Claims:
1. A Single-Phase Induction Motor comprising of:
at least two asymmetrical windings including a main winding and auxiliary winding shifted by 90 degree-electrically; wherein the main winding is made of copper wires; and wherein the auxiliary winding is made of enameled aluminium wires.

2. The Single-Phase Induction Motor as claimed in claim 1, performance parameters like Discharge, Overall Efficiency, Load Current and Speed are equal compared to full copper winding motor.

3. The Single-Phase Induction Motor as claimed in claim 1, wherein the auxiliary winding done in enameled aluminium wire produces high starting torque, lesser noise with reduced cost.

, Description:FIELD OF INVENTION

The present invention relates to a Single-Phase Induction Motor with improved starting torque. More particularly, the present discloses an innovative approach used to optimize cost and improving starting torque without hampering the motor running performance for Single Phase Induction motors. The said innovation includes changing auxiliary copper winding with enameled aluminium improving starting performance and to reduce material cost. The manufacturing cost reduced without affecting Electrical and Thermal performance of the motor.

BACKGROUND ART

Fractional power rating motors are widely used for various application such as house appliances, small electric driven pump, etc. Around 90% of these motors are having rating below 0.75 kW. The small motors are manufactured for dedicated applications in extended production. Due to large quantity, material cost has vital importance, hence it is expected that motor cost should be and with optimum performance. The manufacturing cost is depending on the active material consumed by the motor and performance of the motor. In order to obtain minimum price, consumer selects the motor based on required power output and its efficiency.

Large part of material cost is consisting of active materials like laminations and copper. Other than the material cost, motor starting performance such as motor starting torque and starting current is also important for various application. If we use the aluminium auxiliary winding it increases the auxiliary winding resistance and improves the starting performance.

In the prior art, a Brazilian specification BRPI1101724A2 discloses use of aluminium wire copper coated enamel on spools for appliance controls (known as CCC). Aluminium wire copper coated enamel can be applied to replace the traditional enamel copper wire, allowing the weight reduction of the coil. For each, design, it is possible to designate a particular use of the CCC to meet electrical requirements of the application.

In another prior art, a Japanese specification JP2008148533A recites a solution to a problem for attaining low pricing of a motor by reducing an amount of copper used for the motor. In a conductive wire which forms a coil of an armature, aluminium is used for a main conductor portion, and the main conductor portion is covered by the copper to constitute a copper-covered portion. The amount of the copper used is reduced by using the aluminium for the main conductor portion. Moreover, the armature becomes one rigid body by resin-melded unit, which is moulded by a resin material.
Here BLDC motor with CCA has been evaluated for its performance. On the contrary, the present disclosure addresses electric and thermal performance evaluation with the Single-Phase Induction motor and with enameled aluminium wire.

References
1.A.K Sawhney – Electrical machine design
2.R.K. AGARWAL-Principles of Electrical Machine Design

SUMMARY OF INVENTION

The herein disclosed innovative approach is used to optimize cost and improving starting torque without hampering the motor running performance for Single Phase Induction motors. In this invention of Single-Phase Induction Motor, we have changed auxiliary copper winding with enameled aluminium improving starting performance and to reduce material cost. The manufacturing cost reduced without affecting Electrical and Thermal performance of the motor.

The Single-Phase Induction Motor is not self-starting. To generate starting torque two asymmetrical windings shifted by 90 degree-Elect. Are used i.e. main winding and auxiliary winding. The purpose of auxiliary winding is to generate artificial magnetic field, giving useful torque & it contributes majorly while starting of motor. Resistivity of aluminium is more than copper; hence we have changed the material of only auxiliary winding from copper to enameled aluminium for providing high starting torque. The higher resistivity because of aluminium gives inherently lower eddy current losses in winding, which mitigates the risk of generation hot spots in it.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig 1 Illustrates a graphical representation of pump performance curve (i.e. Pressure head Vs Discharge Curve) in accordance with the present invention;

Fig 2 Illustrates a graphical representation showing variation of load current with pump discharge (i.e. Current Vs Discharge curve) in accordance with the present invention;

Fig 3 Illustrates a graphical representation showing overall efficiency of entire system from the initial input to the final output (i.e. Overall efficiency Vs Discharge Curve) in accordance with the present invention;

Fig 4 Illustrates a graphical representation showing variation in speed with Pump discharge (i.e. Speed Vs Discharge Curve) in accordance with the present invention.

