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?

02/10/2010


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



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Your leaks start here: Take a disciplined approach with your hydraulic system; U.S. presence at Hannover Messe a rousing success
Hannover Messe 2016: Taking hold of the future - Partner Country status spotlights U.S. manufacturing; Honoring manufacturing excellence: The 2015 Product of the Year Winners
Inside IIoT: How technology, strategy can improve your operation; Dry media or web scrubber?; Six steps to design a PM program
Getting to the bottom of subsea repairs: Older pipelines need more attention, and operators need a repair strategy; OTC preview; Offshore production difficult - and crucial
Digital oilfields: Integrated HMI/SCADA systems enable smarter data acquisition; Real-world impact of simulation; Electric actuator technology prospers in production fields
Special report: U.S. natural gas; LNG transport technologies evolve to meet market demand; Understanding new methane regulations; Predictive maintenance for gas pipeline compressors
Warehouse winter comfort: The HTHV solution; Cooling with natural gas; Plastics industry booming
Managing automation upgrades, retrofits; Making technical, business sense; Ensuring network cyber security
Designing generator systems; Using online commissioning tools; Selective coordination best practices

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role that compressed air plays in manufacturing plants.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me