Page 280 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Stone: The grinder stone consists of two parts of stones. One male and one female. The male part grinds the
grains during rotation against conical cavity in the base (female stone). This female part is actually attached to
the stainless steel container which rotates when the motor is energised. Both the stones are manufactured with
hard granite which is usually whitish black in colour.
Pulley: The drum speed is lower than the motor speed, normally 500 to 600 r.p.m. The motor speed is normally
1450 r.p.m. and the speed of the drum is reduced by using a larger diameter pulley than the driven pulley, usually
in the ratio of 1:3. The transmission of force between the driver pulley and the driven pulley is through a V belt of
type No A 36 or A 39 (Fig 4).
Fig 4

Frame and stand: The grinding stones, motor pulleys are all housed in a rectangular frame with sunmica or
stainless steel covering or plastic moulding for decoration as well as safety. A separate vertical stand is provided
on one side of the grinder for holding the male grinding stone. If the MS frame is used, it is usually to be
chromium plated.
Wet grinder- maintenance and servicing: In wet grinders, the trouble may be classified into two types. Electrical
faults and Mechanical faults. Some mechanical faults create electrical faults too.
Some common problems and their rectifications are given in the Table 1.

Safety measures
• Make sure power is turned off before working on electrical equipment.
• Plug to be removed from the socket.
Maintenance practices: An electrical machine or appliance to be maintained according to the programme
already made. Certain maintenance practices to be observed are,
– Daily maintenance
– Monthly maintenance

– Yearly maintenance
Table 1
Sl.No. Complaints Causes Test and remedy

1 Motor does not start Short-circuited windings. Rewind the windings.
Grounded winding. Rectify or rewind the windings.
Grounded winding. Solder the joints; if not possible rewind the
Broken wire from line windings.
cord to windings. Solder the broken wire in the line cord or
Defective capacitor. change the line cord.
Blown fuse. Replace the correct capacitor.
Excessive load. Find the cause and replace the fuse.
Defective centrifugal Reduce the load.
switch. Rectify or replace the defective switch.
Rectify or replace the centrifugal switch.

2 Motor starts but Centrifugal switch not Rectify or replace the centrifugal switch.
heats up rapidly opening.
Short-circuited winding. Rewind the windings.
Grounded winding. Rectify or rewind the windings.

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CITS : Power - Electrician & Wireman - Lesson 101-103