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3-Phase Inverter Motor Drive Analysis
5 Series/6 Series B MSO Option 5-IMDA/6-IMDA Application Datasheet
Measurements and analysis on three-phase power systems are inherently more complex than on single-phase systems. Although oscilloscopes can capture voltage and current waveforms with high sample rates, further calculations are required to produce key power measurements from the data. The oscilloscope based three-phase solution allows to capture three-phase voltage and current waveforms with higher sample rates, longer record lengths using the HiRes acquisition mode that goes up to 16-bits and with the support of automated measurements produce key power test results. The Power converters based on Pulse Width Modulation (PWM), such as variable-frequency motor drives can complicate measurements since it is very important to extract precise zero crossings for the PWM signals, thus making an oscilloscope a recommended test tool for validation and troubleshooting for motor designers. Special software, designed to automate power analysis on inverters, motors, and drives, greatly simplifies important three-phase power measurements on PWM systems and can help engineers get faster insights into their designs. The Inverter Motor Drive Analysis (IMDA) solution from Tektronix helps engineers design better and more efficient three-phase motor drive systems, taking full advantage of the advanced user interface, six or eight analog input channels, and ‘High Res’ mode (16 bits) on the 5 Series/6 Series B MSO. The IMDA solution provides fast, accurate, and repeatable results for electrical measurements on industrial motors and drive systems for AC induction motors, permanent magnet synchronous motors (PMSM), and brushless DC (BLDC) motors. It can be configured to measure DC to three-phase AC converters, such as those used in the electric vehicles.
Key features and specifications
- Accurately analyze three-phase PWM signals used to drive AC induction, BLDC, and PMSM motors.
- Unique oscilloscope based phasor diagrams indicate VRMS, IRMS, VMAG, IMAG, and phase relationships at a glance for the configured wiring pairs.
- Debug motor drive designs by viewing the drive input/output voltage and current signals in the time domain simultaneously with the phasor diagram.
- Three-phase Autoset feature configures the oscilloscope for optimal horizontal, vertical, trigger, and acquisition parameters for acquiring three-phase signals.
- Measures three-phase harmonics per the IEC-61000-3-2, IEEE-519, or custom limits.
- Measures the system efficiency based on the selected wiring configurations.
- Quickly add and configure measurements through the intuitive drag and drop interface on the 5 Series / 6 Series B MSO.
- Analyze Inverter and Automotive three-phase designs for DC input and AC output wiring configuration.
- Displays the PWM filtered edge qualifier waveform during analysis.
- Displays the test results per Record, or per Cycle mode during analysis for specific measurements.
- Supports Time trend and Acquisition trend plots for specific measurements.
- Supports mathematical conversion of Line-Line to Line-Neutral for specific wiring.
- Supports DQ0 measurements with the phasor plot.
Three-phase power converters such as variable frequency drives require a range of measurements during the design process. The Inverters, Motors, and Drives Analysis package for the 5 Series/6 Series B MSO automates key electrical measurements which are grouped into the Electrical Analysis group. The measurements can be configured to measure the Input or Output wiring configuration.
The measurements can be set to measure 1V1I (1-Phase-2-Wire), 2V2I (1-Phase-3-Wire), 2V2I (3-Phase-3-Wire), 1V1I (1-Phase 2-Wire DC) or 3V3I (3-Phase-3-Wire), and 3P4W (3-Phase-4-Wire) to support various supply and motor configurations. Measurements can be performed line-to-line or line-to-neutral, to support delta and wye or star configurations.
Power waveforms are rarely textbook sinusoids. Harmonics measurements break down non-sinusoidal voltage or current waveforms into their sinusoidal components, indicating the frequency and amplitude for each component.
Harmonics analysis can be performed up to 200th harmonic order. The maximum harmonic order can be set to suit your needs by specifying the range in the measurement configuration. THD-F, THD-R and fundamental values are measured for each phase. Measurements can be evaluated against the IEEE-519 or IEC 61000-3-2 standard, or custom limits. Test results can be recorded in a detailed report indicating pass/fail status.
