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Description
3.4 Components
The power semiconductors are connected via the gating electronics. The gating command is
transmitted from the power stack adapter (PSA) to the gating electronics via a plastic fiber-
optic cable connection.
3.4.1.2
Submodule capacitors
For the M2C inverter unit, the submodule capacitors represent distributed DC link capacitors;
this means that a central energy storage device (DC link capacitor) is not necessary. The
submodule capacitors smooth and store the energy of the DC link and protect the power
semiconductors against switching overvoltage. They are maintenance free and self-healing.
The drive is switched off when the circuit-breaker is disconnected. The submodule capacitors
are discharged via the gating electronics and discharge resistors.
3.4.2
Door limit switch
Door limit switches monitor the doors. The circuit breaker opens when a door is opened.
3.4.3
Electromechanical door interlocking system
The electromechanical door interlock system is designed to protect personnel, and is an
integral part of the safety concept. During operation all the doors are interlocked (with the
exception of the door for the Control Module).
The electromechanical door interlocking system prevents access to the power unit while
operational. The following conditions must be fulfilled in order to open the doors. You can open
the doors once released by the control.
For more information see section "Open device" in the "Maintenance" chapter.
The device cannot be switched on again until all the doors are closed. The doors remain
interlocked if the auxiliary voltage fails. For more information on this topic, see section "Repair"
in the "Maintenance" chapter.
See also
Opening the device (Page 95)
3.4.4
Precharging
To prevent overcurrents and temporary overvoltages in the DC link when the line voltage is
connected, the DC-link capacitors must be precharged. The DC link is precharged via the
auxiliary supply.
The precharging circuit comprises the following components:
● Precharging transformer
● Diode bridge
34
SINAMICS SM120 6SL38855?B
Operating Instructions 12/2015
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