Deepakkumar Yadav
Causes of Heat in Bush-bearings of Electrical Machines Q. What are the causes of heat in bush-bearings of electrical machines ? Following are the causes of heat in bush-bearings : Worn out bearings / sleeves. Worn out shaft. Loss of lubrication. Mis-alignment of shaft pulleys couplings. Heavy vibration and noise due to uneven air-gap in … Read more
Various Methods of Heating the Machine Q. Explain the various methods of heating the machine. The various methods of heating the machine are as follows : External heat : It is the method of drying insulation most frequently used. The various methods of applying external heat are : Baking in the oven : It is … Read more
Properties of Good Transformer Oil Q. State and explain any four properties of good transformer oil. The properties of good transformer oil or mineral oil are recommended by IS 335-1963. To maintain the properties. IS 1866-1961 is referred. Usually mineral oil grade B is used for switchgears, transformers. It should posses the following properties : … Read more
Factors on Which Life of Insulation Depends Q. State the factors on which life of Insulation depends. Temperature : The insulation resistance decreases with temperature. The dielectric loss increase with temperature. The resistivity of the insulating material decreases by increse in temperature. The same can be expressed as Rt = R0 (1 – α0t ), … Read more
Factors Governing Selection of Induction Motor Q. State the factors governing the selection of induction motor Electrical motors are universally adopted as electric drive. Hence, has become necessary for the manufacturer to manufacture motors of various designs according to suitability and use in various classes of Industry. This has resulted into numerous types of motors. … Read more
Automatic Star-Delta Starter Q. Automatic Star-Delta Starter. Automatic Star Delta Starter is used to save energy during variable load conditions in three-phase induction motor. This is done by using a micro controller. The three-phase winding inside the motor can be connected in star or delta. About 25-30 % of energy gets saved by incorporating delta … Read more
How Following Crackle Test is Carried for Transformers Q. Explain how following test is carried for transformers : Crackle test. Crackle test The objective of this test is to determine the presence of water or moisture in the oil. In this test a sample of transformer oil under test is taken in a test tube. … Read more
Due to Improper / Poor Maintenance In case of transformer following faults may develop due to improper or poor maintenance : Loose core bolts and clamps results into more vibrations of stampings and more noise. Improper supports and clamps for windings result in collapse of winding during external short circuit fault. Bad solding results into … Read more
Function of Foundation Bolt and Bed Plate Q. State function of foundation bolt and bed plate. Function of foundation bolts : to make grip of machine to ground rigidly and locate the space exactly. Function of base plate : to make the perfect location of machine on the foundation and support the machine and take … Read more
How to Prevent an Electrical Machine During its Inactivity Q. How to prevent an electrical machine during its inactivity? If the machine remains un-operated and kept idle for a long time it will not work properly and even may fail to operate. The reasons being : Moisture, din, dust from the surroundings is absorbed and … Read more