2008 Sep 01 201
Ferroxcube
Material specification 3R1
Fig.4 Specific power loss as a function of peak
flux density with frequency as a parameter.
handbook, halfpage
MBW001
10
2
10
3
10
B (mT)
110
10
4
P
v
(kW/m )
3
3R1
10
2
10
3
1 MHz
400 kHz
10 kHz
25 kHz
100 kHz
Fig.5 Specific power loss for several
frequency/flux density combinations
as a function of temperature.
handbook, halfpage
04080
800
600
200
0
400
MBW002
120
T ( C)
P
v
(kW/m )
3
3R1
o
f
(kHz)
B
(mT)
100
100
30
200
10 200
Remark:
When 3R1 ring cores are driven exactly at their natural
mechanical resonant frequencies a magneto-elastic
resonance will occur. With large flux excursions and no
mechanical damping, amplitudes can become so high that
the maximum tensile stress of the ferrite is exceeded.
Cracks or even breakage of the ring core could be the
result. It is advised not to drive the toroidal cores at their
radial resonant frequencies or even subharmonics (e.g.
half this resonant frequency).
Resonant frequencies can be calculated for any ring core
with the following simple formula:
where:
f = radial resonant frequency (kHz)
D
o
= outside diameter (mm)
D
i
= inside diameter (mm).
f
r
5700
π
D
o
D
i
+
2
-------------------
----------------------------
kHz=
