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

Explain buffer storage, Discuss the layout configuration of FMS with neat a...

Discuss the layout configuration of FMS with neat and clean diagram? Write the disadvantages and advantages of FMS? Write the short note on following: a) Applications of FMS

Give a brief description of differentiating circuits, Q. Give a brief descr...

Q. Give a brief description of differentiating circuits ?                Differentiation is a measure of the rate of change. A differentiating circuit produces an output voltag

Principals applied in product design, What are the broad principals that wi...

What are the broad principals that will be applied in product design to facilitate automated assembly ?

Semiconductor diode, Semiconductor Diode: the semi conductor diode is ...

Semiconductor Diode: the semi conductor diode is formed by simply bringing n and p tripe material together (constructed from same base ge and si), at the instant the two mater

Working of hartley oscillator, Working of Hartley oscillator : When the...

Working of Hartley oscillator : When the collector supply voltage Vcc is switched on, the capictor gets charged. The capacitor discharges through the inductor, setting up oscil

State the drawbacks of in band and out band voice signalling, a. Enlist the...

a. Enlist the benefits and drawbacks of in band and out band voice signalling? b. Describe Channel Associated mode, Channel Non-Associated mode and QuasiAssociated mode of commo

Register addressing , Register Addressing In this  mode the operand ar...

Register Addressing In this  mode the operand are microprocessors  registers only i, e  the operations is performed  within  various  registers of the  microprocessors  only.

Banking system , banking system is the collection of financial entities, in...

banking system is the collection of financial entities, infrastructure and practices which support financial transactions . system tech is a software system to handle their transa

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