Shunt dc motor, Electrical Engineering

Assignment Help:

Shunt DC motor

In this arrangement, the armature and field coils are connected in parallel (the motor is called 'shunt connected').

 

1845_shunt DC motor.png

 

Analysis

With reference to the diagram above,

1226_shunt DC motor  1.png

Normally If is a approxmetely constant and Ra is very small (so V>>Ia.Ra).Therefore the motor speed is approximately constant for a given supply voltage, V. The speed may be controlled by reducing the field If  by increasing the field resistor Rf   is reduced and the so Φ speed  increases.

 

  • If  is approximately constant in this motor configuration, determined by the supply voltage and the resistance of the field coils. 
  • Since Ra is very small, V>>Ia.Ra.Hence, although Ichanges significantly with change in motor speed, (and hence also the torque), the motor speed need only change very slightly to cause a large change of armature current and torque produced. This means that the torque can overcome any imposed mechanical load  with very little change of motor speed (so shunt motor has approximately  onstant speed vs load characteristics)
  • Since the armature winding resistance is small, measures must be taken to limit the surge of armature current when it is first
    switched on (i.e. increase the supply slowly to allow the motor to gain speed before full supply voltage is applied). 
  • Methods for controlling the speed are:

    i)    vary the resistance of the field circuit, Rf . Increasing Rf  a increases the speed.

    ii)   change the applied voltage. Increasing V increases the speed.

    iii)  change Ra by means of an extra (small) resistance in the armature circuit. Increasing Ra  reduces the speed.

    iv)  increasing the mechanical load reduces the speed only slightly. (Approx. constant speed vs load characteristics)

    The preferred method of speed control atconstant supply voltage is method (i)because the field current is low compared to the armature current, and a resistance added in series with the field windings results in less power being wasted.

 


Related Discussions:- Shunt dc motor

Determine the atomic weight of an atom, Atomic weight of an atom is (A...

Atomic weight of an atom is (A) Sum of the number of protons and neutrons. (B) Sum of the number of protons and electrons. (C) Sum of the number of electrons and n

Define the objectives of load flow analysis, Define the Objectives of Load ...

Define the Objectives of Load Flow Analysis The objectives of load flow analysis are: (i) To analyse an existing power system, future expansion or a new power system plan.

Switching, With neat diagrams explain the configuration of a step-by-step s...

With neat diagrams explain the configuration of a step-by-step switching system

., ABOUT ASSIGNMENT ON MAGNETIC INDUCTION NEAR A LONG WIRE

ABOUT ASSIGNMENT ON MAGNETIC INDUCTION NEAR A LONG WIRE

State the nyquist sampling theorem, (a) Which one of the four digital-to-a...

(a) Which one of the four digital-to-analog conversion techniques (ASK, FSK, PSK or QAM) is most susceptible to noise? Explain your answer. (b) Given the bit pattern 01001110,

What is the voltage gain, Q. What is the voltage gain? voltage gain is ...

Q. What is the voltage gain? voltage gain is the ratio of output voltage to input voltage. It is represented as Av,vo-voltage output,Vi-voltage input,Ic-collector current,Ie

Electricity hazards in the laboratory, ELECTRICITY HAZARDS IN THE LABOR...

ELECTRICITY HAZARDS IN THE LABORATORY : You've probably read about, or heard of, people falling onto high voltage rails or cables and surviving thousands of volts. As a contra

Determine the disadvantages of expert systems, Determine the Disadvantages ...

Determine the Disadvantages of expert systems -  Lacks common sense in some decision making processes -  Errors in the knowledge base can result in incorrect decisions being

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