### Inductors Caution & Terms

```Caution & Terms
inductors
Inductors in General
• Characteristics such as the inductance, Q value etc. are frequency
dependent.
• The stress from resin coating and molding can result in change
of inductance.
• Since the inductors use ceramic materials, chipping and crack can
occur. Please be careful when handling. Excessive vibration and
impact could destroy the parts.
• Keep magnetic tweezers and other magnets away from the inductors
to avoid change of inductance caused by magnetization. Do not
press the wire wound part of the chip inductor with sharp objects.
• The inductance could decrease according to magnetic saturation
when the inductor is used exceeding the allowable current. There
is also a possibility of disconnection and short-circuit or emitting
smoke and ignition caused by the heat generation of the inductor.
• There is a risk of disconnection when excessive current (inrush
current) is applied. Change of the characteristics may occur by the
magnetization of the core when excessive current is applied to a
DC circuit.
• When the parts are used at high-frequency, the heat generation
will be larger and the part temperature will be higher compared
with DC or low-frequency. This is caused by increasing iron loss
and copper loss. Please be careful not to exceed the operating
temperature range of the parts.
Nominal Inductance
• Inductance that the inductor is designed to have and generally
indicated on the body.
Q Value (Quality factor)
• A coefficient that shows the quality of the inductors. It is calculated
from the following formula shown below.
Q = wL
w = Angular Frequency (w-2 π F)
R
L = Inductance
R = Resistance
Self-Resonant Frequency
• Frequency that resonance occurs by the distribution capacity
and inductance of the inductor.
DC Resistance Value
• Resistance value at DC.
Allowable DC Current
• Upper limit of the current which is set to assure the safe
use of the inductor.
• It is defined as the smaller DC current value of either the DC
superposition or the surface temperature rise characteristics.
• DC superposition characteristic is a phenomenon which occurs
when the inductors, made with magnetic materials such as ferrite,
have a large DC current applied. When this occurs, the inductance
drops because of the magnetic saturation.
• The plot below shows the relationship between the DC superposition
and the surface temperature rise..
200
180
AC=2 .5A
160
AC=2 .0A
Measuring point
: Winding wire
(Hot spot)
AC=1 .5A
140
AC=1 .0A
120
AC=0 .5A
100
80
60
40
20
0
300
100
500
Frequency (kHz)
1000
700
L-Frequency Characteristics
2500
Inductance area
Inductance (nH)
1500
Capacitance area
1000
500
0
-500
Self Resonant Frequency(SRF)
-1000
0
50
-2
45
-4
40
-6
35
-8
30
DC Bias Characteristics
ΔL/L = -10 % Down
-10
25
Temperature Rise
ΔT=20 Up
-12
20
-14
15
-16
• The electrical characteristics change from the variation of frequency
of the parts. When the part is used above the frequency band of the
SRF (self-resonant frequency), it will function as a capacitor. Please
do not use the parts above the SRF.
2000
DC Bias Characteristics
ΔL/L(%)
Temperature (°C)
AC=3 .0A
-1500
10
ex. Allowable DC Current
-18
5
-20
0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Iron Loss
• Electrical energy that is lost when the wire wound magnetic
material is magnetized by the applied AC. It is calculated by
the sum of hysteretic loss and eddy-current loss.
Copper Loss
• Energy that is transformed into Joule heat by the resistance
of the wound wire. The Copper loss increases in the high frequency
band from the skin effect.
Current (A)
-2000
-2500
Mounting
• Some inductors have polarities.
• The inductance and Q values of a non-magnetically-shielded inductor
could change from magnetic coupling affected by other components,
chassis, patterns, etc. When mounting in high density, check the
take care of the positioning of the components since closely mounted
inductors may cause magnetic coupling. Do not place large magnetic
materials like audio speakers, etc. near the inductors.
• Do not expose the inductors to the heat radiation from other high
temperature parts.
0
500
1000
1500
2000
2500
3000
Frequency (MHz)
Reference
• For basic precautions, please refer to the Technical report of
JEITA RCR-2501 Safety application guide for inductors for use
in electronic equipment.
Specifications given herein may be changed at any time without prior notice. Please confirm technical specifications before you order and/or use.
1/22/14
KOA Speer Electronics, Inc. • 199 Bolivar Drive • Bradford, PA 16701 • USA • 814-362-5536 • Fax: 814-362-8883 • www.koaspeer.com
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inductors