Basic DC Generator Separately Excited Shunt Generator If

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 “countertorque” 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

Basic DC Motor – Shunt Motor

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