William K.
User Rank
Re: The decision between motor types
William K.   1/20/2014 8:54:22 PM
We have an interesting statement here, "AC motors must generate a magnetic field in order to operate. As a result, AC motors typically have high inrush currents." My experience is that ALL motors must generate a magnetic field to operate. Sort of an interesting argument. PM motors don't need to generate two magnetic fields, so they are a bit more efficient in that aspect. 

What is indeed certainis that some kinds of motors are easier to control than others, and some are much simpler to ramp up the speed with than others. But just running on a lower voltage actually reduces efficiency because the resistance losses are greater. The 24 volt DC motor is probably a lot simpler to use as an intermittant duty motor with the speed ramped up and down, and it is undoubtedly more efficient than an AC motor running constantly with a slip clutch slipping when things are halted. 

My point here is that the benefits come from the application of more complex control schemes, not because of some particular technology. Variable speed AC drives can also deliver some real savings. 

Cabe Atwell
User Rank
Re: The decision between motor types
Cabe Atwell   1/20/2014 5:36:50 PM
Indeed, some factories require both AC and DC, which can further complicate matters.

William K.
User Rank
The decision between motor types
William K.   12/6/2013 8:57:24 PM
This is an interesting post that does provide some useful insight. But the slant toward brushless low voltage motor controls is sort of obvious. So clearly the choice needs to be based at least partly on just exactly what the motor need to do. But other concerns include the cost of controls and the maintenance of those controls. A standard small three-phase motor can go for many years with no attention at all, and if something does eventually fail there are lots of folks qualified to do the repairs. Brushless motors are quite a bit more complex, and servicing their systems requires a good bit more skill and education.

So the choice is not always simple and straight-forward.

Rob Spiegel
User Rank
AC or DC?
Rob Spiegel   12/5/2013 10:53:12 AM
Good article, David. You showed just how complex this question actually is.

Partner Zone
Latest Analysis
Imagine being able to illegally download a physical product the same way you can with music and videos. That’s basically what’s happening with 3D printing and digital manufacturing, with huge repercussions in the intellectual property domain.
Our latest Design News Quick Poll reveals that readers are facing serious cyber security challenges.
Ford will be the first automaker to commercially use Alcoa's tough & fast Micromill aluminum alloy process and materials, debuting on several 2016 F-150 truck components. Alcoa will also license its Micromill process and materials technology to Danieli Group.
Even as an increasing number of instrument manufacturers migrate toward modern touch screens, many engineers say they still prefer the tactile feel of knobs and buttons, a new survey says.
Caterpillar Inc. demonstrated this week at Design and Manufacturing Philadelphia that heavy industry can reap big benefits from 3D printing.
Design News Webinar Series
10/1/2015 11:00 a.m. California / 2:00 p.m. New York
9/10/2015 11:00 a.m. California / 2:00 p.m. New York
10/20/2015 8:00 a.m. California / 11:00 a.m. New York
11/10/2015 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 5 - 9, Standards for the Internet of Things (IoT)
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2015 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service