Twenty-five years ago, Ziehl-Abegg laid the foundations for the launch of energy-saving EC motors in ventilation technology. The company says this came as the result of Germany's telephone exchanges changing to digital technology. The new technology required safe and reliable cooling of the operating rooms. The Austrian post and telegraph administration service (the forerunner of today's Telekom Austria) also moved to modern technology in the 1990's.

The call for tender by the Deutsche Bundespost (predecessor of today's Deutsche Telekom) paved the way for the use of EC motors. Until then, fans in ventilation systems were driven using uncontrolled asynchronous motors. The first attempt to significantly reduce power consumption was the use of frequency converters as a control device.

"Back then, the postal service wanted to have the energy requirement included in the offer," said Gerhard Leutwein. Leutwein was head of development at Ziehl-Abegg for control technology.

The new call for tender took into account the power consumption for the next 10 years when calculating the retail price for the ventilation systems. Or to put it simply, fans could be fitted with a much more expensive motor, as long as this resulted in an energy-saving product when combined with the fan.

Developers at Ziehl-Abegg had been working on mains-powered EC drives since the mid 80's. But the much higher costs always prevented them from being used en masse. In 1989 came the first serious discussions with Hansa, a company that made air-conditioning units, about the use of the new motors as part of the postal service tender. However, another two years passed before the motors went into full production. In order to meet Deutsche Post's requirements, both the fans (centrifugal impellers) and the motors were reconsidered and optimized again and again. By the end, the volume ran into many thousands of units.

RD40K-4KW.4R.1L was the type designation of the first fan fitted with energy-saving EC motors. Back then, the flexible rotor was still made from steel, and today they are made using aluminum. The first serial products were delivered in 1991 and were first used in the digital exchanges at the Deutsche Bundespost. Due to the  efficiency of the EC fans from Ziehl-Abegg, they were increasingly used by all leading manufacturers of digital exchanges.

"In the first EC applications, the motor and the electronics were separate units," says Leutwein. From 1998 on, Ziehl-Abegg supplied the first axial fans from the FH035-065 and FC040-063 model series with integrated EC controller. These fans from the "ETAvent" model series were mainly deployed in the fields of thermodynamics and agriculture. The product range was extended from 2000 onwards with three-blade agricultural fans, the models FE071 and FE091.

In order to make the operation and electrical connections of all devices as identical as possible, Ziehl-Abegg spent the following years standardizing the control devices. It now makes virtually no difference to the operator whether the new device is controlled by phase control, frequency converters, or EC controllers. If they decide on an EC device, officials said the savings in energy costs soon become clear.