Rockwell Automation Allen-Bradley E300, User Manual

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156 Rockwell Automation Publication 193-UM015D-EN-P - February 2015
Chapter 6 Protective Trip and Warning Functions
When the Underload Warning conditions are satisfied, the:
• TRIP/WARN LED flashes a yellow 6-short blink pattern
• Bit 5 in Current Warning Status (Parameter 10) sets to 1
• Bit 1 in Device Status 0 (Parameter 20) sets to 1
• Any relay outputs configured as a Warning Alarm close
Underload Warning Level
Underload Warning Level (Parameter 258) allows you to define the current at
which the E300 Electronic Overload Relay indicates a warning. It is user-
adjustable from 10…100% for the FLA Setting (Parameter 171).
Table 192 - Underload Warning Level (Parameter 258)
Current Imbalance Protection
A current imbalance can be caused by an imbalance in the voltage supply, unequal
motor winding impedance, or long and varying wire lengths. When a current
imbalance exists, the motor can experience an additional temperature rise,
resulting in degradation of the motor insulation and reduction of life expectancy.
The E300 Electronic Overload Relay can monitor for this condition with its
Current Imbalance Trip and Warning function to detect for a rapid current
imbalance fault to minimize damage and loss of production.
Current Imbalance can be defined by the following equation:
%CI = 100% * (I
d
/I
a
)

where
%CI = Percent Current Imbalance

I
d
= Maximum Deviation from the Average Current

I
a
= Average Current
Default Value 70
Minimum Value 10
Maximum Value 100
Parameter Type USINT
Size (Bytes) 1
Scaling Factor 1
Units %FLA
IMPORTANT
The Underload Warning function does not include a time delay feature. Once
the Underload Inhibit Time has expired, the Underload Warning indication is
instantaneous.