Crane Motor Power Calculator: Hoist, Travel & Luffing
Key Takeaways
Selecting the right motor power is the first step in crane design—undersize it and the motor burns out; oversize it and you waste money. This quick-reference chart is based on the formulas in the ISO 4301 Crane Design Standard, covering the hoisting, travel, and luffing mechanisms. It provides calculated power, recommended motor models, and alternatives across 16 capacity steps from 5t to 100t, with a cross-reference of the YZR/YZE/YZP motor series.
Three Core Formulas for Accurate Motor Power Selection
Crane motor power calculation follows the fundamental principle of P = Force × Speed / Efficiency, but the source of force differs significantly across the three mechanisms:
| mechanism | core formula | force source | typical efficiencyη |
|---|---|---|---|
| Hoisting mechanism | P = (Q×g×v) / (1000×η) | gravity —— most direct, Qis Rated Lifting Capacity(kg) | 0.88~0.92 |
| travel mechanism | P = (F_static×v) / (1000×η) | static resistance —— including friction resistance+gradient resistance+wind resistance | 0.82~0.88 |
| Luffing mechanism | P = (M×ω) / (1000×η) | Torque —— Load×radius, also including jib Dead Weight | 0.85~0.90 |
Hoisting Mechanism — Full Tonnage Range 5t–100t
The hoisting mechanism is the heart of any overhead crane, and motor power directly determines lifting speed and hoisting efficiency. This table is based on a two-speed design: slow speed for precise positioning, fast speed for normal lifting. Take a 20t double-girder bridge crane as an example: slow speed at 0.7 m/min requires only 18.5 kW, while fast speed at 2.0 m/min requires 22 kW. The YZR wound rotor motor (slip ring motor) with resistance speed control is the most economical solution for achieving two-speed operation.
| Lifting Capacity | speed(slow/fast)m/min | calculationk W | recommendedk W | recommended Model |
|---|---|---|---|---|
| 5t | 0.8 / 5.0 | 7.5 | 7.5 | YZR160M2-6 |
| 20t | 0.7 / 4.0 | 18.5 | 18.5~22 | YZR200L-6 |
| 32t | 0.5 / 3.0 | 22 | 22~30 | YZR225M-6 |
| 50t | 0.4 / 2.5 | 30 | 30~37 | YZR250M2-6 |
| 75t | 0.3 / 2.0 | 37 | 37~45 | YZR280S-6 |
| 100t | 0.25 / 1.5 | 45 | 45~55 | YZR280M-6 |
The full PDF includes all 16 capacity ratings plus the complete YZR series model recommendations. η = 0.90, JC = 40%.
Travel Mechanism — Quick Reference for Bridge & Trolley
The travel mechanism motor must overcome static friction, rolling resistance, and additional drag (including wind load and incline). The Long Travel (bridge) is configured with 4 wheels and 2 driven wheels, while the Cross Travel (trolley) motor power is approximately 50%–60% of the bridge motor. Variable Frequency Drive (YZP series) enables smooth start/stop and prevents load sway.
| Lifting Capacity | Spanm | recommendedk W×quantity | recommended Model×2 |
|---|---|---|---|
| 5t | 10.5 | 1.1×2 | YZE100L2-4 |
| 20t | 19.5 | 3.0×2 | YZE132S-4 |
| 50t | 25.5 | 5.5×2 | YZE160M-4 |
| 100t | 31.5 | 11×2 | YZE180M-4 |
| Motor Series | Best For | Key Features |
|---|---|---|
| YD Series | Constant-speed applications with simple control needs | Cost-effective, reliable, easy to maintain |
| YZR Series | Demanding cyclic duty with frequent starts, stops, and reversals | High starting torque, excellent heat dissipation, rugged construction |
| YZP Series | Variable-speed applications requiring precise control | Wide speed range, smooth acceleration, energy-efficient operation |
How to Choose the Right Motor Series
Selecting the appropriate motor series depends on your specific operating conditions and performance requirements. Here's a quick guide to help you decide:
- YD Series – Ideal for applications where the motor runs at a constant speed and control complexity is minimal. This series offers a balance of affordability and dependable performance.
- YZR Series – Designed for heavy-duty cyclic operations involving frequent starting, stopping, and reversing. These motors deliver high starting torque and robust thermal performance, making them suitable for demanding industrial environments.
- YZP Series – The go-to choice for variable-speed applications that demand precise speed regulation. With a broad speed range and smooth acceleration, these motors enhance process control and energy efficiency.
For applications that combine frequent starts with variable-speed requirements, the YZP series offers the most flexibility, while the YZR series remains the preferred option for constant-speed, high-torque duties. If your operation is straightforward and cost-sensitive, the YD series provides a practical solution.
| series | Powerrange | features | applicable mechanism | cost |
|---|---|---|---|---|
| YZRwound rotor | 0.75~200kW | starting Torquehigh(2.5~3times), external Resistancestepless speed regulation | Hoisting / Lifting·Luffing | medium |
| YZEsquirrel cage Asynchronous | 0.55~90kW | simple structure, maintenance-free, overload capacityrobust | Crane Bridge·Cross Travel / Trolley Travel | lower |
| YZPVariable Frequency Speed Control | 0.55~200kW | 0~100Hzwide range Speed control, low energy consumption, anti-sway control | premium full mechanism | higher |
FAQ: Motor Power & Selection
Q: Why add a safety margin to the calculated power?
A: The calculation formula yields steady-state running power. Real-world crane duty involves starting impact (starting torque can reach 2–3 times the rated value), grid voltage fluctuations (±10%), and reduced heat dissipation efficiency in high-temperature environments. A 10%–20% margin is therefore recommended. The cyclic duration factor (CDF) is also critical—crane motors are rated for intermittent duty; at CDF 40%, the motor can be selected one frame size larger than for continuous duty.
Q: What's the difference between YZR and YZP motors? Is a VFD upgrade worth it?
A: YZR motors use external resistors for speed control—low cost, but brushes and slip rings require periodic inspection. YZP motors paired with a VFD deliver smooth speed control from 0 to 100 Hz, eliminating start/stop shock, providing effective anti-sway control, and cutting energy use by 15%–25%—at a 30%–50% higher initial cost. For frequent start/stop applications (e.g., port portal cranes), YZP is the recommended choice; for standard workshop hoisting duty, YZR is sufficient.
Q: Is the trolley travel power really only 50% of the crane bridge power?
A: Yes. The total trolley weight (trolley frame + hoisting mechanism + suspended load) is far less than the full crane weight, and although trolley travel speed is typically close to bridge speed, the driving force required is much lower. Rule of thumb: trolley power ≈ 0.5–0.6 × bridge power for the same capacity. However, the trolley starts and stops frequently, so motor heating and the CDF rating deserve close attention.
Q: How do I select a motor for non-standard operating conditions?
A: High-speed hoisting (>10 m/min), high altitude (>1,000 m with derating for reduced cooling), high-temperature environments (>40°C), and explosion-proof applications (ExdIICT4) all require individual engineering review. For a precise solution, contact the Kelude Heavy Industry engineering team for a custom motor selection calculation report. Phone: 13903802779, Email: 3915269@qq.com.
Crane Motor Power Quick-Reference Table.pdf
64KB · 16 hoisting + 8 travel + 7 luffing duty ratings · YZR/YZE/YZP series comparison · A4printable
This quick-reference table is compiled and provided free of charge by Henan Kelude Heavy Industry Co., Ltd. in accordance with ISO 4301. The results are for selection reference only; the final design shall be based on the official design documents issued by the engineering department. For custom selection calculations or technical consultation, please contact our technical service team.
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