Publication: Effects of voltage unbalance on the efficiency and power factor of three phase induction motors
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Date
2010-04-01
Authors
Ismail, Mohd Riduan
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Abstract
Overall project includes the effects of three phase unbalance voltage of the three phase induction motor. Among the effects to be studied is the motor efficiency and power factor value for the unbalance voltage in a phase and two phases. Unbalance voltage can be cause by single phase load user that makes three phase line voltage that receive by induction become unbalance. Unbalance voltage can occur on single phase, two phases or even on the three phases, that’s the most crucial problem of quality power distribution if it’s happen. The definition used in this project to define the unbalance voltage is phase voltage unbalance in percent (PVUR) defined in IEEE Std 141. To analyze motor efficiency and power factor the speed, input power, output power, torque and current values is taken during conducted the experiments in power laboratory. In the normal usage, the allowable percentage of phase unbalance factor is 5%. But for the experimental purpose, unbalance voltage until 7% is take for consideration and experimented. For the study to compare results, simulation studies are conducted using the software PSIM 4.5. To conduct research using this software, two tests in the laboratory is needed first, the blocked rotor test and no-load test. Both tests are conducted to obtain the parameter values in the three-phase induction motor, the value of this parameter must be included in the motor parameters in the software to produce features with the same motor used in carrying out experiments in power laboratory. Squirrel cage Induction motor with 4 pole, 175 Watt, 415V and 0.46A in rating is used in experiment and this project. For simplicity, analysis was conducted using a per phase analysis. This is to facilitate the analysis of motor, without change or disrupt the value of the motor parameters. For the experiments in power xvii laboratory, there are two variants of a variable defined, the first is power output and second is torque. And others variable are changes according to changes in voltage. When conducted an experiment and simulation for constant torque, generally motor efficiency is dropping for unbalance on single phase and unbalance on two phases unbalance. While for the constant output power also shows the same trend of graph. As that, it can be conclude that the efficiency is decreasing with increasing of PVUR in percentage. Power factor of the motor show different result, for both constant torque and constant output power experiment and simulation it shows that power factor is increasing even though it’s just a small amount.