Basic Electrical Engineering ModuleV Electrical Machines Lecture1 By
Basic Electrical Engineering Module-V Electrical Machines Lecture-1 By, Ravi Kumar Assistant Professor Faculty of EEE Department Darbhanga College of Engineering Darbhanga
Electrical Machines • The Machines which convert Electrical energy to mechanical energy or, vice-versa are known as electrical Machines. • The Process of conversion is known as Electromechanical conversion. • The machine which convert mechanical energy into electrical energy is called generator • Machine Which Convert Electrical Energy Mechanical energy is called Motor
• There are several type of electrical machine few of them are given below 1. 2. 3. 4. DC Generator DC Motor Induction Motor Synchronous Generator etc. DC Machine AC Machine
DC Machine •
CONSTRUCTION OF D. C. MACHINE • The construction of DC machine basically remain same whether it is a generator or a motor. • Any DC generator can be run as a DC motor and vice-versa. • All DC machine have four Main components.
1. Yoke or frame: It is the outer cover of the DC machine in which main poles are fixed. The yoke or frame serves the following function: (a) It provides mechanical support to the inner parts of the machine and protect the winding and insulating material of the machine from harmful atmospheric element like moisture and dust. (b) It provide a low reluctance path for the flux.
2. Magnetic field system: It is the stationary part of the machine. It produces the main magnetic flux in which the armature rotate. Field system consist of pole core and curved pole shoe as shown in the Fig. The pole shoe serves two purposes: (a) It support the field coil (b) It increases the cross section area of the magnetic circuit.
3. Armature: The rotating part of d. c machine is called armature. The purpose of armature is to rotate the conductor in the uniform magnetic field. The armature consist of a shaft and a laminated cylinder is mounted on the shaft called armature core. This armature core has slots on its outer surface. The conductor are placed on slots and known as Armature winding. The working emf is induce in the Armature winding. On the basis of the connection of the Armature conductors there are two type of armature winding. (a) Wave Winding (Number of Parallel Path ‘A’ =2) it is suitable for high voltage and Low current. (b) Lap Winding (Number of Parallel Path ‘A’ =Number of Pole ‘P’ ). It is suitable for low voltage and High Current.
4. Commutator & Brushes: • The nature of emf induced in the armature conductor is alternating but out side the machine there is DC Voltage therefore a convertor is required AC to DC conversion or vise-versa. • A commutator and Brushes is a mechanical Convertor which Serve the Purpose. • It work as Rectifier and converts AC to DC in case of generator. • It work as Invertor and converts DC to AC in case of motor. • Commutator is fitted on shaft and rotate with the armature commutator has several segment which is connected to the several portion of the armature winding. The Carbon Bruses are fitted on the stator and slide on the surface of the commutator collect or supply the current to the armature.
Type of DC Machine • As the construction of DC motor and DC generator are same and both the machines has two windings armature winding and field winding • On the basis of supplying of current in both the winding DC machines are of following type. DC Machine Self Excited Separately Excited Series Machine Long Shunt Short Shunt Machine Cumulative compound Compound Machine Differential Compound
PRINCIPLE OF D. C. GENERATOR •
• Equation of EMF
Type of DC Generator • DC Generator Self Excited Separately Excited Series Generator Shunt Generator Compound Generator
Separately Excited DC Generator •
Self Excited DC Generator •
Series Excited DC Generator •
Compound DC Generator •
Compound DC Generator •
Thank You
- Slides: 19