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PowerPoint ® Presentation Chapter 4 Transformer Connections Voltage Transformation Three-Phase Circuits Delta Connections Wye Connections Delta-to-Wye Connections Wye-to-Wye Connections Wye-to-Delta Connections Delta-to-Delta Connections Open Delta Connections Delta Connection with High Leg to Ground Three-Phase Transformer Polarity

Post on 29-Mar-2015

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PowerPoint® Presentation

Chapter 4Transformer Connections

Voltage Transformation Three-Phase Circuits

Delta Connections Wye Connections

Delta-to-Wye Connections Wye-to-Wye

Connections Wye-to-Delta Connections

Delta-to-Delta Connections Open Delta

Connections Delta Connection with High Leg to Ground Three-Phase Transformer Polarity

Chapter 4Transformer Connections

The low‑voltage winding of a standard distribution transformer connected to a single-phase circuit is normally made with two equal coils. These sections are arranged so that they may be connected in series or parallel.

Chapter 4Transformer Connections

Transformer polarity may be subtractive or additive.

Chapter 4Transformer Connections

The polarity of a transformer may be determined using a known transformer or with AC voltage.

Chapter 4Transformer Connections

A delta connection has the wires from the ends of each coil connected end-to-end to form a closed loop.

Chapter 4Transformer Connections

Studying the current in a delta-connected system at both 0° and 90° illustrates the current flow in a delta-connected system.

Chapter 4Transformer Connections

A wye connection has one end of each coil connected together and the other end of each coil left open for external connections.

Chapter 4Transformer Connections

Studying the current in a wye-connected system at both 0° and 90° illustrates the current flow in a wye-connected system.

Chapter 4Transformer Connections

A 3-phase delta-to-wye connection is often used for distribution where a four-wire secondary distribution circuit is required.

Chapter 4Transformer Connections

Three single-phase transformers may be connected in a wye-to-wye connection to form a 3-phase transformer.

Chapter 4Transformer Connections

A wye-to-delta connection permits single-phase and 3-phase loads to be drawn simultaneously from the delta-connected secondary at the same voltage.

Chapter 4Transformer Connections

In a wye-to-delta connection of three single-phase transformers, one unit may be disconnected from the circuit and service maintained with the secondary operating in open delta connection at 57.7% of normal bank capacity.

Chapter 4Transformer Connections

In a delta-to-delta connection, the voltage of each transformer is equal to the 3-phase line voltage and the current in each of the transformers is only 57.7% of the line current.

Chapter 4Transformer Connections

Grounding one of the midpoints of the windings provides 240 V/120 V, single-phase, 3-wire service for lighting applications.

Chapter 4Transformer Connections

An open delta connection makes 3-phase power available anywhere along the distribution line with the use of only two transformers rather than the usual three.

Chapter 4Transformer Connections

A delta connection with a high leg to ground provides 240 V, 3-phase power to equipment and 120 V power for lighting and receptacles.

Chapter 4Transformer Connections

The phase sequence on the secondary of a three-phase transformer is the same as the phase sequence on the primary.

Chapter 4Transformer Connections

Transformers are classified into connection groups according to their phase shift.

Chapter 4Transformer Connections

Chapter 4Transformer Connections