Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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Page II-10
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 volt-
age or
(b) A multi-section output transformer
2.
A continuously variable Vernier 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 out-
put transformer.
3. An output transformer with one or more isolated low voltage, high
current secondary.
4. Power control circuitry consisting of switches, relays, protective de-
vices, 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 Vernier adjustment. This voltage is stepped down by the output trans-
former to provide the desired current into the load impedance.
PI-2500 Main Unit Circuitry
Main power is applied to the PI-2500 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 connector is also pro-
vided for a solid ground connection.
Primary protection is provided by high capacity 100 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 (K1
and K2).
Transformer T6, 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
