ACS580 & ACS880 Marine & Offshore Solutions

High-Performance Variable Frequency Drives for Ships, Offshore Platforms, and Port Equipment

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Overview

The marine environment is one of the most demanding for electrical drives. High humidity, salt spray, extreme temperatures, continuous vibration, and strict space constraints require equipment that is not only robust but also intelligent and efficient. Whether you operate container ships, tankers, dredgers, offshore supply vessels, research vessels, or port cranes, your propulsion, thrusters, winches, pumps, fans, and shaft generators must perform reliably in all conditions.

At Inomax Technology, we provide dedicated marine and offshore VFD solutions using our ACS580 (general purpose) and ACS880 (high-performance with Direct Torque Control) drive platforms. Our drives are available with type approval certificates from major classification societies (CCS, DNV, ABS, BV, LR, RS), ensuring seamless compliance with international maritime regulations.

What we deliver for the marine industry:

• Ultra-low harmonic AFE technology – THDi <3% at typical loads, eliminating interference with sensitive onboard navigation and communication equipment

• Regenerative energy savings – Return >95% of braking energy to the grid, reducing fuel consumption and generator loading

• Master-follower load sharing – Perfect torque distribution for multi-motor winches, windlasses, and propulsion systems

• Common DC bus – Energy sharing between motoring and regenerating axes, reducing installed power and fuel costs

• High overload capability – 200% torque for 60 seconds, essential for windlass breakaway and crane lifting

• Proven in harsh conditions – Conformal-coated circuit boards, IP54/IP66 enclosures, -20°C to +50°C operation

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Key Marine Applications & Solutions

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Product Series for Marine Applications

Classification Society Approvals: CCS (China), DNV (Norway), ABS (USA), BV (France), LR (UK), RS (Russia). Our drives are fully type-approved and have been installed on hundreds of vessels globally.

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Technical Highlights for Marine

Direct Torque Control (DTC) – ACS880

• Full rated torque at zero speed – essential for anchor handling and crane lifting

• Torque response <5 ms – critical for active heave compensation

• Speed accuracy ±0.01% with encoder – precise winch positioning

• No encoder needed for >95% of applications – higher reliability in salty, vibrating environments

Active Front End (AFE) – Ultra-Low Harmonics

• Total Harmonic Distortion (THDi) <3% at 80-100% load – protects sensitive navigation and communication equipment (radar, GPS, sonar)

• Unity power factor (>0.99) – reduces generator loading and fuel consumption

• Regenerative braking – returns >95% of braking energy to the grid, used for shaft generator and winch lowering

• Meets IEEE 519 and IEC 61000 – no external harmonic filters required

Common DC Bus Configuration

• Energy sharing between motoring and regenerating axes – ideal for winches (one lowering, one lifting) and thrusters

• Reduced installed rectifier power – lower capital cost and footprint

• Simplified braking – smaller or no braking resistor needed

Master-Follower Torque Control

• Perfect load sharing between multiple motors on same mechanical load (e.g., twin winch drums, dual pinion thrusters)

• Eliminates “nodding” and “shaking” caused by speed mismatch

• Redundant master capability – if one drive fails, another automatically takes over

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Marine Application Case Studies

Case Study 1: National Key Scientific Research Vessel – 10,000m Cable Winch (China)

Customer: Ministry of Science & Technology, China
Vessel: Xiangyanghong (world-class oceanographic research ship)
Application: Main cable winch for deep-sea towing and sampling, 10,000m cable length
Power: 75 kW – 900 kW AFE drives

Challenge: The winch required extremely low harmonic distortion (<3%) to prevent electromagnetic interference with sensitive onboard scientific instruments (sonar, magnetometers, seismic equipment). Additionally, dual-motor torque synchronization had to be perfect to maintain constant cable tension during launch and recovery in rough seas. Traditional drives could not meet both the harmonic and master-follower accuracy requirements.

Solution: Inomax supplied ACS880 multi-drive system with AFE active rectification (AIM + ALM) and SMM motor modules. Direct Torque Control (DTC) enabled precise torque response in open loop. Master-follower torque distribution was implemented between the two traction motors – master in speed control, follower in torque control receiving torque reference via internal drive-to-drive link.

Results:

• Harmonic distortion maintained below 3% throughout all operating conditions – scientific instruments operated without interference

• Cable tension variation <±2% during launch and recovery in sea state 4

• Torque balance between dual motors achieved within ±3%

• System successfully passed multiple sea trials in extreme cold (Arctic), extreme heat (Equator), high humidity, high salinity, and high wave vibration environments

• Replaced a previously imported European system that could not achieve the required harmonic performance

Customer feedback: “Inomax provided a complete, independent, and controllable drive solution that outperformed foreign systems in both harmonic control and torque coordination.”

