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...

  The above diagram shown connection of Kirloskar AVR model KAVR-1. This type of AVR is used in some brush-less alternators manufactured by Kirloskar Electric Company Ltd . This is a single phase sensing AVR. Sensing voltage and working voltage are taken from the main armature (output supply) of the alternator. This is not recommended for unbalanced load. As the AVR is is sensing only the voltage of one phase regulation will not be proper for unbalanced load. Most of the AVR are two phase sensing were as there are some three phase sensing AVR also available. This AVR was used in smaller alternators. Now it is replaced with KAVR-2 which is two phase sensing. This AVR has 3 multy tern potentiometers that are used to adjust the output voltage (P1) Under frequency cut-off (frequency roll off) (P2) and Voltage Stability (P3) By Adjusting P1 clockwise we can increase the output voltage and counterclockwise adjustment of P1 will decrease the output voltage.  AVR is supposed to main...