Servo motor versus induction motor systems

Cover story tutorial: Choosing between permanent magnet servo motor or induction motor systems depends on application performance criteria. Consider this advice for the best fit. See more information and photos online, including comparative table.
By Mark T. Hoske October 31, 2012

Control Engineering, October 2012Motor selection: When deciding between permanent magnet (PM) servo motor or induction motor systems, consider dynamic performance, torque density, inertia matching, and control schemes. Choosing between servos and induction motors depends on the level of application performance and costs. Induction motors are simple, low cost, and straightforward.

Servo motors can offer higher performance, faster speeds, and smaller sizes. PM synchronous motors offer advantages on high-energy- consuming and high-dynamic applications, compared to induction motors. Variable frequency drives used with asynchronous motors also can be used with synchronous servo motors, producing higher efficiencies than an asynchronous motor, using perhaps 30% less energy in positioning applications.

Induction motor systems (lower cost, rugged, reliable, and well known) can offer an alternative to servo motor systems (the traditional, established solution) for certain applications. This, of course, is based on similar electronic controls being used (with the latest technology and approximately the same cost), leaving the cost of motors the differentiating issue.

Thanks to Frank Bartos, Control Engineering contributing editor, and to the four authors below, for the information above. In this issue, “Inside Machines” has a direct drive rotary motor technologies article.

– Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, mhoske@cfemedia. com.

The articles below were in the cover story in a shorter format. Links to the longer online versions follow.

Permanent magnet motors outperform induction motors in many applications

Permanent magnet synchronous motors offer significant advantages on high-energy-consuming and high-dynamic applications, compared to induction motors. See table, photo gallery.

Permanent magnet servomotors versus induction motor systems

Motor selection: When deciding on the use of permanent magnet (PM) servomotors or induction motor systems, consider dynamic performance, torque density, inertia matching, and control schemes.

Servos versus induction motors: Look at performance, costs

Choosing between servos and induction motors depends on the level of performance required by the application and costs. Induction motors are simple, low-cost, and straightforward. Servos can offer higher performance, faster speeds, and smaller sizes.

Drives and designs can make synchronous servo motors more efficient

Information in the last section of the cover story was summarized from this article. Energy-saving drive solutions – Industrial Energy Management: Intelligent concepts cut costs and protect the environment while saving energy; high-efficiency energy conversion and recovery of braking energy also can help.