FAQ FROM SHIPOWNERS

Summary of Customer Questions and Answers

1. Does installing a shaft generator with EPL require recalculations?

   • Yes, recalculations are necessary. The engine manufacturer performs the calculations and implements necessary modifications.

2. What vessel types have we applied shaft generators, ducted propellers, and energy-saving fins to? What is the payback period?

   • Sales department to provide answers.

3. Differences in energy efficiency, cost, and time between propeller replacement and blade cutting?

   • Propeller replacement:
     • Designed based on reduced EPL speed and existing engine power.
     • Lighter and better matched to the engine.
     • Energy savings: 5-11% (varies per vessel).
     • Cost depends on copper price; payback period is about 1.5 years.
     • Design to delivery: ~3 months.
   • Blade cutting:
     • Modifies existing propeller geometry for better adaptation to reduced EPL speed.
     • Energy savings: 1-2%.
     • Completed during drydock; takes 2-4 days.

4. If the vessel speed suddenly drops, can the shaft generator still generate power? If the shaft stops, does the shaft generator still generate power? Where is the stored energy?

   • The shaft generator operates by using the main engine to drive a permanent magnet rotor, generating electricity through electromagnetic induction.
   • It has a speed range (e.g., 50-70 rpm, 60-80 rpm) within which it produces stable power.
   • If speed drops below this range for an extended period, the system will alert PMS to start auxiliary engines and disconnect the shaft generator.
   • If the shaft stops, the generator ceases power generation.

5. Is the shaft generator a three-phase generator? A three-phase asynchronous generator? Does it output three-phase AC?

   • It is a marine three-phase permanent magnet shaft generator, a synchronous generator that outputs three-phase AC.

6. How do the principles of three-phase motors and frequency converters apply to the shaft generator?

   • Permanent magnet motor operation:
     • The rotor creates a rotating magnetic field, inducing AC voltage in the stator.
     • Output AC power is rectified, stabilized, and converted to a constant frequency for ship power supply.
   • Variable frequency drive (VFD):
     • Uses two PWM converters sharing a common DC bus.
     • Motor-side converter stabilizes DC voltage.
     • Grid-side converter supplies stable AC power to the ship’s electrical system.
     • Ensures stable and continuous standalone or grid-connected power generation.

7. Can the shaft generator reverse the shaft in an emergency? Where is the stored energy?

   • The system has PTO (Power Take-Off) mode for power generation and PTI (Power Take-In) mode for emergency propulsion.
   • In PTI mode, the ship’s generators supply power, and the shaft generator acts as a motor to turn the shaft for emergency maneuvering.
   • This function requires pre-design and integration into the VFD and system.

8. Can the shaft generator and auxiliary engines supply power together?

   • Yes, they can operate simultaneously and are integrated with the PMS system for functions like synchronization, load transfer, and load sharing.

9. Do we have classification society certificates for the shaft generator, ducted propeller, and energy-saving fins?

   • Shaft generators have individual component certificates meeting various classification societies’ requirements.
   • Ducted propellers undergo certification per ship’s classification society.
   • Energy-saving fins generally do not require classification society certification but can be reviewed upon request.

10. Which countries provide warranty services?

• Answer provided by Mr. Hao.

11. Energy-saving effects of shaft generators and high-efficiency propellers on 57,000 DWT and 170,000 DWT vessels?

• Shaft generator savings:
  • 57,000 DWT: 0.7 tons of fuel/day.
  • 170,000 DWT: 2 tons of fuel/day.
• High-efficiency propeller savings:
  • 57,000 DWT: 7%.
  • 170,000 DWT: 7.5%.

12. Differences between high-efficiency propellers and standard design propellers? Design and installation time?

• High-efficiency propellers:
  • Custom-designed for optimal energy conversion.
  • Uses hydrodynamic optimization to reduce losses (cavitation, turbulence).
  • Requires balancing efficiency, strength, and manufacturing precision.
  • Design: 4 weeks; approval: 1 month; production: 2 months.
• Standard design propellers:
  • Based on experimental or simulated performance data.
  • Suitable for standardized applications but lacks innovation.

13. Does the shaft generator require spare parts for maintenance?

• No routine spare parts are required; faulty components are repaired as needed.

14. Does installing a shaft generator affect main engine power?

• Yes, the main engine load increases slightly. However, engines have ample power reserves, making the impact negligible.
• The increase is approximately equal to the shaft generator’s output power.

15. Why use water cooling instead of air cooling?

• Air cooling: Lower cost, but less effective cooling, requires ventilation and space, unsuitable for retrofits.
• Water cooling: Compact, effective cooling, can be placed in enclosed spaces (e.g., spare parts room, electrician’s room).
• Air cooling is available for systems below 1000 kW if cost reduction is prioritized.

16. How is the shaft generator’s current collected and output? Does the stator casing contain magnets?

• See shaft generator operating principles.

17. Can a shaft generator be removed and reinstalled on another vessel of the same tonnage if the original vessel is scrapped?

• Yes, if the new vessel has the same tonnage, main engine speed, power requirements, and shaft diameter.
• The installation feasibility depends on engineering costs.

18. How does the shaft generator maintain stable power output at varying ship speeds without fluctuations?

• The generator’s voltage and frequency vary with shaft speed, requiring a VFD and rectifier-inverter system (constant voltage and frequency system) to stabilize the output.
• See answer to question 4.