SAF OPAL SS6 - Manual (Page 31)

OPAL SS6 Reduced Voltage Starters
Page 24
5.4 SHORTED SCR DETECTION
CA395 - SHORTED SCR CARD
This option provides protection against the unlikely event of a shorted Silicon Controlled Rectifier
(SCR). This card only functions when the OPAL is not running and should be used in conjunction
with a shunt trip circuit breaker or an in-line contactor.
In the event of a shorted SCR, it is not sufficient to merely trip the starter. The incoming 3ø power
must be removed. The danger associated with a shorted SCR is that even when the starter is not
running, current may pass freely through the motor.
If a shorted SCR is detected, the Shorted SCR relay is energized. The form C relay contact rated at 1
Amp, 120 VAC on terminals 1, 2 and 3 of J1, is provided for means of opening the circuit breaker
or contactor used. Large contactors require a control relay to handle the high in rush current to the
coil. A red LED, LD1 will illuminate during this condition of a shorted device.
The CA395 will indicate a shorted SCR if the motor is not connected. In reversing applications, two
shorted SCR cards must be used. When using an OPAL with an integral DC Injection option, the
DCI contact from the OP-STOP must be used in conjunction with the shorted SCR contact to
eliminate erroneous trips during DC injection.