Induction motors are considered asynchronous. This is because while their speed depends upon the external sine wave, it is not precisely synchronized to it. In an induction motor, the ac power supply connects directly to the field coils that are part of the stator. The alternating power produces a rotating magnetic field. This field induces […]
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Synchronous motor basics: what you need to know
Rotary electric motors involve the interaction of two magnetic fields, that of the stator and that of the rotor. In a brushed-type dc motor, the dc voltage is applied to the stator, creating a stationary magnetic field. DC is also fed to the commutator, which is attached to the armature, part of the rotor. Because […]
Basics of servomotors
Functionally, servomotors and steppers overlap. Both can rotate their shaft a portion of a turn and hold that position for any length of time as determined by an external controller. A step motor is one of several specific positioning motor constructions whereas servocontrol refers to a type of control that involves feeding back information about […]
Basics of stepper motors
There are several varieties of stepper motors, having somewhat different types of commutation and operating characteristics, but they all have in common the ability to spin continuously in either direction or to turn a part rotation and then stop, with or without holding torque. In this, they resemble the servomotor. But the servo typically operates […]
Basics of dc motors
The first motors were exclusively dc powered, getting energy from primitive voltaic piles that were unsuitable for most applications. Consequently, pre-Edison motors were scientific curiosities rather than industrial work horses made possible by serious utility generation and distribution systems. All rotary motors, dc included, operate by the interaction of two magnetic fields, one firmly mounted […]
Explained: The earth’s magnetic field
Since ancient times, terrestrial explorers and mariners at sea have known that a magnetized needle would point north. This beneficial effect of the earth’s magnetic field helps make life on earth possible. The earth’s magnetic field keeps the solar wind at bay. Without it, this stream of plasma released by the sun would strip off […]
Gallery: Cool instruments at the 2015 International Microwave Symposium
Some 600 companies exhibited at the recently concluded International Microwave Symposium in Phoenix. Microwave design is an instrumentation-intensive endeavor, so a lot of show floor space was devoted to new developments in test gear. Here are a few things in that area that caught our attention. Garbled signals, instruments to the rescue National Instrument’s RFIC […]
Understanding skin effect
Ohm’s law states that E = I X R — volts (electromagnetic force) is equal to amps (intensity) times ohms (resistance). When the equation is used together with the power law — volts times amps equal watts — it is possible to derive several formulas, solving for various unknowns. All of this is conveniently organized […]
The standard model of particle physics
Isaac Newton’s classical view of light (consisting of very small material bodies) appeared to lose validity following Thomas Young’s double-slit experiments. These convincing demonstrations in the first decade of the nineteenth century showed that light must propagate like ocean waves, but transverse rather than normal to the direction of travel. Then, once again, uncertainty reigned […]
Thomas Young and the double-slit experiment
Isaac Newton propounded in his great work Opticks (1704) that light consists of a flow of particles. Generations of students and researchers have accepted this idea. Light was believed to be composed of large numbers of billiard-ball type material bodies, visualized as spherical objects that traveled through vacuum and non-opaque regions with no luminiferous medium […]