Application of Xindashida Inverters in the Technical Retrofit of Electrically Excited Direct-Drive Shaft-Driven Generation Systems
2025-07-28
Application of Xindashida Inverters in the Technical Retrofit of Electrically Excited Direct-Drive Shaft-Driven Generation Systems
Project Background
In the field of upgrading and retrofitting ship power systems, technological innovation in conventional permanent-magnet shaft-driven generators has consistently faced significant barriers to commercial adoption. Specifically, upgrading existing systems often involves complex structural modifications—requiring not only the complete removal of older electro-excited generators but also the simultaneous replacement of matching mechanical coupling devices and auxiliary systems. This full-system replacement approach results in prohibitively high costs per vessel; according to industry data, the typical upgrade cost for a medium-sized cargo ship can easily reach several million RMB. Even more critical is that such upgrades usually necessitate a vessel’s停运 for 45 to 60 days. In the context of tight shipping capacity, this prolonged downtime directly impacts shipowners’ operational revenues and market competitiveness. These characteristics—high costs and lengthy upgrade periods—largely constrain the progress of upgrading ship power systems toward efficient permanent-magnet technologies.
Customer needs
In the field of ship power system upgrades, upgrading traditional permanent-magnet shaft-driven generators often comes with high retrofit costs—requiring not only the complete removal of the existing electro-excited generator but also the simultaneous replacement of the associated mechanical coupling devices. This results in high retrofit costs per vessel and lengthy downtime periods, significantly impacting vessel operational schedules. However, this longstanding industry challenge has now found a breakthrough thanks to Xinshidada’s technological innovation in electro-excited shaft-driven frequency converters: This system innovatively adopts a lightweight, modular design that eliminates the need to remove the original generator. Instead, simply adding the company’s independently developed shaft-driven frequency converter can upgrade outdated electro-excited systems into intelligent, adjustable, and highly efficient power supply solutions. As a result, the retrofit period is shortened, and costs are reduced by more than 40%, offering shipowners a new, more economical and convenient retrofit option beyond permanent-magnet technology.
Schematic Diagram of the Electro-Magnetic Direct-Drive Shaft-Driven Power Generation System
Xinshida Solution
High-performance drive technology
Like the permanent-magnet direct-drive shaft-generator technology developed by Xinshida, this system employs encoderless vector control and a rotor-angle adaptive control algorithm, enabling direct startup within a host speed range of 70% to 1.2 times the rated speed.
Dual-PWM conversion technology
It features adjustable power factor, extremely low THD (≤5%), and can deliver stable DC output within a speed range of 70% to 1.5 times the rated speed of the main unit. This ensures stable, high-quality three-phase AC voltage at the inverter side, guarantees safe operation of the equipment, optimizes system efficiency, and reduces energy losses.
Adaptive Dynamic Excitation Technology
Centered around the advanced AS710M series inverter, the system can dynamically adjust the stator and rotor flux of the generator in real time during operation, thereby preventing voltage dips or spikes that might occur due to wide-speed variations or sudden load changes in the prime mover, and enhancing system reliability.
Core features
Equipped with three core functions—online hot plugging and parallel operation, virtual synchronous generator control, and independent load carrying—it can easily handle complex operating conditions such as sudden changes in main generator speed and abrupt load variations.
Associated products
AS710M Marine Engineering Dedicated Variable Frequency Drive
Project Results
The Xindashida AS710M engineering-grade frequency converter, specially designed for offshore applications, has been successfully deployed on a bulk carrier equipped with a 75,000-ton electrically excited shaft-driven generator system.
At 87% of the host’s rated speed, the electrically excited shaft-driven generator system operated independently under a load of 390 kW, and the shaft-driven frequency converter was functioning normally. When the load was suddenly increased to 450 kW at 87% of the host’s rated speed, the shaft-driven generator system continued to operate in a stable condition.
Significantly reduces fuel consumption and emissions.
After installing the electrically excited shaft-driven generator system, the use of auxiliary diesel generators has been reduced, resulting in an average daily fuel savings of approximately 0.7 tons during operational periods. This system complies with IMO carbon emission regulations (CII/EEDI).
Enhance the flexibility of ship operations
Adapts to wide fluctuations in the main engine’s rotational speed range, enabling seamless switching between grid-connected and island-mode operation. Supports sudden load changes, ensures continuous power supply even under harsh marine conditions, and is suitable for a variety of application scenarios, including coastal and offshore operations.
Reduce maintenance costs
Reduce daily maintenance of diesel generator sets, lower spare-part replacement costs, and decrease labor input. Electrically excited generators eliminate the risk of demagnetization, reducing lifecycle maintenance costs by 30%.
Enhance navigational reliability and redundancy.
Reducing the frequent start-stop cycles of the auxiliary diesel generator can minimize its susceptibility to failures and ensure safe navigation of the vessel. The auxiliary diesel generator originally retained on the vessel serves as a redundant power source, enabling rapid switchover in the event of an axle-driven system failure and thereby guaranteeing the secure power supply for critical loads.
