An Improved Technique for Energy-Efficient Starting and Operating Control of Single Phase Induction Motors

ABSTRACT:

 The recent increase in electricity prices and the usage of single-phase induction motors (SPIMs)provide a stimulus for a focused research on energy-efficient optimization of SPIM load such as air-conditioners and refrigerators. Variable speed control of SPIM provides a promising way forward to reduce its power consumption. However, during variable speed operation under the popular constant V=f method, SPIM is required to operate at non-rated conditions. The operation of SPIM at non-rated conditions disturbs its symmetrical and balanced operation, thus degrading its efficiency. Moreover, soft-starting of SPIM at non-rated conditions is also challenging due to the resulting reduction in starting-torque. In this article, after a detailed analysis of SPIM energy-efficiency, an improved sensor-less optimal speed control strategy is developed to enable the symmetrical and balanced operation of SPIM at all the operating points over the entire speed-range to improve its performance. A novel algorithm, termed as the phase-shift algorithm, is also devised for efficient implementation of the proposed optimal speed control strategy. In addition, a unique framework for efficient soft-starting of SPIM at very low frequencies is also developed. The simulation-based results of the motor operated through the proposed phase-shift algorithm validate the energy-saving potential of the proposed control strategy.

KEYWORDS:

1.      Energy-efficient control

2.      Variable speed drives

3.      Speed-sensorless induction motor control

4.      Magnetic field control

5.      Inrush current reduction

6.      Starting torque

7.      Pulsating torque

8.      Energy savings in HVAC

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 

Figure 1. Switching Pattern Generation Using The Phase-Shift Algorithm For Efficient Variable Speed Operation Of Spim.

EXPECTED SIMULATION RESULTS:

Figure 2. Simulation-Based Results Of Spim Operation Under The Proposed Optimal Control At F D 30 Hz.

Figure 3. Simulation-Based Results Of Spim Operation Under The Constant V =F Control Method At F D 30 Hz.

 

 

Figure 4. Simulation-Based Results Of Spim Operation Under The Proposed Optimal Control Strategy At F D 60 Hz.

 

Figure 5. Simulation-Based Results Of Spim Operation Under The Constant V =F Control Method At F D 60 Hz.

 

Figure 6. Simulation-Based Results Of Spim Operation Under The Proposed Optimal Control Strategy At F D 10 Hz.

 

 

Figure 7. Simulation-Based Results Of Spim Operation Under The Constant V =F Control Method At F D 10 Hz.

 

Figure 8. Simulation-Based Results Of Spim Soft-Starting At F D 10 Hz Under The Proposed Soft-Starting Strategy.

 

 

Figure 9. Simulation-Based Results Of Spim Soft-Starting At F D 10 Hz Under The Constant V =F Control Method.

 

CONCLUSION:

In this article, it is demonstrated that conventional techniques for speed control of SPIMs are inefficient because they cause the formation of elliptical magnetic fields inside them at non-rated starting and operating conditions. After a detailed analysis of SPIM energy-efficiency, a novel sensor-less con- trol strategy was devised to improve the performance at non-rated conditions by enabling the symmetrical and balanced operation of SPIM. Formation of circular magnetic field inside SPIMs over the entire speed range is achieved by dynamically and optimally controlling the auxiliary volt- age and phase-difference between the windings voltages simultaneously with constant V=f control using the developed phase-shift algorithm. Simulation-based evaluation of the optimal control strategy demonstrates an improvement of more than 400% in energy-efficiency as compared to maximum 18% reported in case of conventional SPIM energy-efficiency optimization techniques. The developed control algorithm also enables the soft-starting of SPIM with substantial starting torque at low-frequencies, resulting in a significant reduction in inrush current. Simulation-based results of the proposed sensor-less optimal control strategy confirm an inrush current reduction of more than 84%. This efficient soft-starting results in further energy-savings.

REFERENCES:

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[3] Z. B. Duranay and H. Guldemir, ``Selective harmonic eliminated V/f speed control of single-phase induction motor,'' IET Power Electron., vol. 11,no. 3, pp. 477_483, Mar. 2018.

[4] A. Sampathkumar, ``Speed control of single phase induction motor using V/f technique,'' Middle-East J. Sci. Res., vol. 16, no. 12, pp. 1807_1812, 2013.

[5] E. R. Collins, ``Torque and slip behavior of single-phase induction motors driven from variable-frequency supplies,'' IEEE Trans. Ind. Appl., vol. 28, no. 3, pp. 710_715, May/Jun. 1992.