An Innovative Solution for the Power Quality Problems in Induction Motor by Using Silica and Alumina Nano Fillers Mixed Enamel for the Coatings of the Windings

Abstract

Power quality has always been a concern of power engineers. Certainly an argument can be successfully made that most parts of power engineering have the ultimate objective to improve power quality. AC motors were widely used in industrial and domestic applications. Generally, AC motors were of two types: Induction and Synchronous motors. In motor many parameters like different load cycling, switching, working in hot weather and unbalances creates harmonics which creates major reasons for temperature rise of the motors. Due to high peak value of voltage, harmonics can weaken insulation in cables, windings and capacitors and different electronic components. Higher value of harmonics increase the motor current and decrease the power factor which will reduce the life time of the motor and increase the overall rating of all electrical equipments. Harmonics reduction of all the motors in India will save more power. Coating of windings of the motor with nano fillers will reduce the amount of harmonics in the motor. Based on the previous project works, actions were taken to use the enamel filled with various nano fillers for the coating of the windings of the different AC motors. Ball mill method was used to convert the micro particles of Al₂O₃, SiO₂, TiO₂, ZrO₂ and ZnO into nano particles. SEM, TEM and XRD were used to augment the particle size of the powder. The synthesized nano powders were mixed with the enamel by using ultrasonic vibrator. Then the enamel mixed with the nano fillers was coated to the windings of the several AC motors. Harmonics were measured in terms of various indices like THD, VHD, CHD and DIN by using Harmonic analyzer. There are many other measures and indices to describe power quality, but none is applicable in all cases and in many instances, these indices may hide more than they show. Sometimes power quality indices were used as a basis of comparison and standardization. The efficiency of the motors was increased by 5 – 10 %. The thermal withstanding capacity of the motor was increased by 5º to 15º C. The harmonics of the motors were reduced by 10 – 50%.

1. Introduction

In recent years, a great deal of attention has been given to the applications of nano fillers in the field of electrical insulating materials. It has been examined that the use of nano fillers to the enamel used in the motors can greatly improve the thermal, mechanical and electrical properties of it [1, 3]. The efficiency of the induction motor depends upon the properties of the enamel used for the coating of the windings of the motor [2]. For single phase induction motors, the enamel was used for three purposes: impregnation, coating and adhesion. The efficiency of the single phase induction motor could be increased by adding the nano fillers with the enamel which was used as coating for the windings of the motor. In this paper, the efficiency of the normal single phase induction motor, SiO2 nano filler mixed enamel coated single phase induction motor and Al2O3 was analyzed and the results were compared with each other [8]. Heat run test was performed on the single phase induction motors to determine the total loss of energy dissipated as heat [4]. It was well-known that the operating temperature of the motor has a very strong relationship with the life duration of the insulation. The enamel used for coating of the machine windings were organic in nature and were adversely affected by thermal decomposition. Harmonics create a major problem in the field of power system. Due to high peak value of voltage, harmonics can weaken insulation in cables, windings and capacitors and different electronic components. Higher value of harmonics increase the motor current and decrease the power factor which will reduce the life time of the motor and increase the overall rating of all electrical equipments. Harmonics reduction of all the motors in India will save more power. Coating of windings of the motor with nano fillers will reduce the amount of harmonics in the motor. Harmonics will cause the following problems:

(1). Reduction of efficiency of the motor (2). Ageing of the electrical components (3). Malfunctioning and failure of electronic equipment (4). Overheating and failure of electric motors (5). Excessive measurement errors (6). Electromagnetic interference (7). Spurious operation of protective devices.

 

2. Coating of the Nano Filler Added Enamel to the Windings of the Motor

Ball mill method was used to prepare the nano powders of SiO2 and Al2O3. SEM was used to augment the particle size of SiO2 and Al2O3 [5]. Figs. 1 and 2 shows the SEM images of SiO2 and Al2O3 before ball mill process.

Fig. 1.SEM analysis of SiO2 at 50 μm

Fig. 2.SEM analysis of Al2O3 at 50μm

2.1 Figures

Figs. 3 and 4 shows the SEM images of SiO2 after ball mill process. The sizes of the particles are in the range from 40 to 100 nm size.

