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

NEMA Resistor Classes and Application Table
Approximate percent of full-load current on first point starting at “Rest”. Class numbers applying to duty cycles
30 sec. on Out of each 15 min. 5 sec. on Out of each 80 sec. 10 sec. on Out of each 80 sec. 15 sec. on Out of each 90 sec. 15 sec. on Out of each 60 sec. 15 sec. on Out of each 45 sec. 15 sec. on Out of each 30 sec. Continuous Duty
25
50
70
100
150
200 or over
101
102
103
104
105
106
111
112
113
114
115
116
131
132
133
134
135
136
141
142
143
144
145
146
151
152
153
154
155
156
161
162
163
164
165
166
171
172
173
174
175
176
91
92
93
94
95
96
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
APPLICATION (NEMA CLASS)
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
Machines

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)
Hoists
– Slope (172
– Vertical (162)
Jigs, Picking Tables (135)
Rotary Car Dumpers (153)
Shaker Screens (135)

Compressors

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)

Hoists

Winch (153)
Mine Slope (172)
Mine Vertical (162)
Contractor’s Hoists (152)

Larry Cars (153)

Lift Bridges (152)

Machine Tools

Bending Rolls (163 or 164)
Boring Mills (135)
Bulldozers (135)
Drills, Gear Cutters (115)
Grinders (135)
Hobbing Machines, Lathes (115)
Milling Machines
Presses, Punches (135)
Saws, Shapers (115)

Metal Mining

Ball, Rod and Tube Mills (135)
Car Dumpers-Rotary (153)
Converters-Copper (154)
Crushers (145)
Conveyors (135)
Tilting Furnace (153)

Paper Mills

Beaters (135)
Calenders (154-92)
Chippers (145)

Pipeworking

Cutting and Threading (135)
Expanding and Flanging (135-95)

Power Plants

Clinker Grinders (135)
Coal Crushers (135)
Conveyors
– Belt, Screw (135)
Pulverized Fuel Feeders (135)
Pulverizers
– Ball Type (135)
– Centrifugal (134)
Stokers (135-93)

Pumps

Centrifugal (134-93)
Plunger (135-95)

Rubber MillsBanbury, Crackers (135)Calenders (155)

Mixing Mills, Washers (135)

Steel Mills

Accumulators (153)
Casting Machines-Pig, (153)
Charging Machines
– Bridge (153 or 163)
– Peel (153 or 163)
– Trolley (153 or 163)
Coiling Machines (135)
Converters-Metal (154)
Conveyors (135-155)
Crushers (145)
Furnace Door, Gas Valves, (155)
Gas Washers
Hot Metal Mixers (163)
Ingot Buggy, Kickoff, (153)
Levelers
Manipulator Fingers (153 or 163)
Pickling Machine, (153)
Pilars-Slab, Racks
Reelers (135)
Saws-Hot or Cold (155)
Screw Downs (153 or 163)
Shears, Shuffle Bars (155)
Side Guards (153 or 163)
Sizing Rolls, Slab Buggy, (155)
Soaking Pit Covers
Straighteners (153)
Tables
– Approach (153)
– Lift (153 or 163)
– Main Roll (153 or 163)
– Roll (153)
– Shear Approach (153 or 163)
– Transfer (153)
Tilting Furnace (153)
Wire Stranding Machine (153)

Woodworking Plants

Boring Machines, Lathe, (115)
Mortiser, Moulder, Planers,
Power Trimmer and Mitre,
Sanders, Saws, Shapers,
Shingle Machine