In times of rising fuel prices and climate change, electric drive vehicles are the mobile future. By 2020, the Federal Government in Germany would like to have at least a million electric cars on highways making Germany a leading market for electric cars. Therefore, every large automobile manufacturer must have at least one electric car in its product line.

To continuously improve the efficiency of electric motors, Bertrandt Ingenieurbüro GmbH in Wolfsburg, Germany tests the drive components of electric vehicles for their customers. The Bertrandt Group offers services related to all aspects of the product development value-added chain for the automobile and aviation industry. Over 11,000 employees stand for future-proof solutions at 46 locations in Europe, China and the USA. This development service provider has been using the eDrive testing solution from HBMfor tests on electrical components such as electrical machines and inverters since mid-2014.

The goal is to achieve the best setting for the motor. Important factors to consider include better efficiency, higher maximum power and optimized handling. Up until recently, Bertrandt has used a traditional power analyzer design for static operating points, to determine a characteristic efficiency diagram. However the disadvantage to that is is  it does not save  raw data nor the calculated values over an extended period of time. With the new measurement system from HBM, that's all history. Raw data is supplied synchronously and displayed quickly – and we can save it with automatic trigger control," says Max Bernholz, Team Leader of E-Drives Testing at Bertrandt.

The current transformers in the control cabinet in the background and, in the foreground, the GEN3t measuring unit, remotely controlled from the control room.

The Importance of Raw Data

The integral measurement system from HBM combines three modules

  • a torque transducer
  • a data acquisition system with the real-time computing functions of a power analyzer
  • a temperature satellite.

The eDrive testing solution shows all relevant data in high resolution during the test process; such as electrical currents, output levels, efficiency levels, torque and rotational speed. "This motor torque in particular is subject to high-frequency fluctuations, so the “live FFT” function of the device is very convenient for us. It's also useful for analyzing torque in a temporal relation to the phase currents," says Bernholz.

The motors are all controlled by power electronics in which the power semiconductors form the rotary field from the direct current of the lithium-ion battery. "The high time resolution of the device is especially advantageous for analyzing the switching patterns of power semiconductors and seeing all the other relevant quantities on the screen in parallel," explains Bernholz. All recorded raw data can later be analyzed directly in the integral systemNo other programs are needed, which saves time and keeps the error rate low. "This solution is very flexible in terms of processing different measured quantities," notes Bernholz in conclusion. Continuous acquisition of raw data makes it possible to analyze the drive very accurately – clearing the way for even more efficient electric motors.

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