Control Systems and Power Electronics — Practice

Question 1

Find the percentage overshoot for zeta = 0.5.

Accepted Answer

Mp = e^(-pi x 0.5/0.866) = e^(-1.81) = 16.3 percent.

Question 2

A buck converter has Vs = 100 V and D = 0.4. Find the output.

Accepted Answer

40 V.

Question 3

For s^3 + 6s^2 + 11s + K = 0, find the range of K for stability.

Accepted Answer

First column 1, 6, (66 - K)/6, K. Stable for 0 < K < 66.

Question 4

A unity feedback system has G = K/(s(s + 2)). Find Kv and the error for a unit ramp.

Accepted Answer

Kv = K/2, so the ramp error is 1/Kv = 2/K.

Question 5

A second-order system has zeta = 0.5 and omega n = 10 rad/s. Find the 2 percent settling time.

Accepted Answer

ts = 4/(0.5 x 10) = 0.8 s.

Question 6

A single-phase full converter has Vm = 325 V and firing angle 60 degrees. Find the mean output voltage.

Accepted Answer

Vdc = (2 x 325/pi) cos60 = 206.9 x 0.5 = 103.5 V.

Question 7

A boost converter has Vs = 50 V and D = 0.5. Find the output voltage and say what happens as D approaches 1.

Accepted Answer

Vo = 50/(1 - 0.5) = 100 V. As D approaches 1 the ideal output grows without bound; in practice losses limit it.

Question 8

Which is larger, the latching or the holding current of an SCR?

Accepted Answer

The latching current.

Practice — Control Systems and Power Electronics