.2425
wire turns length
53 8.751237 feet
core edge radius
1.657399 in .3153355 in
coathanger
length diam number
36 in .07 in 15
Nick
raised its power factor from 0.69 to 0.98, with an audible spark. A series
choke with 18/2 lamp cord ($31 for 250' at Home Depot) wound on a square
varnished steel coathanger core might limit the switch inrush current.
R. Clarke's nice web page on magnetism
http://www.ee.surrey.ac.uk/Workshop/advice/coils/terms.html#efarea
says magnetic flux Phi = IL/N = 0.04/N webers, and the max flux density
B = Phi/Ae = 1.6 teslas, to avoid saturating steel, so NAe = 0.04/1.6
= 0.025 = NPir^2, for a core cross section of radius r, and L = 0.004
= Mu0MurN^2r^2/Le henrys, where Le is the core perimeter in meters...
10 PI=4*ATN(1)'powfac
20 V=120'load voltage (rms)
30 P=61'load power (watts)
40 PF=.69'uncorrected power factor
50 XC=V^2*PF/(P*SQR(1-PF^2))'reactance (ohms)
60 C=1/(377*XC)'ideal PF correction capacitor (farads)
70 PRINT V,P,PF,1000000!*C
80 CS=12'standard cap value (microfarads)
90 C=CS/1000000!'standard cap value (farads)
100 IC=V*377*C'cap current (amps)
110 IMAX=20*P/V'peak cap current (amps)
120 DT=V*SQR(2)*C/IMAX'charging time (seconds)
130 L=V*SQR(2)*DT/IMAX'series inductance (henrys)
140 FRES=1/(2*PI*SQR(L*C))'resonant frequency (hertz)
150 PRINT CS,IMAX,L,FRES/60
170 MU0=PI*.0000004'free-space permeability
180 MUR=200'relative steel permeability
190 MU=MU0*MUR'absolute steel permeability
200 B=1.6'allowable max flux density (teslas)
210 NR2=IMAX*L/B/PI'Nr^2 constant
220 N2R2=4*L/MU/PI'n^2r^2 constant
230 WA=.1*.1/(39.37^2)'wire area (m^2)
240 NL=50'initial number of turns
250 R=SQR(NR2/NL)'core radius (m)
260 E=2*R+SQR(NL*WA)'square core edge (m)
270 N=N2R2/NR2*E'iterate
280 IF ABS(N-NL)>.1 THEN NL=N:GOTO 250
290 N=2*INT(N/2+.5)'round to even number
300 WIRELENGTH=3.281*PI*N*R'bifilar wirelength (feet)
310 PRINT N/2,WIRELENGTH
320 ECORE=39.37*E'core edge (inches)
330 RCORE=39.37*R'core radius (inches)
340 PRINT ECORE,RCORE
350 VCORE=4*ECORE*PI*RCORE^2'core volume (in^3)
360 LCOAT=36'coathanger length (inches)
370 DCOAT=.07'coathanger diameter (inches)
380 VCOAT=LCOAT*PI*DCOAT^2/4'coathanger volume (in^3)
390 NCOAT=INT(VCORE/VCOAT+.5)'number of coathangers
400 PRINT LCOAT,DCOAT,NCOAT
volts watts Power factor ideal PF cap (uF)
120 61 .69 11.78694
standard peak current inductance 60 Hz
PF cap (uF) (A) (H) harmonic
12 10.16667 3.343618E-03 13.2425
wire turns length
53 8.751237 feet
core edge radius
1.657399 in .3153355 in
coathanger
length diam number
36 in .07 in 15
Nick