Conditions of AC Motor in Electrical Laboratory
Keywords:
Digital multimeter (DMM), Clamp-on ammeter, Megohmmeter, Non-contact thermometer, Power quality analyzerAbstract
To ascertain the conditions of three phase ac motors requires many approach such as virtual inspection of the motor, shaft checking to ensure smooth rotation and bearing situation then proceeding to insulation resistance and winding resistance tests. Meggar instrument was used for the insulation test while digital Multimeter was used for the Winding test. The first test carried out was insulation resistance test using megger. The motor (1) has an insulation resistance of 8 Megaohms across the ground to phase recorded reading and 10 Megaohms across the phase to phase. The recorded megger reading value is higher than the calculated insulation resistance value of 1.38 Megaoms signifying the 3 phase ac motor has a high insulation resistance to accomplish safety rules of operation. The motor (2) has an insulation resistance of 1 Megaohms across the ground to phase and the phase to phase which is equal to the calculated 1.22 Megaoms signifying the 3 phase ac motor has a low insulation resistance and bad. Hence, the motor under went maintenance to increase the insulation resistance by heating the windings via ovum. The insulation value increased to 1.7 Gigaohms. For the winding test, the motors phase reading result is zero signifying no contact of the winding to the frame. For the open circuit test of continuity shows the (U1-U2, V1-V2 and W1-W2) recorded a 0.5ohms and 0.6 ohms across the two ac motors. For the short circuit test between the phases recorded zero hence, there is no short circuit across the phases. Therefore, the conditions of the three phase ac motors were ascertain and recommended for use.
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