Section Ii: Detailed Description; Theory Of Operation; High Current Test Sets - ETI PI-800 Instruction Manual

Electrical Test Instruments PI-800 and PI-1600
Section I - General Information and Specifications
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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-800 Main Unit Circuitry
Main power is applied to the PI-800 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 60 ampere input fuses F1 and
F2. After that, the control section is protected by smaller 2 ampere fuses F3 and
F4, and the power section is isolated by means of a high current contactor K1.
The input is connected, through voltage selector switch S1, to a wide range
switching power supply to provide 12 VDC to the control circuitry and fans. Input
voltage is sensed by voltage relay K8, and when the primary voltage is greater
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Copyright(C) 1994-2003
SECTION II
DETAILED DESCRIPTION
Electrical Test Instruments, LLC. All Rights Reserved