What two factors affect the frequency of an alternator? What is the advantage of taking the output from the stator in a rotating-field alternator What is an exciter? What is the purpose of the diodes in an automobile alternator? A

a.) full loadb.) half load

What are the differences between a Flyback Converter and a Push-Pull Converter in Electrical Engineering?

32. An alternator requires an alternating current of 2.1 A to produce on short circuit its full-load current of 50 A. The same on open-circuit an emf of 320 V. The armature resistance is 1Ohms . Find the full-load percentage regulation with a lagging p.f. of 0.6 when terminal p.d. on load is 2000 V. A. 7.2% B. 28.8% C. 3.6% D. 14.4%

2. A 250 kVA, 480 V, 50 Hz, delta-connected alternator with a rated field current of 5 A was tested and the following test data were obtained: • Open circuit terminal voltage from OC test data is 540 V at the rated IF. • Short circuit current from SC test data is 300 A at the rated IF. • A dc current of 20A is flowing through any two stator armature terminals, when a DC voltage of 10 V was applied to two of the terminals. Evaluate the following from above tests data the armature resistance, the approximate synchronous reactance and voltage regulation at rated load and 0.7 pf lead.

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Determine the efficiency of a 1200 kVA, 4160 Volts, 3-phase, Y-connected alternator, which operates at rated output with a power factor of 83%. The DC armature resistance at 70 degree C between terminals is 0.10 ohm. The field takes 75 amps at 115 Volts from the exciter equipment. Friction and windage losses are 15 kW, iron loss is 40 kW and stray load losses is 1.75 kW. Assume the effective armature winding resistance is 1.65 times the DC value.

What are the disadvantages of low power factor?