(A) 12
(B) 10
(C) 100
(D) 25
Answer: (B) 10
Explanation:
Concept:
The capacity of the battery is represented in terms of Amp-hour.
The capacity of battery = current delivered × duration of time
Calculation:
The capacity of battery = 100 Ah
Current delivered = 10 A
Duration of time = 100/10 = 10 hrs
Which of the below can improve power factor?
(A) Single phase induction motor
(B) Over-excited synchronous motor running without mechanical load
(C) Alternator
(D) Three phase induction motor
Answer: (B) Over-excited synchronous motor running without mechanical load
Explanation:
Applications of Synchronous motors:
The important characteristics of the synchronous motor is its constant speed irrespective of the load conditions and variable power factor operation.
Due to constant speed characteristics, it is used in machine tools, motor generator sets, synchronous clocks, stroboscopic devices, timing devices, belt driven reciprocating compressors, fans and blowers, centrifugal pumps, vacuum pumps, pulp grinders, textile mills, paper mills line shafts, rolling mills, cement mills etc.
Over-excited synchronous motors draw leading current and hence acts as synchronous condenser. So, they are used to improve the power factor and to improve the voltage regulation.
Synchronous motors are generally used for voltage regulation of long transmission lines but not the current regulation.
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