GE MULTILIN 269 MOTOR MANAGEMENT RELAY Series, Инструкция по эксплуатации

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2 INSTALLATION
2-17
Figure 2.10 RTD Wiring
2.11 RTD Sensor Connections
Up to six resistance temperature detectors (RTDs)
may be used for motor stator temperature monitoring.
The remaining RTD inputs may be used for motor
and load bearing, or other temperature monitoring
functions. All RTDs must be of the same type. RTD
#8 may be used to monitor ambient air temperature.
This is done to enhance protection in environments
where the ambient temperature varies considerably.
The number of stator RTDs used together with RTD
trip and alarm temperatures must be programmed
into the 269 (see sections 3.16, 3.17). The RTD type
to be used must be specified when ordering the 269
relay. If the type of RTD in use is to be changed, the
269 must be returned to the factory.
Each RTD has four connections to the 269 relay as
shown in Figure 2.4, Figure 2.6, and Figure 2.7.
Since the RTD indicates temperature by the value of
its resistance, it is necessary to compensate for the
resistance of the connecting wires, which is
dependent on lead length and ambient temperature.
The 269 uses a circuit to cancel this resistance and
reads only the actual RTD resistance. 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 ohm copper RTDs are to be
used, special care should be taken to keep the lead
resistance as low as possible.
If RTD #8 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 temperature use in page 5 of
SETPOINTS mode.
If no RTD sensor is to be connected to any of the
RTD terminals on the 269, the terminals may be left
open.
If fewer 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
to be used they should be connected to the terminals
for RTD1, RTD2, and RTD3 (terminals #1-12). Other
RTDs should be connected to the terminals for RTD7-
RTD10 (terminals #13-28) as shown in Figure 2.4.
The connections are made via terminal blocks which
can accommodate up to #16 AWG multi-strand wire.
Note: 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, 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 269. This arrangement prevents noise pickup
that would otherwise occur from circulating
currents due to differences in ground potentials
on a doubly grounded shield.