Common Terms are Not So Common

I have worked around electric motors for a long time. It still blows my mind that we can’t seem to settle on common terms and definitions of things we work with on a daily basis. When is a motor AC Synchronous or DC Brushless? They are identical. Same motor.

So you have to start from the beginning of the motor family tree and work your way through it. What makes a motor AC versus DC. The only definition I know of that makes any sense is this:

An AC motor has only one magnetic field, in the stator, and induces a second magnetic field through induction, into the rotor. The rotor becomes magnetized and follows the circulating magnetic field in the stator by passive attraction. This is why most AC motors are referred to as induction motors, because the magnetic polarity in the rotor is induces. AC motors as a result are constant speed machine based on the frequency of the electrical excitation. Since that’s mostly 60 hertz in the USA, its usually some multiple of 60, most commonly 1800 RPM (minus some rotor slip). AC machines require an inverter to change AC into DC and then DC into variable frequency AC in order to achieve variable speed performance. Due to decreasing costs for the AC motor and recent cost breakthroughs in inverter technology, AC variable speed is the dominant solution. Read more

Motor Industry and the New Year

Hope everyone had a great holiday and a successful year in 2007.

I was reviewing the Department of Commerce figures for electric motors. Hey, its just something I do.

A few years ago when I was hired to help a young high tech motor company in Denver understand the marketplace, we started with the Department of Commerce data for electric motors and generators. We studied the data and went into an interesting exercise in analyzing the market. At that time the US produced approximately $12B in electric motors. That includes all the industrial and high tech stuff, as well as starter motors on cars, alternators, generators and fractional horsepower fans you find around the house. Big numbers, lots of parts. Read more