Overview Of Functions - Siemens SINAMICS Series Operating Instructions Manual

10.23 Dynamic overload capability of the power unit
10.23.1

Overview of functions

The rated DC current specified on the unit rating plate (= maximum permissible continuous
DC current for p50077 = 1.00) may be exceeded in operation. The extent to which this value
is exceeded and how long this lasts are subject to certain limits, which are explained in more
detail in the section that follows.
The absolute upper limit for overload currents is 1.8x the rated unit DC current × p50077
(= 1.8 × r50072[0] × p50077). The maximum overload duration depends on the overload
current's time characteristic as well as on the unit's load history, and differs from power unit
to power unit.
Each overload must be preceded by an underload (load phase with load current < p50077 ×
rated unit DC current). Once the maximum permissible overload duration has elapsed, the
load current must return to at least ≤ p50077 × rated unit DC current.
The dynamic overload for the power unit is monitored by a software algorithm (I
of the power unit). I
to calculate the time characteristic for the thyristors' temperature rise above the ambient
temperature. When the converter unit is switched on, the calculation process starts with the
initial values that were determined before the electronic power supply was last shut down.
The environmental conditions (ambient temperature, installation altitude) can be taken into
account by setting parameter p50077. In the delivery condition, the ambient temperature is
always set to the maximum possible value without derating (i.e. 45 °C for self-ventilated units
and 40 °C for units with forced ventilation).
I t monitoring responds when the temperature rise calculated in the thyristors becomes too
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high. However, it is also possible to set the following alternative responses using
parameters:
p50075 = 0:
p50075 = 1:
p50075 = 2:
Parameters r52310 and r50014[1] show the calculated thyristor temperature rise as a % of
the maximum permissible thyristor temperature rise. This maximum temperature rise differs
from power unit to power unit, but falls approximately between 80 °C and 90 °C.
SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A
t monitoring uses the time characteristic for the actual load current value
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I t monitoring is disabled. The armature current is limited to p50077 × rated
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unit DC current (= p50077 × r50072[0]).
Alarm A60039 with reduction in armature current setpoint to p50077 × rated
unit DC current
Fault F80139 with unit shutdown
10.23 Dynamic overload capability of the power unit
Descriptions of functions
t monitoring
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