Configuration

Characteristic curves

Planning of dynamic overload capability

The planning sheets contain the following information:

• The maximum overload period tan for starting with cold power section and specified constant overload
• The maximum current interval tab (maximum cooling time) until the power section reaches the “cold” state
• Limit characteristic fields for calculating overload capability in thermally settled, intermittent overload operation (periodic load cycles).

Note: The power section is in the “cold” state when the calculated equivalent junction temperature corresponds to less than 5 % of its maximum permissible value. This state can be scanned via a binary selectable output.

Structure of limit characteristic fields for intermittent overload operation

Each characteristic field refers to a load cycle of intermittent overload operation with a total period of 300 s. This type of load cycle consists of two periods, i.e. the base-load duty period (actual armature current ? rated DC current) and the overload duty period (actual armature current ? rated DC current).

Each limit characteristic represents the maximum base-load current specified as a percentage of rated DC current) for a certain overload factor over the minimum base-load duty period (limit base-load duty period) for a specific unit. For the remainder of the load cycle, the maximum permissible current then corresponds to the overload current determined by the overload factor. If no limit characteristic is specified for the desired overload factor, then the characteristic for the next higher overload factor is applicable.

The families of limit characteristics are valid for a load cycle period of 300 s. However, simple rules of calculation can be applied to configure load cycles that are longer or shorter than 300 s. These are illustrated below by two basic planning tasks.

Rating classes

To enable the SIMOREG DC MASTER converters to be adapted to the loading profile of the machine as easily as possible, they can – in addition to individual dimensioning on the basis of the limit curves for dynamic overload capability – also be dimensioned using preset and easily parameterized load cycles.

The adjustment is made on the SIMOREG DC Master using Parameter P067.

Note

The SIMOREG DC Master does not monitor compliance with the rating class set using parameter P067. If the power section permits it, longer overload periods than specified by the rating class can also be used. In this case, however, there is no protection for the driven maschine or the mechanical system against overloading!

The overload duration actually permitted for the specific power section is always larger than the overload duration corresponding to the rating class. Compliance with the overload duration actually permitted for the power section is monitored by the SIMOREG DC Master.