Operation
7.11 Closed-loop control
SINAMICS DCP
Operating Instructions, 09/2019, A5E34382853K
329
7.11.3 Current correction controller
See function diagram 6806 in the SINAMICS DCP List Manual.
The current correction controller is used to improve the accuracy of the current control, by
feeding in an externally measured current actual value.
A BICO input (p55156) is provided, which allows an externally derived input current actual
value or output current actual value to be used in the calculation internally. The external
current transformer should have a precision greater than +/-0.5 %.
If the external current actual value is used, it is continuously compared with the internal
current actual value. The maximum deviation that can be tolerated can be specified using
p55161. This parameter is scaled to reference current (r50071). If the deviation is greater
than the tolerance, then fault message F60511 is output. Even when the current correction
control is active, the DCP is still protected against overload as a result of the internal current
actual value sensing.
The external current actual value can be fed in via analog inputs of the CUD or via fieldbus.
Note
As a result of the sampling and the dead times of the actual value channels, as well as the
structure of the current correction controller, this is not suitable for respondi
ng to dynamic
7.11.4 Dynamic overload capability
See function diagrams 6808 and 6810 in the SINAMICS DCP List Manual.
The SINAMICS°DCP permits operation with overload profiles.
For the appropriate ambient conditions, the 30 kW and 120 kW devices can be loaded with
120 % of the rated current for an unlimited time.
In addition, the 120 kW device can be operated with up to 160 % of the rated current for a
limited time. The maximum duration of this overload depends on the overload current
characteristic with respect to time, the previous load characteristic and the intake
temperature. The thermal state of the power unit is continually determined based on a
temperature model.
Each overload phase must be followed by a recovery phase with a current below the rated
current. The overload current characteristic is monitored using a load counter (r55091); it is
incremented for operation above the rated current and decremented for operation below the
rated current.
As soon as this counter has exceeded a value of 100 %, fault F60530 (dynamic overload
time overflow (timeout)) is output and the device is shut down. Independent of this, the
device monitors the power semiconductor temperature. If its maximum permissible
temperature is exceeded, then the device limits the maximum reactor current to the rated
current and Alarm A60039 (dynamic overload temperature too high) is output.
Operation in the overload range is only again possible if the power semiconductor
temperature has decreased and is again in the permitted range and the reactor current is
less than the rated current. Alarm A60039 is then also reset.
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