Imeasured
IBase * IPickup
Pickup hysteresis
THETA
100
PICKUP
TRIP
ReclsLevTheta
tReset
t
t
t
ANSI12000015-1-en.vsd
ANSI12000015 V1 EN-US
Figure 319: Operating principles of the rotor overload function
Under current protection of rotor winding
One undercurrent protection level with definite time delay is available within the function. It can be
used to either alarm or trip for low-excitation/loss-of-excitation condition of the machine. This
built-in feature monitors the level of the measured current. As soon as it is lower than the pre-set
value (i.e. parameter
37 PICKUP
) it will start a timer (i.e defined by parameter
37 trip delay
). Once
this timer has expired the signal 37 TRIP will be given. In order to avoid unwanted tripping of this
1MRK 502 066-UUS B Section 8
Current protection
595
Technical manual
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