Rockwell Automation 150 USE MN/SMC DIALOG + CONTROLLER - Manual (Page 37)

Installation 2-11
Protective Modules Protective modules containing metal oxide varistors (MOVs) and
capacitors can be installed on controllers rated 24A to 360A to protect
the power components from electrical transients and/or high electrical
noise. The protective modules clip voltage transients generated on
the lines to prevent such surges from damaging the SCRs. The
capacitors in the protective modules are used to shunt noise energy
away from the controller electronics. Surge protection is provided as
standard for controllers rated 500–1000A.
Motor Overload
Protection Thermal motor overload protection is provided as standard (though it
must be programmed) with the SMC Dialog Plus controller. If the
overload trip class is less than the acceleration time of the motor,
nuisance tripping may occur.
Three special applications require consideration: bypass, two-speed
motors, and multi-motor protection.
Bypass
In a bypass configuration, the SMC Dialog Plus controller loses
current sensing capability. It is recommended that a Bulletin 825
converter module be used to provide current feedback to the SMC
Dialog Plus controller for these applications to maintain the thermal
memory and to maintain the SMC Dialog Plus controller’s power
monitoring capability. It is possible, however, to use a traditional
electromechanical overload relay for bypass configurations.
Two-speed Motors
The SMC Dialog Plus controller has overload protection available for
single speed motors. When the SMC Dialog Plus controller is applied
to a two-speed motor, the Overload Class parameter must be
programmed to OFF and separate overload relays must be provided
for each speed.
Multi-motor Protection
If the SMC Dialog Plus controller is controlling more than one motor,
individual overload protection is required for each motor.
!
ATTENTION: When installing or inspecting the
protective module, make sure that the controller has
been disconnected from the power source. The
protective module should be inspected periodically for
damage or discoloration. Replace if necessary.
!
ATTENTION: Overload protection should be
properly coordinated with the motor.