BisonConvey
ENGINEERING TOOLS

CONVEYOR MOTOR POWER CALCULATOR

Size the drive motor for a belt conveyor

Estimate the effective tension Te, mechanical power at the pulley, shaft power after drive losses, and the next standard IEC motor size for a troughed belt conveyor. Inputs follow the CEMA simplified formula; the standard-motor pick assumes a single squirrel-cage induction motor.

Units

Conveyor

Material & belt

Drive

Result
Effective tension Te
8.92
kN
2005.5 lbf
Mechanical power
17.84
kW
23.9 hp
Shaft (motor) power
20.99
kW
28.1 hp
Recommended motor
22.00
kW
29.5 hp
Formulas
  • α = arcsin(H / L)
  • Wm = Q × 1000 / 3600 / v (material mass per length, kg/m)
  • Te = f · L · g · (2·Wb + Wm · cos α) + Wm · g · H
  • P_mech = Te · v
  • P_motor = P_mech / η
  • Round up to next standard IEC size (4 – 315 kW)

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How motor power is computed

Effective tension Te is the net force the drive applies at the head pulley to keep the belt moving — friction over the idlers plus the gravitational lift of the material. Mechanical power at the pulley equals Te times belt speed.

Shaft (motor) power adds the drive-train losses: gearbox, coupling, sometimes a fluid coupling for soft-start. Divide mechanical power by efficiency η to get the shaft power the motor must continuously deliver.

The recommended motor is the next standard IEC frame size above the computed shaft power. Always add a service factor for startup torque, accelerating a loaded belt, and material build-up — typically 15–25 % above this value for routine industrial service.

Drive efficiency by drive type

Steady-state efficiency at full load. Values drop at partial load and for very small drives.

Drive typeη
Direct drive (no gearbox)0.97
Helical gearbox, single stage0.96
Helical gearbox, two-stage0.95
Bevel-helical gearbox0.94
V-belt drive0.93
Worm gear (single start)0.75 – 0.85
Fluid coupling + gearbox0.92

Common pitfalls

  • Sizing the motor to exactly P_motor. Add 15–25 % for startup torque, accelerating loaded belts, and dust / material build-up.
  • Forgetting that decline conveyors have negative Te. The drive becomes a brake — use a holdback or regenerative VFD, not a plain motor.
  • Ignoring the gearbox service factor. Long, heavily loaded belts need AGMA service factor 1.5–2.0 — verify gearbox catalogue rating against actual shaft torque.
  • Using one f value for all conveyors. Short, end-loss-dominated conveyors need a 1.05–1.10 multiplier on Te.
  • Picking a motor near the next standard size below the result. Always step up — the cost difference is small but the headroom prevents nuisance trips.

When you need a full drive design

This calculator gives a first-pass motor size. Real installations need a coordinated drive package: motor frame, gearbox ratio, soft-start or VFD, holdback (for inclines), and brake (for declines). For overland conveyors, multi-drive trains, or any installation requiring a full DIN 22101 / ISO 5048 drive selection, talk to a BisonConvey engineer.

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