Power Electronics Questions and Answers –
Applications of Power Electronics
This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “Applications of Power Electronics
1. _________ is used for critical loads where temporary power failure can cause a great deal of inconvenience.
Explanation: Uninterruptible Power Supply (UPS) is utilised in loads where a temporary power outage could be extremely inconvenient.
2. __________ is used in the rotating type UPS system to supply the mains.
a) DC motor
b) Self excited DC generator
d) Battery bank
Explanation: When the supply runs out, the diesel engine fires up, which powers the alternator, which then feeds power to the mains. Non-rotating UPS units are no longer in use.
3. Static UPS requires __________
a) only rectifier
b) only inverter
c) both inverter and rectifier
d) none of the mentioned
Explanation: Rectifier for converting the battery’s dc to ac. To charge the battery from the mains, use an inverter.
4. No discontinuity is observed in case of
a) short break static UPS configuration
b) long break static UPS configuration
c) no break static UPS configuration
d) rotating type UPS configuration
Explanation: In the case of a no break static UPS arrangement, there is no dip or discontinuity because the battery inverter set immediately takes over the mains.
5. Usually __________ batteries are used in the UPS systems.
c) Lead acid
d) All of the mentioned
Explanation: Lead acid batteries are less expensive and offer some advantages over other varieties. However, NC batteries are the best, but they are three to four times more expensive than Lead Acid batteries.
6. HVDC transmission has ___________ as compared to HVAC transmission.
a) smaller transformer size
b) smaller conductor size
c) higher corona loss
d) smaller power transfer capabilities
Explanation: Because there is no sink effect, the conductor is smaller and the entire conductor is used to carry electricity.
7. The negative polarity is used in the monopolar link because it
a) uses less conductor size
b) is safer
c) produces less radio interference
d) has less resistance
Explanation: Because it produces less radio interference and corona, the monopolar link requires only one conductor, which is usually negative.
8. SMPS is used for
a) obtaining controlled ac power supply
b) obtaining controlled dc power supply
c) storage of dc power
d) switch from one source to another
Explanation: SMPS (Switching mode power supply) is used for obtaining controlled dc power supply.
9. SPMS are based on the ________ principle.
a) Phase control
b) Integral control
Explanation: The chopper idea is used in SMPS (switching mode power supplies). The duty cycle of the chopper circuit is used to control the output dc voltage.
10. Choose the incorrect statement.
a) SMPS is less sensitive to input voltage variations
b) SMPS is smaller as compared to rectifiers
c) SMPS has low input ripple
d) SMPS is a source of radio interference
Explanation: SMPS has higher output ripple and its regulation is worse.
Power electronics applications range in size from an AC adapter’s switched mode power supply, battery chargers, audio amplifiers, and fluorescent lamp ballasts, to variable frequency drives and DC motor drives used to operate pumps, fans, and manufacturing machinery, all the way up to gigawatt-scale high voltage direct current drives. The chopper idea is used in SMPS (switching mode power supplies). The duty cycle of the chopper circuit is used to control the output dc voltage. Low loss in power semiconductor devices results in high efficiency. The power electronic converter system has a high level of reliability.