# B.VIGNESH Edited By Sarath S Nair

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B.VIGNESH Edited By Sarath S Nair www.technologyfuturae.com
Series Wound DC Motor Modeling and Simulation, Considering Magnetic, Mechanical and Electric Power Losses B.VIGNESH Edited By Sarath S Nair

Contents Introduction DC Series motor ideal model
Series wound DC motor losses Mechnical losses Magnetic losses Electrical losses Additional losses Conclusion References

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

Diagram of DC series motor (dotted line showing electrical, mechanical and magnetic component)

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)])

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)

Power loss Pp(τ)=Pe(τ)-Pm(τ) Efficiency η (τ)=Pm(τ)/Pe(τ)

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

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

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

Cooling of motor is determined by
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

Magnetic power loss Eddy current losses Pf(t)=w2[ea]2/(12ρ (NA)2 )

Electrical power losses
Armature copper loss Pcu=R ia2

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]]

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)

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.

Angular velocity with deterministic and no deterministic disturbances

Friction power losses in the slip bearings

Brush friction power loss

Ventilation power loss

Eddy current power loss

Electrical power loss

Temperature fluctuation

Armature resistance fluctuation

Torque vs angular speed

Torque vs electric current

Angular speed vs electric current

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

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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