Siemens SINAMICS G130 Engineering Manual page 371

The required continuous braking power of the Braking Module P
according to the following equation
Note:
The factor 1.125 = 1 / 0.888 makes allowance for the fact that the permissible mean power for load duty cycles such
as the P or the P cycle equals only 88.8% of the permissible continuous braking power due to the thermal time
20 40
constants involved.
2. Checking the required peak braking power P
In addition to the mean braking power P
selection of a Braking Module. It is therefore important to check whether the Braking Module with the continuous
braking power P calculated according to 1. is also capable of producing the necessary peak braking power P
DB
during the specified load duty cycle. If it does not have this capability, the continuous braking power P
must be increased as far as necessary to ensure that the peak braking power requirement is also covered.
The flowchart below illustrates the process for doing this.
Flowchart illustrating the process for calculating Braking Module and braking resistor
To reduce the voltage stress on the motor and converter, the response threshold of the braking unit and thus also the
DC link voltage V which is generated during braking can be reduced in operation at low line supply voltages
DC link
within the relevant line supply voltage ranges (380 V to 400 V, 500 V or 660 V). However, this also means a
corresponding decrease in the attainable peak braking power due to P
k = (lower response threshold / upper reponse threshold)
The upper response threshold is set in each case at the factory. The settable response thresholds and corresponding
reduction factors k are shown in the table below. Please take into account in the selection process that Braking
Modules for 500 V to 600 V 3AC or for 660 V to 690 V 3AC (depending on the line supply voltage on site) must be
provided for units with the supply voltage range from 500 V to 690 V 3AC.
Line supply voltage
380 V – 480 V 3AC
500 V – 600 V 3AC
660 V – 690 V 3AC
Response thresholds of Braking Modules and associated reduction factors k
For examples of how to calculate the required Braking Modules and braking resistors, please refer to chapters
"Converter Chassis Units SINAMICS G130" and "Converter Cabinet Units SINAMICS G150"
P ≥ 1.125 • P
DB
peak
, the peak braking power P
mean
Response threshold V
DC link
774 V (k=1) or
967 V (k=1) or
1158 V (k=1) or
is calculated from the mean braking power P
DB
.
mean
peak
~ (V
peak DC link
2
.
with associated reduction factor k
673 V (k=0.756)
841 V (k=0.756)
1070 V (k=0.853)
SINAMICS Engineering Manual – November 2015
SINAMICS S120
Engineering Information
is also a determining factor in the
requirement
DB
2
) / R with the reduction factor
Ó Siemens AG
mean
peak
371/528