What Role do Laminations Play in Electric Motors and Generators?
Two main components make up a DC motor such as the stator and the rotor. An iron core in a ring shape comprises the rotor along with slots that support the windings and coils. Once the core rotates in a magnetic field, this generates a voltage in the coils that results in eddy current.
In simpler terms, eddy currents are a type of magnetic loss. When losing power due to eddy current flow, this condition is called eddy current loss. Multiple factors impact the amount of power loss attributed to the flow of eddy current These include the magnetic material’s thickness, the frequency of the EMF induced, and the density of the magnetic flux.
What are Laminations in Motors?
The resistance of the material in which currents flow impacts how eddy currents develop. For instance, when there is a decrease in the cross-sectional area of the material, this results in a reduction in eddy currents. Thus, it is essential to keep the material thinner to minimize the cross-sectional area and lower the amount of the eddy current flow and loss.
Reducing the amount of eddy current is the reason why there are several thin pieces or sheets of iron that make up the armature cores. Instead of having just a solid and large piece of material, these thin pieces are capable of generating a higher resistance. As a result, fewer eddy currents take place, which ensures a lower amount of eddy current loss taking place. These individual pieces of iron are called laminations, which an armature comes with.
Motor Laminations — Benefits These Offer
In the case of a solid core, there are far greater eddy currents measured, as compared to what takes place in a laminated core. With the use of a lacquer coating, there is an insulation formed to protect laminations since eddy currents are incapable of bouncing from one lamination to the next. Adequate lacquer coatings are the main reason why manufacturers make sure that armature core laminations remain thin — both due to the cost factor and manufacturing purposes. There are modern DC motors that use laminations with a thickness of between 0.1 and 0.5 millimeters.
One component for laminated steel sheets is silicon. Silicon protects the core of a generator’s or motor’s stator, as well as the transformer. Once cold-rolled and ensured with a special grain orientation, the said steel is used for lamination purposes. This material typically has a thickness of about 0.3 millimeters. Then, both sides are insulated, as well as positioned on top of each other. By doing so, this reduces the eddy current because of its inability to flow over a broad portion of a cross-section.
It is not enough that the lamination has the right thickness level. More than anything, the surface must be spotless. Otherwise, foreign particles may form and lead to laminar faults. Over time, laminar faults result to damages to the core.
Laminations are either welded or stacked loosely together. The means in which these are put together depends on your preferred or required application. Whether laminations are loose, bonded, or welded, these are preferred over a solid material for the sake of reducing eddy current losses.
More About Motor Laminations
Electrical steel laminations may be used to create motor laminations. Manufacturers may use silicon steel, which primary includes steel combined with silicon. This combination is one of the most common materials used due to its reliability and strength. The electrical resistance improves with the silicon and steel combination, as well as the occurrences of magnetic fields penetrating the material. Moreover, silicon steel is responsible for minimizing chances of corrosion. The material also enhances the hysteresis loss of the steel.
In various applications that put importance to electromagnetic fields, silicon steel is a common choice. Among these applications include the magnetic coils, transformers, electrical motors, and electrical rotors and stators.
By incorporating silicon to steel, this promotes the speed and efficiency of the steel when it comes to producing and maintaining some magnetic fields. With steel as the material’s magnetic core, any device or equipment becomes more effective and efficient to use.
This entry was posted in Electric Motors and tagged electric motors. Bookmark the permalink.
Originally published at www.lselectric.com on April 25, 2017.
