Induction motors with autotransformers

Bruce Konzak writes:Dear Control Engineering: Does a single phase 240 Vac induction motor have the same performance characteristics when powered by an autotransformer with a line to neutral feeder, as it does when powered normally by a line-to-line connection 120 degrees out of phase?

02/11/2010


Bruce Konzak writes:Dear Control Engineering: Does a single phase 240 Vac induction motor have the same performance characteristics when powered by an autotransformer with a line to neutral feeder, as it does when powered normally by a line-to-line connection 120 degrees out of phase? I’m having some trouble getting consensus on this one.

We put the question to Joe Pottebaum, senior application engineer for Yaskawa Electric America, Inc. He answers:

“To answer this question definitively requires more information than what is given. Nevertheless, if we assume that the auto-transformer is suitably rated for the motor, then the motor will suffer virtually no degradation in its performance when powered through the auto-transformer. The motor will be happy as long as it sees 240 volts. However, there are some considerations.

“Typical household 240 Vac single phase service is grounded at the center-tap of the transformer secondary feeding the building. The grounded center-tap becomes the neutral (white wire) for two 120 Vac circuits throughout the building. Therefore, when 240 Vac is used directly to power a 240 volt motor, the maximum voltage with respect to ground is 120 Vac. In the description, it appears that the auto-transformer is being used to step up or step down voltage from a feeder with one side grounded. If the motor is connected between that grounded side and the auto-transformer 240 Vac tap, then the maximum voltage with respect to ground is 240 Vac, double the 120 Vac from a conventional service. Generally, this is not a problem, but does merit checking with the motor manufacturer.”

Read Who’s using industrial drives? for links to additional motor related topics.

Posted by Ask Control Engineering on February 20, 201



The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me