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Consider following statements :
The overlap angle of single phase fully controlled bridge converter would increase an increasing
Of these statements
Effect of source inductance on 1ϕ full controlled rectifier:
For 1ϕ full wave converter, the average reduction in dc output voltage due to source inductance is:
where, Δ V_{o} = Average reduction in dc output voltage
V_{m} = Maximum value of source voltage
α = Firing angle
μ = Overlap angle
L_{S} = Source inductance
Hence, option 4 is correct.
A halfwave, controlled rectifier with a purely resistive load has delay α = π/3, Calculate form factor.
Concept
If a gate signal is applied to the SCR at ωt = α, where α is the delay (firing or triggering) angle. The average (dc) voltage across the load resistor is
The rms voltage Across the Resistor is
FORM factor for Rectifier is given by
Given:
α = π/3
What is the maximum output voltage of 3phase full bridge rectifier supplied with a line voltage of 420 V?
Concept:
The average output voltage of a threephase bridge rectifier is given by
Maximum possible output voltage
Calculation:
Given that, line voltage (V_{L}) = 420 V
Maximum line voltage = 420 × √2 V
Maximum possible output voltage
Maximum possible output voltage
A singlephase, fullbridge, fully controlled thyristor rectifier feeds a load comprising a 10 Ω resistance in series with a very large inductance. The rectifier is fed from an ideal 230 V, 50 Hz sinusoidal source through cables which have negligible internal resistance and a total inductance of 2.28 mH. If the thyristors are triggered at an angle α = 45°, the commutation overlap angle in degree (rounded off to 2 decimal places) is _______
Concept:
In a singlephase full wave rectifier with source inductance is given by,
Average output current
Where, V_{m} is the maximum value of supply voltage
α is the firing angle
μ is the overlapping angle
L_{s} is the source inductance
R is the load resistance
Calculation:
Given that, supply voltage (V_{rms}) = 230 V
Firing angle (α) = 45°
Source inductance (L_{s}) = 2.28 mH
Load resistance (R) = 10 Ω
Frequency (f) = 50 Hz
The average output voltage is
⇒ I_{0} = 14.003 A
⇒ μ = 4.8°
The figure below shows an uncontrolled diode bridge rectifier supplied from a 220 V, 50 Hz, 1phase ac source. The load draws a constant current I_{0} = 14 A. The conduction angle of the diode D_{1} in degrees (rounded off to two decimal places) is ________.
Concept:
The small inductance connected with supply work as a source inductance Due to this inductance, there will be overlapping takes place between two diodes. As a result, this will cause an overlap angle 'μ'.
During overlap period, both diode D_{1} & D_{2} will conduct.
Calculation:
The output voltage (V_{0}) & current waveform is shown below,
Output voltage in terms of load current is given by,
For diode α = 0°,
⇒ V_{0} = 170.06 V
In terms of overlap angle,
Since, for an overlap angle of μ, all four diodes conduct & each diodes conducts for (180 + μ) degree.
So,
conduction angle (γ) = 180 + μ = 180 + 44.17
γ = 224.17°
A threephase three pulse converter, fed from threephase 400 V, 50Hz supply, has a load R = 2 Ω, E = 200 V, and large inductance so that load current is constant at 20A. If the source has an inductance of 2 mH, then the value of overlap angle for inverter operation is
Concept:
Effect of source inductance: The presence of source inductance affects the rectifier output voltage
V_{0} = Vd_{0} cos α – ΔVd_{0}
μ is the overlap angle
Also, ΔV_{d0 }= f Ls I_{0} (1 pulse)
= 4 f Ls I_{0} (2 pulse)
= 3 f L_{s} I_{0} (3 pulse)
= 6 f L_{s} I_{0} (6 pulse)
Calculation:
V_{0} = E_{0} + I_{0} R
V_{d0} cos α – 3 f L_{s} I_{0} = 200 + (20)(2)
On solving we get cos α =  0.57
⇒ α = 124.76°
For three pulse converters:
On solving the above equation for overlap angle (μ) we get
cos (α + μ) = 0.6145
μ = 3.15°
For the 3ϕ full converter having resistive load, the ripple frequency f ripple is __________.
Concept:
Ripple Frequency: Ripple frequency is the output frequency of a converter which is some integral multiple of the supply frequency.
f_{ripple}= n × f_{s}
f_{ripple}= Ripple frequency
f_{s} = Supply frequency
n = No. of pulses in the time period
Calculation:
The 3ϕ full converter has 6 no. of pulses in the time period of the output waveform.
f_{s} = 50 Hz
f_{ripple} = 6 × 50
f_{ripple} = 300 Hz
Directions: The question consists of two statements, one labeled as ‘Statement (I)’ and the other labeled as ‘Statement (II)’. You are to examine these two statements carefully and select the answers to these items using the codes given below:
Statement (I): Inductive voltage regulation of singlephase fullwave rectifier increases with increasing supply frequency of the converter.
Statement (II): The overlap angle of a singlephase fullwave rectifier increases with the increase in the supply frequency of the converter.
Concept:
Source inductance effect of singlephase fullwave rectifier:
By considering the source inductance effect the average output voltage of a singlephase fullwave converter is given by
Where,
α = firing angle, ω = 2πf = angular frequency of supply
μ = overlap angle, I_{0} = load current
Inductive voltage regulation of singlephase fullwave rectifier is given by
Application:
From equation (1), we can observe that
As frequency (ω) of supply increases the cos (α + μ) term decreases. Hence the value of the overlap angle inceases.
Now from equation (2),
As value of overalp angle increases cosμ decreses. Hence the inductive volatge regulation increses.
A single phase full converter feeds power to RLE load with R = 8Ω, L = 8 mH and E = 46.42 V, the ac source voltage is 230 V, 50 Hz, for continuous conduction. Find the average value of load current for a firing angle delay of 45°
The average output voltage of a 1ϕ full converter with RLE loads for continuous conduction.
V_{0} = 146.42 V
V_{0} = E + I_{0}R
I_{0} = 12.50 A
The frequency of ripple in the output voltage of a three phase controlled bridge rectifier depends on
The frequency of ripple in the output voltage of a threephase controlled bridge rectifier depends on the supply frequency. The output frequency is
f_{0} = n f_{S}
Where n is the number of pulses in the output of the converter and f_{s} is the supply frequency
Note: Ripple factor depends on the firing angle, load inductance, and resistance.
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