Verification of Power Fluctuation and Waveform Synchronization during Acceleration / Deceleration of EV Motors

Introduction

To advance the development electric vehicles and support a transition to sustainable transportation, it is essential to measure electrical and mechanical parameters. Voltage, current, power, power factor, and frequency values can change abruptly or fluctuate. Such variations may indicate anomalies in the waveform data, which serve as the basis for arithmetic computations.
To identify the causes of these numeric changes, a waveform measuring instrument can be utilized to capture and analyze the waveform data. Possible causes for these phenomena, aside from changes in the device under test, include power supply fluctuations or issues within the measurement environment or the instruments themselves. Although these occurrences are rare, it is imperative to identify and isolate any abnormal events. This can be achieved by using a power analyzer in conjunction with a waveform measuring instrument or by correlating numerical values with waveform data using the power analyzer’s waveform capture function.

Challenges

Power analyzers perform a wide variety of computations, making it challenging to identify abnormal values if they appear briefly among the many displayed on-screen. After data capture, creating a trended graph can simplify the process of spotting outliers.
However, it can also be challenging to consistently reproduce an anomaly, as the same phenomenon might not recur due to differing external conditions such as air temperature, humidity, and device temperature. This can result in persistent, unresolved issues. Fluctuations in the numeric data from a power analyzer alone are often insufficient to pinpoint the cause of an abnormality, necessitating the use of a waveform measuring instrument. Yet, setting trigger conditions to isolate relevant waveforms can be difficult. Additionally, synchronizing measurements between the power analyzer and waveform measuring instrument is challenging due to each instrument’s internal timekeeping, which can lead to time skew, missing partial data, or effects of different cabling.
In addition, synchronization over long durations is challenging because waveform measuring instruments such as oscilloscopes typically operate in the order of GS/s, while power analyzers capture numeric data in the order of milliseconds or seconds.

Solutions

Synchronized Measurements with DL950, WT5000, and IS8000

• WT/DL time synchronization display with IEEE1588
• Data management with link files/split files
• Utilizing highly reliable power data with guaranteed accuracy
• Reporting using waveforms and power analyzer data

Cycle-by-Cycle Waveform
Computations using the PX8000

• Sample rate at a maximum speed of 100 MS/s
• Large memory capacity up to 100 M points/channel
• ransient power measurements by per cycle trend calculations
• Calculations for a specific interval set by a cursor
• Perform same calculation with the PX8000 using PowerViewerPlus

Explanation of Each Solution

Synchronized Measurements with DL950, WT5000, and IS8000

Power measurements using data from an oscilloscope or DAQ instrument cannot provide highly accurate power values with traceability. The IS8000 Integrated Software Platform can employ IEEE1588 time synchronization of data between a DL950 ScopeCorder and WT5000 power analyzer, with less than 10 μs timing error. It can continuously display eight channels of waveform data (from the DL950) at up to 20 MS/s on the same time axis with power data from the WT5000. This allows correlation of subtle power fluctuations and any associated abnormal waveforms.

Figure 1. Observation example 1: Waveform data during a power
value abnormality

Figure 2. Observation example 2: Waveform data during a power
value abnormality

Figure 3. Observation example 3: Waveform data during a power
value abnormality

Cycle-by-Cycle Waveform
Computations using the PX8000

In addition to displaying voltage and current waveforms, the PX8000 simultaneously calculates and displays instantaneous power as trended data. This instantaneous power value can be read using a cursor, which also allows for distance measurements between two cursors. Horizontal, vertical, and marker cursors support simultaneous differential measurements of time, voltage, current, and power intervals.
Moreover, user-defined math waveforms are supported with a maximum of 4 M points. The cursor function allows for the observation of cycle-by-cycle power values and measurement of differences between cycles.
The 760881 PowerViewerPlus application software enables comprehensive waveform and numerical analyses of largevolume data when measurement data is transferred to a PC.

Figure 4. Example of instantaneous power waveforms with the PX8000

Figure 5. Example of the cursor interval calculation with the PX8000

Figure 6. Example of the cycle-by-cycle trend calculation with the
PX8000

Utilizing Exceptionally Reliable Power Data with Guaranteed Accuracy

In recent years, many waveform measuring instruments have the capability to compute power data. While this is convenient for observing waveform data simultaneously with power values, product design decisions should be based on accurate, traceable measurements to national standards.
The primary purpose of waveform measuring instruments are to observe the shape of measurement signals with voltage and current probes at high bandwidths and sample rates. Consequently, the power computation results often differ significantly from those measured by dedicated power analyzers, necessitating additional verification.
On the other hand, Yokogawa’s power analyzers have established and maintained high-accuracy, traceable and guaranteed measurements. This ensures the provision of reliable data for voltage, current, and active power. The IS8000 Integrated Software Platform provides traceable power measurements from a Yokogawa power analyzer with synchronized waveform observation of eight channels at up to 20 MS/s. This provides highly reliable power analyzer data and waveform data on the same time axis.
*Power traceability: Calibration technology guaranteeing the performance of the WT5000. Additional information in the following White Paper:
https://cdn.tmi.yokogawa.com/1/8690/files/ Yokogawas_power_calibration_ technology_to_support_high-precision_power_analyzer.pdf

Figure 7. Traceability Structure of the New Power Calibration System