Complete Motor Drive Power Analysis with 8 Channel 12-bit Oscilloscope

Motor Drive Power Analysis software for Teledyne LeCroy HDO8000 High Definition Oscilloscopes (8 analog channels with 12-bit ADC resolution) provides three-phase numerical and waveform power analysis from motor drive input through motor mechanical output. Included are real, apparent, and reactive power measurements, power factor and phase angle, efficiency, and various voltage and current parameters. Both two-wattmeter and three-wattmeter methods are supported, as well as line-line to line-neutral voltage conversion. Motor speed, position, and torque integration are the most complete available.

Power electronics is one of the fastest growing electronics market segments, with growth driven by government mandates for motor efficiency, “green” (environmental) initiatives, and complex control requirements. Power electronics are commonly used in a variety of power conversion devices such as switch-mode power supplies, DC-DC converters, AC-AC drives, and DC-AC inverters. Higher power (1 kW) and/or three-phase power conversion devices typically utilize complex embedded control designs to regulate performance, and these complex embedded control systems can contain very high speed (100s of MHz) microprocessors with mixed-signal (analog, digital, serial data) interface architectures. Power Analyzers have been the tool of choice for measuring input/output system power consumption and efficiency, and oscilloscopes have been utilized for embedded control and system debug. However, several new developments are occurring that could change the existing test paradigms.

Complete drive system debug

A complete drive system is a complex mix of three-phase power electronics, motor/mechanical analog and digital sensors, and embedded controls, with a complex variety of analog, digital, serial data and pulse-width modulated (PWM) signals. The HDO8000 oscilloscope with Motor Drive Power Analyzer software permits waveformcaptures from the drive power section, individual power transistors, and embedded control system, and performs coincident three-phase power analysis of the power section waveforms in one high-performance instrument, enabling debug and analysis of all aspects of the complete motor drive.

Numeric power table

A user-configurable table is provided for display of a selection of power (real, apparent, reactive), power factor, phase angle, efficiency, voltage, current or motor mechanical parameters. Up to 120 values total may be displayed in 10 rows and 12 columns for any selection of input or output individual phase or total three-phase values, DC bus/link, or motor mechanical. Efficiency can be also be displayed. The Power Table values displayed are mean values from a statistical data set that is calculated on a “per-cycle” basis using a user-defined synchronization source signal. This display corresponds to what is normally provided by a power analyzer.

Detailed waveforms

In addition to the mean table values, a waveform showing any per-cycle measurement parameter variation can be displayed by simply selecting a table value. This waveform is time-correlated with other waveforms acquired by the HDO8000 oscilloscope and can be used to correlate complex drive behaviors to other control or power system waveforms, and to debug drive system problems. Statistical detail of the measurement set can also be displayed. This additional information goes well beyond what is provided by a Power Analyzer.

Dynamic drive response

The long acquisition memory in the HDO8000 (up to 250 Mpts/Ch) provides unique capabilities for motor and drive dynamic response analysis. For example, 25 seconds of continuous acquisition capture is possible at a sample rate of 10 MS/s. This permits complete understanding of dynamic drive behaviors, such as startup, application of load, or fast changing load conditions, and correlation of drive response problems to control system instructions or power section failures.

Motor mechanical integration

The combination of analog and digital inputs on the HDO8000 series of mixed-signal oscilloscopes provides more motor integration capability than a power analyzer. For instance, not only can standard analog and digital (pulse) tachometers be integrated for speed sensing, but analog Resolvers, digital Quadrature Encoder Interface and Brushless DC Hall Sensors may also be used to provide speed, direction, and absolute position information, not normally possible with a power analyzer.

Flexible setup capability

The eight analog input channels provide capability for direct measurement of three voltage and three current signals from a drive input or output. However, support is provided for a two-wattmeter measurement method for three-phase power, which allows three-phase measurements to be made using two voltage and two current signals. Therefore, input/output effi ciency measurements of a complete drive can be performed using the eight analog input channels. Support is also provided for a line-line to line-neutral voltage conversion so as to allow intuitive line-line probing with per-phase line-neutral reported results.

Complete drive status debug

A complete drive system is a complex mix of three-phase power electronics, motor/mechanical analog and digital sensors, and embedded controls, with a complex variety of analog, digital, serial data and pulse-width modulated (PWM) signals. The HDO8000 oscilloscope with Motor Drive Power Analyzer software permits waveform captures from the drive power section, individual power transistors, and embedded control system, and performs coincident three-phase power analysis of the power section waveforms in one high-performance instrument, enabling debug and analysis of all aspects of the complete motor drive

Most complete motor mechanical integration

Simple integration is provided for nearly any type of speed, rotation or position sensor, including analog and digital (pulse) tachometers, Brushless DC (BLDC) Hall sensor, Quadrature Encoder Interface (QEI), and Resolvers. Additionally, Hall sensor and QEI signals can be integrated through digital inputs, preserving valuable analog input channels for other signals.

Summary

Teledyne LeCroy is offering some compelling new solutions to the fast-growing power electronics and power conversion markets. Whether the new solutions will give drive engineers pause before they purchase a new power analyzer remains to be determined. But if the Teledyne LeCroy HDO8000 Oscilloscope with Motor Drive Power Analyzer software delivers on its promises, it is sure to carve out a niche with those engineers looking to debug complex drive and control system interactions, and provide very reasonable power analysis numerical results as well.

www.teledynelecroy.com


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