Question 1. A single-stage impulse generator has its components adjusted to produce a 1/50 μs impulse wave when testing an object of capacitance, 10nF. The respective values of α1 = 1.42 x 104/s and α2 = 6.08 x 106/s. The front resistance is 20Ω and the charging voltage has a maximum of 100kV. Neglecting the stray capacitance, what is the largest peak value of impulse voltage that can be applied to a test object of 10nF?
Question 2. A 12-stage impulse generator has 0.126 μF condensers. The wave front and tail resistances connected are 800Ω and 5000Ω, respectively. If the load capacitance is1000 pF, find the front and tail times of the impulse wave produced.
Question 3. An eight-stage impulse generator has 0.12μF capacitors rated for 167kV. What is its maximum discharge energy? If it has to produce a 1/50 μs waveform across a load capacitor of 15nF, find the values of the wave front and wave tail resistances.
Question 4. A breakdown voltage was measured in a laboratory using a standard sphere-gap, and the corresponding table reading is 132 kV. The laboratory temperature is 30oC, the atmospheric pressure is 100 kPa. Calculate the breakdown voltage corresponding to the above laboratory conditions. The relationship between the relative air density factor and the correction factor for breakdown voltage calculations is shown in table below.
| Relative air density (δ) |
Correction factor |
| 0.7 |
0.72 |
| 0.75 |
0.77 |
| 0.8 |
0.82 |
| 0.85 |
0.86 |
| 0.9 |
0.91 |
| 0.95 |
0.95 |
Question 5. In the circuit shown below; three means of high voltage measurements are utilized through a resistive potential divider, a capacitive potential divider, and a potential transformer. What will be the multiplication factor for each of the low voltage voltmeter readings if you know that R1 = 200 MΩ R2 = 100 kΩ, C1 = 10 pF, C2 = 10 nF, N1: N2 = 3000:1
Question 6. A two-stage Cockcroft-Walton voltage doubler is constructed from 0.05 μF capacitors and a transformer with 100kV, 50Hz output. The output voltage is measured by an ammeter in series with a 100 MΩ resistor, connected across the output terminals. Find the output terminal voltage and the peak-to-peak ripple for the following external load conditions:
(a) No connected load.
(b) 30 MΩ load.
(c) 3 MΩ load.
Solve the impulse problems using the following approximate expressions for time constants that define the front and tail times of an impulse voltage waveform. C1 and C2 represent the generator and load capacitances respectively.
t1 = 3R1.(C1C2/C1 + C2)
t2 = 0.7(R1 + R2) (C1 + C2)