2 Engineering
2.11 Motor connection
DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com 49
2.11.11 Bypass circuit
2.11.12 Bypass circuit for emergency operation
In pump applications there is a frequent requirement for the bypass
contactor to provide facility for emergency operation. A service switch is
used to select between soft starter operation and DOL starter operation via
a bypass contactor (Q22). This is used to fully isolate the soft starter. In this
case, it is important that the output circuit is not opened during operation.
An interlock ensures that a switchover is only possible after a stop.
The electrical and/or mechanical interlocking of contactors Q22 and Q31
ensures a safe operating state.
CAUTION
The output of a soft starter must not be connected to any
capacitive loads (capacitors)!
This would damage the soft starter.
￫
Devices of the DS7-34… series are already equipped with
integrated bypass contacts.
An external bypass is therefore not required.
￫
Unlike simple bypass operation (parallel contact with the
thyristors in continuous operation), the bypass contactor must
be designed here in accordance with utilization category AC-3
since it must be able to start the motor directly. For a suitable
contactor, the contactor recommended in the Appendix
(￫ page 223) can be used.
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