Electric Hoist Guide: CD1, MD1, HC Lifting Speed & Duty Cycle
Key Points Three engineering parameters are critical when selecting an electric hoist: lifting speed is determined by motor speed and gearbox ratio (v=πD₀n/i·m), the work duty dictates the duty cycle (JC value) — select 25% for M3~M4, 40% for M5, and 60% for M6 — and the pulley block ratio balances wire rope tension against lifting speed (m=2 gives higher speed with lower tension; m=4 gives lower speed with higher tension; m=4 gives lower speed with higher tension). The CD1 model suits M3~M4, MD1 suits M4~M5, and HC suits M5~M6. This article covers the full selection parameters and calculation procedures for the 1–20 t range.
The electric hoist is the most critical hoisting component of any crane. Kelude Heavy Industry manufactures the CD1, MD1, and HC series electric hoists covering the full 1–20 t range, with every unit load-tested and insulation-tested before leaving the factory. The CD1 (single-speed), MD1 (two-speed), and HC (square box hoist) models span M3~M6 different work classifications. Proper engineering selection requires matching three dimensions simultaneously — lifting speed, work duty, and pulley ratio — and skipping any one of them compromises performance. This article presents a systematic approach to matching selection parameters across the full hoist series, complete with calculation procedures.
For pricing references and basic selection FAQs across hoist capacities, see 5t Electric Hoist Technical Parameters & Selection Guide and Electric Hoist Pricing FAQ. For detailed engineering calculations of the hoisting mechanism (wire rope, drum, motor), refer to Electric Hoist Hoisting Mechanism Engineering Calculations.
CD1/MD1 electric hoist structural diagram
CD1 / MD1 / HC electric hoist selection parameter comparison
Lifting Speed Calculation & Matching
The lifting speed v of an electric hoist is determined by motor speed n, gearbox ratio i, drum diameter D₀, and pulley ratio m: v=π×D₀×n/(i×m×60). Here, D₀ is the nominal drum diameter (m), n is the rated motor speed (rpm), i is the gearbox ratio (approximately 100–120 for the CD1's three-stage gear reduction), and m is the pulley block ratio. The same motor paired with different gearbox ratios and pulley ratios covers a speed range from 3.5 m/min (heavy-load, low-speed) to 8 m/min (light-load, high-speed).
Standard speeds by model: CD1 single-speed at 8 m/min (1–5 t), MD1 two-speed at 8/0.8 m/min (5 t) or 7/0.7 m/min (10 t), and HC two-speed at 3.5/0.35 m/min (16–20 t). The HC model can also be fitted with a variable-frequency motor for stepless control from 0.5 to 8 m/min. Selection guidelines: choose the high-speed 8 m/min option for high-frequency lifting where throughput is the priority; choose the low-speed 3.5 m/min option for heavy-load precision assembly where safety is paramount; and choose the MD1 two-speed model when both are required.
Work Duty & Duty Cycle (JC) Matching
The work duty determines the motor's duty cycle (JC value) — the percentage of time the motor is energized during a work cycle. For M3 (light load, low frequency), select JC=25%, where the downtime after each run is at least three times the running time; for M4 (medium load, medium frequency), JC=25%; for M5 (medium-heavy load), JC=40%; and for M6 (heavy load, high frequency), JC=60%. The CD1 comes standard with JC=25% (suited to M3~M4), the MD1 offers JC=25%/40% (suited to M4~M5), and the HC offers JC=40%/60% (suited to M5~M6).
For the same motor power rating, the rated output at JC=40% is approximately 15–20% lower than at JC=25%, because a higher JC value requires greater thermal capacity for heat dissipation. Never use a JC=25% motor for duty classifications above M5 — continuous operation will cause the motor to overheat and burn out. To upgrade the work duty, select a higher-power motor or switch to the HC square box hoist.
Pulley Ratio & Wire Rope Tension
The pulley ratio m directly affects the balance between wire rope tension and lifting speed. With m=2 (two rope falls), the wire rope tension is F≈(Q+q)/(2×η) and the lifting speed is v=2v₀ (where v₀ is the drum surface speed); with m=4 (four rope falls), F≈(Q+q)/(4×η) and v=v₀/2. For smaller capacities (1–10 t), m=2 is the common choice — it offers a simpler structure, lower cost, and faster operation. For larger capacities (10–20 t), m=4 is typically used: halving the rope tension allows the rope diameter to be reduced by roughly 1–2 standard sizes, and while the pulley block and drum dimensions increase, the bending fatigue life of the wire rope improves by 30–50%.
