ET ONLINE 5

1 . T h e s l i p r i n g s o f a n d i n d u c ti o n m o t or a r e m a d e o f ( a) c o p p e r ( b ) c a r b on ( c ) p h o s p h or b r o n z e ( d ) A l u m i nu m


2 . T h e s q u i r re l c a ge i n d u c t i on m ot o rs a re p r ov i d e d w i th b l ad e s i n o r d e r t o ( a) E l i m i n a t e n o i s e ( b ) Fa c i l i t a te c o ol i n g o f ro t or ( c ) b a l an c e t h e r o to r d y n am i c al l y ( d ) u nb al a n c e th e r ot o r d y n am i c a l l y


3 . U n d e r o p e r a ti n g c on d i t i o n s t h e r o t or c i rc u i t of an i n d u c t i on m ot o r i s ( a) o p e n e d o r c l o s e d f r e q u e ntl y ( b ) n o rm a l l y o p e n ( c ) a l way s c l os e d ( d ) n o rm a l l y c l o s e d

4 . I n an i n d u c t i o n m o to r t h e r at i o o f s t ar t i n g c u r r e nt t o f u l l l o ad c u r r e nt i s 12 . 65 an d t h e r a t i o of s t a r ti n g to r qu e t o f u l l l oa d t or q u e i s 1 . 6. T h e p e rc e nt s l i p a t f u l l - l oa d i s ( a) 1 % ( b ) 0 . 01 % ( c ) 2 % ( d ) 1 2. 6 4%

5 . . I f t h e r o to r p f of a 3 - p h a s e I M i s 0 . 86 6, t h e n s p at i a l d i s p l a c e m e nt b e twe e n t h e s t at o r m ag n e t i c fie l d a n d r ot o r m a gn e t i c fi e l d w i l l b e
( a) 1 50 0 ( b ) 3 0 0 ( c ) 9 0 0 ( d ) 1 20 0


6 . R ot o r e ffi c i e n c y = ( a) s / (1 + s ) ( b ) ( 1- s ) / s ( c ) ( 1+ s ) / s ( d ) s / (1 - s )

7 . A vo l tm e te r gi ve s 12 0 os c i l l at i o n s p e r m i nu t e w h e n c on n e c t e d t o t h e r ot o r of an I M . T h e s t a t or f r e q u e n c y i s 5 0H z . T h e s l i p o f th e m ot o r i s ( a) 5 % ( b ) 2 % ( c ) 2 . 5% ( d ) 4 %

8 . T h e s p e e d o f r ot a t i n g fi e l d d u e to r o t or c u rr e nt r e l a t i ve t o s t at or c or e i s ( a) s l i p * N s ( b ) N s / s l i p ( c ) N s ( d ) N

9 . W h e n l oa d i s p l ac e d o n a 3 - p h a s e i n d u c t i o n m o t or , i t s s l i p ( a) r e m a i n s c o n s t ant ( b ) i n c r e a s e s f o r s o m e va l u e an d re ma i n s c on s ta nt ( c ) d e c r e a s e s ( d ) I n c r e a s e s

1 0. A 5 0 H z 3 - p h a s e i n d uc ti o n m o t or h as a f u l l - l o ad s p e e d o f 1 44 0 r p m . T h e nu mb e r o f p o l e s of t h e m o t or a r e ( a) 4 ( b ) 8 ( c ) 6 ( d ) 1 2

1 1. I n an I n d u c t i on m ot o r i f t h e r ot o r re s i s t an c e i s e q u al t o s t an d s t i l l r e a c t a n c e , t h e m ax i mu m t o rq u e i s ( a) e q u a l o r l e s s t he n s t a rt i n g t o rq u e ( b ) E q u a l t o s t ar t i n g t or q u e ( c ) L e s s t h e n s t a r ti n g t o rq u e ( d ) m o re t h an s t ar t i n g t or q u e

