testing Methodology

We are committed to testing, as every product is only as good as its testing Strategy.

The term power electronics generally refers to components that transform electrical energy. Due to the associated energy losses caused by the heating of components, this conversion mainly takes place by means of switching electronic components.

Power electronics, namely the inverter, is one of the three central elements in any electric powertrain (hybrid or EV): energy storage – inverter – e-motor. In this context, the inverter (in addition to other power electronic devices such as charge controllers, voltage converters or auxiliary units such as power steering, electric brakes, etc.) plays a special role.

From an electrical engineering point of view, the inverter converts the energy of the battery, i.e. direct current, into a suitable polyphase alternating current for the electric motor. For this purpose, the inverter detects the position of the e-motor rotor and supplies current to the phases of the e-motor in such a way that the desired torque is generated at the e-motor output shaft. That means, there is no “intelligence” in the e-motor itself. The same applies to the energy storage system (battery or fuel cell) – apart from the necessary safe operational management, there is no intelligence there in the form of software.

Heart and brain of electric powertrains

In this context of the three central electric drive elements, the inverter therefore plays a central role. This component not only converts the drive energy direct current into alternating current, but also regulates the torque of the electric motor in real time. For this purpose, it contains, in addition to the necessary power electronic elements, a mini-computer and extensive software for functions such as anti-skip, anti-slip, recuperation, etc. The inverter communicates with higher-level devices, performs diagnostics and monitors the load on the e-motor. This makes the inverter the “heart and brain” of any electric drive.

Testing makes the difference

A product is only as good as the testing process. This is a maxim, but the logic hidden behind it only becomes apparent on closer inspection. Everything that has been specified for a future product must also be validated. This means that the defined characteristics must be proven in the development process – otherwise the specification of characteristics for a product becomes pointless. Of course, this also applies to the product “power electronics”.
The more product requirements are being defined, the more extensive the validation process – the “testing” – has to become. In the case of power electronics, the requirements are not only extensive but also complex. On the one hand, demanding electrical characteristics must be verified, and on the other hand, complex software algorithms or safety functions must be tested. The testing of software functions is a particularly interesting aspect, as software constantly “grows” and gets “debugged”. This process accompanies the power electronics product over its entire life cycle and usually has to be mapped for several product variants.

This is, where our motivation comes from – to provide a test methodology for power electronics that is as realistic and efficient as possible. Because power electronics is the “heart and brain” of an electric powertrain.

Horst Hammerer
Founder & CEO, AVL SET GmbH

Realistic test environment

It is important that tests are carried in a way that mirror realistic situations as closely as possible. Tests on power electronics in which all power elements are “switched off” do not meet this requirement. Tests that produce a different result in the laboratory than in the actual application are, at best, a waste of time. A good test strategy for power electronics pays off as soon as the power electronics are brought together with the e-motor. If inverter deficiencies only become apparent during the integration with the e-motor, this reveals weaknesses in the test strategy. The effort required to eliminate defects is then significantly more expensive than if this had already been identified during the development process of the power electronics component. The consequences of an inadequate test strategy are: additional project costs, project delays, recalls and safety risks!

Production testing

Once a power electronics system has been successfully validated by means of meaningful, realistic tests – also with regards to the expected service life and environmental requirements – it is time for series production. Once again, the topic of “testing” is on the agenda. How can it be ensured that quality deviations, i.e. devices with production defects or component faults, are detected? Test requirements are changing. We provide adapted solutions for this, with which power electronics can be tested in a few seconds in an end-of-line application.