AnsaldoSTS F-42, Установка, эксплуатация и обслуживание

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DESCRIPTION
1-2 SM 5924, Rev. 1, June 2009
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Overvoltage Protection
Overvoltage protection is provided by a crowbar circuit comprised of SCR-1 and printed
circuit board CB3.
The input voltage trip point is controlled by diode Dl which triggers the SCR-1 gate with
input voltages between 95V and 105V and will blow fuse Fl. The crowbar circuit is
immediately reset by the opened circuit. Replacement of fuse F1 should restore operation of
the unit.
Similar protection is provided across the pre-regulator output capacitor C3 to protect against
a malfunction of the input circuit. The trip point is controlled by diode D4 between 40.8V
and 45.2V and prevents excessive voltage being applied to the output circuits.
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Transient Voltage
The converter input is designed to withstand a surge voltage of 20,000V for 5 micro seconds
from line to ground, and a 3000V, 60 Hz dielectric test at 1 milliampere maximum for 1
minute as follows:
a. Input terminals shorted to chassis.
b. Output terminals shorted to chassis.
c. Input terminals shorted to output terminals.
A diode is placed across the input circuit to prevent a reverse polarity application and also to
suppress inductive transients that occur on the battery line when the battery is disconnected.