Tracker-2800-2800S.pdf - 第50页
50 Effect of Resistance Changes on Inductive Signatures Select 2V, 10 , 60Hz. Then Select 50 and 200 . R S = 10 R S = 50 R S = 500 Figure 3-20 . Effect of V ary in g R S on 12,000 µH Inductor Signatures. Note…
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Effect of Frequency Changes on Inductive Signatures
Select 10V, 50, 60Hz. Then Select 1KHz and 2KHz.
F
S
= 60 Hz F
S
= 1KHz F
S
= 2KHz
Figure 3-18. Effect of varied F
S
on 12,000 µH Inductor Signatures.
Note that the signature changes from a vertical position to a horizontal position as the frequency
increases. This means the resistance of an inductor increases as frequency increases.
Effect of Voltage Changes on Inductive Signatures
Select 200mV, 50, 60Hz. Then Select 5V and 10V.
V
S
= 200 mV V
S
= 5 V V
S
= 10 V
Figure 3-19. Effect of varied V
S
On 12,000 µH Inductor Signatures.
Note that the signature does not change at the three test signal voltages. This means that the inductor's
resistance is not affected by changes in the test voltage.
50
Effect of Resistance Changes on Inductive Signatures
Select 2V, 10, 60Hz. Then Select 50 and 200.
R
S
= 10 R
S
= 50 R
S
= 500
Figure 3-20. Effect of Varying R
S
on 12,000 µH Inductor Signatures.
Note that the signature changes from a horizontal to a vertical position as the Tracker 2800's internal
resistance R
S
increases. This means the inductor's resistance can be analyzed by matching it with the
Tracker 2800's test signal resistance.
Understanding Inductive Signatures
Figure 3-21. Tracker 2800 Tracker Core Circuit Block Diagram with an Inductor.
The Tracker 2800's block diagram shows an inductor between the test terminals. The current is
represented by the vertical axis and is derived as a series current that flows through Tracker 2800’s
internal resistance, R
S.
The voltage is represented by the horizontal axis and is derived as a voltage
across the inductor.
The formula for the reactance X
L
of an inductor is:
X
L
= 2fL
As the test signal frequency increases, the inductive reactance X
L
becomes larger. As a result, the
inductor’s analog signature will change from a rounder elliptical to a flatter resistive type pattern. The
size and shape of the ellipse depend on the inductor value, test signal frequency, and the selected
resistance R
S
.
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Since inductors in reality are not pure inductors, the elliptical signatures they form on the Tracker 2800
display usually is distorted. Inductors constructed with a ferrite core makes the inductive
characteristics different from those constructed without. The Tracker 2800 responds with a unique
analog signature for each inductor type.
R
S
F
S
=
20 Hz. F
S
= 2 kHz
100 k
100H – 1000H 50mH – 1000mH
10
1H – 100H 1uH – 10mH
Table 3-2. Tracker 2800 Minimum and Maximum Inductor Values.
REVIEW
Inductors display elliptical signatures similar to capacitors. Since the inductor also exhibits
resistance, due to its construction, the ellipse may be distorted.
As the Tracker 2800 test signal’s frequency is increased, the ellipse signature becomes flatter. This
response is opposite to that of a capacitor.
As the Tracker 2800 internal resistance R
S
increases, an inductor's signature becomes more vertical
(like the capacitor signature).
When an inductor has a ferrite core, its signature distorts from a non-ferrite inductor’s ellipse.
APPLICATIONS
The Tracker 2800 is excellent for troubleshooting inductors. It can reveal shorted or open windings
in large variety of inductive components.
Components that are inductors or have inductive characteristics can be found in many real world
applications. For example, some of these are power transformers, relays, solenoids, flybacks,
speakers, magnetic sensors, stepping motors and motor windings.
The best technique for testing inductors is the comparison of a known good component's signature
to a suspect component. For example, a motor armature has typically numerous windings so every
winding should have a similar analog signature. This fact is true whether it's from an elevator or a
tape deck. The armature of a DC motor can be tested by simply connecting to the motor brush
leads and then adjusting the test range for the most pronounced or descriptive signature. Slowly
turn the armature. Observe the Tracker 2800’s signature display. This test will check continuity,
the inductance, and the condition of each brush contact without disassembling the motor.
A computer switching power supply contains inductors. For example, a computer is reported
“dead." To make a quick diagnosis of the possible problem first make sure the computer is