Thyristor bridge rectifier (Half controlled) Flashcards
What is the circuit for a half controlled thyristor bridge rectifier?
[Picture19]
Draw the waveforms for vS, vO, iO, iS
[Picture20]
What is the main difference between a half controlled vs fully controlled thyristor bridge rectifier?
> In a half controlled circuit, there are 2 thyristors and 2 diodes.
> This half controlled method avoids having an output current that ever goes negative.
What is the point in a highly inductive load?
> An inductor is normally used to improve the output current waveform
> If the inductor the inductor is sufficiently large (≈ ∞)then the output current constant.
What is control parameter ‘a’ for a half controlled thyristor bridge rectifier?
> For T1 ‘a’ represents the angle difference between 0° and the point when the pulse is applied to the gate of the thyristor.
> For the control of T2 ‘a’ represents the angle difference between π° phase and the point when the pulse is applied to the gate of the thyristor.
Describe the operation of a half controlled thyristor bridge rectifier for one full cycle
ωt = a
> T1 is fired
> D2 is conducting because it is forward biased
> D1 and T2 are off
ωt = a ⇒ ωt = π
> vS = vO
> iS = iO
ωt = π
> D2 stops conducting
> D1 is turned on
> T2 is off off
> T1 remains on
> All current from the load is flowing through D1 and T1
> No current if flowing between the source and load
ωt = π + a
> Current flows in the reverse direction
> T2 is fired
> D1 is conducting because it is forward biased
> D2 and T1 are off
ωt = π + a ⇒ ωt = 2π
> -vS = vO
> iS = -iO
ωt = 2π
> D1 stops conducting
> D2 is turned on
> T1 is off off
> T2 remains on
> All current from the load is flowing through D2 and T2
> No current if flowing between the source and load
What is the equation to calculate the average output voltage?
VOavg = 1 / π ∫aπ vS dωt
What is the simple equation for the output voltage in terms of the RMS value for the supply voltage and the value ‘a’? Derive it
VOavg = 0.45VS(1 + cos(α))
[Picture21]
For a lossless rectifier, what is the equation for the output power?
Pout = VO × IO
For a lossless rectifier what is the relationship for input and output power?
Pin = Pout
What is the equation for power factor for a half controlled thyrstier bridge rectifier?
PF = Pout / VSIS
What is the equation for the average output power?
POavg = 0.45VS(1 + cos(α))IO
What is the equation to calculate IS from IO for a half controlled thyristor bridge rectifier?
IS = IO√(1 - (a / π) )