DETAILED DESCRIPTION

As discussed in the prior art problems and in the conventional production, most of manufacturer prefer copper or aluminium conductor for both main and auxiliary winding. The current density of copper is 30% higher compare to enamelled aluminium, whereas price of or enameled aluminium is one third that of copper. If we consider the conductivity of copper, it is 63% higher than that of the aluminium. Hence resistance of aluminium winding is higher compared to copper winding and gives improved starting performance. Considering the operating point of motor at application we can replace the copper auxiliary winding with or enameled auxiliary winding motor.

To validate the approach of the present disclosure, the inventors have tested two Single Phase Induction Motors, one with full copper stator winding and other with auxiliary winding is made with enameled aluminium conductor and main winding with copper. Both have identical characteristics and used for pump application, in output only small difference has been tolerated.

Based the results of this study, one can observe that for Single Phase Capacitor Run motor enameled aluminium shown equal performance as copper auxiliary motor. This study also considers the mechanical characteristics in order to compare the rated and starting torques by shaft’s speed function. The temperature of the motor in continuous functioning is just as important, and the noise and vibration level. The methods for testing are according to standard procedures of product and size measurement. The motors tested are single phase motors, with following parameters;
a. Rated Voltage – 180V-260 V
b. Rated Power of 0.25 kW to 1.1 kW.
c. Speed 2800 rpm
d. Rated Torque of 0.85 Nm to 3.75 Nm

In order to obtain the representative curves of motors, pump motor set up is tested in laboratory. This way we can settle dynamic measurements and input parameters such as currents and voltages and output parameters, shaft speed and torque. Tested motors are used in Pump application for this usage it is necessary that the motor can operate in counterclockwise rotation.

The experimental measurements are focused on two Single Phase Induction motors, one with both windings are in copper and the other one with auxiliary winding in enameled aluminum. Both these motors are tested with pump application, the output characteristic of the pump is expected to be same.

Suction Lift:
In a suction lift configuration, a centrifugal pump takes suction from a source of liquid located below the pump centerline. Results shows that Motor with auxiliary winding in enamelled aluminum have better suction capability due to high resistivity of aluminum give better torque for suck the water.

Suction lift Regular motor with both windings is in copper Motor with auxiliary winding in enamelled aluminum
Height(m) Time Time
3 2 min 12 sec 1 min 45 sec
5 6 min 9 sec 4 min 7 sec
6 11 min 28 sec 6 min 38 sec

Table 1: Suction lift Performance for Full Copper and Enamelled Auxiliary Winding
Starting Torque:

Most of the application demands the high starting torque based on load profile. The Starting torque is the torque transferred by the shaft coupling during run-up (Start-up process). By using enameled aluminum in auxiliary winding provides better starting torque as compare to copper winding. This deviation occurs due to high resistivity of aluminum winding.

Parameter Regular motor with both windings is in copper Motor with auxiliary winding in Enamelled aluminum
Starting Torque 23-40% 27-47%

Table 2: Starting Torque Performance for Full Copper and Motor having Enamelled Aluminium Auxiliary

Performance of Pump:
As shown in Fig 1, the pump performance curve indicates how a pump will perform regarding pressure head and flow. In both the sample, performance deviation is negligible. We have achieved performance as per our declaration in reduced cost.

Results show in Fig 2, that motor almost draws same current at rated voltage.

The overall efficiency is defined as the ratio of the mechanical output to the electrical input. Overall efficiency as shown in Fig 3, looks at entire systems from the initial input to the final output. or it is the ratio of energy output to energy input. The experimental results show that overall efficiency drop is also negligible.

The rotational speed (also called speed, or speed of rotation) can be quantified as the number of revolutions a rotating system makes within a defined period. The discharge of pump is totally depending on speed. The present invention aims to achieve max speed as possible, results shows that the speed of both the motor is almost constant as shown in Fig 4.

Temp Rise of Pump

For evaluating the thermal performance and reliability of the motor, we have performed temperature rise test on motor, and found satisfactory results.

Following is the main alternative approach which is in existence currently:

1. Both main and auxiliary winding done in enameled aluminium wire, it gets higher starting torque, lesser noise with reduced cost, disadvantage is life of motor will reduce.

2.List out the features of your invention which are believed to be new and distinguish them over the closest technology.

Inventive step
a. The present invention uses enameled aluminium auxiliary winding to reduce material cost by 5 % and achieved the same performance as pure copper winding.
b. Thermal performance of the motor has been maintained within the tolerance compare to pure copper auxiliary winding motor.
c. Motor speed maintained constant and starting torque improved by 5% on application.
d. Suction lift capability of pump improved with auxiliary aluminium winding.

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.