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CHAPTER 2: INSTALLATION
239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
considerations are more important than protection, program non-failsafe and wire
the contactor to the NC/COM trip relay terminals. When control power to the 239 is
lost, no protection is available and the motor will continue to run. This has the
advantage that the process will not shut down, however the motor may be
damaged if a fault develops under these conditions.
Breaker: Wire the breaker trip coil to the NO/COM trip relay terminals. The breaker
auxiliary 52a contact (closed when the breaker is closed) should be wired in series
with the trip relay to break the current to the trip coil as soon as the breaker opens.
Program the trip relay as non-failsafe. Breaker close coil control is not provided by
the 239 as it is a protection device. Control for closing the breaker must be
provided externally.
•
ALARM RELAY (26/27/28): A selected alarm condition will cause the alarm relay to
activate. Alarms can be disabled for each feature so that only desired conditions
cause an alarm. Alarm conditions that can be programmed to activate the alarm relay
are: ground fault, undercurrent, phase unbalance, overload, RTD 1-3, thermistor,
option switch 1, option switch 2, test and loss of control power (failsafe mode). If an
alarm is required when control power is not present, indicating that protection is not
available, select
FAILSAFE
RELAYS\ALARM RELAY\ALARM OPERATION
open going to a closed state on an alarm. Since the service relay gives a fault
indication for loss of control power, it may be preferable to have no alarm on loss of
control power and use the service relay for this indication to distinguish it from a
process problem. In this case, wire the external alarm to the NO/COM terminals which
will be normally open going to a closed state on an alarm condition. If
mode is selected using setpoint
the alarm relay automatically resets when the alarm condition
ACTIVATION
disappears. For
LATCHED
reset command received) to reset the alarm relay.
•
AUXILIARY RELAY (29/30/31): An additional output relay is provided which can be
configured for:
short circuit/ground trip: Contactors are not rated to open under a short circuit.
Use this output to trip the main feeder breaker in the event of a short circuit at the
motor. See setpoint
S4: PROTECTION\PHASE CURRENT\PHASE S/C\PHASE S/
C TRIP.
undercurrent: Use as a process control output such as in a conveyor where an
undercurrent condition controls flow of product onto the conveyor or in a pump
situation to control a valve. Also can be used as an independent alarm. See
setpoint
S4: PROTECTION\PHASE
CURRENT\UNDERCURRENT\UNDERCURRENT FUNCTION.
serial port command: For remote control via the RS485 communications link, a
command can be issued to directly control this relay. This may be useful for control
applications. See 239 Communications Guide.
For further process control the auxiliary relay can be assigned to option switch 1,
option switch 2, or thermistor function.
•
SERVICE RELAY (32/33/34): If the 239 detects an internal failure during its self
monitoring or if control power is not present, the NO/COM terminals of the service
relay will be open to indicate that service is required. This relay is internally
operation for the alarm relay using
. Contacts NC/COM will be normally
S3: OUTPUT RELAYS\ALARM RELAY\ALARM
mode, the
key must be pressed (or serial port
RESET
S3: OUTPUT
UNLATCHED
2–25
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