3RW3 semiconductor motor control unit
SIRIUS System Manual
8-8
GWA 4NEB 430 0999-02b
Frequency converter
A frequency converter converts the AC voltage from the grid to direct volt-
age, which can then be converted to any voltage and frequency.
The illustration below shows how a frequency converter works:
Figure 8-3: Method of operation of a frequency converter
Disadvantages:
• Relatively complicated wiring needed in order to meet radio interference
suppression requirements; filters are often essential
• Line capacitances limit the lengths of motor feeder cables; it may be nec-
essary to use chokes, sinus filters, or even dV/dt filters.
• Expensive
• System startup is complex and time-consuming on account of the multi-
plicity of operating parameters
• It can be necessary to use shielded motor feeder cables
Advantages:
• Motor speed is variable; speed can be accurately pegged at constant lev-
els.
The U/f ratio remains virtually constant. It is therefore possible to achieve
high torques at relatively low currents.
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