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Case Study 2: ZPMC – Low Harmonic Windlass (4 x 250 kW AFE)

Customer: ZPMC (Zhenhua Heavy Industries) – world’s largest port machinery manufacturer
Application: 4 x 250 kW AFE drives for ship windlass (anchor handling system)
Vessel type: Large ocean-going vessels

Challenge: The windlass required extremely low harmonics to avoid interference with other onboard electrical systems. Traditional 6-pulse rectifiers would generate THDi >40%, requiring bulky passive filters. Additionally, the system needed high starting torque for breakaway (anchor stuck in mud) and reliable operation in a compact marine cabinet.

Solution: Inomax provided four AFE series drives with common DC bus configuration. Each drive uses Active Front End (AIM+ALM) with LCL filter, achieving THDi <3% at 80-100% load. The common DC bus allows energy sharing between the four drives, reducing peak line current. Built-in braking unit eliminated external brake resistors.

Results:

• Harmonic distortion measured at <3% – well below classification society requirements

• Modular AFE design simplified installation – no external charging circuit needed

• Four AFE units connected to double-winding transformer with redundant design – if one module fails, others continue operation

• Cabinet size reduced by 30% compared to conventional 12-pulse + filter solution

• SMM motor modules provide 150% overload for 2 minutes every 10 minutes – handles anchor breakaway with ease

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Case Study 3: Jiangsu Aerospace – 3200T & 3500T Crane Ships

Customer: Jiangsu Aerospace
Vessels: Yuhang 32 (3200T crane ship), Aerospace 53 (3500T crane ship)
Applications: Main hook, auxiliary hook, luffing, slewing, tool hanger, translation drives

Solution: Inomax supplied complete drive systems for multiple vessel functions:

Key features:

• Direct Torque Control for smooth lifting/lowering, even at very low speeds

• Master-follower torque sharing for dual-motor hooks – perfect load balance

• 12-pulse rectification reduces harmonics without active front end

• All drives are CCS type-approved

Results:

• All crane functions operate with zero speed holding without mechanical brake wear

• Slewing mechanism operates smoothly without eddy current brakes – anti-sway function built into ACS880

• System reliability proven over 2+ years of continuous operation

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Case Study 4: Nantong Liwei – HT4000-282 Crane Ship & Giant 78

Customer: Nantong Liwei
Vessels: HT4000-282 (250/355 kW cranes), Giant 78 (8 x 400 kW)
Applications: Main traction winch, friction storage winch, cable discharge control

Solution for HT4000-282: Two 75 kW VFDs for traction reel, two 55 kW VFDs for friction storage cable reel, plus servo control for cable discharge. Integrated with Xinjie XD5E PLC and HMI.

Key features implemented:

• Automatic constant tension follow control for cable storage reel

• Real-time detection and display of cable length, speed, and tension

• Automatic cable flushing and timed/lubrication functions

• Automatic fault diagnosis and display

Results:

• Tension accuracy maintained within ±5% of setpoint during all operations

• Operator intervention reduced by 70% due to automation

• Fault diagnosis reduces troubleshooting time by 80%

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Case Study 5: Dalian Jialin Shipbuilding – Shaft Generator

Customer: Dalian Jialin Shipbuilding Heavy Industry
Application: Shaft generator (200 kW / 315 kW)
Vessel: Various commercial vessels

Challenge: When the main engine drives the propeller, the shaft generator must produce stable 380/690V 50/60Hz power regardless of engine speed variations. Harmonic distortion must be low to power sensitive onboard equipment.

Solution: Inomax supplied ACS880 AFE drives configured as shaft generator controllers. The AFE rectifier maintains constant DC bus voltage while controlling the generator’s excitation to output constant voltage and frequency across a wide speed range (typically 60-110% of nominal shaft speed).

Results:

• Voltage regulation within ±2% from 60% to 110% shaft speed

• THDi <5% at full load

• Eliminates need for separate auxiliary generator when main engine is running – fuel savings of 15-20%

• Seamless transition between shaft generator and auxiliary generator modes

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Case Study 6: China COSCO Shipping – Azimuth & Bow Thrusters

Customer: COSCO Shipping – one of the world’s largest shipping lines
Application: Azimuth thrusters and bow thrusters (1200 kW – 3600 kW AFE)
Vessel: Large container ships and bulk carriers

Challenge: Thrusters require high starting torque, wide speed range, and very low harmonics to avoid interfering with dynamic positioning (DP) systems. Power levels up to 3.6 MW per thruster demand robust, liquid-cooled drives.

