Siemens 6MD85, Manual

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[dwtime-dependent-110815-01.vsd, 1, en_US]
Parameter: Imax thermal
•
Recommended setting value
(_:107) Imax thermal
=
2.5 A
for l
rated
= 1 A
The
Imax thermal
parameter allows you to set the threshold current for the
Behav. at I> Imax
therm.
parameter. The selected current threshold of 2.5 I
rated, obj
is a practicable value.
Parameter: Temperature rise at Irated
•
Default setting
(_:109) Temperature rise at Irated
=
70 K
i
i
NOTE
For an application as a 1-phase overload protection, the ambient temperature measured via the tempera-
ture sensor is not taken into account. Therefore, the setting has no influence. You can keep the default
setting. If you take into account the temperature, note the following descriptions.
Set the overtemperature as the value that is the result if the equipment is continuously operated with the
rated current and at an ambient temperature of 40°C. Here, the rated current refers to the protected object.
You can find the temperature value in the Technical data of the equipment or you can measure the value. If
you use a temperature sensor when measuring at the rated current, deduct the actual ambient temperature or
the coolant temperature from the measured value.
When selecting the setting value, you can also use the specified temperature class for orientation. Usually, you
will find the overtemperature expressed in Kelvin (K), which can be accepted as is. If the absolute temperature
is given, the ambient temperature must be deducted. As a rule, this is 40 °C.
The overtemperature at maximum permissible current (
ϑmax
) and the
Temperature rise at Irated
(
ϑrated,obj.
) can be converted by using the following formula:
Protection and Automation Functions
7.27 Thermal Overload Protection, 1-Phase
898 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017