Allen-Bradley SMC-50, User Manual

Page: 32 / 292

32 Rockwell Automation Publication 1560F-UM001A-EN-P - June 2019
Chapter 1 Product Overview
Excessive Starts/Hour
The SMC-50 module allows the user to program the desired number of starts per
hour (up to 99). This helps eliminate motor stress caused by repeated starting
over a short time period.
Overtemperature
The power module temperature is monitored during starting and stopping
maneuvers by thermistors. The thermistor is connected to the gate driver board
where it is processed, and the status is transmitted by fiber-optic cable through
the interface board to the control module. When an overtemperature condition
exists (>85 °C), the control module trips and indicates a “PTC Power Pole” fault.
An overtemperature condition could indicate high ambient temperature,
overloading or excessive cycling. After the power module temperature is reduced
to allowable levels, the fault can be cleared (see Troubleshooting on page 157 for
instructions).
Overcurrent Protection
This feature provides protection to the controller from high level of current
during starting and stopping. The trip level is hard-coded to be 9 times of the
controller's rated current and this protection cannot be disabled. Also, SMC
provides user-adjustable overcurrent trip level through Parameter 351 (800% to
1000% of motor FLC). This user-adjustable overcurrent trip can be enabled or
disabled through Par 230 overcurrent bit.
Total Harmonic Distortion (THD) Fault and Alarm
Power Quality THDV (Fault Code 55) and Power Quality THDI (Fault Code 56)—Fault and
Alarm
The SMC-50 control module lets you read power line THD which is the average
of 32 line frequency harmonics. The calculation for THDI and THDV (THD
x
)
is:
TIP
Refer to Appendix B on page 241 for duty cycles of the controller highlighting
recommended starts per hour.
THD
x
=

(THD
2
2 +
THD
2
3
…THD
2
31
)
THD
1