Power Requirement of Double Girder EOT Cranes
Capacity and Duty Based Analysis

Introduction

Double girder EOT cranes are a common sight in heavy industrial environments—steel plants, power stations, machinery workshops, and material yards. These cranes are built for serious lifting. With two main girders supporting the hoist trolley, they provide better stability, higher lifting heights, and longer spans compared to single girder cranes. In many of these applications, especially where heavy loads are frequent or continuous, a heavy-duty open winch hoist is used instead of a compact wire rope hoist. These open winch systems are made for tough jobs—handling loads from 10 tons all the way up to 200 tons or more. They're strong, durable, and built for long service under hard conditions.

Now, here's something many buyers overlook: the power supply. It's not just about plugging in a crane. These cranes draw serious power—especially the ones with heavy-duty open winch systems—and the facility's electrical system must be ready for it. If the power system isn't compatible or strong enough, you might face unstable operation, breakdowns, or worse, electrical hazards.

So why is power supply planning so important?

• It ensures the crane operates smoothly without overloading your site's electrical system.
• It avoids power surges, tripping, or voltage drops that could damage motors and controls.
• It helps you size transformers, cables, and protection devices properly from the start.
• And it saves money—because when your power system and crane match well, everything runs more efficiently.

For cranes using heavy-duty open winches, this matters even more. These winch motors are large, and they pull heavy current, especially during lifting and starting. The bigger the capacity and the harder the working conditions, the more careful you need to be with power planning.

In short, if you're buying or installing a double girder EOT crane—especially with a heavy-duty open winch—don't leave the power requirements as an afterthought. Plan early, check your site's supply, and talk to the crane supplier about motor specs and total electrical load. It'll save you time, trouble, and costs in the long run.

What Influences Power Requirements?

Not all double girder EOT cranes draw the same amount of power. The total power demand depends on how the crane is built, how it's used, and what kind of hoist it's running. It's not just about the lifting capacity—there are several key factors at play.

Lifting Capacity (Tons)
The heavier the load, the more power the QDX open winch double girder overhead crane needs to lift it. That might seem obvious, but it's worth emphasizing.

• A 10-ton crane and a 50-ton crane won't use the same size motor.
• Higher-capacity cranes often require multiple motors or larger open winch systems to handle the strain.
• Power consumption increases sharply with load weight—not linearly. Lifting 50 tons doesn't just use five times the power of 10 tons; it can be much more when you factor in motor torque and system resistance.

Crane Duty Class (A3 to A8)
Duty class tells you how often the crane operates and under what conditions. It directly affects motor size and power usage.

• A3–A5: Light to moderate use. Lower power motors, less frequent operation.
• A6–A8: Heavy to continuous use, like in steel mills or foundries. These cranes need robust motors that can run for long hours without overheating.
• Higher duty means the motors must be built for longer run times, stronger cooling, and more energy input.

Type of Hoisting System
This makes a big difference. Open winch hoists are designed for heavy-duty performance—and they use more power than compact wire rope hoists.

• Open winches use larger motors, more gear stages, and heavier frames.
• They are more powerful and durable but also consume more electricity, especially during frequent or high-speed lifting.
• If your operation calls for high capacity or high duty class, an open winch is usually the right choice—but it comes with higher electrical demand.

Travel Speeds, Lift Height, and Frequency of Use
These factors may not seem major at first, but they add up.

• Higher speeds mean more powerful motors are needed to accelerate loads quickly and safely.
• Greater lift height increases the time and energy needed to move the hook from bottom to top.
• Frequent lifting cycles increase total energy consumption over time and may require better motor cooling and electrical protection.

When sizing power requirements for your double girder EOT crane with open winch, consider all of these factors together. Capacity alone won't give you an accurate picture. Think about how the crane will be used daily—how often, how fast, and how hard. That's what drives the real power demand.

Typical Power Requirements by Crane Capacity

Power usage in a double girder EOT crane with a heavy-duty open winch isn't one-size-fits-all. The total power requirement depends heavily on the crane's lifting capacity and how it's used. As the load increases, so does the size of the motor—and that means higher power consumption.

Estimated Power Consumption by Capacity
These figures cover typical total installed power for cranes with open winch hoisting systems. Keep in mind that actual values can vary depending on hoist speed, lifting height, duty class, and site conditions.

