Siemens SINAMICS GL150, Operating Instructions Manual

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Transformers for start-up operation
For short-time operation, the converter as well as the associated step-down and step-up
transformer (if being used) are utilized to a higher degree. In the case of starting converters in
the LCI design version, usually only the DC link reactor is affected. If just one or two motors
have to start up consecutively, the transformers can be significantly overloaded. In this case the
only limits are thermal load capacity of the winding and the iron core. When specifying/ordering
the transformer, mention heavy-duty starting (>> 2 min).
When using a step-up transformer, the following applies: Starting at zero speed, the
transformer can transfer up to 100% converter output current for a specific time. However, in
order to avoid the risk of saturation when starting from standstill, at low speeds, the converter
current is initially reduced to approximately 50% (no heavy-duty starting).
A transformer only becomes saturated when a certain voltage-time area is exceeded. This is
only indirectly linked to the current to be transferred, because the current that is fed in causes
a certain voltage (at least i*r), which also leads to saturation after the relevant time.
Transformer specification
For the transformer, as minimum take into account the following specifics:
● Converter transformer for a B6C bridge
● Percentage of the current harmonics
● Voltage load
● Control angle for feedback (90° or 40° electrical)
● Transformation ratio during idling
● Short-circuit voltage u
K
for the step-up transformer
4.1.3 Requirements for the circuit breaker provided by the customer
To ensure adequate protection for converters, the circuit breaker provided by the customer
must fulfill the following conditions:
● The tripping time of the circuit-breaker must not exceed 80 ms.
● The circuit-breaker must be equipped with an undervoltage release. The undervoltage
release (undervoltage release coil) is controlled via the release circuit, into which the
"undervoltage release" output of the converter must be integrated as well. The auxiliary
voltage from the switchgear (this is a reliable supply) is used as the supply.
Note
In power converters, the undervoltage release is not normally supplied from voltage
transformers that are connected to the main supply network. As a consequence, an
undervoltage condition in the main line supply does not result in shutdown/trip by the
switchgear or the voltage transformer.
● Avoid additional delay times when controlling the circuit breaker. All commands from the
converter to the circuit breaker must act directly without intervention of coupling relays.
Preparations for use
4.1 Notes for system integrators
SINAMICS GL150 6SL38555UN113KA0Z
Operating Instructions Rev.201910281450 EXAMPLE
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