ELECTRIC MACHINES

Automatic Voltage Regulator (AVR) is one of the main component of an Alternator. Main functions of AVR is to built-up the rated voltage and maintain the output voltage within the limit at no-load and on-load conditions. There will not be any output or abnormal output when an AVR fails. What are to be checked before replacing an AVR Disconnect the  AVR. Then check all windings of alternator for continuity and insulation resistance. If any defect is found then rectify it. Never replace the AVR if any winding is having a very low IR value or winding is defective. Connect the AVR after rectifying the defect and then start the machine. If there is no output voltage go to step 2. Check the condition of diodes in RRA. If found defective then replace the defective diode of Rotating Rectifier Assembly (RRA). Start the DG Set. If alternator does not develop  voltage go to step 3. Then run the alternator at idle speed without connecting AVR and note the output voltage. The output volta...

Elgi Electric & Industries Ltd manufactures alternators in technical collaboration with Guinault France. There was 20kVA to 380kVA Alternators available. Now Elgi Electric has stopped production of Alternators and they are more concentrating in AC Motors and DC Motors. Sara Elgi is a group of companies from Textiles, Software, Building etc. The following figure shows a schematic diagram of Elgi Electric make Alternator. There are five windings in Elgi alternators. Exciter Field, Exciter Armature, Main Field, Main Armature, Auxiliary Winding. The Auxiliary Winding is wound over the Main Armature (Stator). This winding gives 40V, 6A AC supply for AVR. Exciter Field is also fitted with Permanent Magnets. This will avoid break down of alternator due to loss of residual magnetism. Due to the permanent magnets there will be around 100V output between phase without AVR. If alternator does not produce 80 to 100V at rated speed with out AVR we can suspect any internal fault with the alte...