Siemens SINAMICS S120 Function Manual page 598

Monitoring functions and protective functions
10.1 Power unit protection
The following thermal monitoring functions are active:
● I
I
compared with semiconductors. An overload with regard to I
load r0036 is greater than 100% (load in % in relation to rated operation).
● Heat-sink temperature - A05000 - F30004
Is used to monitor the temperature r0037[0] of the heat sink on the power semiconductors
(IGBT).
● Chip temperature - A05001 - F30025
Significant temperature differences can occur between the IGBT barrier junction 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 (I
shutdown (trip) values.
Overload responses
In order to reduce thermal stress and thus losses in the power unit, the following methods and
overload reactions are available.
Reducing the pulse frequency
Reducing the pulse frequency is an effective procedure for reducing losses in the power unit.
This is due to the fact that the switching losses make up a very large portion of the total losses.
In many applications, a temporary reduction in pulse frequency is tolerable.
Disadvantage:
Reducing the pulse frequency increases the current ripple. At a small moment of inertia, this
may cause an increase in the torque ripple on the motor shaft and a noise level increase. We
recommend using the overload reaction with pulse frequency reduction for applications in
which the control engineering is not critical (e.g. for pump and fan drives).
Note
This procedure can be used only if the power unit has a cycle with a pulse frequency greater
than the minimal pulse frequency and a reduction of the pulse frequency is permissible.
Reduction of the output current
We recommend this procedure if a pulse frequency reduction is not desired or permissible (e.g.
if the pulse frequency has already been set to the lowest level).
Disadvantage:
This procedure makes sense exclusively for drives that must tolerate a rotational speed
deviation and must not be operated at a constant torque.
596
t monitoring - A07805 - F30005
2
t monitoring is used to protect components that have a high thermal time constant
2
t monitoring) can be parameterized relative to the
2
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
t is present when the converter
2
Drive functions