Impact of pulley ratio on cost: m=4 requires 2–4 additional pulleys compared to m=2, increasing pulley block manufacturing costs by 10–15%, but the reduced wire rope diameter lowers future replacement costs. Wire rope diameter is selected based on breaking force ≥ F×n (with n=5 for M5 duty), and the full calculation procedure is detailed in Electric Hoist Hoisting Mechanism Engineering Calculations.
CD1/MD1/HC Series Selection Parameter Comparison
| Model | Lifting Capacity(t) | Speed(m/min) | Motor(k W) | JC Value | Work Duty |
|---|---|---|---|---|---|
| CD1 1t | 1 | 8 | 1.5 | 25% | M3~M4 |
| CD1 2t | 2 | 8 | 3.0 | 25% | M3~M4 |
| CD1 3t | 3 | 8 | 4.5 | 25% | M3~M4 |
| CD1/MD1 5t | 5 | 8/0.8 | 7.5 | 25%/40% | M4~M5 |
| MD1 10t | 10 | 7/0.7 | 13 | 40% | M4~M5 |
| MD1/HC 16t | 16 | 3.5/0.35 | 13 | 40% | M5~M6 |
| MD1/HC 20t | 20 | 3.5/0.35 | 18.5 | 40% | M5~M6 |
When selecting a model, note that the speeds listed in the table above are standard configurations. Non-standard speeds can be achieved by adjusting the gearbox speed ratio to suit specific application needs. Kelude offers custom speed options, and every non-standard configuration is re-verified for wire rope safety factor and motor thermal capacity (e.g., reducing a 5 t hoist's lifting speed from 8 m/min to 5 m/min to increase lifting capability). The HC square box hoist can also be equipped with Variable Frequency Speed Control (requires adding a VFD and encoder, at a surcharge of approximately 20%–40%). Any non-standard speed selection must be re-verified for wire rope safety factor and motor thermal capacity.
Related Standards
• JB/T 10220-2014 — Brakes for Electric Hoists
• JB/T 10218-2014 — Cone Rotor Motors for Electric Hoists
• JB/T 10219-2014 — Gearboxes for Electric Hoists
Frequently Asked Questions
Q: How do I choose between the CD1 and MD1 models?
A: For general lifting applications, the CD1 (single-speed) offers a lower cost solution. If precise positioning is required, the MD1 (two-speed) provides a slow speed of 0.8 m/min for accurate load spotting. The HC square box hoist is designed for heavy-duty, high-frequency duty cycles (M5~M6) — it carries the highest price tag but delivers the longest service life.
Q: Is a faster or slower lifting speed better?
A: It depends on the application. For high-frequency lifting (100+ cycles per day), choose the 8 m/min high speed to maximize throughput. For heavy-load precision assembly, the 3.5 m/min low speed ensures safety and control. The MD1 two-speed model offers the best of both — 8 m/min for fast lifting and 0.8 m/min for fine positioning.
Q: What is the duty cycle (JC) rating, and what happens if I choose the wrong one?
A: Duty cycle = energized time / (energized time + de-energized time) × 100%. The CD1 comes standard with a 25% duty cycle, meaning the motor can be energized for no more than 25% of each operating cycle. It is not suitable for duty cycles above M5. If the CD1 is mistakenly used in a M5 application (requiring a 40% duty cycle), the motor will overheat and burn out within 30–60 minutes due to insufficient heat dissipation.
Q: How does the pulley ratio affect price and service life?
A: A pulley ratio of m=4 uses 2–4 more sheaves than m=2, increasing the pulley block manufacturing cost by 10%–15%. However, the wire rope tension is halved, allowing the rope diameter to be reduced by 1–2 sizes. This extends the rope's bending fatigue life by 30%–50%, resulting in a lower total cost of ownership. For heavy loads (≥10 t), a pulley ratio of m=4 is recommended.
