Electrical Test Instruments PI-6000
Section II - Detailed Description
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Page II-7
SECTION II
DETAILED DESCRIPTION
THEORY OF OPERATION
High Current Test Sets
High current test sets generally consist of the following:
1.
One or more coarse taps accomplished by:
(a) A tapped autotransformer providing several equal steps of
voltage or
(b) A multi-section output transformer
2.
A continuously variable rheostat adjustment between coarse taps by
means of:
(a)
A variable autotransformer and boost transformer, or
(b)
A variable autotransformer connected to a section of the
output transformer.
3. An output transformer with one or more isolated low voltage, high
current secondary.
4. Power control circuitry consisting of switches, relays, protective
devices, etc.
5. Current measurement circuitry consisting of sensors, current meter,
and timer.
In general, a primary voltage is selected by means of a combination of coarse
tap and rheostat adjustment. This voltage is stepped down by the output
transformer to provide the desired current into the load impedance.
PI-6000 Main Unit Circuitry
Main power is applied to the PI-6000 by means of standard high current plug
and socket connectors, which are supplied for the customer to connect to the
power source with appropriate flexible leads. A ground terminal with wing nut
and washers is provided for a solid ground connection.
Primary protection is provided by high capacity 200 ampere input fuses (F1 and
F2). After that, the control section is protected by smaller 5 ampere fuses (F3 and
F4), and the power section is isolated by means of high current contactors (K13
and K14).
Transformer T3, protected by fuse F6, steps down the primary voltage by a factor
of ½, and is connected to a wide range switching power supply in the indicator
