Why the armature of dc motor is laminated?
Matthew Underwood
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To minimize the eddy current loss we increases the resistance in the path of eddy current by laminating it. Eddy current losses are directly proportional to area of armature or more precisely the path of motion. ... That is why armature of DC machines (either motor or generator) is laminated.
What is the purpose of laminating the armature?
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.
Why lamination is used in motor?
Stator laminations reduce eddy current by insulating the core. Thin silicon steel plates are stacked on top of one another around the center, preventing eddy current flow. With the eddy current reduced, the stator core can maintain constant power, keeping your motor running.
What is lamination in motor?
What Are Motor Laminations? Motor laminations form the core of an electric motor's stator and rotor. They consist of thin metal sheets that are stacked, welded, or bonded together. By making them from individual pieces of metal rather than a solid pieces, they experience less eddy current losses.
Why do we laminate?
Lamination increases the durability of print materials, allowing them to withstand frequent use. Lamination adds protection against fingerprints and smudges, stains and spills, tears and wrinkles, marks and abrasions, plus oil, grease, dirt, moisture and other contaminants. ... Lamination has a reasonable cost.
WHY IS THE ARMATURE OF A DC MACHINE MADE OF SILICON STEEL ??
Why laminated core is used in induction motor?
Lamination is necessary since a voltage is induced along the axial length of the steel as well as in the stator conductors. The laminations are insulated from each other usually by a varnish layer. This breaks up the conducting path in the steel and limits the losses (known as eddy current losses) in the steel.
Why is armature resistance low in DC motor?
There need to be sufficient winding resistance within the field winding to restrict the current drift. ... However, it is necessary that the armature resistance is low because the DC generator generates excessive currents and any DC armature resistance will cause decrease in generator performance.
Why is the armature core in DC machines is constructed with laminated steel sheets instead of solid steel sheets?
Why the armature core in d.c machines is constructed with laminated steel sheets instead of solid steel sheets? Lamination highly reduces the eddy current loss and steel sheets provide low reluctance path to magnetic field.
What is the reason behind the armature structure for both DC and AC machines being laminated?
Explanation: The armature windings of both the DC and AC machines have to deal with alternating current only; this is the reason why the armature structure of all rotating machines are laminated in order to reduce the eddy current losses.
Why the pole core stampings are laminated in DC generator?
Although a DC generator provides direct current but induced current in the armature is alternating in nature. That is why, cylindrical or drum shaped armature core is build up of circular laminated sheet.
Why rotor core is laminated?
The Importance of Lamination
The lamination process consistently reduces the loss of iron. Since the lamination is made of steel, the assembly will also reduce Eddy current loss. Because of this, the rotor core will not be subjected to iron losses since the frequency of the rotor current is low.
What is armature resistance of DC motor?
The resistance of the armature windings, measured with an ohmmeter when the motor is at rest, unpowered, is 2.45 ohms.
What is the resistance of armature winding?
Armature Winding resistance is the ohmic resistance of the copper winding wires. A brush is used to provide electrical contact between the stationary contacts and moving parts like commutator or slip rings. Brushes are mainly made of carbon material which is high resistance brushes compared to copper brushes.
What is armature resistance of DC motor formula?
V − O = I a R a ∴ I a = V R a . As the resistance of a motor armature may be less than an ohm, then the armature current at starting if the armature applied voltage were 230 V would be in excess of 230 A.
Why is armature core laminated instead of solid?
The development of eddy currents is influenced by the resistance of the material in which they flow. ... One way to achieve a reduction in cross-sectional area is to make the material thinner. This is why armature cores are made up of many thin pieces of iron, rather than a large, solid piece.
Why do laminations reduce eddy currents?
As 4 laminations are stacked together, hence the cross-sectional area of each lamination perpendicular to the magnetic field will become (A/4). Thus, the flux linking through each lamination will be Ø = BA/4. ... Thus the use of thin lamination reduces the Eddy Current Loss.
How is armature resistance measured in a dc motor?
A practical way to measure the winding resistance is to use the Ohm's law: Resistance = Voltage / Current. If you apply a power source to the windings and measure the voltage and current flowing through them, a simple division will yield an accurate value for the resistance.
What is an armature resistance?
[′är·mə‚chər ri′zis·təns] (electricity) The ohmic resistance in the main current-carrying windings of an electric generator or motor.
What factors affect resistance of armature winding?
Generally the armature resistance is measured by applying the known d.c. voltage and measuring the d.c. current through it. The ratio of applied voltage and measured current is the armature resistance. But due to the skin effect, the effective resistance under a.c. conditions is more than the d.c. resistance.
What is armature winding and field winding?
Armature Winding is the winding, in which voltage is induced. Field Winding is the winding in which the main field flux is produced when the current through the winding is passed.
What is armature control method?
In the armature control method, the speed of the DC motor is directly proportional to the back emf (Eb) and Eb = V- IaRa. When supply voltage (V) and armature resistance Ra are kept constant, the Speed is directly proportional to armature current (Ia). ... The motor back EMF (Eb) and Speed of the motor can be changed.
Why will armature draw heavy current when motor is directly switched on to the main supply?
When the motor is at rest the speed of DC motor is zero, therefore back emf is zero and if a DC motor is connected directly to the supply mains a heavy current (about 10-12.5 times of rated current) will be drawn because from emf equation of armature circuit , armature current at starting is given as Ia = Vt / Ra and ...
What is laminated core?
Laminated Core is a rectangular shaped type of soft magnetic core. ... Laminated terms such as each layer are made up of insulated layers of steel plate that are nicely glued together and compacted into a solid core rather than a single piece of a solid block.
Why pole shoes are laminated where as pole core not?
The pole core use to provide housing to the field winding. When field winding excites, it behaves like a magnet. The pole shoes provide mechanical support to the field winding and due to a large area, it reduces the magnetic reluctance. ... The pole shoe is always laminated because it is close to the armature.
Why solid pole shoes are used in DC generators?
Detailed Solution. Pole core basically carries a field winding which is necessary to produce the flux. It directs the flux produced through air gap to armature core, to the next pole. Pole shoe enlarges the area of armature core to come across the flux, which is necessary to produce larger induced emf.