Fig. 3.SEM analysis of SiO2 at 50 nm

Fig. 4.SEM analysis of Al2O3 at 50 nm

5 wt% of nano powder of SiO2 and Al2O3 was taken and it was mixed with the enamel by using ultrasonic vibrator. Then this enamel was coated on the windings of the single phase induction motor. The specifications of the single phase induction motor were shown in the Table 1.

Table 1.Specifications of the Single phase induction motor

 

3. Experimental Analysis

3.1 Load test

The load test was done as per the circuit diagram and arrangement shown in the Figs. 5 and 6. The maximum efficiency obtained from an ordinary induction motor was 69%. The maximum efficiency obtained from SiO2 nano filler mixed enamel coated induction motor was 74%. The maximum efficiency obtained from Al2O3 nano filler mixed enamel coated induction motor was 75%. Al2O3 nano fillers have excellent electrical, thermal, mechanical and physical properties. SiO2 nano fillers have high level of resistance to partial discharge, high purity, large surface area, good thermal, electrical and mechanical properties. One of the reasons for the increase in efficiency of the motor by adding nano fillers was mainly due to the reduction in the dielectric losses and harmonic losses.

Fig. 5.circiut diagram

Fig. 6.circuit arrangement

The output power, current, efficiency, and speed were measured on the ordinary and nano coated single phase induction motor. The readings were shown in the Table 2 to 4.

3.2 Tables

Table 2.Experimental values of V, I, P, N, T and η for the normal single phase induction motor

Table 3.Experimental values of V, I, P, N, T and η for SiO2 nano coated single phase induction motor

Table 4.Experimental values of V, I, P, N, T and η for Al2O3 nano coated single phase induction motor

3.3 Temperature test

Heat run test was done on electric machines to determine the total loss of energy dissipated as heat [6, 7]. It was well-known that the operating temperature of an electric machine has a very strong relationship with the life duration of the insulation. Heat run test was conducted on the single phase induction motor as per IEC 60851. The temperature of the motor was measured under different conditions and the readings were shown in the Table 5. The life time of the motor was dependent on the losses of the motor. When the losses were reduced, the heat rise in the motor will also be reduced. Generally, the energy due to losses was dissipated in the form of heat energy. The thermal withstanding capacity was increased due to the reduction in dielectric and harmonic losses present in the motor.

Table 5.Measurement of temperature on the windings of the single phase induction motor

3.4 Measurement of harmonics

The total harmonic distortion was a measurement of the harmonic distortion present and was defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. THD was used to characterize the linearity of audio systems and the power quality of electric power systems. In power systems, lower THD means reduction in peak currents, heating, emissions, and core loss in motors. Total harmonic distortion was measured as the percentage. Lower percentages were better. In reality, total harmonic distortion was hardly perceptible to the human ear. Voltage distortion consists of very sharp notches and spikes in voltage. When applied to the equivalent circuit, that high frequency voltage does not cause much change in the inductive magnetizing current, but causes a change in the load current. Current THD was caused by the motor itself due to non-linearity of the magnetizing current. The current THD will be higher when the motor was unloaded. The THD was the means to express the distortion affecting a current or voltage flowing at a given point as a single number. THD analysis was done according to the standard IEC 61000-2-2. The harmonics of the motors were reduced by 10 - 50%. Fig. 7 shows the comparison of VHD for motors with and without nano coating.

Fig. 7.Comparison of VHD for motors with and without nano coating

 

4. Conclusions

The following observations were clear as per this research:

The efficiency of the induction motor was increased by 5 % by adding nano filler of SiO2 to the enamel used as the coating for the windings of the single phase induction motor. The efficiency of the induction motor was increased by 6 % by adding nano filler of Al2O3 to the enamel used as the coating for the windings of the single phase induction motor. The increase in efficiency of the motor by adding nano fillers was mainly due to the reduction in the dielectric losses and harmonic losses. The addition of SiO2 nano fillers to the enamel has also improved the temperature withstanding capacity of the induction motor by 5.26 %. The addition of Al2O3 nano fillers to the enamel has also improved the temperature withstanding capacity of the induction motor by 7 %. The thermal withstanding capacity of the motor was increased due to the reduction in dielectric and harmonic losses present in the motor. Hence the life time of the motor will be increased. The harmonics of the motors were reduced by 10 – 50 %.