# High Voltage Engineering Questions and Answers – Marx Circuit

This set of High Voltage Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Marx Circuit”.

1. High voltage is produced by charging a bank of capacitors in ________ and discharged in __________
a) series, series
b) series, parallel
c) parallel, parallel
d) parallel, series

Explanation: To produce voltage beyond 200kV, a single capacitor may not be sufficient. In this case, bank capacitors are used. High voltage is produced by charging a bank of capacitors in parallel and discharged in series.

2. Modified Marx circuits are used for multistage impulse generators.
a) True
b) False

Explanation: Multistage impulse generators are used to produce very high voltages. Marx proposed a circuit the charge the capacitor in parallel and discharge them in series. Nowadays, modified Marx circuits are used for multistage impulse generators.

3. The charging resistance limits the charging current to __________
a) 100-200mA
b) 10-20mA
c) 50-100mA
d) 20-30mA

Explanation: Multistage impulse generators are used to produce very high voltages. Several charging resistances are used in each stage. The charging resistance limits the charging current to 50-100mA.

4. What is the discharge time constant for n stages?
a) CR1
b) nCR1
c) CR1/n
d) 2CR1

Explanation: The discharge time constant for n stages is CR1/n where C is the capacitance and is the wave shaping resistor. During the discharging period, the capacitors are connected in series. During the charging period the capacitors are connected in parallel.

5. What is the charging time constant for n stages?
a) CRs
b) nCRs
c) CRs/n
d) 2CRs

Explanation: The charging time constant for n stages is CRs where C is the capacitance and is the charging resistor. The charging time constant is only few seconds compared to the discharge constant which is in the order of microseconds.

6. What is the efficiency of the Marx circuit when wave shaping resistors are distributed?
a) $$\frac{V_o}{nV}$$
b) $$\frac{V_o}{V}$$
c) $$\frac{nV_o}{V}$$
d) $$\frac{n^2 V_o}{V}$$

Explanation: The efficiency of the Marx circuit when wave shaping resistors are distributed is $$\frac{V_o}{nV}$$. Vo is the output voltage, V is the input voltage and n is the number of stages in the impulse generator. The control resistors are smaller when the wave shaping resistors are distributed.

7. A single capacitor can be used for voltages up to 1000kV.
a) True
b) False

Explanation: A single capacitor can be used for voltages up to 200kV. To produce voltage beyond 200kV, a single capacitor may not be sufficient. In this case, bank capacitors are used.

8. Impulse generators are nominally rated by _____
a) total voltage
b) number of stages
c) gross energy stored
d) total voltage, number of stages and gross energy stored

Explanation: The total nominal output voltage is the product of charging voltage and number of stages. $$\frac{1}{2} C_1 V^2$$ is the nominal energy stored. Total voltage, number of stages and gross energy stored denotes the rating of an impulse generator.

9. What is nominal energy stored?
a) $$\frac{1}{2} C_1 V^2$$
b) $$C_1 V^2$$
c) $$\frac{1}{4} C_1 V^2$$
d) $$2C_1 V^2$$

Explanation: The nominal energy stored is $$\frac{1}{2} C_1 V^2$$. C1 is the discharging capacitance which is equal to the generator capacitance divided by the number of stages. V is the nominal charging voltage. The total nominal output voltage is the product of charging voltage and number of stages.

10. The height of the generator used is about _____
a) 15m
b) 10m
c) 2m
d) 22m

Explanation: The multi stage impulse generator circuit employs generator of height 15m. The generators used occupies a floor area of 3.25 X 3m2. The energy rating, nominal voltage will depend on the number of stages present in the circuit.

Sanfoundry Global Education & Learning Series – High Voltage Engineering.

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