DC Choppers and Circuits Quiz

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What is the primary function of chopper circuits?

To stabilize fluctuating dc voltage
To step up fixed ac voltage
To convert ac voltage into dc voltage
To convert fixed dc voltage into adjustable dc voltage (correct)

Which type of chopper circuit is a two-stage conversion process?

DC chopper
Current Limit Chopper
AC Link Chopper (correct)
Time Ratio Chopper

Which type of control strategy is NOT used in DC choppers?

Time Ratio Control
Voltage Regulation Control (correct)
Current Limit Control
Pulse Width Modulation Control

Why is dc to dc conversion necessary for household power supply systems?

Household devices need dc input with adjustable voltage. (A) Signup and view all the answers

What makes DC choppers more efficient than AC Link Choppers?

They execute single-stage conversion. (A) Signup and view all the answers

Which of the following describes a chopper circuit?

A circuit designed to convert fixed dc voltage into adjustable dc voltage. (D) Signup and view all the answers

In chopper circuits, what does the term 'static power electronics device' imply?

It operates without mechanical movement. (A) Signup and view all the answers

What happens in the DC Chopper circuit?

It varies the fixed dc input voltage to another level. (B) Signup and view all the answers

What is a common application needing adjustable dc voltage?

Electronic devices powered by batteries (D) Signup and view all the answers

What is the main characteristic of constant frequency operation in time ratio control?

The ON time is changed while keeping frequency constant. (D) Signup and view all the answers

Which disadvantage is associated with variable frequency operation?

It can cause interference with telecommunications. (A) Signup and view all the answers

What does the current limit control method in a DC-DC converter aim to achieve?

Keeping the current within upper and lower limits. (D) Signup and view all the answers

What is a key feature of a voltage-commutated chopper?

It uses large reverse voltage for thyristor commutation. (B) Signup and view all the answers

In forced commutation, which elements are primarily used to turn off the thyristor?

Inductor and capacitor. (A) Signup and view all the answers

What effect does applying reverse voltage across a conducting thyristor have?

It reduces the anode current to zero and turns off the thyristor. (B) Signup and view all the answers

Which commutation technique stops conduction when the load current reaches zero?

Load Commutation. (C) Signup and view all the answers

What mechanism allows a chopper to change fixed DC voltage into adjustable DC voltage?

Duty Cycle Control. (C) Signup and view all the answers

How is the time ratio control defined in the context of DC-DC converters?

By changing the duty ratio, K, which is TON/T. (A) Signup and view all the answers

What is a significant drawback of the frequency modulation technique in DC-DC converters?

It causes irregular load current due to large OFF times. (B) Signup and view all the answers

What happens when the main thyristor TM is triggered in the circuit?

The supply input appears across the load. (D) Signup and view all the answers

What occurs to the charging current ic between the capacitor voltage equaling the supply input and reaching zero?

It rises from zero to maximum value. (D) Signup and view all the answers

Which of the following describes the function of the diode D in the circuit?

It keeps the voltage across the capacitor constant at –Vs. (C) Signup and view all the answers

What is the load voltage V0 at instant t2 when the capacitor discharges through the load?

Vdc + Vdc = 2 Vdc (C) Signup and view all the answers

What is one characteristic of the step-up chopper?

It increases the output voltage from the input. (A) Signup and view all the answers

What happens during the half-cycle when the auxiliary thyristor TA is triggered?

TM gets reverse biased and becomes non-conducting. (D) Signup and view all the answers

What assumption is made about the load current in the chopper circuit?

It is of invariable nature. (C) Signup and view all the answers

What is indicated by the term 'voltage commutated chopper'?

The voltage across the capacitor turns off TM. (A) Signup and view all the answers

In which application are AC choppers typically used?

For speed control of AC motors. (D) Signup and view all the answers

What is the role of the thyristor TA during the operation of the chopper?

It assists in transitioning the current away from load. (C) Signup and view all the answers

What happens to the charging current once the thyristor TA is triggered?

It decays to zero. (A) Signup and view all the answers

What is the load voltage V0 at instant t2 when the capacitor discharges through the load?

