• • • ELECTRIC VEHICLES • • • Putting electric vehicles to the test


Although many governments are mandating electric vehicles and planning to phase out sales of internal combustion engine vehicles, the success of the take up demands that users have confidence in them. They need to know that electric vehicles have the range, performance, reliability and handling characteristics they demand, says Terry Marrinan, vice president and chief marketing officer at Yokogawa Test & Measurement


T


his means that manufacturers need extensive testing regimes to ensure their new car can achieve the parameters expected. With tests


needed of battery and motor, drivetrains and transmission, electronic and communication systems, steering, braking and suspension, manufacturers require highly capable test equipment that can measure waveforms accurately and in high detail. Large amounts of data need to be captured over hundreds of hours in order to achieve the insights they need to improve their designs.


Looking at subsystems In electric vehicles, there are four major subsystems that manufacturers need to test, each requiring their own combination of test equipment. These are:


• Charging – of battery, charging monitoring systems, regenerative braking;


• Powertrain – the power inverter sub-system for power delivery, and associated control signals;


• Motors – Three-phase brushless DC motors used in various applications; and


• Steering systems – Steering characteristics and electronic power steering (EPS).


Charging The charging system is critical to consumer confidence as the electric vehicle driver must know that the vehicle has the range and efficiency required. A thorough evaluation of the charging and


discharging characteristics of the battery is vital. A suitable measurement solution for this use case would need the ability to measure positive and negative cycles of power captured at high sampling rates to evaluate charging and discharging characteristics. Another aspect is regenerative braking, which is


increasingly seen as a mainstream way to save energy from braking and use it later to provide acceleration. Multichannel power analysers are particularly suited to the measurement of electrical output, efficiency and losses of regenerative systems in combination with the braking and motor generator systems. With range anxiety such a block to the adoption


of electric vehicle, wireless charging has emerged as a solution. Dependent on two electromagnetic coils being configured to support particular


24 ELECTRICAL ENGINEERING • NOVEMBER 2021 electricalengineeringmagazine.co.uk


frequency profiles, efficient power transfer and the prevention of power loss are particularly important. Assessing these criteria often involves evaluating performance at high frequencies - up to several hundred kHz – and at low power factors, attributes found in precision power scopes.


“ The charging system


is critical to consumer confidence


These instruments bring oscilloscope-style time-


based measurement combined with the features of power analysers. As such, they can perform standard multi-phase power measurements while also having oscilloscope style specific time-period measurements to analyse waveforms having transient components. Power scopes offer transient analysis, measurement of harmonics and time domain analysis through the ability to analyse trends cycle-by-cycle.


” Another need with charging system analysis is


to evaluate electromechanical relationships between components and systems as well as the ability to record over long periods of up to 200 days. Yokogawa has extended manufacturers’ options here with the development of the ScopeCorder. This is a data acquisition recorder that combines a mixed signal oscilloscope with a multi-channel, multiple speed data acquisition system that can be used for long-term recording. It also supports real-time data capture and analysis. This device provides ultimate versatility for


electric vehicle testing, as it can be connected to 21 types of input modules. These include 12-, 14- and 16-bit isolation modules, universal voltage/temperature modules, acceleration/voltage modules, strain modules and frequency modules. As well as acceleration and braking, developers


need to take account of other events that affect the load and efficiency of the battery system such as activated sensors and communications systems. Devices such as a data acquisition recorder allow the developer to assess the effect of these events.


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