One of the electromagnetic principles that governs the operation of an electric motor is Faraday’s law, which states that when the magnetic environment of a coil of wire is changed — whether by moving the magnet and coil relative to each other or by changing the magnetic field — a voltage, or electromotive force (EMF), will […]
FAQs + basics
What are inductive encoders and how do they differ from resolvers and LVDTs?
Position measuring devices that rely on the principle of mutual induction include resolvers, linear variable differential transformers (LVDTs), and inductive encoders. Two of these technologies — resolvers and LVDTs — are based on the construction and operation of a transformer. In the case of an LVDT, voltage is applied to a primary winding and induced in […]
What are double- and triple-stack hybrid stepper motors ?
Of the three primary stepper motor designs — permanent magnet, variable reluctance, and hybrid — hybrid stepper motors are arguably the most popular in industrial applications, combining the best performance characteristics of permanent magnet and variable reluctance types. Hybrid stepper motors are constructed with a rotor made of two sections, or cups, with a permanent […]
What are different ways to express a gear ratio?
In motion control systems, gears are used to change the torque and speed delivered by a motor to a driven component. Depending on how the gears are arranged, they can either increase the delivered torque and decrease the output speed (the most common arrangement in motion control applications) or decrease the delivered torque and increase […]
Absolute encoder interfaces: Differences between SSI, BiSS, Hiperface, and EnDat
Absolute encoders can communicate with controllers through parallel or serial wiring, over a fieldbus, or via an Ethernet-based protocol such as EtherCAT. Of these options, serial communication is a simpler solution than parallel wiring (which requires a twisted pair of wires for each bit of output) and is well-suited for applications that aren’t complex enough […]
What are multi-stage gearboxes and when are they used?
Gearboxes are commonly used in motion control applications to change the output speed and torque from a motor to a driven component. By using a smaller gear with fewer teeth (commonly referred to as a pinion) to drive a larger gear with a higher number of teeth, the torque delivered to the load is increased while […]
What is a tachogenerator and when is it used?
There are several ways to measure the position of a rotary axis, and some position measuring devices, such as incremental and absolute encoders, can also derive the speed of the axis by evaluating a combination of distance, time, and pulses. But for applications that require only speed measurement — without position information — a tachogenerator may […]
What are radial and axial runout and how do they affect rotary tables and stages?
Runout is a dimensional specification that defines error in the motion of a surface as it moves relative to a datum. The official geometric dimensioning and tolerancing (GD&T) definition of runout applies to the variation of a circular feature — such as a shaft or spindle — as it rotates over 360 degrees, although the term […]
How to calculate required input power for a gearmotor
The first place to start when sizing a gearmotor is to determine the required output torque and speed. But once torque and speed are defined, you’ll also want to know the required input power for the motor — particularly if the gearmotor uses an AC induction motor, where the power rating (typically given in horsepower) […]
What is AS-I Safety and what are its benefits for motion systems?
When sensors, actuators, and other lower-level components are used in a functional safety capacity, AS-Interface Safety at Work offers a simple, efficient, bus network for monitoring these safety devices — alongside standard, non-safety devices — on the AS-Interface cable. Recall that actuator-sensor interface (AS-Interface, or simply AS-I) is a master-slave bus that operates at the […]
