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
Days after a massive, distributed denial-of-service attack took down dozens of major websites around the country, ARM Holdings plc is rolling out a pair of new processor architectures aimed at shoring up IoT security.
Dow Chemical and several other companies have launched a program in Omaha, Neb. to divert about 36 tons of plastics from landfills in its first phase, and convert it into energy used for cement production.
Both traditional automation companies and startups are developing technologies to improve processes on the factory floor, while smart sensors and other IoT-related technologies are improving how products are handled during transport and across the supply chain.
Remote monitoring now looks beyond the individual motor or conveyor and instead views the process from end to end.
BASF is partnering with Hyundai on a high-performance concept car that showcases both eco-friendly, sustainable materials and materials to enable lighter weight cars.
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 10 - 14, Embedded System Design Techniques™: Getting Started Developing Professional Embedded Software
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7 | 8 | 9 | 10

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.
Next Course September 27-29:
Sponsored by 3M
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Technology Marketplace

Copyright © 2016 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service