New inverter testing procedure from AVL

  • 22-Nov-2011 09:36 EST
AVL inverter TB.jpg

AVL's new inverter testbed with electric motor emulator provides a complete testing and validation environment to facilitate research and analysis of an inverter's electrical, mechanical, and thermal properties.

AVL recently unveiled a testing method that uses an electric motor emulator as a substitute for a traditional inverter testing process that relies on dynamometers and electric motors.

"The electric motor emulator (EME) uses embedded real-time software modeling and fast-switching electronics to emulate identically the loads put on an inverter so that the testing of the inverter's functionality can be independently done without the need of a physical electric motor and a high-voltage battery," Dr. Roland Greul, Product Manager of Electrification Products, Business Unit Electrification Test Systems, at AVL List GmbH, explained to AEI.

Intended for inverters that will be used in electrified light passenger vehicles as well as commercial vehicle applications, the development timeline for this unique AVL testbed lasted more than five years.

"The current development program is focused on enlarging the testbed portfolio with systems that can accommodate higher voltages and higher power ranges," noted Greul, adding that the aviation industry was the original application area of the EME test system.

AVL's inverter testbed with EME substantially reduces the time needed to complete performance and durability tests compared to conventional methods.

"Additionally, with this testing process the functional behavior of the inverter at safety-critical conditions and/or simulated errors can be easily addressed and validated," according to Greul.

Test engineers can determine the electrical, mechanical and thermal properties of the tested inverter in various real-world functional scenarios.

"For maintenance, durability, and especially for safety reasons, it is mandatory to characterize the inverter behavior through a set of test runs in a proper environment. This can be done with a prototype vehicle or by frontloading such tests to a test bed where the e-drive system is properly emulated. Typical driving cycles of the vehicle are used as inputs for a propulsion system model which calculates the load profile for torque and speed of the EME," Greul explained.

AVL's inverter test system can accommodate various applications needs.

"The EME power module is designed for a specified power and voltage range of the original electric motor, which is why we are offering a system with a dc voltage of 400 V and with different phase current ranges—125 amp, 250 amp, and 400 amp. We're currently in the development phase with an 800-amp system as well as systems with a dc voltage of 800 V in the same phase current ranges," said Greul.

In addition, the embedded software model can be matched to a specific type of electric motor, such as a brushless dc, permanent magnet synchronous, or ac synchronous motor.

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