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LAB 1: STUDY OF SINGLE PHASE HALF WAVE CONTROLLED RECTIFIER USING
R-LOAD AND RL-LOAD
Method · January 2017
DOI: 10.13140/RG.2.2.28949.01760
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Ajay Singh
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#LAB 1
STUDY OF SINGLE PHASE HALF WAVE CONTROLLED RECTIFIER USING
R - LOAD AND RL - LOAD
OBJECTIVE
To familiarize with the SCR in controlled rectification with resistive (R) and inductive
(L) load.
APPRATUS REQUIRED
1. Thyristor Kit
2. Connecting Wires
3. Oscilloscope
4. Multimeter
THEORY
Single-Phase Half-Wave Controlled Rectifier using R - load
The single-phase half-wave controlled rectifier uses a single thyristor with a load and also
the output voltage and current waveform as shown in figure 1. In a positive half cycle of
source voltage ( 𝑉𝑠 = 𝑉𝑚𝑎𝑥 𝑠𝑖𝑛 𝜔𝑡), thyristor is forward biased and when gate current iG is
applied to the gate terminal at firing angle α then thyristor strarts to conduct. The output
voltage will appear from ωt = α to ωt = π. At ωt = π, thyristor goes turned OFF. In a negative
half cycle, ωt = π to ωt = 2π, thyristor is reverse biased and output voltage is zero during
this period. Therefore, by changing the value of firing angle (α) the output voltage can be
controlled.
The average output voltage is given by:
𝑉𝑑𝑐
1 𝜋
𝑉𝑚𝑎𝑥
(1 + 𝑐𝑜𝑠𝛼)
=
∫ 𝑉𝑚𝑎𝑥 𝑠𝑖𝑛 𝜔𝑡 𝑑𝜔𝑡 =
2𝜋 𝛼
2𝜋
(1.1)
And rms value of output voltage is given by,
1 𝜋
𝑉𝑚𝑎𝑥
1
1
∫ (𝑉𝑚𝑎𝑥 sin 𝜔𝑡)2 𝑑𝜔𝑡 =
((𝜋 − 𝛼) + sin 2𝛼) ⁄2
2𝜋 𝛼
2
2√𝜋
𝑉𝑟𝑚𝑠 = √
(1.2)
Figure 1 Single Phase half wave controlled rectifier with resistive load
Single-Phase Half-Wave Controlled Rectifier using RL – load
The single-phase half-wave controlled rectifier uses a single thyristor with a RL load and
aslo the output voltage and current waveform as shown in figure 2. In a positive half cycle
of source voltage ( 𝑉𝑠 = 𝑉𝑚𝑎𝑥 𝑠𝑖𝑛 𝜔𝑡), thyristor is forward biased and when gate current iG
is applied to the gate terminal at firing angle α then thyristor starts to conduct. The output
voltage will appear from ωt = α to ωt = π. At ωt = π, thyristor goes turned OFF but current
does not decay to zero because of the energy stored in inductor. The negative voltage will
appear from ωt = π to ωt = β. The load current decays to zero at ωt = β and value of β
depends upon the ratio R/L. During ωt = β to ωt = 2π, the output voltage is zero during this
period. The angle β is called extinction angle and γ = (β – α) is called conduction angle.
The average value of output voltage is given by,
𝑉𝑑𝑐 =
1 𝛽
𝑉𝑚𝑎𝑥
∫ 𝑉𝑚𝑎𝑥 𝑠𝑖𝑛 𝜔𝑡 𝑑𝜔𝑡 =
(𝑐𝑜𝑠 𝛼 − cos 𝛽)
2𝜋 𝛼
2𝜋
(1.3)
And the rms voltage is given by
𝑉𝑟𝑚𝑠
1 𝛽
𝑉𝑚𝑎𝑥
1
1
= √ ∫ (𝑉𝑚𝑎𝑥 sin 𝜔𝑡)2 𝑑𝜔𝑡 =
{𝛽 − 𝛼 + (sin 2𝛼 − sin 2𝛽)} ⁄2
2𝜋 𝛼
2
2√𝜋
β
Figure 2 Single phase half wave controlled rectifier with resistive-inductive load
(1.4)
OBSERVATION
1. Input Parameter
a. Input voltage
b. Frequency
c. Cycle time period
…………..
.…………..
...…………
2. Observation Table
Half wave controlled rectifier with R - load
S.N.
Triggering
Time (t)
Firing
Angle (α)
Observed Output voltage
Avg. voltage
rms voltage
Theoretical Output Value
Avg. Voltage rms voltage
1
2
3
4
5
Half wave controlled rectifier with RL - load
S.N.
1
2
3
4
5
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Triggering
Time (t)
Firing
Angle (α)
Observed Output
voltage
Avg.
rms
voltage
voltage
Theoretical Output
Value
Avg.
rms
Voltage
voltage
Extinction
Angle (β)
Observed Calc