Print this page Wye-Delta Motor Starters
David A. Snyder, P.E.
Course Outline
This 4 PDH course includes descriptions of various types of wye-delta motor starters used in typical industrial control systems. More than 40 illustrations are included.
This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.
Learning Objective
The following learning objectives are included in this course:
- Understand the types of motors that can be used with a wye-delta starter;
- Understand the difference between the line and phase current values for a delta-connected three-phase motor;
- Understand how connecting the wye-start/delta-run motor in a wye configuration affects the voltage applied to the motor windings;
- Understand how connecting the wye-start/delta-run motor in a wye configuration affects the starting torque output of the motor;
- Understand how connecting the wye-start/delta-run motor in a wye configuration affects the line current going to the motor windings;
- Understand how connecting the wye-start/delta-run motor in a wye configuration affects the input impedance of the motor windings;
- Understand the terminal numbering for NEMA and IEC wye-start/delta-run motors;
- Understand the currents and voltages for dual-voltage wye-start/delta-run motors;
- Understand the concept of a wye-start/delta-run motor as three (3) single-phase loads;
- Understand the similarities and differences between open-transition and closed-transition wye-delta motor starters;
- Understand how the proper NEMA sizes of contactors are selected for wye-delta motor starters;
- Understand the principles of reversing wye-delta motor starters;
- Understand how to size the power conductors from the power source to a wye-delta motor starter;
- Understand how to size the power conductors from the wye-delta motor starter to the motor; and
- Understand how to select the thermal overload units for a wye-delta starter application.
Intended Audience
Any engineer, designer, contractor, or technician who is involved in the selection, operation, and trouble-shooting of wye-delta motor starters will benefit from this course. It is assumed that the Reader is familiar with vector representation of three-phase voltages and currents.
Benefit to Attendees
Upon successful completion of the course, the reader will have a thorough understanding of the methods used for various types of wye-delta motor starting, plus advantages, disadvantages, and limitations of those methods.
Course Introduction
The starting current of a typical low-voltage (600 V or less) motor in an industrial application is approximately 600% of the motor’s full-load current. For larger motors, this starting current can exceed 1,000 A, which can be challenging for some power systems to supply. A wye-start/delta-run motor, when started in wye, will require only one-third of the motor’s ‘normal’ delta-connected starting current, which is approximately 200% of the motor’s full-load current.
Course Content
This course content is in the following PDF document:
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Course Summary
Wye-delta motor starters are a common type of electromechanical reduced-voltage motor starters. The main advantage of wye-delta motor starters is reduced starting current, but the inherent reduced starting torque can also be a benefit in certain applications. A special type of motor, with either six leads or twelve leads, is required when using a wye-delta motor starter. The six power leads from the wye-delta motor starter to the wye-start/delta-run motor are sized differently than those for a ‘regular’ motor application. This course describes the similarities and differences between a wye-delta motor starter application and a full-voltage motor starter application.
Also discussed are reversing wye-delta motor starters, as well as the similarities and differences between NEMA and IEC starters and designations.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
