Principle Of Operation; Fuseless Technology - Siemens SINAMICS GL150 Operating And Installation Instructions

3.3.3

Principle of operation

3.3.3.1

Fuseless technology

The converter is of fuseless design. In the event of a fault, limiting of the overcurrent at the
input terminals should be ensured by an appropriate transformer design. In addition, the
converter requires matched circuit breakers with a tripping time of 80 ms. The closed-loop
control system triggers the circuit breakers. Each circuit breaker must be equipped with a fail-
safe OFF contact and an undervoltage coil.
Internal current transformers sense the current and evaluate it electronically. The open-loop
and closed-loop control systems prevent an impermissible rise in any overcurrent by switching
the line-side converter to inverter operation.
NOTICE
Fault due to incorrect configuration of line supply and transformer impedances
On the line side, the converter is designed for short-circuit-proof operation. Short-circuit-proof
operation is only guaranteed if the line supply and transformer impedances are in
conformance with the respective specifications in the system-specific data.
If the supply and transformer impedances cannot be maintained, material damage to the
converter can occur.
Observe the system-specific values in the "Technical data and drawings" chapter.
Work during braking operation, the motor-side converter (MSR) as rectifiers and the line-side
converters as inverters. In the event of a fault during braking, the two motor-side converters
immediately switched over to inverter operation. The current in the DC link is suppressed as
a result. After that, the circuit breaker is opened.
The leakage reactances of the line transformer or the machine and the supply line from the
feeding supply system limit overcurrent in the event of internal short-circuits. In this case, the
circuit breaker responds sufficiently quickly to prevent consequential damage.
If there are control errors on the machine side, serious damage to the converter may occur.
The short-circuit current is limited by the machine reactances. On designs with output
transformers, the short-circuit current is limited by the machine reactance and the transformer
reactance (uk). Subsequent faults can be limited by independent disconnecting elements
between the converter and the motor. This is not included in the scope of supply.
The thermal utilization of the semiconductors is selected so that, after a short-circuit current,
the thyristors still have sufficient blocking ability in accordance with the figure shown below,
"Short-circuiting sequence".
The converter can cope with virtually any incident using the fuseless technology and will switch
itself off.
SINAMICS GL150 6SL38503UM114PA0Z
Operating Instructions 04/2017
Description
3.3 Power unit
35