{"sections":[{"heading":"Check the model","steps":["Verify that every referenced inductor exists and its inductance is finite and nonnegative.","Check each signed k value and the orientation convention. The mutual inductance is Mij = kij × sqrt(Li × Lj).","Check the whole connected group's symmetric inductance matrix for positive semidefiniteness. The magnetic energy must be nonnegative for every current vector.","Check duplicate pair declarations: the maintained reference says their mutual inductances add."]},{"heading":"Interpret the current diagnostic","paragraphs":["The maintained source documents validation of each connected coupled group, including source locations. Consistent perfect coupling can be valid; changing every k away from 1 is not a general physical correction.","Changing a load resistance or reducing the timestep can obscure an invalid circuit mode without making its inductance matrix passive. Fix the physical model first, then check timestep convergence."]}],"canonical_url":"https://www.sun-magnetics.com/knowledge-base/josim-coupling-validity","url":"/knowledge-base/josim-coupling-validity","known_issues":[],"search_record":{"execution":true,"relatedProducts":[],"version_tags":["JoSIM-Pro 2.9 target"],"text":"Coupled inductors cause divergence or invalid-matrix errors Check the complete inductance matrix for passivity. Keeping each coupling factor between -1 and 1 is necessary but does not guarantee a valid multi-inductor model. JoSIM-Pro 2.9.0 release target; review-build/source evidence Troubleshooting invalid mutual inductance network positive semidefinite nonpassive coupling Check the model Verify that every referenced inductor exists and its inductance is finite and nonnegative. Check each signed k value and the orientation convention. The mutual inductance is Mij = kij × sqrt(Li × Lj). Check the whole connected group's symmetric inductance matrix for positive semidefiniteness. The magnetic energy must be nonnegative for every current vector. Check duplicate pair declarations: the maintained reference says their mutual inductances add.  Interpret the current diagnostic The maintained source documents validation of each connected coupled group, including source locations. Consistent perfect coupling can be valid; changing every k away from 1 is not a general physical correction. Changing a load resistance or reducing the timestep can obscure an invalid circuit mode without making its inductance matrix passive. Fix the physical model first, then check timestep convergence. ","id":"josim-coupling-validity","keywords":"invalid mutual inductance network positive semidefinite nonpassive coupling","kind":"Troubleshooting","title":"Coupled inductors cause divergence or invalid-matrix errors","product":"JoSIM-Pro"},"version":"2.9.0 release target; review-build/source evidence","id":"josim-coupling-validity","related":["/knowledge-base/josim-singular-circuit","/knowledge-base/josim-noise-settings"],"downloads":[],"publication_status":"published","numerical_output":null,"provenance":{"execution_checks":[{"scope":"CLI passive control and non-passive three-coil rejection","result":"passed","articles":["josim-coupling-validity"],"version":"Installed JoSIM-Pro 2.9.0 Windows","id":"VAL-009","records":["troubleshoot-coupling-valid","troubleshoot-coupling-nonpassive"],"limit":"Tests validation behaviour, not solver accuracy across coupled models.","observed":{"each_invalid_pair_k_within_unit_bounds":true,"group_rejected":true}}],"figure_evidence":[],"review_notes":["The owner accepted the modelling explanation on 2 November 2026. Applicable release/platform and unrecorded walkthrough checks remain pending."],"scope":"Recorded inputs/builds only. Complete walkthrough and final-package acceptance remain separate.","verification_requirements":{"gui_method":"not-required-for-this-answer","status":"review-incomplete","illustrations":"not-required-for-this-answer","required":["technical-review","release-applicability","execution","recovery"],"legacy_walkthrough_field":"pending retained; not evidence of a complete scenario"},"sources":[{"id":"support:SUP-013","section":"Generalised editorial finding; outcome qualification retained"},{"id":"josim-pro:docs/manual_source/sections/syntax.tex","section":"Mutual inductive coupling"},{"id":"validation:windows-cli-20261102","section":"VAL-009; scope and limits recorded"},{"id":"owner:technical-review-20261102","section":"JoSIM-Pro 2.9 chosen as the public starting path; release availability must be checked before publication"}]},"title":"Coupled inductors cause divergence or invalid-matrix errors","type":"Troubleshooting","markdown_url":"/_functions/kbResource?path=markdown%2Fjosim-coupling-validity.md","summary":"Check the complete inductance matrix for passivity. Keeping each coupling factor between -1 and 1 is necessary but does not guarantee a valid multi-inductor model.","product":"JoSIM-Pro"}