Observation

This is a popular question, and majority of the candidates responded to it.
In part (a), majority of the candidates exhibited good knowledge of corrective maintenance.
In part (b), majority of the candidates did not understand conduit fittings.
In part (c), majority of the candidates showed poor knowledge of IEE regulations on conduit       installations.
In part (d), majority of the candidates did not understand  d.c. machine and a.c. generator. 
In part (e), majority of the candidates could not state four methods of starting a three – phase    induction motor.

The expected answers are:
1 (a) (i)    Corrective maintenance is the type of maintenance / repairs carried out on a
machine / device / equipment to put it into use after a breakdown / damage has
occurred  OR This is the type of maintenance done after an installation has been
damaged  to restore it to active installation.                                                                                                                                                                                                                                          
(ii) Disadvantages of corrective maintenance
-    stoppage / delay of work
-    It is expensive / costly
-    It wastes time / it is time consuming
                                                           
(iii) Types of electrical machine enclosures
-   Pipe ventilated
-   Drip-proof
-   Screen protected
-  Totally enclosed
-   Flame proof
-   Open type                                                                      

 (b)  Uses of named conduit fittings
(i)      It is used to link / connect pipes at an angle           
(ii)     It is used to link the pipes / conduit to the back entry boxes / looping boxes / joint boxes  
(iii)    It is used to hold conduit firmly in place  
(iv)    It is used to join two lengths of conduit / pipes    

(c)       IEE regulations on conduit installations
-    conduit must be erected before cables are drawn into it
-    the space factor must not exceed 40%
-    extra low and low voltage cables must not be installed in the same conduit
-    conduit installed in a damp environment must have water resistance finishing
-    all exposed metals must be bonded
-    all joints must be mechanically sound and electrically continuous
-    it is essential that the whole of the conduit system be efficiently earthed
-    all burrs must be removed to prevent abrasion
-    proper precautions must be taken against corrosion
-    PVC conduit must not be used where the ambient temperature exceeds 600C
                                    

(d) (i)    Information on the name plate of a three-phase machine
-   Supply / Rated voltage
-   frequency
-   horse power
-   speed
-   winding connection
-   current rating 
-   manufacturer’s name and address
 
(ii)    Constructional features of a d.c. machine   
-   eye bolt
-   pole shoe
-   main pole
-   field winding
-   interpole
-   commutator
-   armature (windings)
-   yoke                                                                                                                            

(iii)     Causes of low voltage output of an a.c. generator
-   low speed
-   faulty A.V.R
-   lost of residual magnetism 

                                                             
(e)        Methods of starting a three-phase induction motor
-    Direct-on-line starter
-    star-delta starter
-    primary resistance starter
-    auto transformer starter
-    rotor resistance starter
-    stator resistance starter