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1. Effect Of Load and Field Current Changes in
Synchronous Motor
Name :Mir Rafsan
Student ID :1711013
Presentation -01

2. Objective:
For Load and Field Current Changes We
will see how Internally Generated Voltage
(EA ) power factor (Pf) and Armature
current (IA ) changes
Synchronous motor are Synchronous
machines used to convert electrical
power to mechanical power

3. Effect Of Load Changes in Synchronous Motor:
We know Internally Generated Voltage,
E A =K ϕ ω ω and ϕ Constant So E A =Constant
where ω =synchronous speed of Motor and ϕ =Flux
V ϕ
IA
E A
J IA X s
δ
θPhasor Diagram
For lagging condition Phasor Diagram

4. Leading power factor Unity Power factorLagging Power Factor
θ1
θ2
δ2
δ1
θ4
θ3
δ3
δ4
δ5
V ϕV ϕ
V ϕ
IA5
IA3
IA4
IA2
IA1
EA5
EA3
EA4
EA1
EA2
Load δ IA θ CosθLoad δ IA θ Cosθ
Locus
point

5. Effect Of load changes in Leading ,Unity
and Lagging Power factor

6. Real Power Supply ∝ Load on synchronous Motor (As Load=Constant So
P=Constant)
p=
3 Vϕ E Sin δ
Xs
EA Sin∝=K P=√3 VICos θ IA Cos θ=k
E=K ϕ ω ω=constant ϕ ∝ If E A ∝ If
P=Real Power
ϕ = Flux
Effect on Field Current Changes:

7. If EA I A θ Cosθ If EA I A θ Cos θ
V ϕ V ϕ
V ϕ
θ2θ1 θ4
θ3
IA4
IA3
IA1
IA2
IA5
E A1
E A2
E A3
E A4
E A5
Lagging PF Leading PF Unity PF
IA Cos θ IA Cos θIA Cos θ
E A Sinδ E A Sinδ
E A Sinδ
Figure:Effect on Field Current Changes

8. Effect of Field
Current in
Leading ,Unity
and Lagging
Power factor
V curve
Synchronous
Motor

9. Thank You