The negative effects of a particular unbalanced voltage on the performance of an induction motor are studied in this paper. The paper suggests that the available definitions of unbalanced voltages are not comprehensive and complete. Therefore, the results of these analyses on motor performance are not very reliable. To prove this claim, a three-phase 25-hp squirrel-cage induction motor is analyzed under different unbalanced conditions. It is shown that it is necessary to define a more precise unbalanced factor for more accurate results. Experimental results verify the theoretical analysis.

Influence of unbalanced voltage on the steady-state performance of a three-phase squirrel-cage induction motor

Flexible ac transmission system (FACTS) devices or their subderivative custom power devices are efficient and often used and recommended power-electronics-based devices for mitigation of voltage sags in electrical power system. With FACTS devices installed, the overall system (and individual bus) sag performance could significantly change depending on the type of the device used. In order to assess this change in sag performance in realistic large power systems, the classical (essentially static) fault calculation procedure should be amended to incorporate the effects of these devices on bus voltages. This paper presents a new approach of quasistatic sag analysis using a system impedance (Z _bus) matrix that incorporates FACTS devices. Three types of FACTS devices which are most often used in practical applications are considered in this study: static compensator, static var compensator, and the dynamic voltage restorer. The case studies based on the 295-bus generic distribution system are used to illustrate the modeling method and the effectiveness of these devices in sag mitigation.

Modeling of FACTS Devices for Voltage Sag Mitigation Studies in Large Power Systems

This paper discusses the theoretical and practical aspects of various methodologies currently used for definition and characterization of voltage sags and short interruptions. Existing power-quality standards and procedures that are recommended for classification and presentation of sags and interruptions are critically reviewed and their shortfalls are highlighted.

Shortfalls of existing methods for classification and presentation of voltage reduction events

In this work, a new method for the detection of the negative effects of a particular unbalanced voltage and inverter harmonics on the performance of an induction motor using fiber sensors is proposed. Supplying a three-phase induction motor with unbalanced voltages causes an oscillating electromagnetic torque that generates vibrations, increased losses, efficiency reduction, and an extra temperature rise that leads to a reduction on insulation life of the machine. A new in-line fiber etalon accelerometer has been designed to detect these vibrations in the range DC-500 Hz. The in-line fiber etalon scheme used provides high robustness and stability, giving enough sensitivity to monitor the low-frequency and low-amplitude oscillations in the stator of the machine that exist in a voltage unbalance situation. To prove this claim, a 1.5-kW squirrel cage induction motor is analyzed under different unbalance levels. It is shown that a precise unbalance factor can be detected without accessing to the electric part of the machine and an accurate monitoring can be obtained using the high-resolution analysis proposed

Unbalance and harmonics detection in induction motors using an optical fiber sensor

Deficiencies like unbalanced voltages in the voltage source could result in problems like excessive losses, over-voltages, mechanical oscillations, and interference with control electronics. Detecting these abnormal conditions in the machine is of great importance in the interaction of the electrical machine and the power grid. In this paper the effect of the unbalanced voltages on the motor performance, have been investigated. Then, monitoring these unhealthy condition using electrical machine parameters is carried out. In this case, motor itself can act as the sensor that detects abnormal conditions. Also this paper investigates the negative effects of unbalanced sinusoidal voltage which always present in the power supply voltage on the performance of induction motor in terms of line currents, power factor and efficiency. According to the test results and analysis, the unbalanced sinusoidal voltage has very negative effects on the motor's performance.

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Effect of unbalanced voltage on operation of induction motors and its detection

This paper aims to present investigation results related to induction motors operation under nonideal supply conditions. The motors are of squirrel cage type and the nonideal conditions are associated to harmonics, unbalances, voltage sag and swell, etc. The studies are carried out using time domain modeling and the SABER simulator. Using this approach, computational results are derived in order to compare the nonideal motor performance to the ideal ones so that the real supply condition effect upon the motor behavior can be highlighted. In addition to technical aspects, the power quality impact on energy and financial waste and is also considered.

Power quality impact on performance and associated costs of three-phase induction motors

This paper aims to analyze disturbance effects related to the loss of power quality on transformers, cables, and induction motors, amongst others. In addition to this, the relationship between power quality and extra costs associated to the increase in power consumption for a typical industry is also taken into account. The study uses a modern computational platform known as the SABER simulator that utilizes the time domain strategy to represent the system components. Qualitative as well as quantitative analysis are carried out to illustrate the phenomenon.

https://ieeexplore.ieee.org/iel4/6146/16440/00760141.pdf

An analysis of costs related to the loss of power quality

This paper deals with thermal behaviour analysis of three-phase induction motors under nonideal supply conditions. The motors are of squirrel cage type and the nonideal conditions are associated to harmonics, unbalances, voltage sag and swell, etc. The studies are carried out using a comprehensive methodology which handles electrical, mechanical and thermal models in a simultaneous way. The approach is then implemented into a time domain program known as the SABER simulator. Computational studies are then performed to evaluate motor temperature rise and life reduction under nonideal conditions.

Induction motors thermal behaviour and life expectancy under non-ideal supply conditions

This paper deals with the thermal behaviour and life expectancy analysis of power insulated cables under distorted voltage and load current conditions. The proposed methodology utilises classical IEC-287 electrical and thermal models and extends the approach to cope with mutual thermal interaction between phases. This allows for independent three-phase representation and both thermal and electric equations are solved in a simultaneous way. This comprehensive manner of representing the phenomenon is then implemented into a time domain program. Computational studies are then performed to evaluate the cable temperature rise as well as the effect upon life reduction under distorted voltage and current conditions.

Insulated cable thermal and life expectancy estimation under non-sinusoidal operating conditions

Nowadays the power quality has emerged as a problem of major concern in the area of Electrical Engineering. In this way, national and international recommendations have been proposed to regulate several topics related to this subject. The voltage and current harmonic distortion appears to be one of the most important areas as they are associated with the widespread application of non linear loads. Thus, this work contributes towards practical proposals to reduce harmonic distortion in electrical power systems. Two equipments are suggested in this paper. The first is a specially designed harmonic blocking device and the second is based on phase-shifting autotransformer. In addition to the physical principles and design considerations, computational results are given to illustrate the overall system and harmonic eliminators performance.

O.C.N. Souto

Papers

Power quality impact on performance and associated costs of three-phase induction motors

An analysis of costs related to the loss of power quality

Induction motors thermal behaviour and life expectancy under non-ideal supply conditions

Insulated cable thermal and life expectancy estimation under non-sinusoidal operating conditions

Practical proposals to reduce harmonic currents in electrical power systems