Supercharging Made Easy

With the technologies of the Electrical Sector we have been able to develop modular solutions that help us save valuable time.
- Mike Lau head of compressor technology & development, Eaton Vehicle Group


Background
Compressors make it possible to increase the performance of an engine by forcing air into the engine intake. The compressor here is mechanically driven by the drive belt. This is a major benefit, since it enables the compressor to respond already at low engine speeds. The Eaton Vehicle Group is one of the world's largest compressor manufacturers for passenger cars. It offers innovative solutions based on a patented Roots-type supercharger with twin multi-lobe twisted rotors and an optimized air inlet and outlet. Eaton's superchargers of the Twin Vortices Series (TVS) are ideal for both petrol and diesel engines as well as for hybrid and fuel cell drives. The TVS technology enables a thermal efficiency of over 70 % as well as pressures of up to 2.5 bar at the outlet. This makes it possible to significantly increase the power of an engine and reduce fuel consumption and harmful emissions at the same time.

An important aspect of compressor development is the ability to adapt them correctly to the engine concerned. This is necessary so that the optimization of the entire system in terms of engine performance and NVH (noise, vibration, harshness) is ensured. Up to some time ago, the development for a new car still required the use of a test vehicle to test the interaction of the compressors with the engine whilst driving. This method involved a great deal of time and effort.

Challenges
The Vehicle Group therefore set up a competence center for compressor test benches at its Rastatt site. The team there develops and operates test benches that are able to simulate a vehicle as well as complete drive profiles. “Thanks to our high-tech test benches we are now able to test noise emission, thermodynamic efficiencies as well as the full functionality of all components of the supercharger – whether driving from the south of France to the north of Sweden or on the Nürburg ring,” explains Mike Lau, head of technology & development for compressors at Eaton. It is also possible to simulate a lifespan test with a detailed damage analysis.

An electric motor to drive the compressor by means of a drive belt forms the basis of the test bench. The electric motor produces the speeds over the specified performance range, and throttle valves are used to simulate the different vehicle states such as idling, driving off from standstill and acceleration.

A special project was recently set up for the operation of compressors at ambient temperatures as low as -25 °C. This required the development of a test bench in order to test in detail the sound signature of the compressor at low temperatures specified by the car manufacturer. This uses a Fourier transformation for the noise measurement. The data collected here makes it possible to determine whether all components are functioning properly. If any damage occurs, the faulty part can be identified precisely. “We are faced here with the challenge of ensuring in all cases extremely safe and stable operation for a test bench as well as maximum efficiency,” the engineer explains. “Particularly when the test bench is used for quality assurance in series production, reliability has top priority. This special sound test bench had to be designed not only for this one test. We also wanted the ability to retrofit it easily at a later date for other testing tasks.”

Solutions
Weingärtner, a company based in Baden-Baden, was a partner company involved in the implementation of the test benches and had already had a good experience with the portfolio of Eaton's Electrical Sector. As a result, the XC-152 compact PLC was used to control the entire test cycle of the sound test bench. This had the benefit that it offers other integrated interfaces such as Ethernet and CANopen, as well as the integrated SmartWire-DT master. The entire sensor system of the test bench is linked to the controller via SmartWire-DT I/O modules. The XV-152 touch panel is used for visualization and operation and is linked to the controller via Ethernet.

The application is programmed in Codesys, and Weingärtner chose Eaton's Galileo interactive software tool for the visualization. “For years we have had a good experience with Eaton products – not only with projects for the Vehicle Group,” explains Philipp Fels, manager at Weingärtner. “We appreciate the easy handling and wide range of options that Galileo offers us and so we use it very often.” Fels is also impressed by SmartWire-DT: “The SmartWire-DT communication system does what it promises as it helps us to complete projects considerably faster and with greater efficiency. It also offers considerable benefits with regard to data transparency, particularly in conjunction with the PKE motor-protective circuit-breaker – for this there is nothing better!"

The electric drive that drives the compressor via the drive belt is controlled with a variable frequency drive. For this the DA1 of the PowerXL series was selected, which is designed for ratings from 0.75 to 250 kW and is suitable for the most demanding applications. The integrated Safe Torque Off function was a key factor in selection since it ensures a safe standstill. “This was one of our first experiences with PowerXL and we are very impressed,” Fels adds. He and his colleagues were not only impressed by the simple handling in the terminal section but also by the ease with which parameters could be set. “This product has really been well thought out. The display is self-explanatory and programming is made really easy. This saves us a lot of time because we no longer have to create any manuals.”

Results
For the Eaton Vehicle Group, the fast implementation of a reliable and at the same time flexible solution for the test bench was critical. Lau sums up as follows: “In our business, speed is the critical factor. With our innovative test benches we no longer need to carry out test drives and are able to start already when the compressors are being developed, as soon as the car manufacturer has finalized his engine specifications – and this is one of the first steps in designing a new model. With the technologies of the Electrical Sector we have been able to develop a wide range of modular solutions like the sound test bench, with hardware and software that can be adapted and retrofitted easily in future to help us save valuable time.”