2 Vdc (A) Signup and view all the answers

What role does the diode D play in the circuit during the charging of the capacitor?

It keeps the voltage across the capacitor constant. (B) Signup and view all the answers

What occurs when the capacitor begins to charge again after the thyristor TM is turned off?

Capacitor charges with reverse polarity. (D) Signup and view all the answers

What assumption about the load current is made in the chopper circuit?

It has a constant nature. (B) Signup and view all the answers

What primarily changes in constant frequency operation to control the output voltage?

The ON time TON (B) Signup and view all the answers

What voltage is across the capacitor when the thyristor TM is turned off?

Vs (B) Signup and view all the answers

In a step-up chopper, what is primarily manipulated to achieve a higher output voltage?

Duty cycle. (B) Signup and view all the answers

What technique uses external components like inductors to turn off a thyristor?

Current Commutation (C) Signup and view all the answers

Which of the following describes the disadvantage of using variable frequency operation?

It may cause load current irregularities (C) Signup and view all the answers

What happens to the voltage across the capacitor after it gets fully charged?

It makes the auxiliary thyristor reverse biased. (B) Signup and view all the answers

What application is a step-down chopper typically used for?

Power supply voltage reduction. (C) Signup and view all the answers

In a voltage-commutated chopper, what occurs to initiate the commutation process?

Large reverse voltage is applied (B) Signup and view all the answers

What is the maximum value of the commutation current ic when the capacitor voltage equals the supply input?

It reaches its maximum value. (D) Signup and view all the answers

What term describes the process of turning off a thyristor in a conducting state?

Commute (B) Signup and view all the answers

What allows the load current to freewheel during the OFF state of a DC-DC converter?

The diode (D) Signup and view all the answers

Which type of control utilizes duty cycle alterations to change output voltage?

Time Ratio Control (C) Signup and view all the answers

What does the term 'duty cycle' refer to in time ratio control?

The ratio of ON time to total time (B) Signup and view all the answers

What characteristic makes pulse width modulation preferable over frequency modulation?

More stable voltage output (A) Signup and view all the answers

What is the main disadvantage noted for control strategies in DC-DC converters?

Difficulty in filter design for wide frequency changes (A) Signup and view all the answers

What is one key function of AC Link Choppers?

They convert fixed DC into AC, then back to adjustable DC. (D) Signup and view all the answers

Which statement best describes the operation of a DC Chopper?

It changes fixed DC input voltage directly to variable DC output. (D) Signup and view all the answers

What is the primary efficiency advantage of a DC Chopper over an AC Link Chopper?

It executes direct fixed to variable DC conversion in one stage. (C) Signup and view all the answers

What is the purpose of Time Ratio Control in DC choppers?

To change the average output voltage effectively. (C) Signup and view all the answers

In what scenario would you likely use a chopper circuit?

To modify the output from a fixed DC voltage source as needed. (A) Signup and view all the answers

What effect do chopper circuits have on input DC voltage?

They adjust the fixed DC voltage to a variable level. (C) Signup and view all the answers

Which of the following accurately describes a characteristic of static power electronics devices like choppers?

They can change voltage levels without mechanical movement. (C) Signup and view all the answers

What is the main purpose of converting fixed DC power to adjustable DC power?

To ensure it fits variable DC voltage device requirements. (C) Signup and view all the answers

What distinguishes the control strategies of Time Ratio Control and Current Limit Control?

Only Time Ratio Control adjusts the average output voltage. (B) Signup and view all the answers

Which of the following statements is true regarding Chopper Circuits and transformers?

Chopper circuits step up or step down DC voltage like transformers step AC voltage. (D) Signup and view all the answers

Chopper Circuit

A circuit that converts a fixed DC voltage into an adjustable DC voltage.

DC Chopper

A static power electronics device that converts a fixed DC voltage to a variable DC voltage, similar to an AC transformer for DC.

AC Link Chopper

A two-stage process that converts fixed DC to adjustable DC by first inverting DC to AC, then stepping up or down the AC using a transformer, followed by rectification to DC.