NEW_DCMT_LAB_Manual_soft.docx - Ex No Date STUDY OF THREE PHASE TRANSFORMER CONNECTIONS OBJECTIVE To perform the three phase transformer in various

NEW_DCMT_LAB_Manual_soft.docx - Ex No Date STUDY OF THREE...

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Ex. No: Date: STUDY OF THREE PHASE TRANSFORMER CONNECTIONS OBJECTIVE To perform the three phase transformer in various modes and to obtain the voltage current relations. APPARATUS REQUIRED S.NO NAME TYPE RANGE QUANTIT Y 1 Ammeter 2 Voltmeter 3 Multimeter 4 3-Φ auto transformer 5 3-Φ loading rheostat THEORY MODES OF CONNECTIONS 1. STAR / STAR 2. DELTA / DELTA 3. STAR / DELTA 4. DELTA / STAR STAR / STAR (OR) Y / Y CONNECTION: Fig shows a bank of three transformers connected in Y on both the primary and secondary sides. If the ratio of transformations of each transformer is K , the same ratio will exists between the line voltages on the primary and secondary sides. This connection will give satisfactory service only if the three-phase load is balanced; when the load is unbalanced, the electrical neutral will shift from its exact centre to a point that will make the line – to – neutral voltages unequal. 1
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Ex. No: Date: DELTA / DELTA (OR) Δ / Δ CONNECTION: Fig shows a bank of transformers connected in Δ on both the primary and secondary sides. This arrangement is generally used in systems in which the voltages are not very high and especially when continuity of service must be maintained even though one of the transformers should fail. STAR / DELTA (OR) Y / Δ CONNECTION The Y / Δ connection is shown in figure. It is principally used where the voltage is to be stepped down, as for example, at the end of a transmission line. It is also employed in moderately low voltage distribution circuits for stepping down from transmission voltages of 4000 or 8000 V to 230 (and 115 V). DELTA / STAR (OR) Δ / Y CONNECTION The three phase Δ / Y connections are shown in figure. This type of connection is employed where it is necessary to step up the voltage, as for example, at the beginning of a high tension transmission system. 2
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AC Breaker & Isolator 220-V 3-Φ Supply R 3- Two winding Transformer 3- Auto Transformer DELTA / DELTA 220-V 3-Φ Supply Y B FUSE FUSE FUSE V L VS4-1 VS4-2 3- Phase Loading Rheostat Of 1 2 3 4 5 Y B R A CS4-1 CS4-2 A CS1-1 CS1-2 V L VS1-1 VS1-2 Ex. No: Date: Circuit Diagram: 3
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AC Breaker & Isolator 220-V 3-Φ Supply R 3- Two winding Transformer 3- Auto Transformer DELTA / STAR 220-V 3-Φ Supply Y B FUSE FUSE FUSE V L VS1-1 VS1-2 A CS1-1 CS1-2 V L VS4-1 VS4-2 3- Phase Loading Rheostat Of 1 2 3 4 5 Y B R A CS4-1 CS4-2 Ex. No: Date: Circuit Diagram: 4
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AC Breaker & Isolator 220-V 3-Φ Supply R 3- Two winding Transformer 3- Auto Transformer STAR / DELTA 220-V 3-Φ Supply Y B FUSE FUSE FUSE V L VS1-1 VS1-2 A CS1-1 CS1-2 V L VS4-1 VS4-2 3- Phase Loading Rheostat Of 1 2 3 4 5 Y B R A CS4-1 CS4-2 Ex. No: Date: Circuit Diagram: 5
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AC Breaker & Isolator 220-V 3-Φ Supply R 3- Two winding Transformer 3- Auto Transformer STAR / STAR 220-V 3-Φ Supply Y B FUSE FUSE FUSE V L VS1-1 VS1-2 A CS1-1 CS1-2 V L VS4-1 VS4-2 3- Phase Loading Rheostat Of 1 2 3 4 5 Y B R A CS4-1 CS4-2 Ex. No: Date: Circuit Diagram: 6
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Ex. No: Date: TABULAR COLUMN: CONNECTION OF MODE PRIMARY SIDE (Voltage / Current) SECONDARY SIDE (Voltage / Current) Voltage ration Curren t ration V PH V L I PH I L V PH V L I PH I L
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