Siemens SINAMICS S120 - Page 321

SINAMICS G150
Engineering Information
SINAMICS Engineering Manual – November 2015
Ó Siemens AG
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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
DC link
which is generated during braking can be reduced in operation at low line supply voltages
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
peak
~ (V
DC link
)
2
/ R with the reduction factor
k = (lower response threshold / upper reponse threshold)
2
.
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.
Line supply voltage
Response threshold V
DC link
with corresponding reduction factor k
380 V – 480 V 3AC 774 V (k=1) or 673 V (k=0.756)
500 V – 600 V 3AC 967 V (k=1) or 841 V (k=0.756)
660 V – 690 V 3AC 1158 V (k=1) or 1070 V (k=0.853)
Response thresholds of Braking Modules and corresponding reduction factors k
Example calculation:
The purpose of this calculation is to determine for a SINAMICS G150 converter cabinet unit with an output power
rating of 132 kW at 400 V whether the available braking unit with a continuous power rating of P
DB
= 25 kW or
P
20
= 100 kW is suitable for the application described below. The diagram shows the braking power characteristics
over time.
Braking power