Installation 2-13
Protective Modules Protective modules containing metal oxide varistors (MOVs) can be
installed on controllers rated 5…1250 A and 200…600V, to protect
the power components from electrical transients. The protective
modules clip voltage transients generated on the lines to prevent such
surges from damaging the SCRs.
Motor Overload
Protection
Thermal motor overload protection is provided as standard with the
SMC-Flex controller. If the overload trip class is less than the
acceleration time of the motor, nuisance tripping may occur.
Two applications require special consideration: two-speed motors,
and multi-motor protection.
Two-speed Motors
The SMC-Flex controller has overload protection available for single
speed motors. When the SMC-Flex 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-Flex controller is controlling more than one motor,
individual overload protection is required for each motor.
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.
Overload protection should be properly coordinated
with the motor.
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