2744040447 Fair-Rite, 2744040447 Datasheet - Page 181

• Manufacturer Part Number: 2744040447
• Description: 44 SM Ferrite Beads, T&R
• Manufacturer: Fair-Rite

14th Edition
P.O. Box J,One Commercial Row, Wallkill, NY 12589-0288
Phone: (888) FAIR RITE / [phone]
Core Selection
Once the proper ferrite material for a specific suppression
application has been decided the required ferrite core is the next
step in solving the EMI problem. The core contribution to the
impedance is expressed in the formula
Lo=
From this formula it is evident that the impedance is proportional
to the square of the number of turns and the core geometry shown
by the core constant C
N
ance significantly for a rather minor cost. Figure 22 shows the
impedance versus frequency curves for one of Fair-Rite’s 43
material cable cores wound with one, two and three turns. By
increasing the number of turns the winding capacitance is
increased resulting in a shift in the maximum impedance to lower
frequencies. If an improvement of the low frequency impedance
performance is needed, this increase in turns can be very
beneficial for the 43 material applications.
The core geometry most often used in suppression applications
is the toroidal core. When the dimensions are in inches, the Lo
for the toroidal core shape is 1.17 N
three core dimensions OD, ID and H (height), the H is the most
significant. This dimension is proportional to the toroidal Lo and
hence of the impedance of the core. Doubling H will double the
volume and also the impedance. Doubling the core volume by
changing the OD and or the ID will only increase the impedance
by approximately 40%.
Overall the process of selecting a bead or cable core that fits the
wire or cable is mainly a mechanical evaluation, but the longer
the selected core the higher the impedance for a given volume
of ferrite material.
2
Figure 21
is often overlooked and yet can enhance the overall imped-
EMI
EMI
Common-Mode Design
4pN
[phone]
C
2
1
10
-9
(H)
I
- I
1
. The advantage of the proportionality of
- H
2
H log
10
H
OD/ID 10
• FAX: (888) FERRITE / [phone] • www.fair-rite.com • E-Mail: [e-mail]
-8
Technical Information
(H). Of the
[phone]
Fair-Rite Products Corp.
1
Suppression Materials
Figure 23
Figure 22
2000
1600
1200
Note: (914) Area Code has changed to (845).
800
400
0
10
73
6
Available Fair-Rite Suppression Materials
vs. Frequency
Impedance vs. frequency for a 14/6/28mm
cable core in 43 material wound with one,
two, and three turns.
10
31
10
Frequency (MHz)
N=3
N=2
N=1
7
Frequency (Hz)
44
43
100
10
8
61
1000
10
9
181