Converter helps save energy

New device digitally controls the speed of electrical drives in the industry

The power section is the heart of the Ultra-Sparse matrix converter. © ETH Zurich
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A compact and energy-efficient two-stage matrix converter, which digitally controls the speed of electrical drives, was developed by researchers at ETH Zurich. With such converters, power consumption can be significantly reduced, especially in industry.

Roughly 60 percent of the industrially required power consumption within the EU is accounted for by electromotive systems. There is an enormous saving potential. Around a third of this power consumption could be saved if the speed and the power of the motors would be regulated as required by power electronic converters. Nevertheless, such converters have not yet been used in many fields of application. The reasons for this are on the one hand costs, on the other hand the relatively high space requirement and the load of the network with high pulse-shaped currents.

Scientists at the Chair of Power Electronics at the ETH Zurich have now developed a two-stage matrix converter, which is characterized by high network friendliness and a very low volume of construction. It can therefore be integrated into existing systems or even motor housings. The previous passive units, which run at constant speed, are thus converted into drives that can be controlled dynamically.

Three decisive advantages

A power electronic converter converts the constant AC voltage of the network at the input into a variable AC voltage at the output. Depending on how fast the drive is to rotate, the amplitude and frequency of the output voltage are adjusted electronically.

The "Ultra-Sparse Matrix Converter" developed at the ETH accomplishes this transformation in a very elegant way: The mains voltage is "chopped" by means of power transistors with high clock frequency and assembled directly to a new voltage with a given amplitude and frequency at the output. The one-stage energy conversion results in a significantly higher efficiency, because the new converter does not require energy buffering, as is common in conventional systems. display

The converter is also characterized by a compact design and can be realized with little effort. It draws the net from a purely sinusoidal current and is characterized by a high electromagnetic compatibility. This is particularly important because electromagnetic disturbances often cause malfunctions, and this often leads to costly business interruptions in industrial production plants, for example.

A contribution to saving energy

With their development, the researchers are also making a contribution to the more efficient use of energy since the converter processes the supplied electrical energy as needed. This is extremely interesting from an economic point of view. For every ten years, an average of energy costs of CHF 100 per invested franc are lost on industrial drives.

Fields of application for the new matrix converter, the researchers see not only in existing systems, but also, for example, in future aircraft. The concept of this "More Electric Aircraft" is to replace the heavy hydraulic control systems, at least in part, with lighter electric drives. Compact power electronic converters, which feed the drives efficiently and reliably, are indispensable.

(idw - Swiss Federal Institute of Technology Z rich (ETH Zurich), 29.05.2007 - DLO)