Mode Of Operation; Converter Design - Siemens SIMOTRAS 6SG7050 Operating Instructions Manual

Description
The converter can also be parameterized on a standard PC with appropriate software connected to
the serial interface on the basic unit. This PC interface is used during start-up, for maintenance
during shutdown and for diagnosis in operation. Furthermore, converter software upgrades can be
loaded via this interface for storage in a Flash memory.
The power section is constructed of isolated thyristor modules. The heatsink is thus electrically
isolated. The housing and terminal covers on power connections provide protection against
accidental contact for operators working in the vicinity. All connecting terminals are accessible from
the front.
The power section cooling system is monitored by means of temperature sensors.
3.3

Mode of operation

3.3.1

Converter design

SIMOTRAS HD is a fully controllable, three-phase thyristor power controller which uses compact
converter technology The converter is used to adjust and control three-phase motors with slipring
rotor for lifting gear drives It is suitable for single and multi-motor drives.
Two additional thyristor modules in the shunt arm of the power section facilitate the torque
switchover and thus the 4Q operation of the drive. Using the auto-reversing stage, the phase
sequence on the converter output is electronically reversed. Depending on the load conditions, the
converter functions in plug braking mode (braking) or it drives the machine in the other direction of
rotation (driving). A driving cycle that is both highly dynamic and gentle is possible because the
conventional stator contactor is no longer required.
The voltage on the motor is adjusted using the stator phase-angle control from three inverse-
parallel thyristor pairs. In this process, the supply frequency of the motor is not changed; it is always
identical to the relevant mains frequency.
The thyristors are controlled by the gating unit. This generates line-synchronous firing pulses. The
control electronics are separated from the line potential by ignition transducers. The operating
states are displayed on the unit via the 7-segment display and LEDs or via the optional OP1S
operator control panel.
All converter settings (e.g. controller parameters, limit values, etc.) are saved in non-volatile
memory in the converter. The adjustment is made digitally via the converter control panel or via the
optional OP1S control panel.
SIMOTRAS HD combines two traditional procedures for adjusting the speed of asynchronous
machines:
changing the motor voltage using the stator phase-angle control
-
gradient of motor characteristic curve using variable rotor resistances
-
This combination permits excellent control response where the advantages of both procedures are
exploited and the disadvantages are largely avoided. Both procedures are described below.
3-2
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The values can therefore be easily reproduced at any time.
SIEMENS AG 6SG7000-0BA76
SIMOTRAS HD Operating Instructions
01.04