Triggering circuit | Power electronics lab report


In this experiment we will construct the triggering panel used as control panel for triggering the thyristors and we will construct the single phase half wave controlled rectifier and study the output R,Rl and RC loads.

Introduction and Theory:

The six-pulse control unit is used to trigger Thyristors and IGBTs in controlled rectifier circuits, choppers and inverters.

The control unit is to be connected with a symmetric supply voltage ±15V.

A clockwise rotating field is to be connected to the synchronization input. The circuit itself produces a center point, for this reason, the N- conductor must not be connected.

When the unit is used as a single-phase control unit, the N-conductor should be connected.

The half wave single phase controlled rectifiers is called 'Controlled' because using the Thyristor rather than a diode, the Thyristor has an extra terminal called the Gate, the Thyristor, in addition to the necessary forward bias voltage, needs a pulse at the gate to start conduction, this process is called the firing or triggering of the Thyristor, also firing angle (α) is controlled using the triggering circuit.

Used equipment

1. Thyristor
2. AC power supply
3. Circuit breakers
4. R, RL and RC loads
5. Oscilloscope
6. Digital Multimeter
7. Connecting wires
8. Pulse generator circuit.


The output voltage is

The output current is
IO = Iav = Idc = Vdc/R

The output power is
Pdc = Vdc * Idc
Pac = Vrms * Irms

The efficiency of the circuit is
Eff.= Pdc /Pac

Form factor and ripple factor


circuit diagram

Output wave form


circuit diagram

Output wave form



  • This circuit the single phase half wave controlled rectifier convert AC voltage to DC voltage.
  • The triggering circuit needs three phase sources to activate it.
  • As the firing angle increase the dc output will decrease as noticed in the previous table.
  • If the firing angle is zero so the output is become as in a diode and by varying the firing angle the wave will shaped as the value of the angle.

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