Since we are on the subject, let me toss in my two cents, even though I
don't believe this to be the problem in this case.
I have seen the characteristics of ferrite cores changed (apparently
permanently) by passing a high current pulse though the inductor winding.
This may seem like an unlikely situation until one thinks about a ferrite
inductor on a power supply rail, and the rail then accidentally shorted to
ground.
The current pulse reduces the inductance substantially.
Donald Borowski
Schweitzer Engineering Labs
Pullman, WA, USA
Kbalasubramanian@
SCMMICRO.CO.IN
Sent by: To
[email protected] [email protected],
[email protected]
cc
10/06/2006 05:02
AM Subject
Inductor mystery
Dear Experts,
We use the inductor part "1812CS-102XJLC" of Coilcraft in our RFID
product as EMI filter. Continuously we face one issue, about 20 to 30 %
products are functionally failing due to this inductor. While we change the
inductor alone the product passes the functional tests. Hence we studied
the characteristics of the inductor.
Measurements carried out using the Agilent Impedance analyser 4294A
shows the failing inductors and passing inductors are identical with
respect to the below listed parameters for the entire measuring range of 40
Hz to 110 MHz. Our frequency of operation is 13.56 MHz and both the failing
inductors and passing inductors are identical in this particular frequency
also with respect to the below parameters.
Is there anything else than the below listed parameters critical for
an inductor? Has any one of you come across such an issue in your devices?
I request your help.
a. Ra.c
b. Conductance - 'G'
c. Reactance - 'X'
d. Susceptance - 'B'
e. Impedance - 'Z'
f. Phase angle of the impedance
g. Value of R, L & C measured using the equivalent circuit method of
measurement.
Sincerely
K.Balasubramanian
Project Leader - Hardware.
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