Please solve all Choose the correct answer1) If speed of a synchronous generator decresed from 1800 RPM to 900 RPM the emf ofone phase becomea) one-fourthb) one-halfc)one-fifthd)Twice2) The voltage regulation of alternator depends on which factor:a) Both of theseb) power factor c)load current d) non of these3) For a synchronous machine three phase armature to have a 0.966 distribution factorthe number of slots per pole per phase, and the number of slots per pole should be,respectively:a) 9,3b)5,15c) 1,3d)2,64) A synchronous machine has its field winding on the rotor and polyphaser armaturewinding on the stator. When running under steady state conditions, its air gap field isb) Rotating at synchronous speed Ns with respectC) Rotating at double the Ns with respect to rotora) Stationary with respect to statorto statord) Stationary with respect to rotore) Rotating at ns in the direction of rotor rotation f) answer b,d,e g)answer c,d,e5) An electric machine is considered as synchronous machine only ifa) Stator flux, rotor speed, stator current frequency have invariant relationship during machineoperationc) All of the aboveb) The rotor speed is equal to stator produced flux speedd) Stator current frequency is equal to rotating flux frequency6) The losses in a synchronous machinea) Mechanical loss b) All of thesesc) stray loss d) Iron loss e) Copper loss7) A three-phase, 250 hp, 2300 V, 60 Hz, Y-connected non salient rotorsynchronous motor has asynchronous reartance of 11 ohms per phase. When itdraws 165.8 kW, the power angle is 15electrical degrees. Neglect ahmic losses,power factor isa) 0.8 lagging b) None of thesec) 0.77 laggingd) 0.77 leading8) For eliminating the 7th harmonic of the emf wave of an alternator the fractional pitchmust bea) 7/6b) 7/8c)none of thesed) 2/39) For which value of power factor the effect of armature reaction is minimum:a) leading10) A 3 phase, 2-pole alternator has 24 stator slots carrying a 3 phase distributed winding.Each coll of the winding in short charded by one slot-pitch The winding factor (Kw) isb) 0.5 P.F lagging or leadingc) laggingd)Unitya) 0.8565b)0.9147c)0.8565c) None of these

In this question , we will solve synchronous machine speed related question , voltage regulation…

1) If speed of a synchronous generator decresed from 1800 RPM to 900 RPM the emf of one phase become a) one-fourth b) one-half c)one-fifth d)Twice 2) The voltage regulation of alternator depends on which factor: a) Both of these b) power factor c)load current d) non of these 3) For a synchronous machine three phase armature to have a 0.966 distribution factor the number of slots per pole per phase, and the number of slots per pole should be, respectively: a) 9,3 b)5,15 c) 1,3 d)2,6 4) A synchronous machine has its field winding on the rotor and polyphaser armature winding on the stator. When running under steady state conditions, its air gap field is a) Stationary with respect to stator b) Rotating at svnchronous speed Ns with resnect

1) If speed of a synchronous generator decresed from 1800 RPM to 900 RPM the emf of one phase become a) one-fourth b) one-half c)one-fifth d)Twice 2) The voltage regulation of alternator depends on which factor: a) Both of these b) power factor c)load current d) non of these 3) For a synchronous machine three phase armature to have a 0.966 distribution factor the number of slots per pole per phase, and the number of slots per pole should be, respectively: a) 9,3 b)5,15 c) 1,3 d)2,6 4) A synchronous machine has its field winding on the rotor and polyphaser armature winding on the stator. When running under steady state conditions, its air gap field is a) Stationary with respect to stator b) Rotating at svnchronous speed Ns with resnect

Electric Motor Control

10th Edition

ISBN:9781133702818

Author:Herman

Publisher:Herman

Chapter39: Synchronous Motor Operation

Section: Chapter Questions

Problem 14SQ: Induction motors and welding transformers require magnetizing current, which causes a. lagging power...

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