Siemens SINAMICS G130 Engineering Manual page 180

Fundamental Principles and System Description
Engineering Information
1. Overload reactions without reduction in pulse frequency (p0290 = 0 or 1)
In this case, reduction of the increased pulse frequency is not possible as an overload reaction. The only two possible
reactions are to reduce the output current of the inverter (p0290 = 0) or trip the inverter immediately (p0290 = 1).
These overload reactions must be selected, for instance, if the high output frequency requirements of the drive
application in question exclude the option of a pulse frequency reduction or if the use of a sine-wave filter means that
the pulse frequency may not be changed.
However, overload reactions which do not involve a pulse frequency reduction constitute a substantial intervention in
the proper functioning of the drive system for virtually all types of applications. The system must therefore be
configured appropriately to reliably prevent overload reactions of this type.
This can be achieved by reducing the conducting losses, i.e. by lowering the output current (current derating), in
order to compensate for the higher switching losses caused by the increased pulse frequency.
The current derating factors k
types, must be applied for both continuous operation and load duty cycle operation for this purpose when the system
is configured. If current derating factors k
they can be calculated by linear interpolation between the stated table values.
For steady-state continuous operation the rated output current I
k . For load duty cycles, the base load currents I
Pulse
reduced by the current derating factor k
By using this configuring approach, it is possible to reliably prevent thermal overloading of the power unit as a result
of the increased pulse frequency and to safely exclude the risk of intervention by the overload reaction.
2. Overload reactions with reduction in pulse frequency (p0290 = 2 or 3)
In this case, the initial overload reaction is to reduce the inverter pulse frequency and, if this is not sufficient, to
reduce the output current as well (p0290 = 2). An alternative is to reduce only the pulse frequency (p0290 = 3). It
must be noted that the pulse frequency can only be reduced by a factor of two.
The factory-set overload reaction for drives with vector or V/f control mode (drive objects of vector type) is p0290 = 2.
Note: For drives with servo control mode (drive objects of servo type), automatic pulse frequency switchover as part
of the overload reaction is not possible.
These overload reactions can be utilized meaningfully, for example, if the increased pulse frequency is used solely to
reduce motor noise in applications with low control requirements and an occasional intervention by an overload
reaction is thus easily tolerated by the drive or process.
Overload reactions involving a reduction in pulse frequency do not constitute a significant intervention in normal drive
operation. Nevertheless, the drive should be configured such that the risk of initiation of such reactions is minimized
or ideally eliminated completely.
This can be achieved basically by reducing the conducting losses, i.e. by lowering the output current, in order to
compensate for the higher switching losses caused by the increased pulse frequency. The current derating factors
k given in the sections on specific unit types for both continuous operation and load duty cycle operation must be
Pulse
initially applied for this purpose when the drive is configured.
With overload reactions involving pulse frequency reduction, it is possible to make beneficial use of the fact that the
current derating factors k
Pulse
many applications than those on which the current derating factors k
and their values included in the current derating factors k
·
Line voltage V
Line
Accounted for in k
·
Ambient temperature T
Accounted for in k
·
Minimum operational output frequency f
Accounted for in k
When the influencing parameters have different values (e.g. low line voltage, low ambient temperature or relatively
small speed setting range with high, minimally used output frequency), the current derating factors k
frequencies corresponding to twice the factory setting can be reduced as a function of the influencing parameters,
which means that current derating for pulse frequencies corresponding to twice the factory setting can be partially or
completely avoided.
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Ó Siemens AG
, which are specified for various pulse frequencies in the sections on specific unit
Pulse
are required for pulse frequencies which are not included in the tables,
Pulse
L
.
Pulse
are dependent on several influencing parameters which have more favorable values in
:
: Maximum line voltage
Pulse
:
A
: Maximum ambient temperature of 40 °C
Pulse
Out-min
: Minimum operational output frequency of 10 Hz
Pulse
must be reduced by the current derating factor
rated
and I , as well as the maximum output current I
H
are based on. The influencing parameters
Pulse
are as follows:
Pulse
:
, must be
max
for pulse
Pulse