Single-phase bridge rectifier
Laboratory exercise 1
Single-phase bridge rectifier
A rectifier is an electrical device that converts AC (alternating current) to DC (direct
current), a process known as rectification. Rectifiers have many uses including as components
of power supplies and as detectors of radio signals. The primary application of rectifiers is to
derive DC power from an AC supply. Virtually all electronic devices require DC, so rectifiers
find uses inside the power supplies of all electronic equipment.
A Single-phase bridge rectifier (2-pulse rectifier) converts both polarities of the input
waveform to DC.
Pic 1 Single-phase bridge rectifier (R load, α = 0º)
An average value (AV) of rectified voltage:

2
2 2
(1.1)
U dAV (0) 
U m sin( t )d (t ) 
U RMS  0,9 U RMS

2 0

Um – peak voltage, URMS – effective supply voltage
Average voltage-control angle dependency (see Pic 4) only for R load:

2
2
1  cos 
U dAV ( ) 
U m sin( t )d (t ) 
U RMS 1  cos    U dAV (0) 

2 

2
(1.2)
Pic 2 Output voltage for R load, α = 60º
1
Ing. Lukáš Odlevák, Ing. Petr Vaculík
Single-phase bridge rectifier
An analytic description of average voltage UdAV for RL load and discontinuous current
doesn’t exist. But it exists for continuous current (in case of higher inductance).
Average voltage in case of continuous current for various types of load (R, RL, RL+E, etc):
 
2
(1.3)
U dAV ( ) 
U m sin( t )d (t )  U dAV (0)  cos 
2 
Pic 3 Output voltage for RL load, α = 30º
R load (L=0), dc
UdAV
UdAV(α)
UdAV(0°)
UdAV(0°)
L load (R=0), cc
RL load,
dc
L load (R=0), cc
0°
90°
180°
Pic 4 Control characteristic UdAV = f (α) for various types of load
cc - continuous current, dc - discontinuous current
Task
1. Measure control characteristic UdAV = f (α) for various types of load (R, RL, RL+V0,
RL+E, RL-E) in case of continuous and discontinuous current.
2. Make the graph of all measured waveforms (use per-unit quantity:
U dAV  
).
U dAV 0
3. Add calculated waveform of R load (1.2) and continuous current (1.3) to the same
graph.
2
Ing. Lukáš Odlevák, Ing. Petr Vaculík
Single-phase bridge rectifier
Pic 5 Wiring diagram
Device:
TR
V1 – V4
V0
S1
A
transformer
Rectifier (2-pulse)
zero diode
switch
Ammeter
V
Voltmeter
R
variable resistor
L
inductor
E
DC motor
Control circuit: α = f(Ucontrol)
Laboratory measurement
Ucontrol [V]
α [ms]
α [º]
UdAV [V]
R
UdAV [V]
RL
UdAV [V]
RL+V0
UdAV [V]
RL+E
UdAV [V]
RL-E
Optional reference:
http://www.falstad.com/circuit/index.html  Circuit Simulator/Circuits/Diodes/Full-Wave
http://en.wikipedia.org/wiki/Rectifier
 Rectifier output smoothing
3
Ing. Lukáš Odlevák, Ing. Petr Vaculík