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In case of synchronous motor, which of the following are true? a. Synchronous motor is not self-starting b. If the rotor poles are excited by field current and the stator terminals are connected to AC supply, motor vibrates. c. Variable frequency supply is used to start synchronous motor. d. By using frequency converter, a synchronous motor can be brought from standstill to its desired speed.
A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
Consider the following statements regarding synchronous machines: 1. When a synchronous motor is over-excited, its back emf is greater than the supply voltage 2. When a synchronous motor is over-excited, its power factor is leading 3. Synchronous motor is used as capacitor where load is so large that construction of a static capacitor is impractical Which of these statements are correct?
When excitation of synchronous motor is increased upto normal excitation from under excitation, armature current
Which of the following statements are true? a. As load increases armature current decreases, regardless of excitation. b. For under and over excited motors, power factor tends to approach zero with increase in load c. With normal excitation when load is increased, change in armature current is greater than in power factor which tends to become increasingly leading. d. Both with under and over excitation, change in power factor is greater than in armature current with increase in load.
A synchronous motor is operated at a bus voltage of 1.5 pu and drawing 1.0 pu at zpf leading current. Its synchronous reactance is 0.4 pu. What is the excitation emf of the motor?
A passage is given with five questions following it. Read the passage carefully and select the best answer to each question out of the given fouralternatives. Teaching about compassion and empathy in schools can help deal with problems of climate change and environmental degradation,” says Barbara Maas, secretary,
Standing Committee for Environment and Conservation, International Buddhist Confederation (IBC). She was in New Delhi to participate in the IBCs governing
council meeting, December 10-11, 2017. “We started an awareness campaign in the year 2005-2006 with H H The Dalai Lama when we learnt that tiger skins were
being traded in China and Tibet. At that time, I was not a Buddhist; I wrote to the Dalai Lama asking him to say that this is harmful and he wrote back to say, “We
will stop this.” He used very strong words during the Kalachakra in 2006, when he said, If he sees people wearing fur and skins, he doesnt feel like living. This sent
huge shock waves in the Himalayan community. Within six months, in Lhasa, people ripped the fur trim of their tubba, the traditional Tibetan dress. The messenger was ideal and the audience was receptive,” says Maas who is a conservationist. She has studied the battered foxs behavioral ecology in Serengeti,Africa. She heads the endangered species conservation at the Nature and Biodiversity Conservation Union (NABU) International Foundation for Nature, Berlin. “I metSamdhong Rinpoche, The Karmapa, HH the Dalai Lama and Geshe Lhakdor and I thought, if by being a Buddhist, you become like this, I am going for it, “says Maas, who led the IBC initiative for including the Buddhist perspective to the global discourse on climate change by presenting the statement, The Time to Act is Now: aBuddhist Declaration on Climate Change, at COP21 in Paris. “It was for the first time in the history of Buddhism that leaders of different sanghas came together to take a stand on anything! The statement lists a couple ofimportant things: the first is that we amass things that we dont need; there is overpopulation; we need to live with contentment and deal with each other and theenvironment with love and compassion,” elaborates Maas. She is an ardent advocate of a vegan diet because “consuming meat and milk globally contributes more toclimate change than all "transport in the world.” Turning vegetarian or vegan usually requires complete change of perspective before one gives up eating their favorite food. What are the Buddhist ways to bringabout this kind of change at the individual level? “To change our behavior, Buddhism is an ideal vehicle; it made me a more contented person,” says Maas, who grewup in Germany, as a sausage chomping, meat-loving individual. She says, “If I can change, so can anybody”. Why did Ms. Barbara Mass say “If I can change, so can anybody”?
When a synchronous motor runs at no load with adjustable excitation over a wide range, power factor can be improved by varying the excitation of its
A synchronous motor on load draw a current at a leading power factor angle ϕ. If the internal power factor angle which is the phase angle between the excitation emf and the current in the time phasor diagram is ψ. Then the air gap excitation mmf lags the armature mmf by
A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have