No Load curve + Back-emf

Positioning and objective

The aim of the test “Characterization - Open circuit – Generator – No Load” is to characterize the behavior of the machine when running in a no–load state.

The analysis of the machine’s no-load characteristics is a first step to evaluate the relevance of the machine design regarding not only parameters such as topology, winding architecture, composition of coils and choice of materials, but also the impact of the applied field current value in the magnetic saturation of the machine.
Warning: When a delta winding connection is considered, the computation doesn’t consider circulation currents. That can lead to a different result than what was expected in transient computation.

In such a case, it is recommended to perform a transient computation in Flux® environment. The application “Export to Flux” allows exporting the model with the corresponding scenario ready to be solved.
Characterization - Open circuit – Generator – No Load - Overview

User inputs

The maximum field current value and the rotation speed are the only necessary standard input parameters to run this test. The operating temperature of the field winding and damper bars, if existing, can be defined in the settings “Thermal”.

Additionally, if the user wants to run a complete back-emf test for a single point, specified with a field current value, the two concerned inputs are available as standard inputs as well.

Main outputs

Test results are illustrated with data, graphs and tables.

Main results
  • No-load characteristics - Phase voltage rms value versus the field current value – No-load (line graph and table)
Graphs & tables
  • Machine performance – Open circuit, Back-EMF characteristics (voltage constant and voltage magnitudes), Flux linkage, Flux in airgap, Flux density in iron
  • Phase voltage (Phase voltage versus time – Open circuit, Phase voltage harmonic analysis – Open circuit (bar graph and table))
  • Line-line voltage (Line-line voltage versus time – Open circuit, Line-line voltage harmonic analysis – Open circuit (bar graph and table))
  • 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))
  • Flux linkage (Flux linkage versus angular position – Open circuit)
Characterization - Open circuit – Generator – No Load – The main outputs