Pi-2500 Indicator Control Panel Circuitry - ETI PI-2500 Instruction Manual

Electrical Test Instruments PI-2500 & PI-5000
Section II - Detailed Description
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PI-2500 Indicator Control Panel Circuitry

The power for the control panel is provided by the INV/2 circuit, which is the
main input voltage divided by 2. This voltage, ranging from 104 VAC to 240 VAC,
powers a wide range switching power supply, which supplies 12 VDC to the rest
of the circuitry. When the CTL ON switch S1 is pressed, DS1 lights and relay K4 is
energized, and latches on if voltage interlocks are OK and the external control
relay energizes. K4 also provides 12 VDC power to the PC board, which has cir-
cuitry for Vernier position display and adjustment, tap selection and display, and
temperature readings. Pressing S2 turns control power off.
If any external interlock is open, as sensed by K1, indicator DS4 will light. Other-
wise, K2 will energize, which energizes K2 and allow operation of S3. When MAIN
ON switch S3 is pressed, relay K3 energizes, MAIN READY lamp DS3 lights, and
power is provided to external main contactor. If it operates, K3 is latched on
through its auxiliary contact.
If the output of the test set is ON, 12 VDC will be applied to DS5, and also will be
sensed by the PC board, which will inhibit tap change.
The INV/4A and B signals provide a voltage equal to ¼ the input voltage. This is
rectified and filtered by the metering PC board and displayed on the panel me-
ter.
Output is inhibited during tap change or when an interlock condition exists. An
interlock (INTLKB) will be asserted if either temperature readouts exceed an ad-
justed setpoint.
The Vernier position signal is supplied to the PC board and displayed as a 0-
100% reading on a ten segment LED bar graph. The signal is about 1.0 to 4.0
VDC.
The bus temperature is from a 10 K ohm thermistor. System temperature is a
variable voltage from the POD, as discussed elsewhere. Circuitry in the PC board
converts these signals to voltages which are displayed on multicolor bar graphs.
When the signal exceeds that which lights one red bar, the interlock is tripped.
The output voltage of the test set is supplied at jacks J1 and J2.
Indicator Control Panel
Input Voltage Meter: This LED panel meter indicates the approximate input
voltage applied to the test set.
Control Power ON switch: This green switch turns on 120 VAC control power to
the test set, and its green lamp lights when ON.
Control Power OFF switch: This red switch turns off the 120 VAC control power
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