Open circuit - Back- emf

1. Positioning and objective

The aim of the test “ Characterization - Open circuit – Motor & Generator - Back-EMF ” is to characterize the behavior of the machine when running in open circuit state.

The analysis of back-EMF characteristics is a first step to evaluate the relevance of the machine design regarding parameters such as: topology, winding architecture, composition of coils and choice of materials.

Note: Warning! When a delta winding connection is considered, the computation doesn’t consider circulation currents. That can lead to a different result than what expected in transient computation.

In such case it is recommended to perform a transient computation in Flux environment. The application “Export to Flux” allows exporting this kind of model with the corresponding scenario ready to be solved.

The following table helps to classify the test “Open circuit – Back-EMF”.

Family Characterization
Package Open circuit
Convention Motor & Generator
Test Back-EMF
Positioning of the test “Characterization - Open circuit - Motor & Generator – Back-EMF”

2. User inputs

From the back-EMF analysis characteristics, it is possible to evaluate the design of the machine on parameters such as: topology, winding architecture, composition of coils and choice of materials.

3. User inputs

The rotation speed is the only necessary input parameter to run this test. The operating temperature of magnets can be defined in the settings “Thermal”.

4. Main outputs

Test results are illustrated with data, graphs and tables.

4.1 Table of results

1) Machine performance – Open circuitBack-EMF characteristics (voltage constant and voltage magnitudes)

  • Flux linkage
  • Flux in airgap
  • Flux density in iron
  • Magnet behavior

4.2 Curves & tables

  1. Phase voltage

    • Phase voltage versus time – Open circuit
    • Phase voltage harmonic analysis – Open circuit (bar graph and table)

  2. Line-line voltage

    • Line-line voltage versus time – Open circuit
    • Line-line voltage harmonic analysis – Open circuit (bar graph and table)

  3. Flux density in airgap

    • Flux density in the airgap versus angular position – Open circuit
    • Flux density in the airgap harmonic analysis – Open circuit (bar graph and table)

  4. Flux linkage

    • Flux linkage versus angular position – Open circuit