Rockwell Automation 150 MNL/SMC DIALOG+/APP-PROD GUIDE - Manual (Page 128)

5-4 SMC Dialog Plus Controller Special Application Considerations
Motor Overload Protection When coordinated with the proper short circuit protection, overload
protection is intended to protect the motor, motor controller, and
power wiring against overheating caused by excessive overcurrent.
The SMC Dialog Plus controller meets applicable requirements as
motor overload protective device.
The SMC Dialog Plus controller incorporates, as standard, electronic
motor overload protection. This overload protection is accomplished
electronically with an I
2
t algorithm.
The controller’s overload protection is programmable, providing th
user with flexibility. The overload trip class can be selected for class
10, 15, 20, or 30 protection. The trip current can be programmed to
the motor full load current rating.
Thermal memory is included to accurately model motor operating
temperature. Ambient insensitivity is inherent in the electronic
design of the overload.
Note: The current sensing capability of the SMC Dialog Plus
controller is disabled during bypass operation. The Bulletin
825 Converter Module is required for providing current
feedback in these applications
Phase Rebalance As little as 4% supply voltage unbalance can result in a 20% current
unbalance and a 25% increase in motor temperature, possibly
triggering a premature failure of the motor. The SMC Dialog Plus
controller incorporates, as standard, a dynamic phase rebalance
feature. The controller continuously monitors the incoming three-
phase line voltage balance. It compensates for voltage unbalance by
automatically adjusting the output voltage to balance the three-phas
currents drawn by the motor. When phase rebalance is achieved,
motor life may be extended, and production can continue without
interruption.
Note: The performance of the Phase Rebalance feature is dependent
upon motor characteristics and loading. Severe unbalances
cannot be corrected.