Rockwell Automation MV SMC Flex Motor Controller (for Series K or later) - Manual (Page 63)

Rockwell Automation Publication 1560E-UM051F-EN-P - June 2013 53
Installation Chapter 2
• The capacitance in combination with the line and motor impedance could
also be excited by the voltage steps from SCR switching to create resonant
voltage swings which could exceed the device voltage withstanding ratings
or surge arrester rating, or cause distorted voltage signals which may be
misinterpreted by the MV SMC Flex control system.
Motor Overload Protection Thermal motor overload protection is provided as standard (though it must be
programmed) with the MV SMC Flex controller. If the overload trip class is less
than the acceleration time of the motor, nuisance tripping may occur.
Two special applications require consideration: Two-speed Motors, and Multi-
motor Protection.
Two-speed Motors
The MV SMC Flex controller has overload protection available for single speed
motors. When the MV 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
The MV SMC Flex controller provides overload protection for only one motor.
When the MV SMC Flex is controlling more than one motor, the Overload Class
Parameter must be programmed to OFF, and individual overload protection is
required for each motor.
ATTENTION: Overload protection should be properly coordinated with the
motor to avoid damage to equipment.