Rockwell Automation 825-P Modular Protection System for Motors User Manual - Manual (Page 91)

Rockwell Automation Publication 825-UM004D-EN-P - November 2012 91
Configuring Protection & Logic Functions Chapter 6
Select LOAD_I to scale the analog output based on motor current if the output
is not of interest during overload conditions. Select either AVG_I or MAX_I
to scale the analog output based on motor current and if the output is required
during overload conditions.
Both LOAD_I and AVG_I use an average magnitude of three phase currents to
drive the analog output; MAX_I uses a maximum magnitude of the three phase
currents.
If the relay includes the voltage input option and you select PWR_kW parameter,
the analog output is scaled using real power. The following defines per unit
FLVA:
1 per unit FLVA := 1.732 • (VNOM) • (FLAn)
where:
VNOM = Nominal voltage setting
FLAn = Full Load Current setting
(n = 1, for Speed-1 or 2 for Speed-2)
If the relay includes the voltage input option and you select PF parameter, the
analog output is scaled using power factor. For power factors 0.8 lag, unity, and
0.8 lead, the analog outputs are 4 mA, 12 mA, and 20 mA, respectively.
Trip Inhibit (Block)
With a Block Protection control input, one or more protective functions listed
in Table 37 can be inhibited when the contact closes.
During certain operational phases, when the level (e.g., motor current) differs
from the normal values, such as in the following situations.
• During starting: earth fault and short-circuit protection
Table 37 - Trip Inhibit Settings
Setting Prompt Setting Range Factory Default
CURRENT IMBALANC Y, N N
JAM Y, N N
GROUND FAULT Y, N N
SHORT CIRCUIT Y, N N
UNDERCURRENT Y, N N
START INHIBIT Y, N N
PTC Y, N N
RTD Y, N N
NOTE: In addition to selecting the functions to be inhibited, you must assign Block Protection to an
input. See Table 44 for a description and Figure 16
for a typical connection diagram.