Section Ii: Detailed Description; Theory Of Operation; High Current Test Sets - ETI PI-800-GEN2 Instruction Manual

Electrical Test Instruments PI-800 and PI-1600

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 GEN2 Main Unit Circuitry
Main power is applied to the PI-800 GEN2 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 Correct
this relay energizes. The Input Select Error indicator DS2 lights if it senses an
SECTION II
DETAILED DESCRIPTION