Page 120 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Fig 6 Fig 7

Edison screw-type lamp-holders: In this type, the holder is provided with inner screw threads and the lamp
is fitted in it by screwing. It has a centre contact which is connected to the live wire and the screwed cap is
connected to the neutral wire.
For lamps with wattage above 200W and not exceeding 300W, Edison screw-type holders are used. (Fig 8).
Goliath Edison screw (GES) type holders (Fig 9): The cover of this type of holder is made of porcelain. Such
holders are used in studios, headlights, floodlights, focussing lights etc.

Fig 8 Fig 9

These holders are used for more than 300W lamps.

Specification of a lamp-holder: While specifying the lamp-holders, the type of material used for construction,
type of gripping, type of mounting, working current and voltages should also be specified.
Socket outlet current rating: The standard ratings shall be 6,16 and 32 amperes and 240 volts.
Two-pin socket: This socket is rated as 6A, 250V, having only two pins without earth connection. These are
suitable only for double insulated appliances (having PVC or insulated body).
Two-pin plug top: It is used for taking the supply from the socket. It has got two pins of the same size.
Three-pin socket: This type of socket is suitable for light and power circuits. These sockets are rated as 6A,
250V or 16A, 250V, and are available as surface-mounting type and flush type (Fig 10). There are three terminals
marked as Line (L) Neutral (N) and Earth (E).

Three-pin plug top : It is used for taking the supply from the socket. It has three pins. Two are similar in size
and the third one is bigger and longer which is for earth (Fig 11). These are also rated as 6A,250V or 16A, 250V.
These are made of bakelite, PVC materials.

Fig 10 Fig 11

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CITS : Power - Electrician & Wireman - Lesson 20-25 CITS : Power - Electrician & Wireman - Lesson 20-25