BMW explain KERS incident

BMW have explained that the KERS incident at Jerez testing last month, which saw a mechanic fall to the ground having received an electric shock from their new car, posed no real danger to either the mechanic or the driver, Christian Klien, despite the fact that high voltages were involved.

BMW have been investigating the incident and have said that Klien was protected from the electric shock by his racing overalls and gloves. The mechanic involved was taken to hospital after the event as a precaution, however he escaped serious injury.

Markus Duesmann, head of BMW s powertrain, answered questions over the incident:

What exactly happened in Jerez?

“The mechanic suffered an electric shock after touching the sidepod and steering wheel of the car. There was a high frequency AC voltage between these contact points, the cause of which has been traced back to the KERS control unit and a sporadic capacitive coupling* from the high-voltage network to the 12-volt network. The voltage ran through the wiring of the 12-volt network to the steering wheel and through the carbon chassis back to the control unit.”

Was there a serious danger to the mechanic and the driver?

“No, as only a small amount of energy can be transferred through this capacitive coupling effect. However, the energy is sufficient to cause an extremely painful reaction. The driver was insulated against the car by his racing overalls and gloves and therefore not in any danger.”

Why did the investigation take so long?

“It was not possible initially to reproduce the capacitive coupling effect in the car, as the problem was caused by a sporadic error in the control unit. Due to the extremely high frequency of the voltage in the steering wheel, the safety mechanisms and data recordings did not pick up on the error. In the absence of data, all the theoretical possibilities had to be systematically investigated and analysed in tests. Furthermore, the capacitive coupling effect only occurs under certain conditions. Without the option of driving the KERS test car used in Jerez again, we had to reconstruct these conditions. We also had to develop a model to be installed between the steering wheel and sidepod which replicated the characteristics of the human body as an electric transfer element.”

What measures are now being taken to solve the problem?

“In addition to the measures required to tackle the issue at hand, the extremely far-reaching analysis we conducted also gave rise to other recommendations which are of great value for the development of electric KERS systems. Among the measures arrived at are changes in the design of the control unit to avoid capacitive coupling effects, extended monitoring functions for high frequencies and a conductive connection of the chassis components to avoid any electric potential.”

What will happen with these findings now?

“We have already handed over this safety analysis, complete with measures and recommendations, to the FIA, and will also make our findings available to the other teams at the next meeting of the Technical Working Group.”

When will the next track test for KERS take place?

“We will resume the testing programme once all the necessary amendments to the safety concept have been implemented. We expect this to be the case in the autumn.”

*Note on capacitive coupling: this refers to an inadvertent transfer of electric voltage between two transfer media by inductive or capacitive coupling.

Team principal Mario Theissen has said that the system is currently undergoing a re-design however they will not run KERS at the next test at Monza on August 27-29.

“Certainly we will run it within one of the tests during the season,” said Theissen. “But definitely not the coming Monza test because that will be totally dedicated to the Monza race package.

“In our view the result is not just a step forward for KERS and F1, but also for future hybrid road cars,” said Theiseen of the diagnosis of the problem. “It’s installation and design related. In the course of the investigation we found not just the reasons for this specific incident, but also some other design principals you should respect when doing high-voltage systems.

“We ended up not just with a solution to the Jerez problem, but also a design guide to high-voltage systems which will be presented to the FIA and to the other teams in detail. We have offered to do a detailed presentation at the next Technical Working Group.”