Doc2vxcvxcv

Colegio de San Juan de Letran CalambaSchool of EngineeringCollege of Mechanical EngineeringDC AND AC MACHINERY LABEE021B-L4ME2

ELECTRICAL MACHINES

ACTIVITY NO.2

GROUP NO. 1

BRAZA, RICK JORGE G.

ENGR. MELVIN DL. MANALO, RMEINSTRUCTOR

Electric Motor

I.Motor(Electric Motor)Electric motor is defined as an electromechanical device that converts electrical energy to mechanical energy; they are the interface between the electrical and mechanical systems of a facility.Electric motors are an important part of any electrical system. They used throughout every manufacturing plant, office, and home consuming about 64% of all electricity generated. There are numerous ways to design a motor, thus there are many different types of motors and each type possess different operating characteristics (that will be listed later). Based on these characteristics the motor can be chosen for a specified application.

Basic Working Principles of an Electric MotorElectrical current flowing in a loop of wire will produce a magnetic field across the loop.When this loop is surrounded by the field of another magnet, the loop will turn, producing a force (called torque) that results in mechanical motion

Basic Parts of an Electric MotorElectric Motors are classified into two categories D.C. and A.C. motorsBasic Parts of an Electric Motor 1. Enclosure.2. Stator.3. Rotor.4. Bearings.5. Conduit Box.6. Eye Bolt.1. Enclosure- The enclosure consists of a frame (or yoke) and two end brackets (or bearing housings). A motor's enclosure not only holds the motor's components together, it also protects the internal components from moisture and containments. The degree of protection depends on the enclosure type. In addition, the type of enclosure affects the motor's cooling.

2. Stator- The motor stator consists of two main parts:

A- Stator CoreThe stator is the stationary part of the motor's electromagnetic circuit. The stator is electrical circuit that performs as electromagnet. The stator core is made up of many thin metal sheets, called laminations. Laminations are used to reduce energy losses that would result if a solid core were used.

B- Stator (Windings)Stator laminations are stacked together forming a hollow cylinder. Coils of insulated wire are inserted into slots of the stator core.

When the assembled motor is in operation, the stator windings are connected directly to the power source. Each grouping of coils, together with the steel core it surrounds, becomes an electromagnet when current is applied. Electromagnetism is the basic principle behind motor operation.

3. Rotor- The rotor is the rotating part of the motor's electromagnetic circuit. Magnetic field from the stator induces an opposing magnetic field onto the rotor causing the rotor to push away from the stator field.

4. Bearings _ Bearings, mounted on the shaft, support the rotor and allow it to turn. Not all bearings are suitable for every application; a universal, all-purpose bearing does not exist. The size of the bearing to be used is initially selected on the basis of its load carrying capacity, in relation to the load to be carried, and the requirements regarding its life and reliability.Other factors must also be taken into consideration, such as operating temperature, dirty and dusty environmental conditions, and vibration and shocks affecting bearings in running and resting conditions.

5. Conduit Box- Point of connection of electrical power to the motors stator windings.

6. Eye Bolt- Used to lift heavy motors with a hoist or crane to prevent motor damage.

ENCLOSURE

STATOR

ROTOR

BEARINGS

EYE BOLTCONDUIT BOX

II. Electric GeneratorsGenerators produce direct current or alternating current. Rotating a coil of wire through a magnetic field generates an electric current. A generator that produces current that flows in only one direction is a DC, or direct-current generator.

Basic Parts of an Electric GeneratorYokeThe outer frame of a generator ormotoris called as yoke. Yoke is made up of cast iron or steel. Yoke provides mechanical strength for whole assembly of the generator (or motor). It also carries the magnetic flux produced by the poles. Poles Poles are joined to the yoke with the help of screws or welding. Poles are to support field windings. Field winding is wound on poles and connected in series or parallel with armature winding or sometimes separately.

Pole shoePole shoe is an extended part of the pole which serves two purposes, (i)to prevent field coils from slipping and (ii)to spread out the flux in air gap uniformly.

Magnetic FieldA permanent magnet produces a magnetic field through which the coil is rotated. Many large DC generators use a field coil instead of a magnet to produce the magnetic field.ArmatureThe armature rotates through the magnetic field, cutting the lines of magnetic force. This produces an electric current within the armature coil.

CommutatorThe commutator is attached to the coil. In a simple DC generator, this is a pair of split rings. The commutator transfers the current from the wire coil to the brushes. In a DC generator, the commutator keeps the current at the brushes positive.

BrushesThe brushes are in constant contact with the commutator and are attached to the wires leading from the generator. The commutator spins while the brushes remain stationary, transferring current from the commutator.

ShaftThe shaft transfers mechanical energy to the generator and turns the coil through the magnetic field. The shaft may be turned by a turbine that operates with water, steam or air, or by other means

Electric Generator

Electric Motor

Electric Generator