Series Wound DC Motor Modeling and Simulation, Considering Magnetic, Mechanical and Electric Power...
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Transcript of Series Wound DC Motor Modeling and Simulation, Considering Magnetic, Mechanical and Electric Power...
Series Wound DC Motor Modeling andSimulation, Considering Magnetic, Mechanicaland Electric Power Losses
B.VIGNESHEdited By
Sarath S Nairwww.technologyfuturae.com
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Contents
Introduction DC Series motor ideal model Series wound DC motor losses Mechnical losses Magnetic losses Electrical losses Additional losses Conclusion References
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Introduction
There are three types of DC motors: shunt wound DC motor, series wound DC motors, compound wound DC motor.
Has relatively high starting torques Has good accelerating torque Have low speed at high loads and high speed at low
loads Under same load conditions rating of series motor
will be less than for a shunt motor
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Diagram of DC series motor (dotted line showing electrical, mechanical and magnetic component)
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SERIES WOUND DC MOTOR IDEAL MODEL here there are no disturbances of any kind are
examined the power losses through the input and output power.
Hence we obtain the following equation Angular velocity ω(τ)= (ξ .k.i(τ).ea+RJ ω(τ - ξ))/
(RJ+ ξ [Rb+k2i2(τ)])
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Armature current
ia(τ)=ea/(R+kω(τ)) Torque
T(τ)=kia2(τ) Mechanical power
Pm(τ)= ω ( τ)*T(τ) Electrical power
Pe(τ)=ea*ia(τ)
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Power loss
Pp(τ)=Pe(τ)-Pm(τ) Efficiency
η (τ)=Pm(τ)/Pe(τ)
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SERIES WOUND DC MOTOR LOSSES
Within the DC motor components energy is exchanged between different sections in these exchange, there are power losses.
Mechanical losses Magnetic losses Electrical losses
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Mechanical losses
the mechanical losses are found in surfaces in contact and constant friction
1.Friction losses in the slip bearings
These losses are due to continuous friction
PRC=0.52dglg√(Vg3 )
Diameter
dg=2.84√(Pm/n) Length
lg=2.5dg Peripheral speed
Vg=(∏.n.dg)/6000
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If the machine has rolling bearings
PRC =150(dg)3n 10-6 the result is multiplied by the number of bearings
PRC= nc.PRC Brush friction power losses PRE
PRE=9.81µePSeVcol
Peripheral speed Vcol=(∏.Dcol.n)/6000 Brushes surface friction Se=∑Brushes surface
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Ventilation Losses
Pv=1.1 V VV2
Cooling of motor is determined by
V=∑losses transformed into heat/1000te The fan speed given by
Vv=(∏.Dv.n)/6000 Mechanical losses of the machine
PMR=PRC+PRE+PV
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Magnetic power loss
Eddy current losses
Pf(t)=w2[ea]2/(12ρ (NA)2 )
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Electrical power losses
Armature copper loss Pcu=R ia2
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Additional losses
In an electric machine there are areas in continuous friction that can contribute to heat emission either by exposing to a long working time and / or by excessive load
The wire conductor resistance R= ρL/A The resistivity is given by ρ= ρα20˚C[1+ α [T-20˚C]] Therefore R(τ)= ρ L/A =L/A ρα20˚C[1+ α [T-20˚C]]
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In developing the mathematical model, there are equations where the resistance and resistivity of the material occurs. Then the following equations are rewritten:
ω(t)= (ξ .k.i(t).ea+R(τ)J ω(τ - ξ))/(R(τ)J+ ξ [R(τ)b+k2i2(t)]) Electrical current
ia(τ)=ea/(R(τ)+kω(t)) Power losses
Pf(t)= w2[e(f)]2 /(12 ρα20˚C[1+ α [T-20˚C]] (NA)2 ) Copper losses
Pcu=R(τ) ia2(τ)
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GENERALIZATION OF A SERIES WOUND DC MOTOR In this section there is a more complete analysis, and
random noises are added aside from considering to the model, considering also the internal losses.
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Angular velocity with deterministic and no deterministic disturbances
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Friction power losses in the slip bearings18www.technologyfuturae.com
Brush friction power loss19www.technologyfuturae.com
Ventilation power loss 20www.technologyfuturae.com
Eddy current power loss21www.technologyfuturae.com
Electrical power loss22www.technologyfuturae.com
Temperature fluctuation23www.technologyfuturae.com
Armature resistance fluctuation24www.technologyfuturae.com
Torque vs angular speed25www.technologyfuturae.com
Torque vs electric current26www.technologyfuturae.com
Angular speed vs electric current27www.technologyfuturae.com
Conclusion
By including the powers losses in the series wound DC motor simulation in addition to the disturbances a series of graphs were obtained which give broader information of the possible behaviour of the system
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References
J. S. Valdez Martínez, P. Guevara López, J. J. Medel Juárez. Series Wound DC Motor Modeling and Simulation, Considering Magnetic, Mechanical and Electric Power Losses. Sept.09
B.L.Theraja.A.K.Theraja.A Textbook Electrical Technology.S.Chand and Company ltd.
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