Introductory Chapter: Induction Motors (IMs) Efficiency Improvement Perspectives

Abstract

Improving induction motor efficiency is vital from an energy-saving point of view in industry and all life categories because energy waste equals money waste without benefits. Maximization of efficiency makes a great saving of electrical energy consumed by the motor and improves power factor. The point of maximum efficiency depends on the machine parameters. There is a unique point at a certain slip or speed, and the voltage reduction could be used to keep this speed of maximum efficiency with any load torque requirements. The speed at max. eff. depends only on the motor parameters, i.e. this speed is constant for the same motor whatever its applied load is. When the motor operates at this optimum slip, the improvements in all characteristics are clear.

1. Introduction

Improving induction motor efficiency is vital from an energy-saving point of view in industry and all life categories because energy waste equals money waste without benefits. Maximization of efficiency makes a great saving of electrical energy consumed by the motor and improves power factor. The point of maximum efficiency depends on the machine parameters. There is a unique point at a certain slip or speed, and the voltage reduction could be used to keep this speed of maximum efficiency with any load torque requirements. The speed at max. Eff. depends only on the motor parameters, i.e. this speed is constant for the same motor whatever its applied load is. When the motor operates at this optimum slip, the improvements in all characteristics are clear. For input current comparison, for the same value of load torque, the input current at optimum slip is always less than that corresponding to the rated voltage. The difference between these two currents is large, especially at light loads, and reduces with load increase. This difference in input current causes a reduction in motor losses as well as its magnetizing current, so the efficiency increases. The input power, with controlled voltage, is less than that at the rated voltage. The difference is also at light loads and narrows towards the rated output. Therefore the input power is saved with voltage reduction at light loads [1, 2, 3, 4, 5].

2. IM efficiency improvement and potential future research

The efficiency, at controlled (reduced) voltage, is constant at its maximum value. This is because efficiency is a function of slip and the constancy of motor parameters. The slip is constant at its optimum slip, and the motor parameters are unchanged due to the motor operation at a base frequency. Therefore, the efficiency is constant at its maximum value. Comparing the efficiency at rated voltage with such one at optimum slip with reduced voltages, a substantial energy reduction is achieved throughout the entire load range. The operation under variable frequency should be done under the standard or general – purpose voltage – frequency pattern. When varying the frequency obeying the mentioned pattern, the power factor peak points move across the speed scale according to the speed value [6, 7, 8].

The more attractive note concerning the variable efficiencies relations, corresponding to each frequency value, is that at each frequency there is a certain speed point at which efficiency could be maximized. Operating at optimum efficiency corresponding to each frequency can be done by the same voltage relation which is deduced in this study at the also deduced slip for each frequency value. Variable frequency operation (Constant V/f) presents speed control by both voltage and frequency variations and keeps the magnetic saturation and insulation not exceeding their specified design values. So, a view on the general – purpose voltage – frequency pattern could be utilized to easily control the induction motor by frequency variation taking into consideration the parameters’ sensitivity to frequency variation, and the motor performance characteristics. However, the operation of optimum efficiency is achieved by driving the motor at a slip of maximum efficiency at each frequency value. Because this slip is a function of IM parameters, which are functions of frequency, it varies with the frequency changes under various load torque types [9, 10, 11].

Various control methods could be utilized and optimized using artificial intelligence techniques. Induction motor control using Artificial Neural Networks. So, an adaptive model of an induction motor using deep learning techniques could be used to estimate its performance accurately based on online real-time measurements. Then, sensorless controllers could be implemented. Due to the benefits of (ANN), would be used too in sensorless speed estimation and thus speed sensorless controller. A speed sensorless controller is an attractive choice. This is because induction motor drives can be controlled without using mechanical speed sensors. The information involving the rotor speed can be obtained by calculation using the measured stator voltages, currents, frequency, and sometimes input power, which can identify the IM speed for all motor characteristics [12, 13, 14, 15].

Additionally, the induction motor needs a regular maintenance procedure to monitor its condition. However, the traditional methods have noticeable drawbacks, especially at high voltage which might weaken isolation provision causing challenging its utilization in industrial conditions. So, nondestructive testing is an excellent candidate for faults diagnosis in induction motors [16]. Finally, the editor himself has some research related to electric machines including induction motors, artificial intelligence, control, and optimization techniques that could be easily applied to the induction machines to improve their efficiency [17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89].