Siemens Sinamics S120 Function Manual page 430

Monitoring and protective functions
8.2 Thermal monitoring and overload responses
The following thermal monitoring options are available:
● I
● Heat-sink temperature - A05000 – F30004
● Chip temperature - A05001 - F30025
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.
Example
The temperature difference between two sensors must not exceed more than 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. Using p0294, it is only possible to change the alarm
threshold so that an alarm is received earlier. This means that an intervention can then be
made 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 parameterized
responses via p0290 at the same time that the alarm is issued. Possible responses include:
● Reducing the pulse frequency (p0290 = 2, 3)
● Reducing the output frequency (p0290 = 0, 2)
428
t monitoring - A07805 - F30005
2
I t monitoring is used to protect components that have a high thermal time constant
2
compared with semi-conductors. An overload with regard to I
converter load r0036 is greater than 100% (load in % in relation to rated operation).
Is used to monitor the temperature r0037.0 of the heatsink on the power semiconductors
(IGBT).
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.
This is a highly effective method of reducing losses in the power unit, since switching
losses account for a high proportion of the overall losses. In many applications, a
temporary reduction in pulse frequency is tolerable in order to maintain the process.
Disadvantage:
Reducing the pulse frequency increases the current ripple which, in turn, can increase the
torque ripple on the motor shaft (with low inertia load), thereby increasing the 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 the fan, that is, a quadratic torque characteristic with
falling speed. Reducing the output frequency significantly reduces the converter output
current which, in turn, reduces the losses in the power unit.
t monitoring) can be parameterized relative to the
2
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
t is present when the
2
Drive functions