The following table is for selecting the NEMA Class for an application in relation to starting torque and duty cycle.


When an armature shunt resistor is added, the class number shall include the suffix “-AS”. Example: Class 155-AS is a resistor which includes an armature shunt and which will allow an initial inrush of 150 percent with the armature shunt open. When a dynamic braking resistor is added, the class number shall include the suffix “-DB”.

NEMA Resistor Application Standards

BlowersCentrifugal (133-93)Constant Pressure (135-95)

Brick Plants

Augers, Conveyors, (135)

Dry Plans, Pug Mills

By-product Coke Plants

Door Machine, Leveler Ram (153)
Pusher Bar, Valve Reversing

Cement Mills

Conveyors (135)
Crushers (145)
Elevators (135)
Rotary Dryers (145-95)
Grinders and Pulverizers (135)
Kilns (135-95)

Coal and Ore Bridges

Bridge (153)
Closing, Holding (162)
Trolley (162 or 163)

Coal Mines

Car Hauls (162)
Conveyors (135 or 155)
Cutters (135)
Crushers (145)
Fans (134 or 95)
– Slope (172
– Vertical (162)
Jigs, Picking Tables (135)
Rotary Car Dumpers (153)
Shaker Screens (135)


Constant Speed (135)
Varying Speed
– Centrifugal (93)
– Plunger Type (95)

Concrete Mixers (135)

Cranes-General Purpose

Hoist (153-163)
Bridge or Trolley with
– Sleeve Bearings (153-163)
– Roller Bearings (152-162)

Flour Mills

Line Shafting (135)

Food PlantsButter Churns, Dough Mixer (135)
Rubber MillsBanbury, Crackers (135)Calenders (155)