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INOMAX ACS580 & ACS880 – Tower Crane Solutions

High-Performance Variable Frequency Drives for Slewing, Luffing, Trolley & Hoisting Mechanisms

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Overview

Tower cranes are the backbone of modern construction. From high‑rise buildings and bridges to power plants and shipyards, these machines lift tons of steel, concrete, and equipment to heights that demand absolute precision, safety, and reliability. The drive system controlling the hoisting, trolley travel, slewing, and luffing mechanisms must deliver smooth acceleration, precise positioning, and fail‑safe braking – often in harsh outdoor environments with extreme temperatures, wind, dust, and rain.

At Inomax Technology, we supply ACS580 (general purpose) and ACS880 (high‑performance) variable frequency drives to tower crane manufacturers, rental companies, and retrofit specialists worldwide. Our drives are engineered for the unique demands of tower cranes: Direct Torque Control (DTC) with full torque at zero speed for safe load holding, built‑in anti‑sway control for accurate load positioning, master‑slave torque control for twin‑motor mechanisms, mechanical brake logic with zero‑speed brake opening/closing, regenerative braking for energy‑efficient load lowering, and harsh environment protection with conformal coating and IP54/IP66 enclosures.

We are also actively expanding our global partner network. If you are a distributor, system integrator, tower crane OEM, or rental fleet operator, we invite you to explore a partnership with INOMAX – factory‑direct pricing, technical support, market protection, and proven technology trusted by leading crane manufacturers worldwide.

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Why Tower Cranes Need High-Performance VFDs

The Challenge – Safety, Precision & Harsh Environments

A tower crane operates under extreme conditions: high winds, temperature variations, continuous vibration, dust, rain, and frequent load changes. The drive system must:

• Hold the load safely at zero speed – Full torque at standstill without mechanical brake drag

• Accelerate and decelerate smoothly – Prevent load swing and structural stress

• Stop precisely – Accurate positioning for hook alignment

• Brake reliably – Mechanical brake logic that works even in emergency stops

• Withstand harsh environments – Dust, moisture, temperature extremes, and voltage fluctuations

Traditional systems using resistor banks or mechanical clutches are inefficient, imprecise, and high‑maintenance. VFD‑controlled AC drives are now the industry standard, offering smooth stepless speed control, energy savings (15-25% on lowering), precise positioning, and lower maintenance.

Energy Savings – Regenerative Lowering

When a loaded hook descends, the hoist motor regenerates energy. Non‑regenerative drives waste this energy as heat in braking resistors. Our ACS880 AFE regenerative drives return >95% of this energy to the grid (or share it on a common DC bus). For a tower crane with frequent lowering cycles, this can reduce energy consumption by 15-25%.

Precision Positioning – Full Torque at Zero Speed

At the landing point, the hook must stop exactly at the target. Our DTC technology delivers full torque at zero speed without an encoder – the motor holds the load without mechanical brake wear, enabling smooth, accurate positioning.

Anti‑Sway – Faster, Safer Load Handling

Load swing wastes time and risks collisions. Our built‑in anti‑sway control (sensorless) uses the drive’s fast torque response to actively dampen load oscillation during trolley travel and slewing. Operators can move loads faster without waiting for the swing to settle – improving cycle times by 15-25%.

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Key Technologies – Professional Solutions for Tower Cranes

1. Direct Torque Control (DTC) – Precision & Zero‑Speed Torque

ACS880 DTC updates the motor model 40,000 times per second, delivering instantaneous torque response without an encoder for most crane applications.

Why DTC matters for tower cranes:

• Full torque at zero speed – The hook holds the load without brake wear; smooth starts from zero speed

• Torque response <5 ms – Instantaneous reaction to operator commands and anti‑sway control

• Speed accuracy ±0.01% with encoder – Precise positioning for high‑accuracy lifts

• No encoder needed for most applications – Higher reliability in dusty, vibrating environments

2. Sensorless Anti‑Sway Control – Built‑in, No External Sensors

Our drives include advanced anti‑sway algorithms that use the drive’s torque response to actively dampen load swing. The drive estimates the load’s swing angle and speed based on motor torque and speed, then adjusts acceleration/deceleration profiles to minimise oscillation.

Key anti‑sway features:

• No external sensors required – No cameras, lasers, or pendulums

• Works on trolley travel and slewing – Both directions

• Adaptive to rope length – Automatically compensates for different hook heights

• Reduces cycle time – Operators can move faster without waiting for swing to settle

Real‑world benefit: Up to 25% faster cycle times and reduced load damage.

