Installation 2-13
1560D-UM051D-EN-P – February 2005
Motor Overload Protection Thermal motor overload protection is provided as standard (though it must
be programmed) with the MV Dialog Plus™ controller. If the overload
trip class is less than the acceleration time of the motor, nuisance tripping
may occur.
Overload protection should be properly coordinated with
the motor to avoid damage to equipment.
Three special applications require consideration: Emergency Bypass,
Two-speed Motors, and Multi-motor Protection.
Emergency Bypass
In standard bypass configuration, the MV Dialog Plus controller relies on a
Bulletin 825 converter module to provide current feedback to the Dialog Plus
module in order to maintain thermal memory and power monitoring
capability. It is possible, however, to use traditional electromechanical or
solid-state overload relays for emergency bypass configurations in situations
where the Dialog Plus module does not initiate the start sequence, and the
MV Dialog Plus controller operates as a full-voltage starter.
Two-speed Motors
The MV Dialog Plus controller has overload protection available for single
speed motors. When the MV 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
The MV Dialog Plus controller provides overload protection for only one
motor. When the MV Dialog Plus is controlling more than one motor, the
Overload Class Parameter must be programmed to OFF, and individual
overload protection is required for each motor.
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