Electric motors have one general application–powering machinery. They achieve this by harnessing the mechanical force, or energy, produced during the interaction of an electrical current and a magnetic field. Electric currents used to power electric motors are either alternating current (AC) or direct current (DC).
Common AC power sources include inverters, generators and power grids, while DC currents are often provided by rectifiers, motor vehicles, and batteries. In addition, some electric motors, known as universal motors, can operate using both alternating and direct currents.
Electric motors power all sorts of machines in countless industries, including electronics, construction, home and office supplies, appliances, and industrial manufacturing. The largest electric motors are used for applications like pipeline compression, ship propulsion, and pumped-storage, while the smallest electric motors can fit inside electric watches.
Generally speaking, electric motors consist of a rotor, a stator, windings, an air gap, and a commutator. In this context, the rotor is a moving part that delivers mechanical power when it moves the shaft. To achieve this turning motion, the rotor is usually designed with built-in current-carrying conductors that interact with the magnetic field generated by the stator.
However, in some cases, the rotor carries the magnets while the stator holds the conductors. Unlike the rotor, the stator does not move. Rather, it is the fixed component of the motor’s electromagnetic circuit. Generally, it consists of a core and either permanent magnets or windings. This core is made up of several thin metal sheets, called laminations, which are used to reduce energy losses. Windings are coiled wires. When they are wrapped around the core, their purpose is to form magnetic poles when energized with current.Read More…
Now, all electric motors have two basic magnetic field pole configurations from which to choose: salient-pole and nonsalient-pole. The magnetic field of a salient-pole machine is generated by a winding wound below the pole face. In the case of the nonsalient-pole machine, also known as a round-rotor machine or a distributed field machine, windings produce a magnetic field while wrapped around pole face slots. A third pole configuration, shaded-pole, delays the pole’s magnetic field phase. To do so, it requires a winding made up of a copper bar or ring, called a shading coil, that goes around a certain part of that pole.
Next, the air gap is the distance between the rotor and the stator. The air gap provides most of the low power factor at which motors operate, by increasing and decreasing the magnetizing current as needed. Because, then, a large air gap has a strong negative effect on a motor’s performance and may present mechanical problems, losses, and noise, the air gap should be as small as possible.
Finally, the commutator is a part used to periodically switch current direction between the external circuit and the rotor. It is used with most DC motors and with universal motors. The commutator is composed of a cylinder made up of several metal contact, or slip ring, segments and an armature upon which the segments rotate. Two or more electrical contacts, called brushes, make sliding contact with the segments by pressing up against them as they turn, allowing the current to flow through them and reach the rotor.
Commutated electric motors are a type of brushed motor; brushed motors are one of the two major types of electric motors, as categorized by internal construction. The other type of motor is the brushless motor. Brushed motors, which almost always use a direct current, get their name from the commutator, which comes accompanied by several brushes. These brushes are always made of a soft conductive material; almost exclusively, manufacturers use carbon, sometimes with copper powder mixed in for improved conductivity.
The five main styles of brushed motors are: separately-excited motors, DC series wound motors, permanent magnet DC motors, DC compound motors, and DC shunt wound motors. While brushed motors have been popular for many years, they are inefficient, and more and more, they are being replaced by brushless motors. These motors, instead of using brushes, use sensors known as Hall effect sensors, to transfer current. They are made up of a 3-phase coil, a permanent magnet external rotor, drive electronics, and the sensor.
A 3-phase coil is a motor element that references another type of motor classification, based on the motor’s means of motion. The most common motor motion classifications include: 3-phase motors, single phase motors, linear motors, stepper motors, and 12V motors. Three-phase motors boast both a fairly simple design and high efficiency. Usually a type of induction motor, 3-phase motors function using three alternating currents, which distribute converted mechanical energy.
Single phase motors are another example of induction motor. This time, they use a single, or single phase, power source, which is generally an alternating current.
The word “linear” in linear motor refers to the fact that they provide mechanical energy in a straight line. In other words, linear motors provide motion over a single plane.
Stepper motors are quite a lot like 3-phase synchronous motors. The main distinction between the two is simply that, while 3-phase synchronous motors rotate continuously, stepper motors must continuously start and stop.
Finally, 12V motors generate motion using twelve volts of electric power, which is standard.
Lastly, electric motors convert energy differently. Motors are divided thus into: synchronous motors, induction motors, electrostatic motors, and servo motors. To learn more about conversion types and to find out the best fit for an application, interested parties should contact a reputable motor manufacturer.