• 10-ton double girder EOT crane: Approx. 12–18 kW
  Suitable for medium-duty workshops or warehouses. Still requires attention to starting current and stable voltage supply.
• 20-ton double girder EOT crane: Approx. 20–30 kW
  Often used in manufacturing, maintenance, or moderate production environments. Power system must handle peak loads safely.
• 50-ton double girder EOT crane: Approx. 40–60 kW
  A strong, heavy-lifting crane often used in foundries or assembly lines. Power infrastructure must be well-prepared with proper cable sizes and protection devices.
• 100-ton and above: Custom power planning required
  These cranes demand serious electrical coordination. Expect dedicated transformers, high-capacity switchgear, and careful load balancing, especially in 24/7 operations.

Peak Load vs. Operating Power

Here's something many people miss: there's a big difference between operating power and starting power.

• Operating power is what the crane uses during normal lifting and travel. It stays relatively stable once the motors are running.
• Peak or starting power can spike up to 2–3 times the normal load, especially when motors start under load or in high-torque applications like open winches.

This is why it's critical to size your electrical system not just for continuous operation, but also for peak demand during motor start-up. Inrush current can trip breakers or overload circuits if not properly accounted for.

Practical Takeaways:

• Always check both rated and peak current when selecting circuit breakers and power cables.
• Consider using soft starters or variable frequency drives (VFDs) to reduce start-up surges.
• Talk to the crane manufacturer for exact power load tables based on your duty class and application.

Accurate power planning keeps your crane running smoothly—and keeps your lights from flickering every time you lift a load.

How Duty Class Affects Power Demand

When planning for power supply in a double girder EOT crane, it's not just the lifting capacity that matters—duty class plays a big role too. The duty class tells you how often the crane operates, how long it runs each time, and how close it works to its maximum rated load.

In simpler terms, a crane working hard all day needs more power than one used a few times a shift—even if both are rated for 20 tons.

Crane Duty Classes (A3 to A8)
These classifications are based on FEM or ISO standards and reflect how demanding the work cycle is:

• A5 (medium duty): Ideal for regular lifting tasks with moderate frequency. Common in machine shops or service bays.
• A6 (heavy duty): Frequent lifting with higher loads. Used in manufacturing, equipment assembly, or general industry.
• A7–A8 (very heavy to continuous duty): Near-constant operation in harsh environments—like steel mills, shipyards, or production lines running 24/7.

The higher the duty class, the more rugged and powerful the crane has to be. And that means larger motors, stronger electrical systems, and a higher energy draw to keep everything running smoothly and without overheating.

Impact on Power Demand for Open Winch Cranes

Heavy-duty open winch hoists, common in A6–A8 class cranes, already use more power than compact hoists. When combined with a higher duty cycle, the power demand goes up even more.

• Motors must be sized not just for lifting heavy loads but for repeated starts and stops, longer run times, and minimal cooling breaks.
• Control systems and gearboxes also need to be built for endurance, which adds to the crane's overall electrical load.

Practical Example
Let's say you have a 20-ton double girder EOT crane:

• In A5 duty, it may require around 22–25 kW of total installed power.
• In A7 duty, the same crane may need 30–33 kW or more.

That's a 25–30% increase in power requirement, just due to the workload and frequency of operation. This affects your electrical planning—from the supply line and transformer size to the thermal rating of cables and protection systems.

Key Takeaways:

• Duty class affects motor sizing, cooling needs, and energy usage.
• Always match crane selection (capacity + duty class) with your actual workload—not just peak lifting needs.
• Higher duty = higher power, so electrical systems must be sized accordingly.

Ignoring duty class during planning often leads to underpowered setups, overheating motors, or tripped breakers during real-world use. Better to plan it right than fix it later.

Power Supply Matching for Industrial Sites

Every industrial site is different—and so is its electrical setup. When installing a double girder EOT crane with heavy-duty open winch, you need to make sure your facility's power supply matches the crane's electrical requirements. It's not just about voltage; it's about the full system being able to support the crane under real working conditions.

Standard Supply Voltages Supported

Most EOT cranes are built to run on 3-phase power and can be designed to suit common industrial voltages:

• 380V / 50Hz – common in China, India, and many parts of Asia
• 415V / 50Hz – widely used in Europe, Australia, and the Middle East
• 440V / 60Hz – used in some regions of Asia and South America
• 480V / 60Hz – standard in North America and parts of South Korea

Before ordering a crane, confirm the exact voltage and frequency at your site. The crane's motors, control panels, and wiring must all be compatible. Even a mismatch in frequency (like installing a 50Hz crane at a 60Hz site) can lead to reduced performance or overheating.

