Powerohm Products

NEMA Standards for Motor Control Resistors

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 LoadCurrent on First Point Starting@Rest 25

CLASS NUMBERS APPLYING TO DUTY CYCLES

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.

30 sec. on out of each 15 min.

Continuous Duty

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

50 70

100 150

200 or over

The following table contains standard NEMA Classification Numbers for a variety of applications. Although these classification numbers have been found to be correct for an average installation, there will be exceptions. NEMA RESISTOR APPLICATION STANDARDS

APPLICATION NEMA CLASS

APPLICATION NEMA CLASS

APPLICATION NEMA CLASS

FoodPlants ButterChurns,DoughMixer..................135 Hoists Winch................................................153 MineSlope............................................172 MineVertical.........................................162 Contractor'sHoists...............................152 LarryCars.................................................153 LiftBridges................................................152 MachineTools BendingRolls.............................163or164 BoringMills...........................................135 Bulldozers..........................................135 Drills,GearCutters...............................115 Grinders............................................135 HobbingMachines,Lathes...................115 MillingMachines Presses,Punches................................135 Saws,Shapers.....................................115 MetalMining Ball,RodandTubeMills........................135 CarDumpers-Rotary............................153 Converters-Copper..............................154 Conveyors..........................................135 Crushers............................................145 TiltingFurnace......................................153 PaperMills Beaters..............................................135 Calenders.....................................154 - 92 Chippers............................................145 Pipeworking CuttingandThreading..........................135 ExpandingandFlanging.................135-95 Power Plants ClinkerGrinders...................................135 CoalCrushers......................................135 Conveyors Belt,Screw.......................................135 PulverizedFuelFeeders.......................135 Pulverizers BallType...........................................135 Centrifugal.....................................134 Stokers...........................................135-93 Pumps Centrifugal......................................134-93 Plunger...........................................135-95

RubberMills Banbury,Crackers................................135 Calenders...........................................155 MixingMills,Washers...........................135 Steel Mills Accummulators..................................153 CastingMachines-Pig,..........................153 ChargingMachines Bridge.....................................153or163 Peel........................................153or163 Trolley.....................................153or163 CoilingMachines...................................135 Converters-Metal..................................154 Conveyors.....................................135-155 Crushers............................................145 FurnaceDoor,GasValves,...................155 Gas Washers HotMetalMixers....................................163 IngotBuggy,Kickoff,.............................153 Levelers ManipulatorFingers....................153or163 PicklingMachine,..................................153 Pilars-Slab, Racks Reelers...............................................135 Saws-HotorCold...................................155 ScrewDowns..............................153or163 Shears,ShuffleBars.............................155 SideGuards................................153or163 SizingRolls,SlabBuggy,.......................155 SoakingPit Covers Straighteners......................................153 Tables Approach.......................................153 Lift..........................................153or163 MainRoll.................................153or163 Roll.................................................153 ShearApproach.....................153or163 Transfer.........................................153 TiltingFurnace......................................153 WireStrandingMachine........................153 WoodworkingPlants BoringMachines,Lathe,........................115

Blowers Centrifugal......................................133-93 ConstantPressure.........................135-95 Brick Plants Augers,Conveyors,............................. .135 Dry Pans, Pug Mills By-product CokePlants DoorMachine,LevelerRam...................153 Pusher Bar, ValveReversing Machines CementMills Conveyors..........................................135 Crushers............................................145 Elevators............................................135 RotaryDryers...................................145-95 GrindersandPulverizers.......................135 Kilns.................................................135-95 Coal and Ore Bridges Bridge.................................................153 Closing,Holding....................................162 Trolley.........................................162or163 CoalMines CarHauls..............................................162 Conveyors...................................135or155 Cutters...............................................135 Crushers............................................145 Fans..............................................134or95 Hoists Slope..............................................172 Vertical...........................................162 Jigs,PickingTables..............................135 RotaryCarDumpers..............................153 ShakerScreens.....................................135 Compressors ConstantSpeed....................................135 VaryingSpeed Centrifugal.......................................93 PlungerType.......................................95 ConcreteMixers........................................135 Cranes-General Purpose Hoist...........................................153 - 163 Bridge or Trolley with SleeveBearings.........................153-163 RollerBearings..........................152-162 FlourMills LineShafting........................................135

Mortiser,Moulder, Planers, Power Trimmer andMitre, Sanders, Saws, Shapers, ShingleMachine

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