Siemens SINAMICS G150 Operating Instructions Manual page 500

Functions, Monitoring, and Protective Functions
9.4 Monitoring and protective functions
Overload responses
The power module responds with alarm A07805. The control unit initiates the responses
assigned via p0290 at the same time that the alarm is issued. Possible responses include:
● Reduction in pulse frequency (p0290 = 2, 3)
● Reducing the output frequency (p0290 = 0, 2)
● No reduction (p0290 = 1)
Function diagram
FP 8014
Parameter
• r0036
• r0037
• p0290
• r0293
• p0294
• r2135.13 Fault: thermal overload in power unit
• r2135.15 Alarm: thermal overload in power unit
498
This is a highly effective method of reducing losses in the power unit, since switching
losses account for a high proportion of overall losses. In many applications, a temporary
pulse frequency reduction in favor of maintaining the process can be tolerated.
Disadvantage:
The pulse frequency reduction increases the current ripple, which can cause increased
torque ripple on the motor shaft (when moment of inertia is low) and increased noise
level. Reducing the pulse frequency does not affect the dynamic response of the current
control circuit, since the sampling time for the current control circuit remains constant.
This variant is recommended when you do not need to reduce the pulse frequency or the
pulse frequency has already been set to the lowest level. Further, the load should also
have a characteristic similar to a fan, that is, a square law torque characteristic with
decreasing speed. Reducing the output frequency has the effect of significantly reducing
the converter output current which, in turn, reduces losses in the power unit.
You should choose this option if it is neither possible to reduce the pulse frequency nor
reduce the output current. The converter does not change its operating point once an
alarm threshold has been overshot, which means that the drive can be operated until it
reaches its shutdown values. Once the shutdown threshold is reached, the converter
switches off with an "overtemperature" or "overload" fault. The time until shutdown,
however, is not defined and depends on the degree of overload. Only the alarm threshold
can be changed so that an alarm is received earlier and, if necessary, steps can be taken
to intervene in the drive process (e.g., reduce the load, reduce the ambient temperature).
Thermal monitoring, power unit
CO: Power module overload I2t
CO: Power module temperatures
Power unit overload response
CO: Power unit alarm threshold model temperature
Power module alarm I2t overload
Converter cabinet units
Operating Instructions, 03/2012, A5E03263466A