Stator voltage control methods - motor control , Electrical Engineering

Assignment Help:

Stator Voltage Control Methods

By  controlling  the applied voltage  the speed  of an  induction motor  can be  controlled. Since  the output  torque of 3-? induction motor  is given by T sI/2 and current  is proportional  to voltage . therefore  as voltage  is reduced to reduce speed  for the  same current motor  develops  lower torque.

If  stator  copper  loss core  loss and friction and wind age  loss are  ignored then motor  efficiency  is given by

Η = Pm /Pg = (1-s)

This  equation shows that the  efficiency  falls  with decrease in speed. The speed  control  is essentially obtained by dissipating a portion of rotor  power in  rotor resistance. Thus  not only  the efficiency if low the power dissipation occurs  in rotor itself which may  overheat the rotor.  Variable voltage for  speed  control  is obtained  using  ac voltage  controllers as shown  in figure.

 By  changing the  conduction  period of the SCR  the magnitude  of stator  voltage  can be controlled from zero  to full supply voltage. Thus  we can obtain the speed variation.  But this  methods is suitable for small and medium  size induction motors because  supply  current contains harmonic components. The  another disadvantage of this method is that a heavy current  flows through  stator if speed is reduced therefore  there may be  undue heat  generation is  stator windings.

 


Related Discussions:- Stator voltage control methods - motor control

Find the meter reading for sine wave, Q. ADMM (digital multi meter) reads t...

Q. ADMM (digital multi meter) reads true rms values of current. If the peak value of each of the following periodic current waves is 5 A, find the meter reading for: (a) a sine wav

Determine the largest crest factor, A quantizer has 130 quantum levels that...

A quantizer has 130 quantum levels that exactly span the extremes of a symmetrically ?uctuating message with step size δv = 0.04 V. Determine the following: (a) |f(t)|max.

Dc generator, Why armature core in a DC machine is constructed with laminat...

Why armature core in a DC machine is constructed with laminated steel instead of solid steel sheets

Insulation resistance, how can we increase insulation resistance of sheet

how can we increase insulation resistance of sheet

Where holes are majority carriers, Holes are majority carriers in (A) ...

Holes are majority carriers in (A) P-type semiconductors.  (B) N-type semiconductors. (C)  Insulators.            (D) Superconductors. Ans: Holes are m

Microwaves, derive the s parameters of a network by smith chart

derive the s parameters of a network by smith chart

Switching characteristics - power semiconductor devices, Switching charact...

Switching characteristics When  a positive signal  is applied GTO starts  conducting before  initiation of  conduction anode  current  is zero  and anode to cathode voltage Va

What are the application specific instruction processors, What are the appl...

What are the application specific instruction processors? Single purpose processor or ASIP (Application Specific Instruction processor) a. Floating point Coprocessor and Gra

Find the effective area of a half-wave dipole, Q. The effective area of a d...

Q. The effective area of a dipole is given by A e =0.13λ 2 . Find the effective area of a half-wave dipole at 3 GHz.

Explain classification of energy band materials, With the help of energy ba...

With the help of energy bands explain how conduction takes place in conductors, semiconductors and insulators. On the basis of energy band materials are categorized as insulato

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd