Light Dimmer Circuit OR Fan Regulator Circuit OR AC Load Control Using TRIAC - DIAC

  • The fan regulator circuit using TRIACDIAC is shown in the figure.
  • The TRIAC and DIAC are bi – directional therefore they are used for alternating circuit. 
  • The RL is load resistance / lamp or two terminal of single phase winding.
  • The charging of capacitor is done through L – RL – R – C – N path.
  • When voltage across capacitor becomes equal to break over voltage of the DIAC, the DIAC turns on. 
  • As soon as the DIAC turns on, the discharging of capacitor is done through C – DIAC – G – MT1 – C path. Now the gate terminal of TRIAC gets signal and TRIAC turns on.
  • The load resistance complete its path through L – RL – MT1 – MT2 – N. 
  • The charging rate of the capacitor is depends upon the variable resistance R. 
  • The firing angle of the TRIAC depends upon variable resistance R. 
  • The charging rate of the capacitor is less for higher value of resistance resulting firing angle of TRIAC increases and voltage across load reduces. 
  • Similarly the load gets higher voltage for low value of resistance due to less firing angle.  
Finally Remember

High variable resistance – Firing angle increases – Low voltage across load
Low variable resistance – Firing angle decreases – High voltage across load

fan regulator circuit

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