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The challenge of voltage variation testing on HV components

Monday, November 29, 2021 | Thomas Handschin
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High voltage EV components are frequently exposed to variations in their supply voltage that occur during different driving conditions (accelerating, braking, battery SOC etc.). It is therefore necessary to test that HV components continue to function correctly under different supply voltages. This includes voltage changes (slow changing voltage ramps) as well as voltage dynamics (dynamic slopes and pulses).

The test setup is relatively simple with “just” a DC source as a dynamic battery simulator which supplies the EUT (plus some measurement devices to monitor the voltage and current):

voltage variation test setup
[click image to enlarge]

ISO 21498, LV123, VW 80300 and other standards define various tests for voltage changes and voltage dynamics: 

VW 80300 electric vehicle voltage variation testing 
[click image to enlarge]

While the shape of the waveforms looks relatively simple, the difficulty lies in the rising and falling slopes. While voltage variations have slew rates (du/dt) in the range of 2V/s and 2000V/s, the voltage dynamics i.e. load dump require slew rates of 250V/ms and higher.

The table shows examples of rise times depending on the system voltage and slew rates:

 Rise time (0 – 100%) System  voltage
 Slew rates 400V  800V
 2 V/s  200 s  800 s
 200 V /s  2 s  4 s
 250’000 V/s  1.6 ms  3.2 ms

High voltage sources that are typically used in e-drive and battery test benches are optimized for precision, stability and cost. The downside of these sources is the limited dynamic of the output. While slower voltage changes are usually possible to generate, the fast voltage dynamics are out of their operating range. 

The solution for e-drive and battery testing

To deliver the required high output dynamic of 500 V/ms or higher, a source designed to match the characteristics of the application is needed. This guarantees to reproduce exactly the required waveform – without over- or undershoot.

Below you can see an oscilloscope trace of a voltage profile 0 – 1000V with 1000V/ms slew rate (generated by PowerWave) - Note: the rise time is measured 10 – 90%

electric vehicle voltage variation testing
[click image to enlarge]

Special focus on high output slew rates is important when choosing a power source for testing drives and batteries according ISO 21498, LV123 and similar standards. AMETEK CTS NetWave and PowerWave are sources specifically designed and optimized to perform the range of demanding dynamic voltage tests.

AMETEK CTS provides a comprehensive range of sources for high voltage component testing. 
 > NetWave from 20 up to 150kW: ideal for auxiliary equipment like on-board charger (OBC), DC-DC converters, etc.
 > PowerWave from 250kW to 1MW: ideal for e-drive and battery testing

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