EOT Crane Motor Power Calculator

Calculate KW for Hoist, Cross Travel (CT), and Long Travel (LT) motions using inertia and friction physics.

Ton
m/min
kg

Typically 2-5% of SWL.

0-1

Typ: 0.85 (Hoist), 0.90 (Travel).

Required Motor Power

0.00 kW
≈ 0.00 HP
Total Force (F): 0 N
Rec. Standard Motor: --
Calculated based on Hoisting gravity + efficiency losses.

Calculation Methodology

Hoist Formula

The hoist motor must overcome gravity for the load plus the hook block assembly.

P = (F × v) / (1000 × η)
  • F (Force): (SWL + Hook Weight) × 9.81 m/s²
  • v (Velocity): Speed in m/s
  • η (Efficiency): Gearbox efficiency (typ. 0.85)

Travel Formula (CT & LT)

Travel motors must overcome rolling friction AND inertia (acceleration force). Inertia is often larger than friction.

P = (F_total × v) / (1000 × η)
1. Friction Force (F_fric) μ × Total Mass × 9.81

Overcomes wheel bearing & flange friction.

2. Inertia Force (F_acc) Total Mass × (v / t)

Force required to accelerate mass from 0 to speed v in time t.

Duty Cycle (CDF) & Efficiency

Efficiency (η)

Energy loss occurs in gears, bearings, and ropes. Lower efficiency requires higher motor power.

  • Helical/Spur Gears: 0.85 - 0.90
  • Worm Gears: 0.60 - 0.70 (Inefficient)
Duty Cycle (%CDF)

Motors aren't rated to run continuous 24/7. Select based on starts/hr.

  • S3-40%: Standard workshop use.
  • S4-60%: Heavy production/Steel plants.

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Engineering notes

From mechanical kW to an actual crane motor

Purpose: estimate mechanical input power for hoisting, cross travel or long travel and identify a preliminary standard motor size for quotation comparison.

Inputs explained

Motion type
Hoist uses gravity load; CT moves trolley plus load; LT moves bridge, trolley and load.
SWL, dead weights and speed
Define moving mass and required linear velocity.
Acceleration time
Controls travel inertia force; shorter time increases required power.
Friction coefficient
Approximates rolling, bearing and flange resistance for travel motions.
Efficiency
Represents drivetrain losses between motor and load.

Formula basis

Hoist: P = [(SWL + hook mass) x 9.81 x speed] / (60 x 1000 x efficiency)

Travel: friction force = moving mass x 9.81 x friction coefficient

acceleration force = moving mass x [(speed / 60) / acceleration time]

P = (friction force + acceleration force) x (speed / 60) / (1000 x efficiency)

The tool rounds calculated kW upward to the next value in its internal standard-size list.

Worked example

Hoisting 10 t plus a 300 kg hook block at 5 m/min with 85% efficiency gives a load force of about 101.0 kN and calculated power of about 9.91 kW. The tool suggests the next listed size, 11 kW. That does not yet prove starting torque, thermal duty, starts per hour, speed-control range or braking suitability.

Assumptions

  • Steady hoist speed and constant efficiency.
  • Travel path is level unless resistance is captured indirectly.
  • No wind, skew, wheel-flange binding or cable-drag allowance.
  • Acceleration is linear over the entered time.

Results interpretation

  • Calculated kW is a mechanical power estimate.
  • Recommended kW is only the next size in the tool's list.
  • Compare vendor torque-speed curves and duty ratings.
  • Large vendor differences should be explained by assumptions.

Limitations

  • No motor thermal model or RMS duty calculation.
  • No starting, pull-out, regenerative or VFD torque check.
  • No altitude, ambient, enclosure or hazardous-area derating.
  • No gearbox, brake or electrical protection selection.

Related standards to check

Confirm the editions and national adoptions named in the project specification.

  • IEC 60034-1:2026 - rotating-machine rating and performance.
  • IEC 60204-32:2023 - electrical equipment of hoisting machines.
  • Applicable crane classification and mechanism standard for duty, load spectrum and motion requirements.

FAQ

Is the next standard kW automatically correct?

No. The motor still needs torque, duty, thermal, control and environmental verification.

Why is travel power sometimes low?

At steady travel the tool sees only rolling resistance and acceleration. Real skew, wind, flange contact and cable drag may dominate.

Does a VFD remove the duty check?

No. Low-speed cooling, torque range, starts, braking energy and insulation compatibility still need review.

Next action: request the motor data sheet

Ask for rated kW, torque-speed curve, duty designation, starts per hour, insulation, enclosure, brake/VFD compatibility, ambient derating and service factor.

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