3. Mechanical Brake Logic – Zero‑Speed Brake Opening/Closing

Tower cranes require coordinated control between the VFD and the mechanical brake. Our drives include dedicated crane brake logic:

• Pre‑excitation before brake opening – Torque is established before the brake releases, preventing load drop

• Zero‑speed brake closing – Brake closes only after the motor reaches zero speed, minimising wear

• Programmable brake open/close delays – Matched to your brake system response time

• Brake response monitoring – Optional feedback input confirms brake status

• Open‑loop zero‑speed brake control – No encoder needed; works with DTC torque estimation

Result: Longer brake pad life (estimated 2-3×), safer operation, and smoother load handling.

4. Master‑Slave Torque Control for Twin‑Motor Mechanisms

Some large tower cranes use two motors on the same mechanism – e.g., twin trolley motors or twin slewing drives. Our master‑slave torque control ensures perfect load sharing:

• Master drive operates in speed control

• Slave drive operates in torque control, receiving torque reference from master

• Result – Both motors produce identical torque; eliminates uneven loading and “nodding”

• Redundant master capability – If master fails, slave can automatically assume master role

5. Regenerative AFE – Energy Recovery During Lowering

When a loaded hook descends, the hoist motor regenerates energy. Our ACS880 AFE drives return >95% of this energy to the grid (or share it on a common DC bus). For a tower crane on a construction site with grid connection, this reduces electricity bills. For a crane on a common DC bus with other machinery (e.g., concrete pumps), the regenerated energy can be used directly.

Key AFE benefits:

• Energy recovery during lowering – 15-25% reduction in hoisting energy consumption

• THDi <5% at 80-100% load – Eliminates harmonic interference with site communications

• Unity power factor (>0.99) – Reduces generator fuel consumption on off‑grid sites

• Constant DC bus voltage – Immune to grid fluctuations common on construction sites

6. High Overload Capacity – Handling Peak Loads

Tower cranes must handle heavy lifts and emergency stops. Our ACS880 provides 200% torque for 60 seconds – sufficient for the most demanding lifts. The drive also includes torque limit protection to prevent mechanical overload.

7. Harsh Environment Protection – Built for Construction Sites

Construction sites are dusty, wet, hot, and cold. Our drives feature:

• Conformal-coated circuit boards as standard – Protects against dust and moisture

• IP54/IP66 enclosure options – For outdoor installation on the crane mast or cabin

• Wide operating temperature range – -15°C to +50°C without derating

• Stainless steel hardware options for coastal or corrosive environments

8. Fieldbus Integration for Crane PLCs

Tower cranes use dedicated PLCs or safety controllers (e.g., from Liebherr, Potain, Wolffkran, Terex). Our drives support all major protocols:

• Profinet IO – For Siemens‑based crane controls

• EtherNet/IP – For Rockwell‑based systems

• CANopen – For many European crane controllers

• Profibus DP – For legacy systems

• Modbus RTU/TCP – For universal compatibility

We provide complete GSDML, ESI, and EDS files, plus sample code for common crane control sequences.

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Tower Crane Mechanisms & Solutions

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Technical Specifications – Professional Grade

ACS580 Series (Cost‑Effective for Trolley, Slewing & Auxiliary)

ACS880 Series – High‑Performance for Hoisting & Full Anti‑Sway

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Real Projects – Proof of Performance

Our drives are used by tower crane manufacturers, rental companies, and retrofit specialists worldwide. Customer names are partially hidden for privacy.

Measured results from these installations:

• Anti‑sway reduced load swing by 80-90% – operators can move faster, cycle time reduced 15-25%

• Energy recovery during lowering: 15-20% reduction in hoisting energy consumption

• Brake pad life extended by estimated 2-3× (zero‑speed brake closing)

• Drive availability in harsh outdoor environments: >99% with proper enclosure

• Payback period (energy savings only): 12-24 months

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For Distributors, System Integrators & Crane Specialists

Why Partner with INOMAX?

Partnership Models

Distributor Support Program

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Frequently Asked Questions

For End Users (Technical)

Q1: How does sensorless anti‑sway control work on ACS880?

The drive estimates the load swing angle and speed based on motor torque and speed feedback. It then adjusts the acceleration and deceleration profiles to actively dampen oscillation. No external sensors (cameras, lasers, pendulums) are needed. The anti‑sway algorithm adapts to rope length and load weight automatically.

Q2: Can ACS880 hold a load at zero speed without mechanical brake drag?

Yes. DTC provides full torque at zero speed without an encoder. The motor holds the load stationary while the mechanical brake remains closed. When starting, the drive builds torque before opening the brake – eliminating any load drop.

