342-86400-431PS
Issue 2.1
March 2013
Page 11
Copyright
GE Multilin Inc. 2001-2013
The low voltage detection circuitry turns the Red LED on (and Green LED off).
The Red LED is powered from the shelf power bus if a second power unit is
installed on the bus. Under normal conditions, the Green LED is on and Red
LED is off. The low voltage detection circuitry also drives the Form-A alarm relay
U7 and sets the contact into alarm state (contact closed) upon failure of U2 or
absence of station battery. The contact is open when the alarm relay is
energized and the unit is operating normally.
The overvoltage protection circuitry is a backup for the primary overvoltage
protection built in the converter module U2 itself and it is set to trigger a few
tenths of a volt higher than the primary feedback system. It would activate only
in the unlikely event of the primary feedback failure thus preventing
uncontrollable rise of the output voltage.
If an overvoltage condition is detected by the secondary feedback circuitry, the
converter module’s PC input (U2(2)) is driven low which forces the converter into
permanent shutdown state. This condition causes the undervoltage detection
circuitry to light the Red LED and turn the Form-A contact into alarm state. The
converter module can then be reset only by power cycling the unit; however, the
unit must remain unplugged from the shelf for at least 2 seconds.
