new challenge for electromobility: Partial discharge


electric vehicles: Prevent failure of 800 V drives

Currently, 90% of the fleet of e-vehicles use the tried-and-tested 400 V technology. However, as more and more vehicles with 800 V drives come into the market due to an growing demand for increasing range and shortening charging times, partial discharging will become a significant challenge in the next five years.

To date, FEV has carried out several tests on various vehicles; partial discharge was detected in almost every model tested. To avoid PD-related failures of electric drive units, FEV supports its customers to identify PD during the development process and initiate appropriate countermeasures at the earliest possible stage.

Background: Good to Know

Partial discharge is a localized electrical sparkover that can occur at voltages of more than 600 volts. Due to the prevailing high electric field strength, single charge carriers penetrate the insulating layer. It makes no difference whether the insulator is solid, liquid or gaseous.

This phenomenon has been known for a long time in the field of electrical systems engineering and high-voltage transmission networks. Corresponding checks are part of the routine tests before the system is put into operation. In the automotive industry, PD is still widely unknown, but is increasingly gaining attention with the growing use of 800 V drives.

Partial discharge can be caused by even the smallest defects or inhomogeneities such as air or dust inclusions in the insulation material or surface contamination. These can either be microcracks or similar caused by the manufacturing process or by improper handling, which can also be caused by the daily use of these components.

If it remains undetected and occurs repeatedly, PD leads to progressive damage to the insulation. Inside electric drive units (EDUs), PD can cause short circuits which, in the worst-case scenario, can lead to premature failure of the drive and thus to the vehicle coming to a standstill.

Most of the current electric vehicle drives operate with voltages in the 400 V range. Whereas partial discharge only occurs at voltages of more than 600 V. With the increasing spread of 800 V technology, PD is now also becoming relevant for electric drive units; electric motors in particular are potentially the most vulnerable components due to their design and the prevailing voltages.

With PD-HVX, FEV offers manufacturers of electric vehicles and suppliers a comprehensive solution for identifying PD during the development phase and initiating appropriate countermeasures at an early stage.

Display of electromagnetic field of an EDU at 100 km/h and 6,000 Nm: unfiltered results (top) and after filtering of the interference signals (bottom)
Display of electromagnetic field of an EDU at 100 km/h and 6,000 Nm: unfiltered results (top) and after filtering of the interference signals (bottom)

What is PD-HVX?

PD-HVX is the first and to date only commercially available solution for detecting partial discharge in the automotive sector.

The specifically developed sensors measure the electromagnetic fields around the drive unit to be examined. The electromagnetic frequency analysis used here is the most precise and reliable measurement method for investigating electric drives.

Modern, inverter-based electric drives generate a measurable electromagnetic field themselves through pulse width modulation (PWM). (displayed at the upper part of the figure)

PD-HVX reliably filters out these interference signals and thus achieves a significant increase in measurement sensitivity. (displayed at bottom of the figure)

The software, which was also developed explicitly for the investigation of electric drives, uses the measurement results to determine whether partial discharges occur within the drive unit during operation.

Thanks to the combination of state-of-the-art hardware and software and a comprehensive service package in conjunction with additional consulting services provided by FEV experts, the customer can detect partial discharge at an early stage in the development process and take appropriate countermeasures.

Our solution: PD-HVX

The basic package includes the physical measuring system and the corresponding software, installation at the customer’s premises as well as a preliminary consultation and two test days.

The customer can then either evaluate the generated measurement data themselves or draw on FEV’s expertise and experience. In a second stage, our engineers carry out further measurements, evaluate them and create a comprehensive report including initial suggestions for improvement. Thanks to the connectivity of PD-HVX, these measurements can also be carried out remotely online.

Finally, our experts offer comprehensive optimization and consulting services.

Any PD events identified are evaluated in detail for their system relevance, the overall system is assessed and corresponding optimization proposals are developed. These are implemented together with the customer.

Why FEV?: Proven expertise

FEV has many years of experience in the area of electric drives, in particular in the fields of power and control electronics, drive electronics and various areas of sensor technology in vehicle construction.

FEV supports leading racing teams in the field of e-racing and has gained and demonstrated extensive practical experience with corresponding EDUs and their weak points.

The company has now poured this expertise into an integrated and smart overall solution and is offering it to interested vehicle manufacturers. PD-HVX can be used in all phases of the EDU development cycle to measure PD phenomena.

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