Page 207 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

MODULE 14: AC & DC Windings

EXERCISE 86 : Demonstrate small transformer winding

Objectives

At the end of this exercise you shall be able to:
• dismantle the transformer cores
• measure and determine the size of winding wire for primary and secondary winding
• take the dimensions of a bobbin and prepare the bobbin from suiTable materials
• wind the primary and secondary windings layer by layer
• stack the cores and fasten them
• terminate the winding end in a terminal board
• test the transformer for insulation, transformation ratio and performance
• design a transformer when power and voltage ratings are known.
Requirements

Tools/Instruments Materials
• Scissors 150 mm - 1 No • Super-enamelled copper wires - as reqd
• Steel rule 300 mm - 1 No • Empire sleeves 1 mm, 2mm - 1m each
• Firmer chisel 20 mm - 1 No • Air-dry varnish - 100ml
• Hammer ball pein 0.5 kg - 1 No • Resin-core solder 16 SWG - 10 g
• Iron soldering 25 W, 240V - 1 No • Soldering paste - 5 g
• DE spanner 6 mm to 25 mm - 1 No • Smooth emery paper - 1 piece
• Mallet hardwood 0.5 kg - 1 No • Fabric based fibre sheet and
• Nylon mallet 5 cm dia. - 1 No 6 mm thick - 3 mm
• D.B. Knife 100 mm - 1 No • Cotton cloth for cleaning - 500 sq.cm
• Insulation papers - as reqd

Procedure

TASK 1 : Dismantling the transformer for rewinding
1 Note down the name plate details in Table 1.
2 Draw the end connection terminal marking of the transformer in your record.
3 De-solder the leads and remove the terminal strips if they are attached to the core.
4 Loosen the nuts of the core assembly and remove the screws if any.
5 Remove the clamps attached to the core.
6 Gently tap the transformer core with a nylon mallet so that the core gets loosened.
7 Remove the stampings starting from the centre of the core using Hylam/fibre knife.
In the case of hard stacked stamping, occasionally use a thinner to loosen the stamping.

Table 1
Transformer raring plate

No of Phase ........................... SI.No..................................
V.A rating ................................ Frequency .........................
Primary voltage........................volt Secondary voltage.............volt
Primary current........................amp
Manufacturer ................................... Secondary current..............amp

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