Siemens SINAMICS G130 Engineering Manual page 297

The diagram below illustrates the power definitions and specifies the load duty cycles for the Braking Modules and
matching braking resistors. The information is valid for the factory-set response thresholds.
Power definitions and load duty cycles for Braking Modules and braking resistors
How to determine which Braking Modules and braking resistors are required
The process for calculating the continuous power rating of the braking unit required for a particular application is
explained below.
1. Calculating the mean braking power P
First of all, the mean braking power P
· For periodic load duty cycles with a duration of T ≤ 90 s, it is necessary to determine the mean braking power
P over the whole load duty cycle duration T.
mean
· For periodic load duty cycles with a duration of T > 90 s or for sporadic braking operations, it is necessary to
determine the mean braking power P
period of 90 s must be applied as the time base for calculating the mean value.
The required continuous braking power of the braking unit P
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 unit. It is therefore important to check whether the braking unit with the continuous braking
power P calculated according to 1. is also capable for the necessary peak braking power P
DB
load duty cycle. If it does not have this capability, the continuous braking power requirement P
as far as necessary to ensure that the peak braking power requirement is also covered.
mean
needs to be calculated on the basis of the specified load duty cycle.
mean
over the time interval during which the maximum mean value occurs. A
mean
DB
P ≥ 1.125 • P
DB mean
peak
, the peak braking power P
mean
SINAMICS Engineering Manual – November 2015
Engineering Information
is calculated from the mean braking power according
.
is also a determining factor in the
peak
Ó Siemens AG
SINAMICS G130
during the specified
peak
must be increased
DB
297/528