CDD3000-HF Operation Manual
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Line chokes are required: 
• Where the drive controller is used in applications with disturbance 
variables corresponding to environment class 3, as per EN 61000-2-
4 and above (hostile industrial environment).
• To comply with the limit values for variable-speed electric drives 
(standard EN61800-3 / IEC1800-3)
• With a dc-link between multiple drive controllers.
Characteristics of environment class 3 include:
• Mains voltage fluctuations > +
 10% U
N
 
• Short-time interruptions between 10 ms and 60 s
• Voltage asymmetry > 3%   
Environment class 3 typically applies where: 
• a major part of the load is supplied by power converters (dc choppers 
or soft-start equipment)
• welding machines are present
• induction or arc furnaces are present
• large motors are started frequently
• loads fluctuate rapidly.