Power analyser provides complete analysis for 3-phase motor drives

March 03, 2015 // By Graham Prophet
Teledyne LeCroy’s MDA800 Series of Motor Drive Analysers (MDAs) combine three-phase power analyser static (steady-state) calculations, dynamic three-phase power and mechanical motor analysis capabilities, and high bandwidth (1 GHz) embedded control system debug into a single instrument.

The Motor Drive Analysers (MDAs) are based on the HDO8000 oscilloscope platform and are standard with eight input channels (16 digital channels optional) with 12-bit resolution, 2.5 Gsample/sec sample rate, up to 1 GHz bandwidth and up to 250 Mpts/ch acquisition memory. A complete set of serial trigger/decode and analysis software options, and a wide variety of voltage and current probes are available to use with the MDAs.

The MDAs are aimed designers and manufacturers of motors, motor drives, variable frequency drives, variable speed drives, industrial automation and motion control equipment manufacturers. Design engineers that integrate motors into their designs (vehicles, power tools, appliances, elevators, fans, blowers, compressors, pumps, etc.) can use the product to validate proprietary controls and complete drive system designs. For three-phase systems without motors, the MDAs can be used for basic three-phase power system analysis and debug.

Positioning the instrument, LeCroy notes that a drive system combines three-phase power electronics, motor/mechanical analogue and digital sensors, and embedded controls, with a complex variety of analogue, digital, serial data and pulse-width modulated (PWM) signals. Conventional 8-bit oscilloscopes are appropriate to capture higher-speed embedded control system or power transistor activities: the [conventional] power analyser is a focussed tool for measuring input/output “black-box” drive power and efficiencies, but provides limited or no waveform capture for embedded control or drive system debug.

The MDA permits waveform captures from a drive’s three-phase 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.

Various voltage, current, power (real, apparent, and reactive), phase angle/power factor, and efficiency parameters are calculated on acquired voltage and current waveforms and displayed in a Numerics table. The table is user-configurable and is displayed along with the acquisition waveform, and corresponds to information normally provided by a Power Analyser that measures in a