SENTROL EM3 Application Guide
Soft Start Application

 

  Load  Conditions 

 

 NEMA-Preferred

   Motor Design

 SENTROL EM3

   Inrush Rating

Standard Inrush Loads
-Centrifugal rotary pumps
-Fans with normal inertia
-Motor-Generator sets
-Sanders
-Grinders
-Circular saws
-Pulp grinders
-Shapers and planers
-Lathes
-Milling machines
Normal Starting Torque
for continuous duty.
Load fluctuations are
infrequent. Has some
capacity to handle
minor, occasional
Overloads. Likely to
draw <300% FLA on a 
reduced voltage start.
NEMA Design B:
Low Starting Current,
Normal Torque,
Normal Slip.
18EM3:
rated for 300% FLA
at 20 seconds. 
Power circuit sized
for normal reduced
voltage starting 
current.
High Inrush Loads
-Reciprocating, positive
 displacement pumps
-Air compressors
-Refrigeration compressors
-Conveyors
-Crushers without flywheels
-Dough mixers
-Hammer mills
-Ball mills
-Turntables
-Car pullers
Heavy Starting Torque
continuous or inter-
mittent duty. Has some
overload capacity.May
draw >300% FLA.

    
NEMA Design C:
Low Starting Current
High Breakaway Torque
Normal Slip
18EM3-H:
rated for 600% FLA
for 5 seconds,
500% for 20 seconds.
Power circuit is 
sized for higher 
current levels which
the motor could draw
at start.
Hard to Start Loads
-Hoists,Lifts and Cranes
-Elevators
-Machine tools
-Punch presses
-Crushers with flywheels
-High inertia flywheels
High Starting Torque
intermittent or 
reversing service,
plugging service,
heavy or fluctuating
loads. Likely to
draw >> 300% FLA at
starting.
NEMA Design D:
High starting Current
High Breakaway Torque
High Slip

    
18EM3-H:
rated for 600% FLA
for 5 seconds,
500% for 20 seconds.
Power circuit is 
sized for higher 
current levels which
the motor could draw
at start.

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