Why Matching Total kW Matters

Your crane's total power requirement (in kilowatts) includes hoisting, trolley, and bridge travel systems. If your power supply isn't strong enough, you might face:

• Tripping of breakers during crane start-up
• Voltage drops that cause motor overheating
• Malfunctions in electronic controls
• Overall system instability, especially during peak operations

You need to match the available power at your site (after factoring in other equipment and machinery) with the crane's power demand, both operating and peak.

Planning for Electrical Infrastructure

Here are a few things to plan ahead:

• Transformer Size: Ensure your transformer can handle the crane's total kW plus inrush current. For large cranes or multiple units, you may need a dedicated transformer.
• Cable Layout: Proper cable sizing is critical. Undersized cables can overheat or cause voltage drops. Plan cable routing for safety and accessibility.
• Power Surge Protection: Use surge protection devices and soft starters to limit inrush current and protect motor windings from sudden spikes.
• Control Panel Positioning: Place electrical panels in accessible, ventilated areas for easy maintenance and reduced heat exposure.

What If You're Running Multiple Cranes?

If your facility uses two or more EOT cranes, electrical planning becomes more complex.

• You must calculate the total simultaneous load if cranes will run at the same time.
• Use individual breakers and isolators for each crane.
• Consider load staggering or using crane management systems to avoid peak load overlap.
• In some cases, a busbar system with capacity reserves is recommended over cable reels or festoon systems.

Bottom line: Your crane is only as reliable as the power you give it. Check your site power, match it carefully with crane specs, and involve your electrical engineer early in the planning stage.

Energy Efficiency in Heavy-Duty EOT Cranes

Powering a large EOT crane isn't cheap—but it doesn't have to be wasteful. Today's heavy-duty EOT cranes with open winch systems can be made more energy-efficient with the right components. This means lower electricity bills, less stress on your motors, and smoother operation.

Variable Frequency Drives (VFDs)

One of the most effective ways to manage power is by using VFDs on hoisting, trolley, or bridge travel motors.

• Soft Starts and Stops: VFDs prevent sudden jerks by gradually ramping motor speed up and down.
• Reduced Inrush Current: At startup, motors typically draw 2–3 times their rated current. VFDs smooth this, protecting your cables and power source.
• Speed Control: Adjust lifting and travel speeds to match the load or process needs, improving safety and energy use.
• Brake Energy Recovery (on some models): In certain systems, energy from lowering loads can be partially recovered and reused.

Energy-Efficient Motors in Open Winch Systems

Modern cranes use high-efficiency motors (IE2/IE3 class) that reduce electrical loss and run cooler.

• These motors may cost more upfront but consume less power per lifting cycle.
• Open winch motors are often oversized for reliability—choosing the right size (not too big or too small) is critical to avoid waste.
• Efficient motors also last longer, which reduces long-term maintenance and downtime.

Long-Term Savings and Benefits

If your crane operates daily, energy efficiency quickly adds up:

• A 5–10% improvement in motor efficiency can save thousands of kilowatt-hours per year.
• Lower energy consumption means less heat, which improves component lifespan.
• Reduces the need for oversized transformers or cooling systems.

Simple ways to improve efficiency:

• Choose a crane with VFDs and high-efficiency motors as standard
• Match motor size to your application—avoid overkill
• Run preventive maintenance to keep motors and brakes clean and properly aligned
• Use cranes at their rated capacity and speed—overloading increases power use and wear

Crane buyers often focus on lifting capacity and price—but energy efficiency affects your operating cost every single day. Spending a bit more upfront for smart power features is a decision that pays you back month after month.

Conclusion

Power requirements for a double girder EOT crane with a heavy-duty open winch are closely tied to lifting capacity and duty class. Both determine how large the motors need to be, how much current the system draws, and how your electrical setup must be designed.

Making the right choices early can reduce your power consumption, avoid electrical issues, and minimize downtime over the crane's working life. It also helps prevent overloading your building's electrical or structural system.

Always treat power planning and structural preparation as part of the crane selection process. The more attention you give to these areas now, the smoother your crane will perform later. And that means better safety, better efficiency, and less headache for your operations team.