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

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 E a >E bat Current I a flows to charge E bat

From a Circuit Point-of-View “Generate” voltage E a When supplying current, the machine develops a “counter- torque” in opposition to the driving torque

Motor-to-Generator Transition “Uncouple” the Prime Mover Eventually, E a will decrease so that E a <E bat I a flows as shown Armature turns in the same direction

From a Circuit Point-Of-View Counter-emf, E a, is induced, opposing the driving voltage E bat 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