Thermal Monitoring And Overload Responses - Siemens SINAMICS G150 Operating Instructions Manual

9.4.2

Thermal monitoring and overload responses

Description
The thermal power unit monitor is responsible for identifying critical situations. Possible
reactions can be assigned and used when alarm thresholds are exceeded to enable
continued operation (e.g., with reduced power) and prevent immediate shutdown. The
parameterization options, however, only enable intervention below the shutdown thresholds,
which cannot be changed by the user.
The following thermal monitoring options are available:
● i²t monitoring – A07805 – F30005
i²t monitoring is used to protect components that have a high thermal time constant
compared with semiconductors. Overload with regard to i²t is present when the converter
load (r0036) is greater than 100% (load as a % of rated operation).
● Heat sink temperature – A05000 – F30004
Used to monitor the temperature r0037[0] of the heat sinks on the power semiconductors
(IGBT).
● Chip temperature – A05001 – F30025
Significant temperature differences can occur between the barrier junction of the IGBT
and the heat sink. The calculated barrier junction temperature is displayed in
r0037[13...18]; the monitoring ensures that the specified maximum barrier junction
temperature is not exceeded.
If an overload occurs with respect to any of these three monitoring functions, an alarm is first
output. The alarm threshold p0294 (i²t monitoring) can be parameterized relative to the
shutdown (trip) values.
Example
The temperature difference between two sensors must not exceed 15 Kelvin (K); a
temperature difference of 5 K is set for the temperature monitoring of the heat sink and the
air intake. This means that 15 K or 5 K below the shutdown threshold an alarm is issued
regarding the pending overtemperature. Parameter p0294 merely allows a change in the
alarm threshold 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).
Overload responses
The power unit 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)
T his 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.
Converter cabinet units
Operating Instructions, 07/2016, A5E03347396A
Functions, monitoring, and protective functions
9.4 Monitoring and protective functions
575