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2–26
Courtesy of NationalSwitchgear.com
programmed to be failsafe so that in the normal condition, with control power applied,
the relay is energized and the NO/COM terminals shown in FIGURE 2–3: Typical Wiring
Diagram on page 2–20 are closed. Connect these relay contacts to a suitable signaling
input of a DCS system.
SWITCH INPUTS
Each switch common terminal 38/39/40/41/42 is internally connected inside the 239. A
single common wire can be connected between any of these terminals and a remote
switch common terminal to reduce wiring if preferred.
RELAY
ISOLATED
POWER
SUPPLY
ISOLATION
•
SETPOINT ACCESS (38/43): The access terminals 38 and 43 must be shorted together
in order for the faceplate keypad to have the ability to store new setpoints. Typically
the access terminals would be connected to a security keyswitch to allow authorized
access only. Serial port commands to store a new setpoint will operate even if the
access terminals are not shorted. When a jumper wire is connected between the
access terminals all setpoints and configurations can be programmed using the
keypad. Once programming is complete the jumper will normally be removed from
these terminals or the connected keyswitch left open. When this is done all actual and
setpoint values can still be accessed for viewing; however, if an attempt is made to
store a new setpoint value the message illegal access will appear on the display and
the previous setpoint will remain intact. In this way all of the programmed setpoints
will remain secure and tamperproof.
•
EMERGENCY RESTART (39/44): When production or safety considerations become
more important than motor protection requirements, it may be necessary to restart a
tripped motor. If it is desired to override relay trips or lock-outs and restart the motor, a
normally open keyswitch should be installed between the emergency restart terminals
239
TYPICAL
SWITCH
TERMINALS
+29VDC
FILTER
TO LOGIC
OPTO
10mA
PULSED
819780A3.CDR
FIGURE 2–6: Switch Input Circuit
239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
CHAPTER 2: INSTALLATION
COM
EXTERNAL
SWITCH
IN
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