Rockwell Automation 592- E300 Overload Relay User Manual - Manual (Page 141)

Rockwell Automation Publication 193-UM015B-EN-P - June 2014 141
Protective Trip and Warning Functions Chapter 5
Voltage Imbalance Protection
A voltage imbalance can be caused by poor power quality and unequal
distribution of power. When a voltage 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 Voltage Imbalance Trip and Warning function
to detect for a rapid voltage imbalance fault to minimize damage and loss of
production.
Voltage Imbalance can be defined by the following equation:
%V
Imb
= 100% * (V
d
/V
a
)
where
%V
Imb
= Percent Voltage Imbalance
V
d
= Maximum Deviation from the Average Voltage
V
a
= Average Voltage
Voltage Imbalance Inhibit Time
Voltage Imbalance Inhibit Time (Parameter 365) allows the installer to inhibit a
voltage imbalance trip from occurring during the motor starting sequence. It is
adjustable from 0…250 seconds.
Table 129 - Voltage Imbalance Inhibit Time (Parameter 365)
Voltage Imbalance Trip
The E300 Electronic Overload Relay will trip with a voltage imbalance
indication if:
IMPORTANT The Over Voltage Warning function does not include a time delay feature. Once
the Over Voltage Inhibit Time has expired, the Over Voltage Warning indication
is instantaneous.
Default Value 10
Minimum Value 0
Maximum Value 250
Parameter Type USINT
Size (Bytes) 1
Scaling Factor 1
Units Sec