This　paper　analytically　investigates　expressions　of　an　oscillating　motor＇s　air-gap　torque　resulting　simultaneously　from　dynamic　electromagnetic　and　dynamic　mechanical　components.　The　electromagnetic　torque　is　generated　in　the　air　gap　when　the　motor　is　supplied　by　variable　frequency　drives　(VFDs),　such　as　pulsewidth　modulated　voltage　source　inverters　or　load　commutated　inverters.　Whereas,　the　mechanical　torque　components　might　result　from　dynamic　mechanical　processes,　such　as　wind　turbine　blades,　oil　and　gas　fluid　fluctuation,　and,　for　emulating　dynamic　mechanical　loads,　a　load-side　VFD.　Simple　and　straightforward　analytical　relationships　between　electrical　and　mechanical　harmonics　are　developed　to　understand　the　propagation　of　mechanical　dynamics　to　the　electric　side　and　vice　versa.　Intensive　numerical　simulations　have　been　carried　out　to　support　the　theoretical　analysis.　Time　and　frequency　domain　results　confirm　the　robustness　of　the　proposed　relationships.　Finally,　laboratory　experimental　test　results　also　confirm　the　accuracy　of　the　proposed　relationships.　©　1982-2012　IEEE.