Cascade Circuit; Motors With Power Factor Correction Capacitor - Eaton DS7 Manual

2 Engineering
2.11 Motor connection

2.11.9 Cascade circuit

2.11.10 Motors with power factor correction capacitor

48
DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com
The DS7 soft starters can be used to start several motors in sequence.
This requires the observance of a specific switching sequence (￫ section 7,
"Connection examples").
￫
When starting several motors with one soft starter the thermal
load of the soft starter (starting frequency, current load) must be
taken into account.
If the starts occur closely in succession, the soft starter must be
dimensioned larger (i.e. the soft starter must be designed with
an accordingly higher load cycle).
If capacitors are to be used for power factor correction and thus to improve
the power factor, they must be connected to the mains side of the soft
starter.
The following Figure 31 shows on the right a safe arrangement.
During the startup and stop phase (generalized phase control), the power
factor correction capacitors are disconnected. After the start time (t-Start)
elapses, they are connected via the TOR signal of the soft starter and the
capacitor contactor Q12, which disconnect them at the beginning of the stop
time (t-Stop).
L1
L2
L3
Q1
Q11
L1 L2 L3
Q21
T1 T2 T3
M
M1
3
Figure 31: Reactive current compensated motor
Left: impermissible connection;
Right: permissible connection
￫
In networks with electronically controlled consumers (e.g. soft
starters), the compensation devices must always be connected
with a series inductance.
L1
L2
L3
Q1
Q11 Q12
L1 L2 L3
Q21
TOR
T1 T2 T3
M
M1
3