5.6
SEL-749M Relay Instruction Manual Date Code 20080918
Metering and Monitoring
Motor Start Report
Motor Start Report
The SEL-749M records motor start data for each motor start. The relay stores
the five latest motor start reports in nonvolatile memory. View any of the five
latest motor start reports using the serial port MSR n command, where n = 1–
5. Each report consists of two parts:
➤ a summary
➤ the start data
Summary Data
The summary shows the following information:
➤ Date and time of the motor start
➤ Number of starts since last reset
➤ Motor start time
➤ Start % Thermal Capacity Used (%TCU)
➤ Maximum Start Current
➤ Minimum Start Voltage, if Voltage Inputs card option installed
The relay calculates motor start time from the time the starting current is
detected until the running state is declared (see Figure 4.22). The %TCU
value is the thermal element capacity used at the end of the start, expressed in
percent of the trip value.
Start Data
The motor start data is taken periodically after the starting current is detected.
The relay stores 720 sets of the data with the period determined by the setting
MSRR (motor start report resolution). The following data are stored:
➤ Magnitude of A-, B-, and C-phase currents
➤ Magnitude of neutral current, IN
➤ % Thermal Capacity Used (%TCU)
➤ Magnitude of AB, BC, and CA phase-to-phase voltages, if
included
The relay outputs start data in a comma-delimited text format for easy
integration into computer spreadsheets for motor starting analysis. Figure 5.5
shows data from an example Motor Start Report.
NOTE: The relay reports %TCU
values during starting based upon the
starting model trip value, thus
providing the appropriate %TCU
magnitude scaling.
Courtesy of NationalSwitchgear.com
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