![]() The influenceof the armature windingrnmf.onmachinebehavioris exploredwith particularemphasis on its effecton cnmmutationand its externalcharacteristics.The subjectof commutation occupiesa position of preeminencein the study of d-c rnachinesbe-Ĭause without good commutation the machine is rendered almost useless.The motor speed-torquecllrves are analyzed anri ¿rlsothe various methods of speed coltrol. ![]() ![]() Here rveinvestigatethe operationalcharacteristicsof the yarioustypes of d-c machines,beginningwith a descriptionof how the direct voltageis obtained. The principlesunderlyiugbasictorque productionanclinducedvoltagesin the d-c machineare outlined in detail in Chapter 3. ![]() Unfortunately, the need for a mechanicalrectifier(in the form of a commutator)to convertthe a-c emf that is inducedin eacharniaturecoil to a unidirectionalvoltagemakesit oueof the leastruggeci of electricmachines¿s well as moreexpensive. Theseare featnresthat are responsible for its usein the really tough jobs in industry, such as are found,in steel mills. It is capableof quick reversals, and speedcontrolovera'rangeof 4 : I is achievedwith relative rvith all otherelectromechanical easein comparison energy-conyersion devices. It can provide high starting torquesas well as high acceleratingand deceleratingtorques. The d-c machineis a highly versatilemachine.
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