MCD 200 Design Guide
MG.17.C3.02 – VLT is a registered Danfoss trademark 23
Soft Start Application Guide
• Starter Current Rating: Maximum FLC rating
of the motor to be connected to the soft
starter given the operating parameters
specified by the remaining items in the AC53a
code.
• Start Current: The maximum start current that
will be drawn during start.
• Start Time: The time taken for the motor to
accelerate.
• On-load Duty Cycle: The percentage of each
operating cycle that the soft starter will run.
• Starts Per Hour: The number of operating
cycles per hour.
2. AC53b: for soft starters used with bypass
contactors.
For example, the following AC53b code describes
a soft starter which, when bypassed, is capable of
supplying 145 A run current and a start current of
4.5 x FLC for 30 seconds with a minimum of 570
seconds between the end of one start and the
commencement of the next.
In summary, a soft starter has many current ratings.
These current ratings are dependent on the start
current and operational performance required by the
application.
To compare the current rating of different soft starters
it is important to ensure that operating parameters are
identical.
■
Model Selection
NB!:
To fully understand the model selection
procedures it is important to have a good
knowledge of the fundamental principles of soft starter
ratings. See Understanding Soft Starter Ratings.
To select the correct MCD 200 model :
1. Determine whether the application requires a
normal duty or a heavy duty rating. The table
below can be used as a guide.
2. See the tables in Ratings and select an MCD
200 model with an FLC rating greater than
that of the motor.
Application Duty
General & Water
Agitator Normal
Centrifugal Pump
Normal
Compressor (Screw, unloaded)
Normal
Compressor (Reciprocating, unloaded)
Normal
Conveyor
Normal
Fan (damped)
Normal
Fan (undamped)
Heavy
Mixer
Heavy
Positive Displacement Pump
Normal
Submersible Pump
Normal
Metals & Mining
Belt Conveyor Heavy
Dust Collector
Normal
Grinder
Normal
Hammer Mill Heavy
Rock Crusher
Normal
Roller Conveyor
Normal
Roller Mill Heavy
Tumbler Normal
Wire Draw Machine Heavy
Food Processing
Bottle Washer
Normal
Centrifuge
Normal
Dryer
Heavy
Mill
Heavy
Palletiser
Heavy
Separator
Heavy
Slicer Normal
Pulp and Paper
Dryer
Heavy
Re-pulper
Heavy
Shredder
Heavy
Petrochemical
Ball Mill Heavy
Centrifuge Normal
Extruder Heavy
Screw Conveyor Normal
Transport & Machine Tool
Ball Mill Heavy
Grinder
Normal
Material Conveyor
Normal
Palletiser Heavy
Press Normal
Roller Mill Heavy
Rotary Table Normal
Lumber & Wood products
Bandsaw Heavy
Chipper Heavy
Circular Saw Normal
Debarker
Normal
Edger
Normal
Hydraulic Power Pack
Normal
Planer
Normal
Sander
Normal
NB!:
The above start current requirements are
typical and appropriate in most circumstances.
However, start torque requirements and performance
of motors and machines do vary. Please contact
Danfoss if the application requires duties other than
listed in this manual.
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