REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-189
E. Setting instructions
Settings:
Reference current IB-Setting
Enabling current I-Start
Multiplier k1-Setting
Minimum operating time t-min
Time inverse characteristic effective tg
Maximum delay t-max
Resetting time t-Reset
The rotor overload function protects the rotor winding of genera-
tors against excessive temperature rise as a result of overcur-
rents. The function is applicable to turbo-alternators designed
according to the American standard ASA-C50.13 or a similar
standard defining overload capability. It is connected to c.t’s in
the AC excitation supply. It may nor be used for brushless exci-
tation systems.
Providing compensation using the reference value of the A/D
channel has not been made, the reference current IB for the
protection is calculated from the AC load current I
B1
of the exci-
tation supply which is usually the same as the full load excitation
current and the c.t. rated currents I
N1
and I
N2
as follows:
IB I
I
I
B
N2
N
=
1
1
The setting is the ratio IB/I
N
, I
N
being the rated current of the
protection.
The multiplier k1 is 33.8 s for units designed according to ASA.
For units with a similar overload capacity:
k
mn
n
1
=
-
t
JJ
J
DD
D
[s; s; K]
where:
t : thermal time constant of the rotor
DJ
m
: maximum permissible temperature rise of the rotor
winding
DJ
n
: rated temperature rise of the rotor winding.
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