Transformer Connections 1

COURSE DESCRIPTION

The purpose of this unit is to teach the common types of transformers and how to reference nameplate information.  Basic concepts of transformers and primary systems are covered as well as single-phase connections. Single-phase distribution transformers can be interconnected to provide three-phase power in a number of different ways, providing a utility with the flexibility of meeting a variety of customer needs. This program demonstrates and explains how three-phase delta connections and three-phase wye connections are made.

COURSE GOALS

• Identify the characteristics that are common to most single-phase overhead transformers.

• Explain the difference between delta and wye primary systems.

• Demonstrate how to make single-phase transformer connections.

• Demonstrate how three single-phase transformers can be connected in a delta-delta configuration on both the primary and secondary sides using one-line diagrams.

• Demonstrate how three single-phase transformers can be connected in a wye-wye configuration on both the primary and secondary sides using one-line diagrams.

SUBJECTS AND OBJECTIVES

Transformer Basics

• Define the term “transformer” and identify some common types of overhead distribution transformers.

• Describe the designations that are commonly used to identify primary and secondary bushings.

• List and explain basic information found on a transformer nameplate.

Primary Systems

• Differentiate between delta and wye primary systems.

• Recognize and explain the one-line diagrams used to illustrate delta and wye systems.

• List and explain basic requirements for connecting transformers to delta and wye systems.

Single-Phase Transformer Connections

• Demonstrate and explain how single-phase transformers can be connected to supply single-phase service.

Three-Phase Primary Connections

• Demonstrate and explain a three-phase delta primary connection using three single-phase transformers.

• Demonstrate and explain a three-phase delta secondary connection that provides zero and 180 degrees angular displacement.

• List and explain the expected secondary voltages of a delta-delta connection.

Three-Phase Wye Connections

• Demonstrate and explain a three-phase wye primary connection using three single-phase transformers.

• Explain how the windings that make up the secondary windings are connected in order to make wye connections.

• Recognize and identify the one-line diagrams used to illustrate a wye-wye connection.

• Demonstrate and explain how a wye-wye connection with zero degrees of angular displacement is made.

• List and explain the secondary voltages that can be supplied from a wye-wye connected three-phase bank.