S2 System Settings - GE 469 Instruction Manual

1.4.4

S2 System Settings

1–30
RTD biasing is a back up protection element, which accounts for such things as loss of
cooling or unusually high ambient temperature. This measured temperature is used to
bias or modify the thermal capacity value stored in the relay.
: Set to 40°C, which is the ambient temperature, obtained from the
RTD BIAS MINIMUM
data sheets.
: The center point temperature is set to the motor's hot running
RTD BIAS MID POINT
temperature and is calculated as follows:
Temperature Rise of Stator + Ambient Temperature
The temperature rise of the stator is 80°C (class F rise by resistance) + 10% hot spot
allowance, obtained from the data sheets. Therefore, the RTD Center point
temperature is set to 90°C + 40°C or 130°C.
: This settings is set to the rating of the insulation or slightly less. A
RTD BIAS MAXIMUM
class F insulation is used in this motor which is rated at 155°C, so the setting should be
"155".
You should now be familiar with maneuvering through and editing settings messages. As
such, we will now limit our discussion to just the values that must be programmed to meet
the requirements of the example application. Any settings not explicitly mentioned should
be left at the factory default value.
The S2 settings page contains settings for entering the characteristics of the equipment on
the motor electrical system. In our example, these characteristics are specified under the
Power System Data and Instrument Transformer Data headings in the previous sub-
section. From this information and the resulting calculations, program the page S2 settings
as indicated.
FIGURE 1–9: RTD Bias Example 1
469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 1: GETTING STARTED
806550A1.CDR