Derating Function For Chassis Units - Siemens Sinamics S120 Function Manual

Basic functions

6.25 Derating function for chassis units

Overview of important parameters (see SINAMICS S120/S150 List Manual)
● p0010 Drive commissioning parameter filter
● r0061 CO: Actual speed value unsmoothed
● p0400[0...n] Encoder type selection
● p0404[0...n] Encoder configuration active
● p0405[0...n] Rectangular signal encoder track A/B
● p0408[0...n] Rotary encoder pulse number
● r0722 CO/BO: CU digital inputs, status
● p0738 BI: CU signal source for terminal DI/DO 8
● p0739 BI: CU signal source for terminal DI/DO 9
● p2530 CI: LR position setpoint
● p2550 BI: LR enable 2
6.25 Derating function for chassis units
An adapted derating function greatly reduces the noise produced by chassis format power
units (Motor Modules and Power Modules) and enables operation at a multiple of the rated
pulse frequency at nearly rated current. This is achieved by monitoring the temperature
difference between heat sink and chip using temperature sensors. When the operating
temperature threshold is exceeded, the pulse frequency or permitted current limit,
respectively, is automatically reduced.
This enables the maximum output current of the power unit to be achieved even at high
pulse frequencies. The derating curve becomes effective at a later point.
The derating function is effective for Motor Modules and Power Modules in the chassis
format. Units that are connected in parallel operate in the same manner as single units. The
dependency of the output current on the pulse frequency for the chassis power units is
described in the S120 Manual, Chassis Power Units.
Operating principle
In order to optimize the use of the power unit also at temperatures below the maximum
permitted ambient temperature, the maximum output current is controlled as a function of the
operating temperature. This function also accounts for the dynamic response of the thermal
performance (rise and decay curves of the operating temperature).
An alarm threshold is calculated that is weighted with the current ambient temperature.
By weighting the alarm threshold with the current ambient temperature, the power unit can
output higher currents close to nominal current even at lower ambient temperatures.
Depending on the setting of parameter p0290 "Power unit overload response", the pulse
frequency or the current will be reduced, or no response will occur if the alarm threshold is
exceeded. An alarm (e.g. A07805 "Infeed: Power unit overload") is generated even if no
response is desired.
314
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
Drive functions