1. Duty cycle (D) is _______
B. Ton÷(Ton+ Toff)
C. Ton÷2×(Ton+ Toff)
2. A 220 V, 1000 rpm, 60 A separately-excited dc motor has an armature resistance of .5 ω. It is fed from a single-phase full converter with an ac source voltage of 230 V, 50Hz. Assuming continuous conduction, the firing angle for rated motor torque at (-400) rpm is _________
3. The unit of angular acceleration in rad/s2.
4. Calculate the value of the angular acceleration of the motor using the given data: J= 50 kg-m2, load torque = 40 N-m, motor torque = 10 N-m.
A. -.7 rad/s2
B. -.6 rad/s2
C. -.3 rad/s2
D. -.4 rad/s2
5. The principle of step-up chopper can be employed for the ________
A. Motoring mode
B. Regenerative mode
D. Reverse motoring mode
6. A Buck-Boost converter is used to _________
A. Step down the voltage
B. Step up the voltage
C. Equalize the voltage
D. Step up and step down the voltage
7. Which of the following converter circuit operations will be unstable for a large duty cycle ratio?
A. Buck converter
B. Boost converter
C. Buck-Boost converter
D. Boost converter and Buck-Boost converter
8. Calculate the shaft power developed by a motor using the given data: Eb = 50V and I = 60 A. Assume frictional losses are 400 W and windage losses are 600 W.
A. 4000 W
B. 2000 W
C. 1000 W
D. 1500 W
9. Which one of the following devices has low power losses?
10. Servo motors are an example of which type of load?
A. Pulsating loads
B. Short time loads
C. Impact loads
D. Short time intermittent loads