Table of Contents
Advertisement
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
ALARM I monitors a series of current sensors. This device will sense a current in excess of
normal in the transistorized bridge and will turn the entire unit off. These sensors will react only
to an imminent failure of the transistors and not to an overload on the unit. A panel-mounted
three-position switch allows an operator to test if the alarm circuits are functioning. The RESET
position will bring the circuits back to normal.
ALARM II monitors output voltage for an over or under-voltage condition, for output current at
three levels of load (125%, 150%, and 200%) , and for the loss of an input phase. The
undervoltage (UV) light will latch only if the undervoltage condition exists longer than 7 seconds
to allow for voltage transients when applying heavy loads. All thresholds are factory-set and
additional adjustment is not necessary. The potentiometer for these thresholds are in the alarm
cards and are not easily accessible. All of the lights on ALARM I and II cards are red and have a
latching circuit which allows for an investigation even after the cause of a fault has disappeared.
ALARM III has 3 green indicators signaling the presence of the internal voltages ( +6V and +12V )
and the integrity of the DC FUSE. When the +12V green light is on, the control circuits on all
cards are powered. The +6V light indicates the proper functioning of POWER SUPPLY I . There
is also a red (IMB/GND) light which indicates a current flow through ground that will shut the
machine down.
(2) Control Cards
Amplifier (AMP) and comparator (COMP) cards generate the driving pulses for the power
transistors. The AMP card contains an oscillator, error amplifier, and voltage ramp-up circuit.
Chapter 1-1
Page 6
Card Cage (Front View)
Figure 5
Nov 01/90
Advertisement
Table of Contents
