Page 108 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

EXERCISE 45 : To perform STAR-DELTA connection of 3

phase transformer

Objectives

At the end of this exercise you shall be able to
• check the construction of 3 phase transformer, identify the parts and ratings.
• identify the primary and secondary terminals of 3 ph. Transformer.
• perform the STAR & DELTA connection in primary and secondary windings of 3 ph transformer.
• connect the transformer to 3 ph. Supply and measure voltage & current in STAR & DELTA connection.
Requirements

Tools/Equipments/Instruments Materials/Components
• Combination plier (165mm, insulated) - 1 No. • PVC copper wire (1.5 sq.mm) - 2 meter.
• Screw driver (150mm, insulated stem) - 1 No. • Test lamp (100 W, 230V) - 1 No.
• Neon Tester (75mm, 500 V) - 1 No. • TPST switch (32 A, 415 V) - 1 No.
• Electrician knife (Insulated) - 1 No. • Cotton waste - as reqd.
• Voltmeter (MI, 600 V) - 2 Nos.
• Ammeter (MI, 10 A) - 2 Nos.
• Multi meter (Digital, 3 digit) - 2 Nos.
1/2
• 3 Ph. Transformer
(5 KVA, 3 Ph. 415 V) - 1 No.
• 3 ph. Auto transformer (0-450 V AC) - 1 No.
• 3 ph. Lamp load (5 KW) - 1 No.
Procedure

TASK 1 : Identify the primary & secondary of 3ph transformer
1 Collect the Tools, equipments and materials required for experiment.
2 Draw the diagram of STAR & DELTA connection and equations.

3 Draw the connection diagram of 3 ph. Transformer with STAR-DELTA connections.
4 Check the construction of 3 ph. Transformer, rating & specifications.
5 Identify the primary and secondary terminals of 3 ph. Transformer and mark the terminals as
Primary terminals U - U , V - V , W - W 2
2
1
1
1
2
Secondary terminals X - X , Y - Y , Z - Z 2
2
1
1
2
1
TASK 2: Perform STAR - DELTA Connection of transformer and connect to the supply
1 Make the STAR connection of primary terminals of transformer as per STAR sequence.
2 Make the DELTA connection of secondary terminals of transformer as per DELTA sequence.
3 Connect the primary terminals U V W to 3 ph. Auto transformer terminals with Voltmeter and Ammeter.
1
1
1
4 Connect the secondary terminals X Y Z to 3 ph. Lamp load terminals with Voltmeter & Ammeter.
1 1 1
5 Check the connections, connect the 3 ph. Auto transformer to main supply & ensure that its knob kept at 0
volts
6 Switch ON the mains with TPST switch, and slowly increase the primary voltage in 3 ph. Auto transformer until
voltmeter reads line voltage of 230 V

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