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

Illustration of embedded web technology, Illustration of embedded web techn...

Illustration of embedded web technology An oven comprise an embedded processor. Owner can use a web ready mobile phone anywhere to control the oven remotely. By accessing a

Show advantages of oscillators, Q. Show Advantages of Oscillators? Alth...

Q. Show Advantages of Oscillators? Although oscillations can be produced by mechanical devices (e.g. alternators), but electronic oscillators have the following advantages:

Draw the power flow diagram showing voltages, For the 3 bus system shown be...

For the 3 bus system shown below all values are given in pu on a 100MVA base (a) Use Matlab functions lf gauss and lf Newton to find power flow solution for the system, accurate

Describe the automated flow lines, Describe the Automated flow lines with s...

Describe the Automated flow lines with suitable diagrams? Also provide the Reason for Automating? Discuss the Work part Transfer Mechanisms in detail? Discuss the requirement fo

What do you mean by frequency response, Q. What do you mean by Frequency Re...

Q. What do you mean by Frequency Response? As with all electronic circuits, op amps have limited frequency response. Because of the negative feedback of the circuit, the passba

Carry flag - sub subtract instruction , Carry Flag CY is  reset  as e...

Carry Flag CY is  reset  as explained  above.  ( in chapter 1 we have  sen in the 2 complement  methods of subtraction that  the carry  is set  when the result is positive. He

Find the inductor current and voltage, Q. The energy stored in a 2-µH induc...

Q. The energy stored in a 2-µH inductor is given by w L (t) = 9e -2t µJ for t ≥ 0. Find the inductor current and voltage at t = 1 s.

What is error-rate control, Q. What is error-rate control? A system is ...

Q. What is error-rate control? A system is said to possess error-rate damping when the generation of the output in some way depends upon the rate of change of the actuating sig

Lc filter, LC Filter To the load resistance R L the ripple factor i...

LC Filter To the load resistance R L the ripple factor is directly proportional in the inductor filter and inversely proportional to R L in the capacitor filter. Hence i

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