Eaton DS7 Series, Manual

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2 Engineering
2.11 Motor connection
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DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com
2.11.6 Long motor supply cables
DS7 soft starters set no limit on the length of the motor cable.
In practical applications, motor cable lengths up to approx. 100 m can be
connected without any additional measures. Larger cable cross sections may
be necessary above this length. From around 300 m upward, a detailed
engineering (cable cross-section, overdimensioning of the soft starter etc.)
is advisable.
2.11.7 Parallel motor connection
Several motors can be connected in parallel at the output of the DS7 soft
starter. This does not, however, allow the behavior of the individual motors
to be controlled. It must be taken into account that an even run-up of all
motors cannot be ensured. If motors are mechanically interconnected, the
load distribution is also uncertain. In this case, the entire drive torque may
possibly only be supplied by a single motor, which may cause this motor to
be overloaded. In this type of application, soft starters should be used for
each single motor and the motors should be started with a current limiting
function. With a DS7-SWD... soft starter this can only be implemented in
conjunction with the networkable PKE motor-protective circuit-breaker.
Alternatively, a soft starter of the DM4 series or its successor may be
required.
￫
In practical applications, three-phase asynchronous motors with
capacitors (Steinmetz circuit) are only started with a soft starter
on the single-phase AC supply if the load requires a reduced
starting torque (such as with continuous flow machines, pumps
or fans).
￫
The operating direction determines the connection (L1 or N) of
the auxiliary line with the capacitor.
￫
When dimensioning the cable, the voltage drop caused by the
cable length to the motor must be taken into account.
Figure 29: Parallel connection of multiple motors to a soft starter (variant 1)
M1 M2
Q21
L1 L2 L3
T1 T2 T3
F12 F11
M
3 ~
M
3 ~