The Harmonics plot shows the test results for all three phases grouped together so user can correlate the test results between the phases. The plot also shows the test results visually. The harmonics bars are highlighted in green color during a pass condition, and highlight to red color when it exceeds the test limits. This gives a quick insight to the user when debugging for harmonics design.
This measurement provides critical three-phase power sub-measurements including: frequency and RMS magnitudes of voltage and current, crest factors of voltage and current, PWM frequency, and phase angle for each phase. It also displays the sum of true power, sum of reactive power, sum of apparent power components.
Additionally, in the Line-Neutral configuration, this measurement displays True Power, Reactive Power, and Apparent Power components of all the three-phases.
Voltage and current vectors can be displayed on a phasor diagram so you can quickly judge phase shift for each phase and the balance among phases. Each vector is represented by an RMS value and phase is computed using the Discrete Fourier Transform (DFT) method.
The Power quality measurement can be configured to provide critical three-phase power measurements on the output side, including: frequency and RMS magnitudes of voltage and current, crest factors of voltage and current, PWM frequency, true power, reactive power, apparent power, power factor, and phase angle for each phase.
Efficiency measures the ratio of the output power to input power. The IMDA solution supports efficiency of three-phase AC and Inverter configurations. By using the 2V2I method, three-phase efficiency can be measured using eight oscilloscope channels (2 voltage and 2 current sources on the input side and 2 voltage and 2 current sources on the output side). The solution calculates efficiency at each phase (for 3V3I configuration) and the total (average) efficiency of the system based on the different input and output wiring combinations.
Ripple is defined as the residual or unwanted AC voltage on a constant DC component. It is typically measured on the DC bus. This measurement helps to understand how efficiently the signal is getting converted from AC-DC on the input side, and the impact of unwanted components on the PWM signal on the output side.
Optimizing the drive system translates directly into improvements in system efficiency. An important challenge is to tune the drive system control logic optimally based on the three-phase AC signals. Analyzing the system in the AC domain is inherently difficult, hence a conversion from AC to DC domain makes it easier to look into the parameters, and measure them. The direct-quadrature-zero (DQZ or DQ0) transformation is a tensor that rotates the reference frame of a three-element vector, or a three-by-three element matrix to simplify this analysis. The transform is used to rotate the reference frames of three-phase AC waveforms such that they become DC signals. Simplified calculations are carried out on these DC quantities before performing an inverse transform (Inverse DQ0) to recover the actual three-phase AC results.
The most common approach to computing a DQ0 transform involves FPGA programming and complex computations. In addition to performing the transform calculations, probing the feedback signals can be very challenging. Tektronix offers a patented on-scope measurement called DQ0 (Direct Quadrature Zero) under the DQ0 analysis measurement category as an added option. This measurement is supported in the 3V3I configuration, takes the three-phase voltage or current signals from the motor as inputs and converts into D-Q-0 coefficients acting as a powerful debugging tool for the motor designers to tune their PWM controller circuit designs.
This offers unique advantages. First, probing needs are simplified as the same configuration is used for DQ0 computation as Input or Output analysis, and second, the DQ0 values are reported on the scope, both using scalar values on the measurement badge, and as vectors on the phasor diagram for easy correlation between the two plots.
The DQ0 feature is available as an option 5-IMDA-DQ0/6-IMDA-DQ0 on the 5/6 Series MSO.
Dynamic measurements using trend analysis
A common requirement in motor drive analysis is an ability to look at the motor response over longer test times, records, and an extended number of acquisitions to monitor the DUT behavior over varying load conditions. This dynamic measurement helps to understand optimal designs and interdependency between different parameters like voltage, current, power, frequency, and their variance based on the load conditions. The user can manually zoom and get the specific region of interest to look at test results at the particular region of the waveform.
