Emergency Restart Terminals - GE 269Plus Instruction Manual

EMERGENCY RESTART TERMINALS

Each RTD has four connections to the 269Plus relay as shown in Figures 2–7: RELAY WIRING DIAGRAM (AC
CONTROL POWER), 2–9: RELAY WIRING DIAGRAM (TWO PHASE CTs), and 2–10: RELAY WIRING DIA-
GRAM (DC CONTROL POWER). Since the RTD indicates temperature by the value of its resistance, it is nec-
essary to compensate for the resistance of the connecting wires, which is dependent on lead length and
ambient temperature. The 269Plus uses a circuit to cancel this resistance and reads only the actual RTD resis-
tance. Correct operation will occur providing all three wires are of the same length and the resistance of each
lead is not greater than 25% of the RTD 0°C resistance. This can be accomplished by using identical lengths of
the same type of wire. If 10 Ω copper RTDs are to be used, special care should be taken to keep the lead resis-
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tance as low as possible.
If RTD #10 is to be used for ambient air temperature measurement, the RTD should be placed and mounted
somewhere in the motor cooling air intake flow. The sensor should be in direct contact with the cooling air but
not with any surface that is at a temperature other than the cooling air. This RTD is selected for ambient tem-
perature use in page 5 of SETPOINTS mode.
If no RTD sensor is to be connected to any RTD terminals on the 269Plus, the terminals may be left open.
If less than 6 stator RTDs are to be employed, they should be connected to the lowest numbered relay RTD
connections. For example, if 3 stator RTDs are used they should be connected to the terminals for RTD1,
RTD2, and RTD3 (Terminals 1 to 12). Other RTDs should be connected to the terminals for RTD7 to RTD10
(Terminals 13 to 28) as shown in Figure 2–7: RELAY WIRING DIAGRAM (AC CONTROL POWER) on page 2–
8.
The connections are made via terminal blocks which can accommodate up to #16 AWG multi-strand wire.
Shielded, three-wire cable must be used in industrial environments to prevent noise pickup.
Wherever possible, the RTD leads should be kept close to grounded metal casings and avoid
areas of high electromagnetic or radio frequency fields. RTD leads should not run adjacent to,
NOTE
or in the same conduit as high current carrying wires. It is recommended to use a three-wire
shielded cable of #18 AWG copper conductors. The shield connection of the RTD should not
be grounded at the sensor end as there is an internal ground on the 269Plus. This arrange-
ment prevents noise pickup that would otherwise occur from circulating currents due to dif-
ferences in ground potentials on a doubly grounded shield.
If it is desired to override relay trips or lock-outs and restart the motor, a normally open keyswitch should be
installed between terminals 54 and 55. Momentarily shorting these terminals together will cause the thermal
memory of the 269Plus to discharge to 0% (if RTD input to thermal memory is enabled, thermal memory can
be reduced to 0% by keeping terminals 54 and 55 shorted together for more than 11 seconds; see Section
3.22: THERMAL MEMORY on page 3–59). The Emergency Restart terminals can thus be used to override an
OVERLOAD TRIP or a START INHIBIT lock-out. Shorting the Emergency Restart terminals together decre-
ments the relay's internal starts/hour counter by 1 allowing the operator to override a STARTS/HOUR inhibit or
time between starts inhibit.
This option should be used only when an immediate restart after a lock-out trip is required for
process integrity or personnel safety. Discharging the thermal memory of the 269Plus gives
the relay an unrealistic value for the thermal capacity remaining in the motor and it is possible
NOTE
to thermally damage the motor by restarting it. Thus, complete protection may be compro-
mised in order to restart the motor using this feature.
A twisted pair of wires should be used. Connection to the 269Plus is made via a terminal block which can
accommodate up to #16 AWG multi-strand wire.
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Courtesy of NationalSwitchgear.com
269Plus Motor Management Relay
2 INSTALLATION
2.12 EMERGENCY RESTART TERMINALS
GE Power Management