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Manufacturing Technology Insights | Wednesday, March 15, 2023
Unlike an electrical motor, an electrical generator converts mechanical power to electrical power by reversing the energy flow.
FREMONT, CA: An electric motor converts electrical energy into mechanical energy. Most electric motors generate torque on their shafts by combining the motor's magnetic field with the current flowing through a wound wire. The mechanical design of an electrical generator is the same as that of an electrical motor, except that it operates in reverse, turning mechanical power into electrical power.
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Inverters can power electric motors with alternating current (AC) or direct current (DC) supplies, such as rectifiers, batteries, or power grids. Electric motors can be classified depending on their power source, application, construction, and movement output. The motors are available in DC or AC power, brushed or brushless, three-phase, two-phase, single-phase, radial flux or axial, and air- or liquid-cooled.
Industrial applications require motors that provide adequate mechanical energy. Machine tools, power tools, home appliances, disk drives, and vehicles are some of the applications of blowers and pumps. Electronic watches contain tiny motors. The reverse operation of electric motors can recover energy that would otherwise be wasted due to friction and heat in certain applications, such as regenerative braking in traction motors. The two mechanical components of electric motors are the fixed stator and the rotating rotor. It also has two electrical components, a set of magnets and an armature, one of which is connected to the stator and the other to the rotor to form a magnetic circuit.
Field magnets generate a magnetic field that permeates the coiling. They may be electromagnets or permanent magnets. In most motors, the field magnet is on the stator, and the winding is on the rotor. Nevertheless, in some motor designs, these roles are inverted.
Electric Motor Bearings
Bearings support the rotor and permit it to rotate about its axis. In turn, the motor housing helps the bearings.
Electric Motor Rotor
The rotor is the mobile component that provides mechanical energy. The rotor typically contains current-carrying conductors, and the stator's magnetic field delivers a force to spin the shaft. Alternately, other rotors feature permanent magnets, while the stator holds the wires. Permanent magnets provide great efficiency over a wider power range and at a faster rate of work.
The air gap between the rotor and the stator permits rotation. The gap width has a significant impact on the electrical properties of the motor. It is often made as small as possible because a huge gap results in poor performance. It is the principal cause of the low power factor required for motor operation. As the air gap increases, the energizing current increases and the power factor decreases; hence narrower gaps are preferable. In contrast, small gaps may cause mechanical issues, losses, and noise.
The motor load is put on the motor's exterior side, where the motor shaft protrudes through the bearings. Because the force of the load exceeds the outermost bearing, the load is overhung.
Electric Motor Stator
The stator encircles the rotor and typically holds the field magnets, which are either electromagnets comprised of wire coiled around an iron core or permanent magnets. They generate a magnetic field that applies force to the rotor winding by passing through it. The stator iron core comprises numerous thin metallic sheets insulated from one another and referred to as laminations.
Lamination reduces the energy loss that occurs when a solid core is utilized. In air conditioners and washing machines, resin-packed motors use the dampening properties of plastic to minimize vibration and noise.
Electric Motor Armature
The armature consists of wire wrapped around a ferromagnetic core. Flowing current via a wire causes the magnetic field to impose a Lorentz force on it, causing the rotor, which produces mechanical output, to rotate. Windings are wires applied in coils, typically wrapped around a soft, laminated, iron, ferromagnetic core to generate magnetic poles when current is applied.
Electric motors come in non-salient and salient-pole designs. In salient-pole motors, the stator and rotor cores have projections known as poles facing each other, with a wire looped around each pole under the pole face, which becomes the south or north poles of the field when current flows through the wire. In non-salient-pole (or round-rotor or distributed field) motors, the core is a cylinder, and the windings are evenly dispersed in slots around the circumference. Continuously rotating poles are generated in the ferromagnetic core when AC current is supplied to the windings. Motors with shaded poles have windings wrapped over a portion of the pole, delaying the magnetic field phase for that pole.
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