23/12/2019

Significance of Ripple Factor


  • The output of the single phase rectifier is not pure DC but it also contains some AC components. 
  • The AC component is called as ripple. The ripple factor indicates magnitude of AC component in the output. 
  • Higher value of ripple factor means higher AC component in the output of the rectifier.
Ripple Factor
  • It is defined as the ratio of RMS value of AC component to the DC component in the rectifier output.
       Ripple factor = RMS value of AC component / DC component
  • Smaller value of ripple factor means effective rectification

Equation of Ripple Factor
The effective value of output current is given by
IRMS =  √ ( IDC2 + IAC2 ) …….( 1 )
 IAC = √ ( IRMS2 IDC2 )  ……( 2 )
Dividing equation ( 2 ) by IDC
( IAC / IDC   ) = √ ( IRMS2 IDC2 ) / IDC2
 Ripple Factor  = √ ( IRMS2 / IDC2 1 )
Ripple Factor For Half wave rectifier
IRMS = IMAX / 2
IDC = IMAX / π
Therefore, the ripple factor for half wave rectifier is
Ripple factor = √ [ IMAX / 2 ]2 / [ IMAX / π ]2 – 1
                     = √ [ π / 2 ]2 – 1
                     = 1.21
  • The AC component exceeds than DC component in the output of the single phase half wave rectifier. 
  • The AC component is 121% than the DC component.

Ripple Factor For Full wave rectifier
IRMS = IMAX / √ 2
IDC = 2IMAX / π
Therefore, the ripple factor for half wave rectifier is
Ripple factor = √ [ IMAX / √ 2 ]2 / [ 2IMAX / π ]2 – 1
                     = √ [ π / 2√ 2 ]2 – 1
                     = 0.48
  • The AC component is 48% that of DC component in the output of the single phase full wave rectifier.

Sr.No
Type of Rectifier
Ripple Factor
1
Single Phase Half Wave Rectifier
1.21
2
Single Phase Full Wave Rectifier
0.48

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