DC Machine DC Generator DC Motor DC Machine: Conductor carrying - PDF document

DC Machine

DC Generator DC Motor DC Machine:

Conductor carrying current when placed in a magnetic field experience Mechanical force. B Fleming’s Left hand Rule F I

DC M/C : Principle of Operation a 1 Field a 2 winding N a a S 1 2 Armature Armature Conductor V f

S DC M/C : Principle of Operation 2 a F F 1 a N

S DC M/C : Principle of Operation a 1 F F 2 a N

DC M/C : Principle of Operation F N a a S 1 2 F Commutator & Brush V a

S DC M/C : Principle of Operation a 1 F a V F 2 a N

DC M/C : Principle of Operation F N a a 1 S 2 F = θ F BIL sin Ia θ � 0 90 V a ∝ φ T I a

Contradiction from Faraday’s Law = θ E 2 BLv sin b ∝ φω E F b N a a 1 S 2 F Fleming’s right hand rule assigns the polarity of V a induced voltage, E

DC M/C : Principle of Operation Fleming’s right F Hand rule _ + N a a 1 S B 2 I F a _ + F V a (E b ) I

A Realistic DC Machine Eb N S _ + I a + _ = φ T K I e V = φω a E K b e

DC Machine: Steady state model and behaviour

Speed-Torque Characteristics _ _ a + a + I I a

ω Feed back between electrical and J dt d + L T = T mechanical world Load T L ω Motor T

DC Machine: Torque vs. speed Characteristics

For Sep. Excited Motor: a

For Series Motor: a

Speed – Torque Characteristic

Speed Control of Separately excited dc motor

Armature Resistance Control

Armature Resistance Control

Combined Armature Voltage & Field Control

Combined Armature Voltage & Field Control Control Philosophy: •For obtaining speeds lower than the base speed: Vary armature voltage •For obtaining speeds higher than the base speed: Vary field flux (field- voltage)