Rockwell Automation 825 Smart Motor Manager User Manual - Manual (Page 61)

Functions 3-28
Publication 825-UM001B-EN-P January 2001
Table 3.O Earth (Ground) Fault — Holmgreen/Residual Setting Parameters
➊ –5…60 °
C (23…140
°
F)
➋ If auxiliary relays #2 and #3 are assigned to the communication (refer to page 5-16 ) they cannot be selected
here.
Earth (Ground) Fault Protection with a Core Balance Current Transformer
This function can be provided by the Cat. No. 825-MST option card.
In isolated, high impedance-earthed or compensated networks, the necessary high sensitivity
is obtained by using a core balance current transformer, whose core surrounds all three of the
phase leads to the motor.
According to the principle of the residual current protection circuit breaker, sensitive
protection against earth (ground) faults is possible. With a low response threshold, quite a
minor insulation fault can lead to a warning or trip at an early stage.
Figure 3.14 Example of 2-Phase Current Sensing
Example of 2-phase current detection and core balance current transformer for sensitive earth (ground) fault protection (3-phase
current detection is also possible)
Trip ➊
Function
Factory setting On
Response Level
Setting range 10…100%
Factory setting 50%
Setting increments 10%
Tripping Delay
Setting range 0.1…5 s ± 0.4 s
Factory setting 0.5 s
Setting increments 0.1 s
Output Relay ➋
Selection (relays) MR, AL, #1…#5
Factory setting MR
825-MCM
P1
P2
S1
S2
L1 L2
P1
P2
S1
S2
L3
3 ~
1
5
3
2
6
4
825-M
M1
S1
S2
·