Rockwell Automation Publication 1560F-UM001A-EN-P - June 2019 127
Metering Chapter 5
Peak Start Current
The SMC-50 control module logs the peak average RMS current during each
start and stores that information in Parameters 29 through 33. The Peak Start
Current data is stored in a first-in, first-out method so the record of the last five
starts is always maintained.
Table 35 - Metering Parameters Associated with Peak Start Current
Total Starts
The SMC-50 control module maintains a Total Start counter which is
incremented each time the controller is started. As shipped, the counter value is
zero. You cannot reset it.
Table 36 - Metering Parameters Associated with Total Starts
Total Harmonic Distortion (THD)
The SMC-50 control module provides the IEEE calculated THD value for the
three Line Voltages (Line-to-Neutral) and the three Motor Phase Currents
(current through controller Power Pole
(1)
). In addition, the average THD is
calculated for both Line Voltage and Phase Current.
The controller algorithm uses a round-robin approach to gather the six signals by
sampling one signal and then calculating the THD value for that signal. In other
words, each power cycle current and voltage THD are calculated for a phase, then
for the next phase and so on.
Parameter Number Name/Description Min/Max
Value
Default
Value
Access Units
29 Peak Current 1 0…15,000 0 R Amps
30 Peak Current 2
31 Peak Current 3
32 Peak Current 4
33 Peak Current 5
TIP The Total Starts counter is not incremented if the controller faults on a pre-
start fault. It is incremented once SCR gating begins.
Parameter Number Name/Description Min/Max
Value
Default
Value
Access Units
23 Total Starts 0…30,000 0.0 R NA
(1) When in external bypass running mode/configuration, you can use an external CT (825-MCM) and a 150-SM2 Option Module to
read current-based (THD Ix) values.
TIP When the motor is not running, the Current-Based THD values read 0.
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