Gearmotors are available in a variety of styles, packages, and options. There are two standard methods for picking a gearmotor. One is simply selecting a pre-engineered unit and the other is choosing a motor and gearbox separately and then assembling them into one finished unit. So the question is, when to pick a pre-engineered gearmotor […]
FAQs + basics
FAQ: What is the closed-loop frequency response of a servo motor?
For a system driven by sinusoidal inputs, such as a servo motor, frequency response is a measure of the amplitude and phase of the output signal relative to the input signal. It is a useful estimate of the limits of servo tuning that will produce a stable system without oscillation. To determine frequency response, a sinusoidal input […]
Field oriented control vs. sinusoidal commutation
Brushless AC (BLAC) motors are driven with sinusoidal AC currents, and due to skewed magnets and sinusoidally distributed windings in their stators, they also produce sinusoidal back EMF. Sinusoidal commutation is a common way to control BLAC motors, as it provides a very consistent torque output with little torque ripple. But at high speeds, sinusoidal […]
What is COF or coefficient of friction? What is conductivity and electrostatic dissipation?
Here we answer the common question: What do the technical terms conductivity, electrostatic dissipation and coefficient of friction mean? Then they relate these values to engineered designs that have rubbing parts that necessitate some way to address static-electricity buildup. What are conductivity and electrostatic dissipation? Conductivity is a measure of the ability of a material to conduct electrical […]
FAQ: What is the Department of Energy’s new Small Motor Rule?
Large motors have been subject to energy efficiency regulations for quite some time. The U.S. began regulating energy efficiency of integral horsepower motors back in 1992 with the passage of the Energy Policy Act (EPAct). Subsequent updates to this original legislation include the EPAct in 2005 and the Energy Independence and Security Act (EISA) of […]
FAQ: What are servo pancake motors and how do they work?
Traditional brushed DC motors are cylindrical in shape and have a stator with permanent magnets surrounding an armature made of windings. Cylindrical motors have a radial air gap and magnetic flux, with current running axially along the length of the motor. A special variation of the DC motor, known as a printed armature motor or […]
FAQ: What’s the difference between contouring and point-to-point motion?
The purpose of motion control is to move an axis, or multiple axes, to a specified position or through a predefined path. For the first case, some form of point-to-point positioning is used. For motion that must pass through a predetermined set of points, a method known as contouring is used. The choice between point-to-point or contoured […]
FAQ: What are common gearmotor types and variations?
Updated May 2018 || A gearmotor is a single component that integrates a gear reducer with either an ac or dc electric motor. Gearmotors can deliver high torque at low horsepower or low speed. This is because the gearhead functions as a torque multiplier and can allow small motors to generate higher torque. Gearmotors can […]
FAQ: What is trapezoidal back EMF?
The primary distinction between brushless DC (BLDC) motors and brushless AC (BLAC) motors is their back EMF waveform. BLDC motors typically have a trapezoidal back EMF, while BLAC motors (also referred to as permanent magnet synchronous motors, or PMSM) have a sinusoidal back EMF. The shape of a motor’s back EMF is important, because it […]
FAQ: What is sinusoidal back EMF with sinusoidal current?
Both brushless DC (BLDC) and brushless AC (BLAC) motors are permanent magnet, synchronous devices. They both produce torque and speed through the interaction of a rotating magnetic field in the stator and permanent magnets on the rotor. But while they have many similarities, differences in their stator construction produce different back EMF waveforms and result […]