1 2. T h e t or q u e s l i p ch ar a c t e r i s t i c o f a n i n d u c ti o n m o t or i s a p p rox i m at e l y a /a n ( a) s t r ai g ht l i n e ( b ) p a ra b o l a ( c ) r e c t a n gu l a r p ar a b o l a ( d ) hy p e r b o la

1 3. A d o u b l e c ag e i n d u c ti o n m o t or i s a ( a) c o mb i n at i on of s q u i r r e l c a ge a n d s l i p - ri n g i n d u c t i o n m o t or s ( b ) s l i p - ri n g ty p e ( c ) c o m mu ta t or ty p e ( d ) s q u i r r e l c a g e typ e

1 4. T h e c r aw l i n g o c c u r s i n i n d u c t i o n m o to r s d u e t o ( a) l owe r l oa d ( b ) h a rm o n i c s d e ve l op e d i n t h e m ot o r ( c ) j a m m e d b e ar i n g s ( d ) L ow s u p p l y vol t a ge

1 5. T h e c or e l os s e s , an d f ri c ti o n a n d w i n d a ge l os s e s i n c a s e o f a n i n d u c t i o n m o to r a re d e t e r m i n e d f r o m t h e t e s t ( a) s t a to r r e s i s ta n c e ( b ) n o - l o ad ( c ) l o ad ( d ) b l o cke d r ot o r

1 6. W h i ch o f th e f o l l ow i n g s t a r ti n g m e t h o d s c an n o t b e u s e d f or s t ar t i n g a 3- p h as e s q u i r r e l c a g e i n d u c t i o n m o to r ? ( a) A u t o- t ra n s f o r m e r ( b ) R ot o r r e s i s t a n c e ( c ) D i r e c t - o n - l i n e ( d ) s t a r- d e l t a

1 7. W i t h D O L s t ar t o f an i n d u c ti o n m o t or t h e h e a ti n g d u r i n g a c c e l e r a ti o n o f i n e r ti a l o ad i s p r o p o rt i o n al to ( a) M a x i mu m t or q u e ( b ) S t or e d k in e ti c e n e r g y ( c ) e l e c tr o m a gn e t i c p owe r d e ve l op e d o n r ot o r ( d ) s l i p at m a x i mu m t or q u e


1 8. C a s c a d e m e t h o d of s p e e d c ont r ol i nvol ve s t h e u s e of two c ou p l e d i n d u c t i on m o t or s . T h e n e c e s s ar y c o n d i ti o n f o r s p e e d c o nt ro l i s t h at ( a) b o t h t h e m o t or s ar e of t h e s q u i r r e l c a g e r o to r typ e h avi n g d i ff e re nt nu mb e r of p o l e s ( b ) o n e m o t or i s of t h e s l i p - r i n g ty p e an d t h e two m ot o rs h ave d i ff e r e nt nu mb e r o f p o l e s ( c ) o n e m o t or i s of t h e s l i p - r i n g ty p e b u t b o t h t h e m o t or s h ave t h e s am e nu mb e r o f p o l e s ( d ) b o t h t h e m o t or s ar e of t h e wo u n d r ot o r typ e h av i n g t h e s am e nu mb e r o f p o l e s .

1 9. T h e s p e e d r e gu l a t i on of a 3 - p h as e i n d u c t i o n m o to r a t f u l l - l oa d i s ab o u t ( a) 2 5% ( b ) 8 % ( c ) 4 % ( d ) 1 5%


2 0. I n w h i ch o f t h e f ol l ow i n g a s p e c t s i n d u c t i on ge n e ra t or d o e s n o t d i ff e r f r o m a s y n ch r o n ou s ge n e ra t or ? ( a) N o s y n ch r on i z i ng i s r e q u i r e d ( b ) i t d o e s n ot ne e d d c e x c i t at i o n ( c ) I t o n l y g e n e r at e s w h e n i t s s t a t or i s c o n n e c t e d t o t h e m ai n s of c o n s t ant f r e q u e n c y ( d ) i t s s ta t or i s d i ff e re nt i n c o n s t ru c ti o n f r o m t h a t of a s y n ch r on o u s g e n e r a t or


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