Thyristor Switch Application

EE3092 – Laboratory Practice V

Thyristor Switch Application

Instructed by:

Name

: K.P.A.I.Perera

Index No.

: 100385H

Course

: BSc. Engineering

Group

: Group 09

Date of Per

: 26/06/2013

Date of Sub : 17/07/2013

OBSERVATION SHEET
Name

: K.P.A.I.Perera

Index No.

: 100385H

Course

: BSc. Engineering

Group

: Group 09

Date of Per

: 26/06/2013

Date of Sub : 17/07/2013
Instructed By :

a) DC switch opening and closing by means of a push button.

Fig 1: Commutation of Thyristor: A-K voltage

Time taken from stopping SR4 to stopping SR3 = 6.2 × 1ms
= 6.2ms

b) DC switch opening with an over current.

Fig 2: Gate voltage of Thyristor

c) C switching opening and closing by means of miniature switch.

Fig 3: Voltage waveform between R5 and R6

Calculation of gate current of SR1 and SR2
Resistance of R5 and R6 = 100 Ω
Peak value of voltage waveform = 50 × 3
=150V
Gate current of SR1 and SR3

= 150/100
= 1.5A

d) AC switch opening and closing with lights.

Fig 4: Waveform across R5 and R6

Calculation of gate current peak in SR1 and SR2
Peak value of voltage waveform = 50 × 3
= 150V
Gate current peak in SR1 and SR2 = 150/100
=1.5A

e) Mechanical switch opening and closing with a magnetic relay.

Fig 5: Voltage oscillogram of coil RL1

Switch on time = 1 × 10 ms
=10ms

DISCUSSION
i.

What are the advantages of using a thyristor switch in place of a mechanical switch.
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Fast Operation. usually less than 10μs. Fast turn-on time allows the thyristor to be easily synchronized with line zero-crossing. This also minimizes EMI and can greatly increase the lifetime of tungsten lamps, of considerable value in applications such as traffic signals.
Lower (if any) minimum output current (latching current) required.
Increased lifetime, particularly if activated many times, as there are no