Industrial power resistors, dynamic braking, load banks, low resistance grounding, high resistance, grounding, harmonic filters, motor controls, resistor element types
NEMA Resistor Classes and Application Table

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

NEMA Classification of Resistors
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
      APPLICATION
NEMA CLASS
      APPLICATION
NEMA CLASS
Blowers
Centrifugal ............................ 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 Plants
Butter 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 Mills
Banbury, 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

 

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