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Basic DC Generator. Separately Excited Shunt Generator. If the Rheostat resistance is reduced, I f increases, Φ p increases, E a increases, as shown in the “Magnetization” Curve. Operating Point. E bat = I f (R f +R rheo ) looks like y=mx + b Superimpose on the Magnetization curve.
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Basic DC Generator Separately Excited Shunt Generator
If the Rheostat resistance is reduced, If increases, Φp increases, Ea increases, as shown in the “Magnetization” Curve
Operating Point Ebat = If(Rf +Rrheo) looks like y=mx + b Superimpose on the Magnetization curve
Operating Point (continued) Intersection with the Magnetization curve yields the operating point
Generator-to-Motor Transition • Permanent-magnet field • One-turn armature • Drive so that Ea>Ebat • Current Ia flows to charge Ebat
From a Circuit Point-of-View • “Generate” voltage Ea • When supplying current, the machine develops a “counter-torque” in opposition to the driving torque
Motor-to-Generator Transition • “Uncouple” the Prime Mover • Eventually, Ea will decrease so that Ea<Ebat • Ia flows as shown • Armature turns in the same direction
From a Circuit Point-Of-View • Counter-emf, Ea, is induced, opposing the driving voltage Ebat • Machine develops a driving torque
Reversing Direction Method 1 Reverse the Armature Current
Reversing Direction – Method 2 Reverse the Direction of the Field
Characteristics of a Shunt Motor • Shunt field provides the pole flux • Power in the field is independent of the LOADing • Generate counter-emf in the armature