AC voltage regulator (AC to AC converter)

AC voltage regulator (AC to AC converter)

AC voltage regulator(controller)  is a device which is convert fixed Alternating voltage to variable Alternating voltage without changing frequency.

  • There are Two types of ac voltage regulator.
  1. Half wave AC controller
  2. Full wave AC contoller

Half wave AC controller

  •  fig shows voltage regulator using one thyristor in Anti-parallel with one diode.load is resistive, by changing the value of firing angle α of thyristor S we can controlled the load voltage.

hlaf  wave AC voltage regulator

Working:
  • In positive half cycle of AC supply SCR S is turn ON at ωt=α. during this load voltage is positive now SCR will be turn OFF due to natural commutation at ωt=π. load current and source current are positive.
  • In negative half cycle of AC supply Diode D1 will turn ON at ωt=π. During these cycle load voltage is negative. and load current and source current are negative.
  • By controlling the firing angle α of the SCR we can control AC load voltage.

Average value of output voltage is given by,

= √2 Es/2π (cosα-1)

If α is varied from 0 to π, output voltage varies from Es to Es/ √2 and average value of output voltage varies from 0 to -√2 Es / π .

wave form is shown in fig…..

waveform of half  wave AC voltage regulator

Full wave AC controller

  • Single phase full wave Ac controller consist two thyristors connected in anti-parallel.
  • Load is resistive for low power application is used ,By controlling the firing angle α of the SCR we can control AC load voltage.
  • Fig shows single phase full wave ac voltage controller with resistive load.

Full wave AC  voltage regulator

Working:
  • During positive half cycle thyristor T1 is forward bias and during thyristor T2 is forward bias.
  • During positive half cycle, T1 is trigger at firing angle α . T1 start conducting and source voltage is given to the load from ωt=α to π. At π Vs and Is fall to 0. after π T1 is reverse bias therefore it is turn OFF.
  • During negative half cycle, T2 is trigger at (π+α) and T2 conducts from π+α to 2π.  After 2π T2 is reverse bias and it is commutated
  • From 0 to α , T1 is forward bias there for VT1 = Vs
  • After π, π to (π+α)  T1 is reverse  bias there for VT1 =Vs

average value of output voltage is given by,

Vs[1/π{π-α+(sin2α/2)}]½

If α is varied from 0 to π, The average output voltage is controlled from voltage Vs to 0.

wave form is shown in fig…..

wave form Full wave AC  voltage regulator

if any query about this AC voltage regulator

comment below…………………. ?

2 Comments

  1. I did not understand any of that, but I’m hoping something like this can help me solve a problem I’m having… My car amplifier is putting out approx 48vac the led strip I want to introduce to this system can only take 12v. The end goal is to have the leds flash with the bass, with the volume up (48v) and not blow the led strip.

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