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OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
The AMPcard allows for adjustments to the output voltage as well as to the load compensation.
The VOLTAGE potentiometer allows an operator to adjust the output voltage in excess of +/-
15%. By setting the output voltage at a low of 100-V or a high of 132-V, the undervoltage (UV)
and overvoltage (OV) alarms should be triggered. In this way, the presence of the protective
thresholds is tested. A clockwise rotation will increase the output voltage.
Another adjustment on the AMP card is the LOAD COMPENSATION. At full load this
adjustment will increase the output voltage by up to 5%, to compensate for the voltage drop on
the cable connecting the load. A clockwise rotation on the potentiometer will bring the
compensation at full load from 0% to 5%.
Also on the AMP card front panel, a two-position toggle switch allows maintenance personnel to
operate the unit for test purposes without connecting the output cable to an aircraft. When this
switch is in the NORMAL position, the interlock circuit is activated and the unit will run only if the
output cable is connected to an aircraft, which is supplying 28VDC to the E/F interlock circuit in
the output cable. In the MAINT position, the unit will turn on and stay on even if the output cable
is not connected to an aircraft. A red light next to the switch will indicate that the aircraft is
disconnected and that the MAINT position on the toggle switch should be used in order to turn
the unit on. The CURRENT adjustment potentiometer determines the point at which the unit
goes into current limiting.
(3) Power Supply Cards
The function of POWER SUPPLY I and POWER SUPPLY II is to generate the voltages
necessary to drive the power transistors. POWER SUPPLY NO. I is a high frequency DC to DC
converter which provides regulated +6V and -6V from an input of 70V. This output is used to
drive all of the transistors with the emitter connected to the -600V bus. To drive the rest of the
transistors, POWER SUPPLY II provides sets of floating +/- 6V sources.
(4) Driver Cards
The driver cards receive width modulated pulse signals from the comparator card, and amplify
these signals from logic power level to switch power modules on and off. Driver cards provide
necessary electrical isolation between control and power electronics.
b. Description of Front Panel Controls (See Figure 6)
The functions of each of the controls and indicators are as follows:
(1) START Button
After the unit input power is turned on and any of the alarms is reset, by pressing the START
button (4) , the unit will turn on. (See start-up procedure) .
(2) STOP/RESET Button
The unit can be turned off by momentarily pressing the STOP/RESET button (5). This button
permits the reset of alarms without opening the front door to access the card cage. This button is
especially useful when the phase loss (0 LOSS) alarm will latch due to a temporary failure in
input power.
(3) INPUT Indicator Light (Green)
This indicator light (3) will turn on upon application of input power.
(4) OUTPUT Indicator Light (Green)
This indicator light, (9) by turning on, indicates the presence of power at the output terminals.
(5) FAULT Indicator Light (Red)
This indicator light (10) turns on whenever there is either an over-current, overvoltage,
undervoltage, ground, phase-loss fault, or inverter section fault. When this light comes on, it is
necessary to look into the front window of the converter unit and look at the ALARM cards I, II,
and III in the card cage to determine possible fault interrupted output power delivery. The
specific fault will be indicated by a fault light on ALARM card I, II, or III.
Nov 01/90
Chapter 1-1
Page 7
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