SINAMICS G150
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
320/528
The diagram below illustrates the power definitions and specifies the permissible 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
mean
First of all, the mean braking power P
mean
needs to be calculated on the basis of the specified load duty cycle.
· For periodic load duty cycles with a duration of T ≤ 90 s, it is necessary to determine the mean braking power
P
mean
over the whole load duty cycle duration T.
· 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
mean
over the time interval during which the maximum mean value occurs. A
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
DB
is calculated from the mean braking power P
mean
according to the following equation
P
DB
≥ 1.125 • P
mean
.
Note:
The factor 1.125 = 1 / 0.888 makes allowance for the fact that the permissible mean power for duty cycles such as
the P
20
or the P
40
cycle equals only 88.8% of the permissible continuous braking power due to the thermal time
constants involved.
2. Checking the required peak braking power P
peak
In addition to the mean braking power P
mean
, the peak braking power P
peak
is also a determining factor in the
selection of a braking unit. It is therefore important to check whether the braking unit with the continuous braking
power P
DB
calculated according to 1. is also capable for the necessary peak braking power P
peak
during the specified
load duty cycle. If it does not have this capability, the continuous braking power P
DB
requirement must be increased
as far as necessary to ensure that the peak braking power requirement is also covered.
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