1–30 469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUALCHAPTER 1: GETTING STARTEDRTD biasing is a back up protection element, which accounts for such things as loss ofcooling or unusually high ambient temperature. This measured temperature is used tobias or modify the thermal capacity value stored in the relay.RTD BIAS MINIMUM: Set to 40°C, which is the ambient temperature, obtained from thedata sheets.RTD BIAS MID POINT: The center point temperature is set to the motor's hot runningtemperature and is calculated as follows:Temperature Rise of Stator + Ambient TemperatureThe temperature rise of the stator is 80°C (class F rise by resistance) + 10% hot spotallowance, obtained from the data sheets. Therefore, the RTD Center pointtemperature is set to 90°C + 40°C or 130°C.RTD BIAS MAXIMUM: This settings is set to the rating of the insulation or slightly less. Aclass F insulation is used in this motor which is rated at 155°C, so the setting should be“155”.FIGURE 1–9: RTD Bias Example 1You should now be familiar with maneuvering through and editing settings messages. Assuch, we will now limit our discussion to just the values that must be programmed to meetthe requirements of the example application. Any settings not explicitly mentioned shouldbe left at the factory default value.1.4.4 S2 System SettingsThe S2 settings page contains settings for entering the characteristics of the equipment onthe motor electrical system. In our example, these characteristics are specified under thePower System Data and Instrument Transformer Data headings in the previous sub-section. From this information and the resulting calculations, program the page S2 settingsas indicated.806550A1.CDR
