Thursday, 15 February 2018

How We Can Speed Control Of Electrical Machine!!

How We Can Speed Control Of Electrical Machine!! 



One Of The Most Useful Method For Speed Control Is Given As Below In Article




It is an application of the Method Of Speed Control by the use of variable voltages to the armature of the motor whose speed controlls required.




 Fig  shows the sehematie diagram of the ward Leonard method or speed of a dc shunt motor.


Recommended Articles For Better Knowledge :


  • The Speed Control Of DC Motor by means of an adjustable voltage generator connected across the armature dc motor terminals of the called Ward Leonard Method. 
  • As shown in figer M1 is the main dc motor whose speed is to be controlled, G is separately excited de generator which can be driven either by a constant speed 3 phase AC motor (M2) or dc motor. The field winding of the main motor (M1) is Permanently Connected across the dc supply. The armature terminals of the main motor (M1) are connected directly to the armature terminals of dc generator.


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In this method, a variable voltage is applied to the Armature Of Main Motor (M1) for controlling the speed.


This variable voltage is obtained a Motor-Generator set (M-G set). The variable voltage of the generator can be obtained by varying resistance (field current) in its field circuit.


Thus, the applied voltage to the main motor can be changed from zero to maximum value and hence any Desired Speed the main motor can be obtained.

This method of Speed Control is most effectively used, where a wide very sensitive type of speed control is needed, such as in paper mills, elevators etc.

Advantages


  • (1)very fine speed control over the whole range from zero to normal rated speed in both directions can be obtained.
  • (2)Uniform acceleration can be obtained.
  • (3)Good speed regulation


Disadvantages


  • (1)This arrangement is costly due to two extra machines.
  • (2)overall efficiency of the system is low.


Question part Of This Article :

(1)give one example  an application of the method of speed control by the use of variable voltages to the armature of the motor whose speed controlls required.???
Ans: ward Leonard method

(2)what is ward Leonard method??? 
Ans:The speed control of dc motor by means of an adjustable voltage generator connected across the armature dc motor terminals of the called Ward Leonard method.

(3) give advantage of ward Leonard method??
Ans:(1)very fine speed control over the whole range from zero to normal rated speed in both directions can be obtained.
(2)Uniform acceleration can be obtained. (3)Good speed regulation

(4) list the disadvantages of ward Leonard method??? 
Ans:(1)This arrangement is costly due to two extra machines.
 (2)overall efficiency of the system is low.

(5)give a example where use ward Leonard method for speed controlled??? 

Ans:paper mills, elevators etc.


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