IMDA solution offers two unique trend plots on the power quality measurement to support such requirements:
- Time trend plot
- Acq trend plot
Each plot has its advantages and can be used to plot the supported sub-measurements under power quality measurement. The time trend plot shows the measured value per cycle, or for an acquired waveform (a record), while the acq trend plot shows a mean of the measured value per record, over each of the acquisitions. The acquisition count can be set by the user during the test configuration. This allows users to capture long records of data to perform deep record analysis and understand the dynamic behaviors of the motor response. The plots can be saved as a CSV file for post-processing.
The IMDA software simplifies data collection, archiving, documentation of your design, and development process. It supports the report generation in MHT or PDF formats with pass/fail results for easy analysis.
- Wiring configuration
- 1V1I (1-Phase-2Wire), 2V2I (1 Phase-3-Wire), 2V2I (3-Phase-3-Wire), 2V2I (DC In-AC Out), 3V3I (DC In-AC Out) or 3V3I (3-Phase-3Wire), and 3P4W (3-Phase-4Wire)
- L-L to L-N conversion
- Applicable for 3 Phase-3 Wire (3V3I)1
- Electrical analysis
- Power quality, Harmonics2, Ripple, DQ03, Efficiency4
- Three-phase autoset
- For all measurements
- Time Trend plot, ACQ trend plot, Phasor diagram and harmonics bar graph5
- MHT and PDF format, Data export to CSV format
- Degauss/Deskew (static)
- Automatic detection of probes, Auto Zero. User can deskew voltage and current probes, degauss the current probe from the menus for each channel
- Source support
- Live analog signals, reference waveforms, and math waveforms
1 For 3 Phase-4 Wire (3V3I) the connection is always Line to Neutral and for 3 Phase-3 Wire (2V2I), it is Line to Line.
2 Supports custom limits.
3 Applicable for 3V3I wiring only.
4 For 2V2I wiring only.
5 Range filter as part of measurement configuration.
|Product||Options||Supported instruments||Bandwidth available|
|New instrument order option||5-IMDA||5 Series MSO (MSO56, MSO58)|
|Product upgrade option||SUP5-IMDA|
|Product||Options6||Supported instruments||Bandwidth available|
|New instrument order option||5-IMDA-DQ0||5 Series MSO (MSO56, MSO58)|
|Product upgrade option||SUP5-IMDA-DQ0|
|Product||Options||Supported instruments||Bandwidth available|
|New instrument order option||6-IMDA||6 Series B MSO (MSO66B, MSO68B)|
|Product upgrade option||SUP6B-IMDA|
|Product||Options6||Supported instruments||Bandwidth available|
|New instrument order option||6-IMDA-DQ0||6 Series B MSO (MSO66B, MSO68B)|
|Product upgrade option||SUP6B-IMDA-DQ0|
6 Option DQ0 requires Option IMDA as a pre-requisite
|Bundle options||Supported instruments||Description|
|5-PRO-POWER-1Y||5 Series MSO||1 Year License Pro Power Bundle for 5 Series MSO|
|5-PRO-POWER-PER||5 Series MSO||Perpetual License Pro Power Bundle for 5 Series MSO|
|5-ULTIMATE-1Y||5 Series MSO||1 Year License Ultimate Bundle for 5 Series MSO|
|5-ULTIMATE-PER||5 Series MSO||Perpetual License Ultimate Bundle for 5 Series MSO|
|6-PRO-POWER-1Y||6 Series MSO||1 Year License Pro Power Bundle for 6 Series MSO|
|6-PRO-POWER-PER||6 Series MSO||Perpetual License Pro Power Bundle for 6 Series MSO|
|6-ULTIMATE-1Y||6 Series MSO||1 Year License Ultimate Bundle for 6 Series MSO|
|6-ULTIMATE-PER||6 Series MSO||Perpetual License Ultimate Bundle for 6 Series MSO|
|TCP0030A||Current Probes||3 for 3V3I wiring7|
|THDP0200 or TMDP0200||High Voltage Differential Probes||3 for 3V3I wiring7|
7 For performing efficiency measurement, four quantities are required.