Siemens 7SR51 - Settings Menu

θ = Thermal state at time t
I = Measured thermal current
I
θ
= 49 Overload setting (or k.I
B
)
The final steady state thermal condition can be predicted for any steady state value of input current where t
>τ,
[fo_7SR5_thermalSteadyState, 1, en_US]
θ
F
= Final thermal state before disconnection of device
The thermal state may be reset from the fascia, a user logic reset or externally via a binary input.
Parameter: Overload Setting
•
Default setting: 1.05 x I
n
(1.05 ⋅ I
rated
)
The pickup level, equivalent to the factor k.I
B
as defined in the IEC 60255-8 thermal operating characteris-
tics. It is the value of current above which 100 % of thermal capacity will be reached after a period of
time and it is therefore normally set slightly above the full load current of the protected plant.
Parameter: Char
•
Default setting: IEC
The operate characteristic can be based on the IEC thermal curve or a user thermal curve can be used.
Parameter: Time Constant
•
Default setting: 10 min
This setting is chosen to match the thermal characteristic of the protected plant.
Parameter: Capacity Alarm Setting
•
Default setting: 50 %
An alarm can be given if the thermal state of the system exceeds a specified percentage of the protected
equipment’s thermal capacity.
Settings Menu
Configuration > Function Config
Parameter Setting Options Settings
Default Gn1 Gn2 Gn3 Gn4
49 Thermal Overload Disabled
Enabled
Disabled
Functions > Protection > 49 > Gn 49-n
Parameter Setting Options Settings
Default Gn1 Gn2 Gn3 Gn4
Element Disabled
Enabled
Disabled
Overload Setting 0.1 to 3 ⋅ I
rated
, Δ 0.01 I
rated
1.05 ⋅
I
rated
5.10.5
Protection and Automation Functions
5.10 49 Thermal Overload Protection
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 203
C53000-G7040-C014-1, Edition 11.2019