Rockwell Automation Publication 1560F-UM001A-EN-P - June 2019 33
Product Overview Chapter 1
Excessive THD indicates a problem in the power source and/or the application.
This can have an adverse effect on the performance of the overall system. THD
Fault and Alarm parameters are available for both voltage THDV and current
THD I. A Fault and Alarm delay time and a level are also available to configure
each of these parameters.
Table 2 - THD Parameter List
Metering
Metering System
Power and operational monitoring parameters include:
• Current—The RMS current value is provided for each phase, plus the
average current of all three.
• Voltage—The RMS line-to-line and line-to-neutral voltage values are
provided while the motor is running and when stopped. The average of all
three is also provided.
• Line Frequency—The SMC-50 control module measures and provides
user access to the line frequency (Hz).
• Power—Real, reactive, and apparent power values are calculated for each
phase plus the total for all 3 phases. In addition, the current power demand
and the maximum power demand is provided.
• Power Factor—The value of the power factor is provided for each phase
and as a total of all three.
• Peak Starting Current—The SMC-50 control module stores the peak
average RMS motor current consumed for the last 5 start cycles.
• Total Harmonic Distortion (THD)—The SMC-50 control module
calculates and provides user access to the THD for the 3 line voltages and
3 motor currents, along with the average value of each.
• Voltage Unbalance—The calculation of the voltage unbalance signal is
provided.
• Current Imbalance—The calculation of the current imbalance signal is
provided.
• Motor Torque—Electromechanical motor torque is calculated based on
current and voltage feedback from the motor.
Parameter
Number
Parameter Name
(1)
(1) As displayed on the HIM or Connected Components Workbench configuration tools.
Minimum/Maximum Value Default Value Access Units
118 THD V F Lvl 0.0…1000.0 1000.0
R/W
%
119 THD V F Dly 0.1…99.0 0.1 SECS
120 THD V A Lvl 0.0…1000.0 1000.0 %
121 THD V A Dly 0.1…99.0 0.1 SECS
122 THD I F Lvl 0.0…1000.0 1000.0 %
123 THD I F Dly 0.1…99.0 0.1 SECS
124 THD I A Lvl 0.0…1000.0 1000.0 %
125 THD I A Dly 0.1…99.0 0.1 SECS
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