Stadt Introduces Energy Saving AC Motordrives

A new technology for speed and power control of bigger machinery operated via AC motordrives has been launched to the shipping market. The patented drive technology was first delivered to the seismic research vessel MS Sanco Star of Norway. In this case the drives was used for the main electric propulsion for the ship, driving two propellers each of 2,500kW.

The company STADT in Norway has developed the new product, STADT STASCHO, over the past five years, based on their long experience in development of megawatt AC motordrives for ship and industry.

The STASCHO product range goes up to 50MW with voltages up to 15kV, optionally also in higher voltage classes. The most interesting feature of the new patented drives is extremely low electric losses – less then 1% at full load – resulting in total electric system losses of only 5%. Given
that equivalent AC drives systems based on twelve-pulse configuration have system losses in the range 11%-12%, this new technology will have a huge impact on energy consumption for the electric propulsion system.

The new STADT STASCHO is expected to be warmly welcomed in naval applications, both for military and commercial vessels with gas – or diesel-electric propulsion systems. The low losses will save fuel in all working conditions for the ship, especially at high power. The difference from 12% loss to 5% is significant, and will result in a new way of evaluating the way that propulsion systems for ships will be designed in the future. New types of ships will most likely turn to electric
propulsion to save oil and pollution, says Hallvard Slettevoll, director of STADT, due to extremely low harmonic distortion (THD) of typically 2%-3% in
the main switchboard. This without requiring the big transformers or filters of other systems that totally depend on sinusoidal technology, or pulse width modulation (PWM).

One of the reasons for the unique characteristics of the new STADT STASCHO drive technology is that it is based on bidirectional sinusoidal voltage and current, both toward the driving electric AC motor, and backwards to the electric switchboard. The basis of this new technology comes from the company NFO Drives in Sweden, which has developed a patented inverter that controls standard AC motors with a pure sinusoidal voltage and current.

The sinus technology gives many advantages compared to the widely used PWM technology, used by the vast majority of drive manufacturers in the world. The most important advantage, is that sinus does not generate any disturbances at all, enabling the user to use unscreened power cables and standard AC motors without getting problems typically found in PWM-driven applications.

It is also worth noting that the STADT STASCHO drive saves space and weight. Pricewise it is also attractive. Information on other benefits, such as the elimination of acoustic noise, etc., can be found on our website.

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