EE8401 Important Questions ELECTRICAL MACHINES 2
EE8401 Important Questions Electrical Machines 2 Regulation 2017 Anna University free download. Electrical Machines 2 Important Questions EE8401 pdf free download.
Sample EE8401 Important Questions Electrical Machines 2
1. What do you mean by single layer and double layer winding? (Apr/may 2017)
In a single layer winding, a slot consists of only one coil side while in double layer it consists of two coil sides arranged one over the other in two layers. EE8401 Important Questions Electrical Machines 2
2. Define Voltage Regulation. (Apr/may 2017) (May/Jun 2016)
The voltage regulation of an alternator is defined as the change in its terminal voltage when full load is
removed, keeping field excitation and speed constant, divided by the rated terminal voltage.
3. Distinguish the use of salient pole and round rotor synchronous machines. (Nov/Dec 2016)
Salient pole types are used for low speed alternators with speeds ranging from 125 to 500 r.p.m. The non
salient pole types are used for high speed alternators called turbo alternators with speeds ranging from 1500 to
3000 r.p.m. EE8401 Important Questions Electrical Machines 2
4. Draw typical open circuit and short circuit characteristics of synchronous machine. (Nov/Dec 2016)
6. Define armature reaction. (Nov/Dec 2015)
The interaction between flux set up by the current carrying armature conductors and the main field
flux is defined as the armature reaction. EE8401 Important Questions Electrical Machines 2
7. What are all the various methods to determine the voltage regulation? (Nov/Dec 2015)
(i) Synchronous Impedance method or EMF method
(ii) Ampere Turns method or MMF method
(iii) Zero Power Factor method or Potier Triangle method
(iv) ASA modified form of MMF method
(v) Two Reaction Theory EE8401 Important Questions Electrical Machines 2
8. Why are Alternators rated in kVA and not in kW? [Nov/Dec 2011]
The continuous power rating of any machine is generally defined as the power the machine or apparatus
can deliver for a continuous period so that the losses incurred in the machine gives rise to a steady temperature
rise not exceeding the limit prescribed by the insulation class. Apart from the constant loss incurred in
Alternators is the copper loss, occurring in the 3 –phase winding which depends on I2R, the square of the
current delivered by the generator. As the current is directly related to apparent power delivered by the
generator, the Alternators have only their apparent power in VA/kVA/MVA as their power rating. EE8401 Important Questions Electrical Machines 2
9. Why is short pitch winding preferred over full-pitch winding? [Nov/Dec 2011]
Advantages
i. Waveform of the emf can be approximately made to a sine wave and distorting harmonics can be
reduced or totally eliminated.
ii. Conductor material, copper, is saved in the back and front end connections due to less coil-span.
iii. Fractional slot winding with fractional number of slots/phase can be used which in turn reduces the
tooth ripples.
iv. Mechanical strength of the coil is increased. EE8401 Important Questions Electrical Machines 2
10. What do you mean by synchronous reactance? [Nov/Dec 2011]
Synchronous reactance X s= (XL + Xa). The value of leakage reactance XL is constant for a machine
based on its construction. Xa depends on saturating condition of the machine. It is the addition of Xa , which
represents the armature reaction effect between two synchronously acting magnetic fields that makes the total
reactance Xa to be called synchronous reactance. EE8401 Important Questions Electrical Machines 2
11. Define distribution factor. [Apr/ May 2009]
The ratio of the vector sum of the emfs induced in all the coils distributed in a no. of slots under one pole
to the arithmetic sum of the emfs induced is known as distribution factor. EE8401 Important Questions Electrical Machines 2
| Subject name | Electrical Machines 2 |
| Short Name | EM 2 |
| Semester | 4 |
| Subject Code | EE8401 |
| Regulation | 2017 regulation |
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