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In the dcdc converter circuit shown, switch Q is switched at a frequency of 10 kHz with a duty ratio of 0.6. All components of the circuit are ideal, and the initial current in the inductor is zero. Energy stored in the inductor in mJ (rounded off to 2 decimal places) at the end of 10 complete switching cycles is ________
Identification of DCDC Converter:
In a BuckBoost converter, the inductor stores the energy for T_{ON} time and release the energy for the time T_{OFF}
Given that, duty ratio (δ) = 0.6
⇒ T_{ON} = δT = 0.6 T
⇒ T_{OFF} = (1 – δ) T = 0.4 T
So, the inductor stores the energy for a time of 0.6 T and releases the energy for 0.4 T.
So, for one cycle, the increase in inductor current is corresponding to a time of (0.6 T – 0.4 T) = 0.2 T
Frequency (f) = 10 kHz
The time period for one cycle,
The waveform of the inductor current is as shown below.
From the waveform, rise in the inductor current for one cycle
Rise in the inductor current for 10 cycles = 0.1 × 10 = 1 A
Energy stored in the inductor for 10 cycles,
For the circuit shown in the figure, assume L to be large enough to ensure linear growth and decay of the current through it and have continuous current. The maximum value of the load current in amperes is _________ (V_{s} = 100 V, V_{o} = 50 V, L = 2mH, f = 20 kHz, R = 10 Ω)
The function of capacitor C acrossload resistance R is to make the output voltage continuous.
In the circuit shown below, if load R = 500 Ω, switching frequency is 25 kHz and peak to peak ripple current of inductor is limited to 0.9 A then the filter inductance L is
For Buck Converter
The peak to peak ripple current is
In chopper circuit the average value of output voltage is controlled by time ratio control (TRC) method. The chopper is operated at a frequency of 5kHz on a 230 V d.c. supply. If the load voltage is 180 V, then the blocking period of thyristor in each cycle is___(in μsec)
V_{o} = V_{dc} × T_{on} × f
f = 5 kHz, V_{dc} = 230 V, V_{o} = 180
but chopping period
blocking period of SCR
T_{off }= T – T_{on} = 0.2 – 0.156 = 0.04347 msec = 43.47 μsec
A dc chopper is fed from constant voltage mains. The duty ratio α of the chopper is progressively increased while the chopper feeds RL load. The per unit current ripple would
Ripple current in the chopper circuit :
Ripple current is the difference between maximum current (Imx) and minimum current (Imin) flowing through the chopper circuit in the steadystate operation of the chopper.
The ripple current of chopper operating in steadystate is given by
Where
α = duty cycle of the chopper, V_{s} = DC supply voltage, R = load resistance, T_{a} = time constant = L/R , and T = time period of the chopper
From the above equation, we can observe per unit ripple current is only depends on the time constant (T_{a}), Time period (T), and duty cycle (α ).
Variation of ripple current with a duty cycle (α) and T/T_{a} ratio:
We can observe the variation of ripple current with duty cycle and T/T_{a} ration in the figure is shown below,
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