A DC motor can be constructed in various ways, and each design has specific performance characteristics, particularly regarding speed and torque production. The rotor is basically the same in all DC motors, being made of windings that generate an electromagnetic field when current passes through them. But the stator can be made of either permanent magnets […]
FAQs + basics
Detent torque and holding torque
One feature of stepper motors that differentiates them from other motor types — particularly servo motors — is that they exhibit holding torque. This means that when the windings are energized but the rotor is stationary, the motor can hold the load in place. But a stepper motor can also hold a load in place […]
FAQ: What are traditional and newer multi-turn measuring systems for encoders?
Edited by Zak Khan || Multi-turn measuring encoders are absolute encoders that can count multiple turns. Three main technologies enable such encoder design — batteries, gearing, and self-powering setups. Batteries and gears are traditional implementations of multi-turn technology; self-powering setups are newer. Batteries: Simple but incur replacement costs Batteries maintain power supply even during machine […]
What is a commutator?
The operating principle of a DC motor is based on the interaction between the magnetic field of a rotating armature and the magnetic field of a fixed stator. As the north pole of the armature is attracted to the south pole of the stator (and vice-versa), a force is produced on the armature, causing it […]
FAQ: What are DC shunt motors and where are they used?
In electrical terminology, a parallel circuit is often referred to as a shunt. Hence, DC motors in which the armature and field windings are connected in parallel are referred to as DC shunt motors. The variations in construction between series-wound DC motors and DC shunt motors result in some differences in operation between the two types, but […]
What’s the relationship between current and dc motor output torque?
Torque is a rotational force produced when a vertical force is applied at some distance from the center axis of the rotating body. The familiar equation for torque is: Where: T = torque F = applied vertical force d = distance from axis of rotation In a DC motor, the output torque is directly proportional to the […]
What’s the difference between BLDC and synchronous AC motors?
The short answer is: brushless DC (BLDC) and synchronous AC motors are similar in construction and operation. Some manufacturers and experts even group them together as similar technologies, in the category of “permanent magnet synchronous motors.” Their key difference, however, lies in the stator coil windings and resulting back-EMF waveform of each motor. This gives them distinct performance […]
Motion systems application examples: Gearmotors
By Miles Budimir • Gearmotors are most common in applications that need a lot of force to move heavy objects. Most industrial gearmotors incorporate fixed-speed ac motors. However, some gearmotors use dc motors, which are common in automotive applications in adjustable side-view mirrors and automatic seat adjustments. Though it’s possible to combine many different motors […]
Pull-Up Resistor Basics
To understand a pull-up resistor, it helps to first understand how encoder output is generated. Incremental encoders can provide several types of digital output, with the three primary types being open collector, push-pull, and line driver. Open collector output is considered sinking, while the line driver type is considered sourcing, and push-pull output is both […]
Gearsets in action — Real-world motion systems applications
Updated November 2018 by Lisa Eitel • Motion applications for gearing are as varied as the motors with which these power-transmission devices pair. Just consider how designs ranging from amusement rides to consumer-grade beard trimmers make use of spur gears. These mostly roll through meshing, so can be 98% or more efficient per reduction, though […]