6 APPLICATION EXAMPLES
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GE Power Management
85
6.1 169 Relay Powered from One of Motor Phase Inputs
If a 169 relay is powered from one of the three motor phase inputs, a single-phase condition could cause control
power to be removed from the relay. In order to ensure that the motor is taken off-line if this condition arises, the 169
output relay (e.g. TRIP, AUX. 1) used to trip the motor must change state when control power is removed from the
169. This is accomplished by making this output relay fail-safe. Factory defaults are:
•
TRIP: Fail-Safe
•
ALARM: Non-fail-safe
•
AUX. 1: Non-fail-safe
•
AUX. 2: Non-fail-safe
These can be changed using the RELAY FAILSAFE CODE in page 5 of SETPOINTS mode.
6.2 Loss of Control Power Due to Short Circuit or Ground Fault
If the input voltage (terminals 41-43) to a 169 relay drops below the low-end specification (90 VAC on 120 VAC
units), the 169 output relays will return to their power down states. If the input voltage drops due to a short circuit or
ground fault on a motor, the 169 relay protecting the motor may or may not be able to trip out the motor. For
example, if a 120 VAC 169 relay is set to trip after 0.5 seconds of an 8.0 XFLC short circuit current, the input voltage
must remain above 90 VAC for at least 0.5 seconds after the short circuit has occurred or else the 169 relay will not
be able to trip. As explained in section 6.1 above, in order to trip the motor when control power for the 169 is lost,
the 169 output relay used to trip the motor must be configured as fail-safe.
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