The inductor has property to store energy In ac current during positive high cycle the inductor stores energy Freewheeling diode At negative half cycle the inductor deenergies so there must be reverse current which will make SCR on ID: 290128
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Slide1
3.4 Freewheeling diode
The inductor has property to store energy
In ac current, during positive high cycle the inductor stores energy
.Slide2
Freewheeling diode
At negative half cycle the inductor deenergies ,so there must be reverse current which will make SCR on .
This may cause reverse damage to circuit
To avoid energy
dissipation freewheeling
diode is used.Slide3
Effect of Freewheeling diode
In negative half cycle ,the freewheeling diode becomes forward biased so that the current will flow through diode
Therefore it
deenergies inductor without making SCR forward biased.
To cut off the negative portion of the instantaneous output voltage & smooth the output current ripple free, a freewheeling diode is used.Slide4
Effect of freewheeling diode on o/p waveforms
O/P WAVEFORMS OF HWR with FWD
O/P WAVEFORMS OF HWR with FWDSlide5
3.5Circuit dig. Of single phase fullwave rectifier with freewheeling diode Slide6
Circuit description
In single phase rectifier , freewheeling diode is connected across the RL load.
Due to freewheeling diode we overcome the problem of FWR with RL loadSlide7
Operation of FWCR with FWD
During positive half cycle
U
pto point
α
the SCR1 is in forward blocking state so it will be in off state.
After the point
α
the SCR1 will be turn on & starts conducting.It continuous in conduction state until it reaches to πSlide8
Operation of FWCR with FWD
During negative half cycle
As the load current tend to go to negative the FWD becomes forward biased & it starts conducting
Therefore SCR1 becomes revered biased & it will be off.
Slide9
Operation of FWCR with FWD
Now
the SCR2 becomes forward biased due to negative half cycle
.
Upto pt
α
it will be in forward blocking state so it is in off state.Slide10
Operation of FWCR with FWD
When i/p voltage becomes more than
α
, SCR2 will be turn on & starts conducting we get o/p voltage .& constant dc current as output.
Due to FWD we get the ripple free output voltage (where the inductive load effect is avoided by FWR)We get constant DC output currentSlide11
w/f of single phase fullwave rectifier with freewheeling diode