The Norwegian drive specialist STADT has introduced the STEALTH AC electric propulsion technology for naval ships in any category. The technology has been on the civil marine market for several years, and has proven its low noise characteristic there. STADT provides the fully integrated scope of electric propulsion, from main switchboards via the STEALTH AC drives and the electric propulsion motors.

The system has a unique set of valuable characteristics not seen from any other electric propulsion systems so far, such as negligible losses in the drive itself, compact design without big transformers, and use of very reliable technology all the way throughout the system.

No electromagnetic interference EMI – the STEALTH feature

STADT offers a real sine wave technology that is very different from the more known Pulse Width Modulation (PWM) type of AC motor drives. The Sine-wave motor control does not generate any Electromagnetic interference, the noise is fully eliminated. Thus complex screening of power cables for the propulsion drives are not needed any more.

An other advantage is the possibility for medium voltage grid, up to 15 kV system voltage for this new system, giving minimal electric field from the ships systems.

No harmonic voltage disturbances THD

The STEALTH drives also pulls linear power from the generators, so no disturbances are generated. The ship grid will operated with a pure un-distorted voltage within all of its main switchboards. This eliminates any overheating of power components and eliminates malfunctions of any kind.

No big transformer needed

Up till now electric propulsion systems has used very big an heavy propulsion transformers, for the purpose of cancelling harmonic distortion from the PWM drives. The STADT STEALTH AC drives do not need such filtering, thus the transformers are obsolete. This contributes to major weight savings, as well as space and loss reduction. And one less item that might fail.

NO-LOSS AC drive, patented

In practical terms, the STADT STEALTH AC drive does not generate any excessive heat during operation, except from electric losses in alternator and electric propulsion motors. This leads to additional system benefits such as:

  • Less fuel consumption, up to 8 % improvement compared to other type of electric systems
  • Longer endurance for the ship
  • Less emission of COx, NOx, etc
  • Less wild heat dissipation, reduced need for air condition systems etc
  • Increased reliability

This also leads to elimination of intricate water cooling systems within the AC drive, again leading to improved reliability.

Compact design saves space

The new drives saves space due to the eliminated need for big transformers, and due to a major reduction of number of components in the inverter topology. Improvements of more than 50 % in weight and volume is possible.

Rugged technology, well proven and approved

Throughout the years of development, STADT has focused very much on how to improve reliability in electric drives for propulsion. Vulnerable components such as capacitors has got a modest role to play in the new STEALTH drives. Insulation strategy is also improved dramatically, and robust thyristors plays an important role in parallel with IGBT switching and bypassing element operating in sequence.

The drive topology takes advantage of the best features in each components type, and utilizes them in the most effective way. Giving a solution with the desired new features mentioned.

The STEALTH drives also operates in conjunction with the CPP propeller systems to perform optimal manouverability and optimal energy efficiency for the vessel.

Redundancy is part of the solution

To avoid the situation where a tiny component failure might stop the ship propulsion, STADT has for this drive system implemented a redundant concept from generators, via MSB, drives and electric propulsion motors that takes redundancy in to account in each level of the system.

Electric Ship Propulsion motors, generators and switchboards

The STADT drive systems can be supplied with custom built AC propulsion motors in different technologies, such as navy approved with water cooling, as well as new designs based on superconducting elements to reach the most compact design with highest efficiency.

Comprehensive product range

The STEALTH AC drives are available from 100 kW and up to 100 MW in different configurations and a full range of voltage classes – 230 V to 15 kV.