Q3: How much energy can I save with regenerative ACS880 AFE on a tower crane?

When a loaded hook descends, the motor regenerates energy. For a typical tower crane with frequent lowering cycles (e.g., high‑rise construction), energy recovery can save 15-25% of hoisting energy. For a 50 kW hoist motor operating 8 hours/day, 250 days/year, annual savings can exceed $3,000-$5,000 depending on electricity rates.

Q4: Do I need an encoder for precise positioning on a tower crane?

No – DTC provides ±0.1% speed accuracy without an encoder, which is sufficient for most tower crane positioning. For applications requiring ±0.01% accuracy (e.g., very precise material placement), we recommend adding an encoder. The ACS880 supports incremental encoders (TTL, HTL), resolvers, and absolute encoders.

Q5: How does the mechanical brake logic work on ACS880?

When a stop command is given, the drive decelerates the hoist to zero speed (using regenerative braking), then issues a brake close command. The brake closes after a programmable delay, and the drive continues to hold torque until the brake is fully engaged. When starting, the drive pre‑excites the motor and builds torque before opening the brake – preventing any load drop. This sequence minimises brake wear and ensures safe, smooth operation.

Q6: What is master‑slave torque control and when is it needed?

Some large tower cranes use two motors on the same mechanism (e.g., twin slewing drives or twin trolley motors). Master‑slave torque control ensures both motors produce identical torque – the master operates in speed control, the slave(s) in torque control receiving torque reference from the master. This eliminates uneven loading, reduces overheating, and extends gearbox life.

Q7: Can ACS880 be installed outdoors on the crane mast?

Yes. We offer IP54, IP55, and IP66 enclosures suitable for outdoor installation. For extreme environments (coastal, high humidity, dust), we recommend IP55 or IP66 with conformal coating (standard on all drives). For very high ambient temperatures, we offer derating guidelines and optional liquid‑cooled versions.

Q8: What is the expected service life of ACS880 drives in tower crane applications?

With proper maintenance, 20+ years. Key factors: enclosure (IP54/IP66 recommended for outdoor), regular cleaning of air filters, annual fan replacement (or 40,000 operating hours), and 5-7 year DC bus capacitor replacement.

For Distributors & Partners (Commercial)

Q9: What is the minimum order quantity (MOQ) for distributors?

No strict MOQ for initial orders. Volume discounts apply from 10 units per order. For OEM/private label, MOQ is negotiated.

Q10: What is the standard warranty period?

2 years from date of manufacture or 12 months from commissioning, whichever comes first. Extended warranty up to 5 years available.

Q11: What is your typical lead time?

Popular models (≤250 kW) – 3-5 working days from our China factory + shipping. Larger units (250-6,000 kW) – 2-4 weeks.

Q12: Do you offer market protection?

Yes. Exclusive territory agreements (subject to minimum commitment) and project registration. Registered projects are protected – we will not quote directly or work with other distributors on that project.

Q13: Can you customize drives for my OEM requirements?

Yes: private labeling, custom parameter presets for specific crane models, special enclosures, modified firmware, custom voltage/frequency ranges.

Q14: What technical support can I expect for my customers?

Free pre-sales support: drive sizing, harmonic analysis, configuration recommendations, brake logic and anti‑sway tuning. Post-sales: remote diagnostics (free), on-site commissioning (fee-based). Product training for your technical staff.

Q15: How does INOMAX compare to ABB, Siemens or Danfoss for tower cranes?

We are legitimate competitors. Our ACS880 uses the same Direct Torque Control (DTC) technology as ABB ACS880. Performance specifications match or exceed competition. Price is 20-30% lower. Lead times are shorter. Customization is more flexible. Our anti‑sway and crane brake logic are specifically designed for tower crane applications and are built‑in (no extra cost).

Q16: Do you offer retrofit kits for converting existing DC‑driven tower cranes to AC VFD?

Yes. We offer pre‑engineered retrofit packages including:

• ACS880 AFE regenerative drive(s) sized for your hoist/trolley/slewing motors

• Optional encoder kits

• Pre‑configured parameters for your crane type

• Anti‑sway and brake logic setup

• Wiring diagram and installation guide

• Commissioning checklist

Contact us with your crane specifications for a quote.

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Ready to Partner with INOMAX?

Join a growing network of distributors, retrofit specialists, and tower crane OEMs who have discovered that INOMAX delivers premium performance at a competitive price – with real factory support.

Apply for distributorship today:

• Fill out the form below with your company information and market focus

• We will contact you within 24 hours to discuss partnership terms

• Receive distributor pricing, marketing materials, and technical documentation