Solution: Inomax provided ACS880 AFE liquid-cooled drives with common DC bus configuration. The AFE front end maintains THDi <4% even at low load. High-frequency output (up to 500 Hz) enables high-speed permanent magnet thruster motors.

Results:

• Thruster response time <100 ms from zero to full thrust

• Harmonic distortion meets DP class 2 requirements

• Liquid cooling allows compact installation in tight engine room spaces

• Energy savings from regenerative braking during dynamic positioning (thrusters reversing)

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Why Inomax for Marine & Offshore?

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Classification Society Approvals

All Inomax marine drives are manufactured in ISO 9001:2015 certified facilities and undergo 100% factory testing including high humidity, temperature cycling, and vibration tests per marine standards.

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Frequently Asked Questions

Q1: What harmonic distortion levels can I expect with Inomax AFE drives?
At 80-100% load, THDi is <3%. At light loads (20-50%), THDi remains below 5%. This is significantly better than 12-pulse rectifiers (THDi 10-15%) and meets the most stringent requirements for ships with sensitive equipment.

Q2: Do I need an encoder for winch torque control?
No. Direct Torque Control (DTC) provides excellent torque accuracy (±5%) without an encoder for most winch applications. For very high precision (active heave compensation with <2% tension error), we recommend an encoder. But 95% of marine winches operate successfully without encoders.

Q3: Can your drives operate with 690V 60Hz shipboard power?
Yes. Our ACS880 drives accept 380-690V, 50/60Hz input, and output 0-690V, 0-500Hz (or up to 1200Hz with optional software). They automatically adapt to frequency variations without derating.

Q4: How do you protect drives against salt spray and humidity?
All marine drives feature conformal-coated circuit boards as standard. For exposed locations, we offer IP54, IP65, and IP66 enclosures with stainless steel hardware. Optional heat exchangers (air-to-air or air-to-water) eliminate the need for cooling fans that draw in salty air.

Q5: Can I retrofit an existing winch or thruster with Inomax drives?
Yes. We have retrofitted hundreds of vessels, replacing drives from ABB (ACS600, ACS800), Siemens (6SE70, Sinamics), and others. We provide detailed retrofit drawings, pre-configured parameters, and on-site commissioning support. Most retrofits are completed within a 7-14 day dry dock period.

Q6: What communication protocols are supported for integration with ship automation systems?
We support Modbus RTU/TCP (standard), Profibus DP, Profinet, EtherNet/IP, and CANopen. For DP (Dynamic Positioning) systems, we provide fast real-time communication via Profinet IRT or EtherCAT with <1 ms cycle times.

Q7: How do you handle redundant drive configurations for critical systems (e.g., thruster)?
We offer both hot-standby (one drive active, one ready) and load-sharing redundant configurations. In load-sharing mode, two or more drives share the load; if one fails, the others automatically take full load. This is commonly used on azimuth thrusters for DP class 2 vessels.

Q8: What is the typical payback period for adding regenerative AFE to a winch or crane?
For a crane that lowers heavy loads frequently (e.g., offshore supply vessel cranes, floating cranes), the regenerative energy returned to the grid can reduce fuel consumption by 15-25%. Payback is typically 12-24 months depending on duty cycle. For a container crane in a port, payback can be as short as 8 months.

Q9: Can your drives handle the high starting torque required for windlass breakaway?
Yes. Our ACS880 drives provide 200% of rated torque for 60 seconds, and 150% continuously. This is more than sufficient for breakaway torque (typically 150-180% of rated). The Direct Torque Control algorithm ensures full torque from zero speed without mechanical shock.

Q10: What is the maximum power available for a single shaft generator drive?
Standard AFE modules go up to 6 MW. For higher power, we offer parallel AFE modules (up to 50 MW). We have supplied shaft generator drives up to 8 MW for very large vessels.

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Ready to Equip Your Vessel with Inomax Marine Drives?

Whether you are building a new ship, retrofitting an existing one, or upgrading port equipment, our marine specialists are ready to help you select, size, and commission the right drive solution.

Contact us today for:

• Free marine drive assessment based on your vessel type and application

• Classification society pre-approval documents (CCS, DNV, ABS, BV, LR, RS)

• Retrofit proposal for replacing obsolete drives (ABB, Siemens, etc.)

• Onboard commissioning and global service support

Inomax Technology