Page 287 - Electronic Mechanic - TP - Volume - 2

ELECTRONICS MECHANIC - CITS

MODULE 20: 3-Phase rectifier controlled & uncontrolled

EXERCISE 199: Construct and test three phase uncontrolled

rectifiers (Half wave and Bridge Rectifiers)

Objectives

At the end of this exercise you shall be able to:
• to demonstrate input and output waveforms of half wave rectifiers
• To demonstrate input and output waveforms of bridge rectifiers.

Requirements

Tools/ Equipments/ Instruments

• Combination Plier 250mm - 1 No. • Variable Resistive Load - 1 No.
• Screwdriver Set 150mm - 1 No. • Three Phase AC Power
• Wire Stripper - 1 No. Supply 220V - 1 No.
• DC Ammeter - 1 No.
Materials/ Components
• DC Voltmeter - 1 No.
• Desktop PC/lap Top • Oscilloscope - 1 No.
Latest Specification - 1 No. • Connecting Wires - as reqd.
• Diodes - 6 Nos.

Note:
Three-phase half-wave and full-wave rectifiers are employed in high-power applications where three-
phase AC power is accessible. uncontrolled rectifiers have lower efficiency than more sophisticated
controlled rectifiers.
Three-phase half-wave rectifier has the advantage of simplicity since it requires only three diodes. output
voltage is lower than other types of rectifiers since only one of the three phases is used at a time.

Procedure

1 Wire up the half wave rectifier circuit after testing all the components.
For a three-phase half-wave rectifier, the supply voltages VA VB and VC are balanced but with a phase
difference of 120° giving:
V A = V x sin(ωt – 0°)
P
V B = V x sin(ωt – 120°)
P
V = V x sin(ωt – 240°)
C P

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