Other Rtd Setpoints; Overload Curve Setpoints - GE 169 Instruction Manual

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GE Power Management
3 SETUP AND USE

3.17 Other RTD Setpoints

A total of 8 RTD inputs is provided on the model 169 with 10 on the 169 Plus. Any RTD inputs not used for stator
RTD protection can be used for other temperature monitoring functions. These will commonly be used for motor and
load bearings. Separate alarm and trip level temperatures can be selected for each RTD in SETPOINTS mode,
page 2.
Trip and alarm level setpoints should be set to "OFF" for any unused RTD terminals. When no connection is made
to a set of RTD terminals or if a sensor becomes damaged, the ACTUAL VALUES display for that RTD will be
"noRTD". If the "No Sensor Alarm" is enabled (SETPOINTS, page 5) the relay will enter TRIP/ALARM mode to warn
the user of any open RTD connection that does not have its trip and alarm level setpoints stored as "OFF".
RTDs connected to the RTD terminals of the 169 relay must all be of the same type. After an RTD temperature trip
or alarm setpoint is exceeded, the 169 relay will not allow the activated output relays to be reset until the
temperature has fallen 4 C below the exceeded setpoint.
To use RTD #8 (RTD #10 on the 169 Plus) for ambient air temperature sensing a setpoint in page 5 of SETPOINTS
mode must be changed (see sections 3.4, 3.20).

3.18 Overload Curve Setpoints

The running overload curve is chosen in SETPOINTS mode, page 3. The curve will come into effect when the motor
phase current goes over the full load value. When this is true the motor thermal capacity will be decreased
accordingly; the output relay assigned to the OVERLOAD TRIP function will activate when this capacity has been
exhausted. Thermal capacity may be reduced by the presence of unbalance and RTD bias as well as overload (if
the U/B and RTD inputs to TC are enabled). Thus the times on the overload curve may be reduced due to phase
current unbalance (see section 3.20). A choice of eight standard curves, as shown in figure 3-2, is available on both
the model 169 and 169 Plus.
If one of the standard curves shown in figure 3-2 is desired for the given application, the answer to the SETPOINTS
question, "CUSTOM CURVE?", should be "NO". In this case the desired curve can be chosen from the 8 standard
curves available. If it is required to have a different curve the answer to the "CUSTOM CURVE?" question should be
"YES". In this case the following lines in SETPOINTS mode will be the choice of breakpoints as shown in section
3.4. These points should be entered carefully and checked since motor overload protection is based largely on this
curve. After a standard curve has been chosen, the numerical values for the breakpoints can be viewed by storing a
"YES" for the "CUSTOM CURVE?" question and then examining the next few lines of setpoint values. The overload
levels and trip times for the standard overload curves are as shown in Table 3-5.
If none of the standard curves match the motor data well enough the model 169 Plus relay allows the formation of a
custom overload curve. Motors with non-standard overload characteristics can be fully protected since almost any
shape of curve can be entered into the relay. The 169 Plus will accept 22 points and will internally form a curve
through these points.
If it is required to have a discontinuity in a custom overload curve, as shown in figure 3-3 (b), the 169 Plus will insert
it at the appropriate place. A discontinuity will occur when a time is entered that is greater than the time entered for
the previous overload level. Examples of custom curves formed by the 169 Plus relay with the breakpoints given are
shown in figure 3-3.
Note: If a new standard curve number or a custom curve point is stored when the motor is running the new
curve or point will not come into effect until the motor stops.
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