Polyphase Motor Analysis

Christoph Wiedner, Power Manager, DEWETRON GmbH

Why polyphase motors are used?

Polyphase motors are used in response to the demand for high efficiency by international standards (like IEC 60034), the rising costs of copper and metal sheeting, and increasing demands for durability and product quality have stimulated the development and use of poly-phase motors and poly-phase-drive-trains. By its design,it’s possible to reduce copper for the windings and metal sheets of the stator. Poly-phase motors are more efficient due to reduced copper and rotor losses as well as the reduction of Harmonic loads. Harmonics, which are the result of direction of the rotor and the opposing rotary field produced by the stator,create a cogging torque that generates noise and vibration. It’s possible to increase the range of electrical vehicles and industrial drives by reducing harmonic loads. Another benefit to polyphase motors is the higher torque of those motors resulting from the lower harmonic load during start up procedures. Reduction of the 5. and 7. harmonic help to reduce losses, noise, and vibration which results in highly efficient motors and drive trains! If we compare a 3-Phase and 6-Phase Motor with 30kW we can see a higher efficiency of 1% on the side of the 6-Phase motor.

Challenges for power analyzer

It’s a fact that conventional power analyzers can manage up to 4 or 6 power channels, max. This leads to the problem of power analysis of polyphase motors and polyphase drive trains. The need for reliable and traceable efficiency calculations requires power analyzers with more than 6 power channels, the capacityto storethe raw data, precision power calculation of several power groups with variable synch sources and the option for the online calculation of mechanical parameters and mechanical power. This is precisely where we come in with our MIXED-SIGNAL POWER-ANALYZER!

The DEWE2-PA7 MIXED-SIGNAL POWER-ANALYZER combines the strengths of a conventional power analyzer, a gapless recorder and a power scope. With up to 12 power channels, online calculation of several power groups with variable sync sources and up to 7 phases for each group, the PA7 is the need based power analyzer for analysis of polyhase motors and drive-trains. Moreover, it’s possible to record and analyze any analog or digital signal,turning the the PA7 into a mixed signal power analyzer.

Intuitive operation of a mixed signal power analyzer

State-of-the-art hard- and software engineering combined with innovative usability makes it easy to concentrate on the important things-completing your tasks! OXYGEN™ Measurement Software is the solution for power analysis,offering minimal configuration effort and intuitive operation. A Touch display, multi touch gestures, predefined schematics and unrivaled stability and precision make the DEWE2-PA7 the iPhone of Power Analyzers.

Application Example: Power Analysis of a 6-phase motor powered by 2 3-phase inverters

Configuration:

  • 1x DEWE2-PA7
  • High precision Power Analyzer with up to 12 Power Channels
  • High resolution 9’’ multi-touch display
  • 7 Slots for TRION-Series Modules
  • Integrated power supply for CT’s
  • 3x TRION-1820-POWER-4
  • 12 High Voltage Inputs
  • 12 Direct Current Inputs or 12 Low Voltage Inputs for Current Transducers
  • 1000 Vrms, 20 Arms direct current input, up to 5000 A with CT’s
  • 1x TRION-BASE for counter inputs
  • 1x OXYGEN-OPT-POWER-ADV
  • Advanced Power Calculation including Harmonics, Higher Frequencies, Supra Harmonics, Flicker, Flicker-Emissions, …

OXYGEN Setup

  • 1x 6-phase power group for polyphase motor analysis
  • 2x 3-phase power analysis for inverters
  • 1x calculation of total power consumption of 2x inverters
  • 2x Efficiency calculation of inverters via math library
  • 1x calculation of mechanical power through counter input and math library
  • 1x calculation of losses between electrical and mechanical power

Online Calculated Parameters and Values:

  • Real periodic values of Voltage, Current, Power
  • RMS Values of Voltage Current, Active Power, Reactive Power, Apparent Power
  • Harmonics, Interharmonics, Higher Frequencies and Supra Harmonics
  • Online energy calculation in positive and negative direction
  • Calculation of losses and efficiency through strong math Library
  • Calculation of Flicker and Flicker Emssions

Benefits of a DEWETRON Power Analyzer:

  • Up to 12 Power Channels in a single device (e.g. 2x 3-phase + 1x 6-phase power group configuration)
  • High precise and reliable interval and cycle-by-cycle power calculation up to 7 Phases
  • DC and AC (0.2 Hz to 1500 Hz for Fundamental) power calculation for several power groups simultaneously
  • Guided, time saving power group configuration through schematics
  • Gapless recording (raw data!) of any digital or analogue signal
  • Distributed Power Analysis with up to 100m between measurement nodes
  • And many more …

Cost Savings:

  • With a DEWETRON Power Analyzer you can replace several devices (A Recorder, a conventional Power Analyzer and a Power Scope)
  • One file format and common data base for your analysis – single point of truth
  • Reduce cost for calibration, maintenance and trainings
  • Substantial time savings due to easy configuration and operation, freeing resources for other important tasks
  • Increase in efficiency, loss reduction due to high quality and high accuracy power analysis
  • DEWETRON’s PA ensures reliability of electrical motors and drive-trains (e.g. supporting TQM and other certifications)

Summary:

A DEWETRON power analyzer is the professional tool for high precision and reliable polyphase power analysis,possessing an unrivaled usability and offering time and cost savings. Gapless recording of any digital or analogue signal and reliable, precision power analysis turn the DEWE2-PA7 into a MIXED-SIGNAL-POWER-ANALYZER.

Where there are polyphase motors there are DEWETRON Power Analyzers!