Voltech AT360, User Manual

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T
ESTS AND
T
EST
C
ONDITIONS
P
AGE
7-50 V
OLTECH
AT
I
U
SER
M
ANUAL
7.1.12 C – I
NTERWINDING
C
APACITANCE
T
EST
(P
ARALLEL
C
IRCUIT
)
Measurement
Range
Test
Voltage
Test
Frequency
Basic
Accuracy
100fF to 1mF 1mV to 5V 20Hz to 3MHz 0.1%
SEE ALSO THE CS AND CP TESTS AND THE CAPACITOR TESTING
SECTION OF THIS CHAPTER.
Capacitance occurs in transformers due to the physical proximity of, and
electrostatic coupling between, different turns of wire.
In general, the capacitance is distributed between different layers within
a winding, and between the outside layer of one winding and the inside
layer of the next. Although the capacitance is distributed across
windings, it is usually represented by a simple equivalent circuit showing
a single capacitance from one winding to the next.
Where Used
An interwinding capacitance test can be used to check for correct winding
position and to check for the correct insulation thickness between windings
where isolation between primary and secondary windings is important.
The test can be used to check for capacitance between windings where, for
example, too large a capacitance may couple unwanted noise signals between
power and control circuits.