Rockwell Automation 1560E SMC Flex Smart Motor Controller - Manual (Page 24)

1-14 Product Overview 
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Ground Fault Trip (cont.)
Parameter 74, Gnd Flt Delay, allows the installer to define the time period
a ground fault condition must be present before a trip occurs. It is
adjustable from 0.1 to 25 seconds.
Parameter 73, Gnd Flt Level, allows the installer to define the ground
fault current at which the MV SMC-Flex will trip. It is adjustable from
1.0 to 5.0 A.
Important: The ground fault inhibit timer starts after the maximum phase
of load current transitions from 0 A to 30% of the device’s minimum FLA
Setting or the GF Current is greater than or equal to 0.5 A. The MV
SMC-Flex does not begin monitoring for a ground fault condition until the
Gnd Flt Inh Time expires.
Ground Fault Alarm
The MV SMC-Flex will indicate a Ground Fault Alarm if:
• No warning currently exists
• Ground fault alarm is enabled
• GF Inhibit Time has expired
• GF Current is equal to or greater than the Gnd Flt A Lvl
Parameter 77, Gnd Flt A Lvl, allows the installer to define the ground fault
current at which an alarm will be indicated. It is adjustable from 1.0 to 5.0 A.
Parameter 78, Gnd Flt A Dly, allows the installer to define the time period
a ground fault alarm condition must be present before a trip occurs. It is
adjustable from 0.1 to 25 seconds.
Thermistor/PTC Protection
The MV SMC-Flex provides terminals 23 and 24 for the connection of
positive temperature coefficient (PTC) thermistor sensors. PTC sensors are
commonly embedded in motor stator windings to monitor the motor
winding temperature. When the motor winding temperature reaches the
PTC sensor’s temperature rating, the PTC sensor’s resistance transitions
from a low to high value. Since PTC sensors react to actual temperature,
enhanced motor protection can be provided to address such conditions as
obstructed cooling and high ambient temperatures.
The following table defines the MV SMC-Flex PTC thermistor input and
response ratings:
Protection and Diagnostics
(cont.)