A step-down chopper has a load resistance of $20 \ \Omega$ and input DC voltage is 200 V. When the chopper switch is 'on', the voltage across semiconductor switch is 2 V. If the chopping frequency is 1.5 kHz and duty ratio is 40%, what is the average DC output voltage?
Step-Down Chopper Voltage Calculation
This problem requires calculating the average DC output voltage ($V_{out(avg)}$) for a step-down chopper, considering the voltage drop across the semiconductor switch.
Given Parameters
- Input DC Voltage ($V_{in}$): $200 \text{ V}$
- Load Resistance ($R_L$): $20 \ \Omega$ (Note: Not needed for this calculation)
- Chopping Frequency ($f$): $1.5 \text{ kHz}$ (Note: Not needed for this calculation)
- Duty Ratio ($D$): $40\% = 0.4$
- Voltage across switch when 'on' ($V_{sw\_on}$): $2 \text{ V}$
Calculating Average DC Output Voltage
The formula for the average DC output voltage ($V_{out(avg)}$) in a step-down chopper, accounting for the switch voltage drop ($V_{sw\_on}$) during the 'on' period, is:
$ V_{out(avg)} = D \times (V_{in} - V_{sw\_on}) $
Plugging in the values:
- $D = 0.4$
- $V_{in} = 200 \text{ V}$
- $V_{sw\_on} = 2 \text{ V}$
Perform the calculation:
$ V_{out(avg)} = 0.4 \times (200 \text{ V} - 2 \text{ V}) $
$ V_{out(avg)} = 0.4 \times 198 \text{ V} $
$ V_{out(avg)} = 79.2 \text{ V} $
Final Answer Determination
The calculated average DC output voltage is $79.2 \text{ V}$. Comparing this result with the given options, $80 \text{ V}$ is the closest value. Therefore, the average DC output voltage is determined to be $80 \text{ V}$.
Important Questions from Choppers
Choppers are _______ converters.
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Chopper converts fixed d.c. input voltage to a controllable d.c. output voltage. The Chopper circuit require forced or load commutation to turn off the thyristors.
Reason R: The Chopper circuits are dependent upon the type of commutation and also on the direction of power flow.
In the light of the above statements, choose the most appropriate answer from the options given below
A load commutated chopper fed d.c. drive uses 100 V d.c. supply. The maximum chopper frequency is 5 kHz. The value of maximum load current is 100 A. The commutating capacitance will be :
In a lossless buck converter, an average power of 20 W to a load with a regulated 12 V output, while operating at a duty cycle of 0.8 with continuous inductor current. Following data is given :
(a) The average value of input voltage is given by 15 V
(b) The average value of input voltage is 16 V
(c) The average value of input current is 4/3 A
(d) The average value of input current is 3/4 AWhich is correct out of the following ?
If T is the time period for a chopper circuit and α is its duty cycle, then the chopping frequency is
