The traditional method of starting an AC induction motor “across the line” results in full voltage, current, and torque being applied immediately when the motor is started, and likewise, being removed immediately when the motor is stopped. While this is the most simple starting method, the high inrush current (often 6 to 7 times the […]
AC Motors
What is DC injection braking and how does it compare with other methods?
AC induction motors excel at driving high-inertia loads at high speeds — in fans, saws, conveyors, and mills, for example — and variable frequency drives make it possible to match the motor speed to the application requirements by varying the frequency of the supplied voltage. But when quick stops are needed — whether for safety reasons or […]
Conveyors with direct-drive motors offer key advantages to Pa. facility
American Axle Manufacturing (AAM) is increasing the functionality of its St. Mary’s, Pa. manufacturing operations with conveyors sporting advanced drive technology. Small yet powerful direct-drive motors from Electric Torque Machines actuate Dorner conveyors that move small parts around the AAM facility. AAM designs, engineers, validates, and manufactures an array of driveline, metal-forming, powertrain, and casting […]
What are leading methods for VFD control of AC motors?
AC motors are often used in equipment that runs at constant speed regardless of load, such as fans, pumps, and conveyors. But when speed control is required, an AC motor is paired with a variable frequency drive (VFD), which regulates the motor’s speed by using one of two control methods — scalar control or vector […]
What are slip rings and why do some motors use them?
Slip rings — also referred to as rotary electrical joints, electric swivels, and collector rings — are devices that can transmit power, electrical signals, or data between a stationary component and a rotating component. The design of a slip ring will depend on its application — transmitting data, for example, requires a slip ring with higher […]
What are the benefits of an active front end (AFE) drive?
A variable frequency drive, or VFD, delivers power from the source — typically the utility — to a motor in three basic steps: A rectifier converts the AC power to DC A DC bus receives, smooths, and stores the power An inverter converts the DC power back into AC with the necessary frequency and voltage […]
What is the Department of Energy’s Integral Horsepower Rule?
The U.S. Department of Energy (DOE) has been regulating energy efficiency for electric motors since 1997, when the Energy Policy Act went into effect, requiring most 1 to 200 hp general-purpose motors to meet NEMA Energy Efficiency standards. Since then, the DOE energy efficiency regulations have evolved, with the Energy Independence and Security Act (EISA) […]
Severe duty motors: What makes them suitable for harsh applications?
While there is no broad standard that defines severe duty motors, the IEEE 841-2009 standard, which addresses “premium efficiency, severe duty, totally enclosed fan-cooled (TEFC), squirrel-cage induction motors — up to and including 370 KW (500 hp),” is often used as a benchmark. However, this standard was written for the petroleum and chemical industries, and many […]
How can a universal motor operate on either DC or AC supply?
A universal motor is a series-wound motor — meaning that the field and armature windings are connected in series — and is mechanically commutated with brushes and a commutator. Although its construction is very similar to a series-wound DC motor, a universal motor incorporates several modifications that allow it operate properly on either DC or AC […]
Thermal time constants and managing PMAC servo motor overloads
When high intermittent power density is required, using classic RMS calculations and speed-torque performance curves as the sole selection methods may be problematic. That’s because such approaches might cause motor or drive undersizing. By Hurley Gill • Senior applications and systems engineer | Kollmorgen Using classic performance curves with RMS calculations is perfectly acceptable for […]
