VOLTECH AT3600 USER MANUAL GENERAL NOTES
4. GENERAL NOTES
The following general notes should be considered when constructing or modifying
fixtures.
4.1. BEWARE OF HIGH VOLTAGES
The AT3600 can apply AC voltages up to 5000 Vrms during the course of a test.
This must be kept in mind when constructing test fixtures.
If possible, always design the fixture with the nodes that experience the same high
voltages grouped together.
An example of this is the common situation of performing hi-pot tests between
the primary windings as a group, and the secondary windings as a group.
The best layout for the test pins in this case (assuming this is not prohibited for
other reasons) is to have all the primary windings connected to test nodes on one
side of the fixture board (say the left-hand side using nodes 1, 3, 5, 7, etc.), and to
have all the secondary windings connected to test nodes on the opposite side (for
example, nodes 2, 4 and 6).
If, in addition, you need to test the isolation between two secondary windings,
use the low-numbered nodes (say 2, 4 and 6) for one winding and a well
separated group of high-numbered nodes (say 14, 16 and 18) for the other.
For PCB mounting transformers, clearly the spacing between the pins is determined
by the transformer itself. If necessary, place pieces of high-voltage insulation
between each Kelvin blade and its nearest neighbors, to prevent any high voltage
flashover.
When separate terminals are used for transformers with flying leads, you should
ensure that there is a generous separation between individual terminals to allow for
the high voltages in your program. Consider both the exposed (high-voltage) metal
parts of the terminal itself, and the free ends of the transformer lead, which may be
carelessly inserted and may bend round to touch an adjacent terminal. Ensure that
there is a separation of at least 3mm per kV between any sharp points in an air gap,
assuming that the air is dry. Increase the separation still further for conditions of high
humidity.
All leads between the terminals, or crocodile clips, and the contact pins on the
AT3600 fixture plate should be covered with insulation capable of withstanding the
test voltages you are using in your programs. They should be kept as short as
possible, and the leads from one power-sense pair should not touch any bare metal
associated with another power-sense pair.
FIXTURES VPN 98 - 024 V07 PAGE 5.4.1.
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