System overview
1.5 System properties
SIRIUS Innovations
System Manual, 01/2011, A8E56203870002-03
31
Example: 3RW soft starters
3RW soft starters are used for soft starting and ramp-down, for pumps and fans, for
example.
G1
G1
0
a
8
/ /
8
/ /
/
/
/
ϕ
α
α
α
α
Figure 1-5 Phase angle control of the thyristor pairs
Technology selection depends on various factors. The table below provides an overview of
the most important aspects:
Table 1- 4 Technology selection
Technology
Electromechanical Electronic
3RT contactors, 3RA
load feeders, or 3RA6
compact starters
3RF solid-state
switching devices
3RW soft starters
Number of starts per
hour
Average High Low
Switching service life Average Long Average
Switching capacity High Low High
Occurrence of current
peaks
High High Low
Occurrence of torque
peaks
High High Low
Reversing operation Yes Yes No
Acoustic noise
generation
Average None Low
Galvanic isolation Yes No No
Shock and vibration
resistance
Average High Average
Power loss Low High Low
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