• • • ELECTRIC VEHICLES • • •


Power train With up to 18% of an electric car’s charge being consumed as electric drive system losses, EV manufacturers need an accurate evaluation of motor and inverter control to achieve higher precision and greater efficiency. They


also need to analyse inverter waveforms without interference from switching noise. Testing the powertrain requires multichannel


electromechanical measurements at high accuracy. An ideal test set up is a single power analyzer connected to the battery, booster, converter and the three-phase motor, together with mechanical measurements from torque and speed sensors. With this, developers achieve simultaneous measurements of torque, rotation speed and direction as well as electrical parameters such as voltage, current and power. Debugging and testing of embedded electronics,


ECUs and communication bus signals can be performed with mixed signal oscilloscopes. However, assessing holistic electromechanical


events, particularly over prolonged periods, is best achieved using a data acquisition recorder. This will offer flexible modular inputs to combine electrical and physical measurements with CAN/LIN serial buses in a single overview. It will also offer measurement of frequency, temperature, distortion, acceleration, and other signals. A power analyser will be needed to measure


efficiency and compare higher order harmonics between input and output. It will also find use in measuring electromechanical parameters like electrical angle, rotation speed and direction. A power scope would be used for cycle-by-cycle


trend analysis. A particular example is during the start-up phase of an inverter and motor, where current increases can be analysed in each cycle.


Motors As well as their use in powertrains, modern vehicles use motors in many other applications, including power steering, automatic doors, windows and mirrors, and oil and water pumps. Many of these applications use brushless direct current motors (BLDCs). Evaluating an electromechanical system such as


a BLDC driven feature often needs real-time, multichannel measurements of parameters such


as DC input power, three-phase inverter output, and motor & sensor feedback of parameters such as vibration, RPM, angle and temperature. For these measurements, ScopeCorders offer


greater signal conditioning and better electromechanical analysis. With flexible modular inputs that can combine electrical and physical measurements, they can provide data on frequency, temperature, distortion, acceleration, and other signals . A further need with BLDCs is to evaluate the


motor’s performance with transient behaviours. Power scopes capture transient phenomena in great detail, at high accuracies that compare well with power analysers.


Steering The testing of steering systems involves analysing the interplay between steering wheel and road wheels as well as examining the sensor signals that direct the electronic power steering (EPS) system. To save costs on physical testing, AC motors are


used to simulate a speed command and implement it as a wheel load. AC servo motors can also be used as a load on the axle side to simulate the ground contact resistance of the road. Evaluating the EPS requires monitoring and


recording of data from sensors on parameters such as car speed, torque, torsion, and the amount of power assist calculated by the ECU, in addition to three phase motor parameters such as electric current, voltage and rotation amount. Another requirement is long memory to continuously record for 10-20 minutes or more. A data acquisition recorder can be used in both


these assessment tasks. It can measure and analyse the transfer characteristic from steering wheel to road wheels, while with its ability to measure and record over long periods from multiple channels, it is ideal for evaluating an EPS system.


Bringing it all together Developers often need to bring in these measurements simultaneously to give an overall view of system performance. The challenges come when trying to operate multiple instruments simultaneously, due to the need to corelate all the differing input signals. This makes it difficult to


find relationships between measurements, lengthening development cycles and increasing time to market. To meet this challenge, Yokogawa has produced


its IS8000 software platform, which provides tight integration of the timing, control, and data collection from several instruments. With one software suite to set up and control all the instruments needed, development engineers can start measuring data more quickly and more efficiently.


Beyond development As well as research and development, there is a need for testing electric vehicles during production. This will require a new generation of more


portable test equipment that allows in-car testing of different parameters in the field in different climatic and road conditions. Test modules from Yokogawa’s ScopeCorder can be used in a handheld version of the instrument to test actual conditions in a driven car. There will also be a growing demand for after


sales testing. Vehicle health checks will need to determine if the battery is actually producing the power demanded and it is not degrading, while systems such as re-generative power will also need assessing. With increasing use of sensors by autonomous


vehicles, these will also need maintenance, with specialist sensors such as LIDAR requiring equipment like optical spectrum analysers. Overall, instruments will need to get faster, be


more adaptable and have larger memories to account for the increasing amounts of data produced by systems such as high-speed inverters. With our instrumentation and calibration


services, we are trying to support the next generation of sustainable technologies and the electric vehicle is a major part of that. “Yokogawa has been producing high precision,


high-quality instrumentation for the automotive industry for years and our latest measurement instruments are being optimised for the types of testing and development tasks that electric vehicles need. As perhaps the leading company in this field, we are determined to be perceived as the industry reference for the most trusted measurements from electric vehicle test instruments.”


electricalengineeringmagazine.co.uk ELECTRICAL ENGINEERING • NOVEMBER 2021 25


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40