DESC:THREE PHASE INDUCTION MOTOR

Field of the invention

The present invention relates to induction motors and more particularly, to a three phase induction motor with ultra-premium efficiency.

Background of the invention

The growing social awareness of recent years in environmental issues such as global warming, have raised interest in technology which increases the efficiency of electrical equipments and reduces energy consumption. Thus from energy conservation point of view, there is a growing need worldwide to replace industrial equipment with high efficiency motors, as the electric motors are estimated to consume about 65% of the electrical energy consumed by an industry. Moreover, energy costs over typical life cycle of a motor can be as high as fifteen times the original capital cost thereof. Energy efficient motors thus offer an opportunity to significantly reduce energy costs and their collateral environmental effects. The ever increasing cost of fuel and electricity adds to the complexity, and directly affects not only industries but entire economies.

Thus, there is a strong economic and environmental reason for choosing high efficiency motors over conventional ones. There are existing methods to achieve Ultra-Premium Efficiency motors (IE5 efficiency motors) such as permanent magnet motor and synchronous reluctance motor. With the use of line start permanent magnet in the permanent magnet motor, it can support on line (DOL) starting only and also the motor requires low voltage starting drive. In case of synchronous reluctance motor additional devices like invertors and variable-frequency drive (VFD) would be needed. Also, such motors suffer from low power factor, humming noise, etc. and require synchronization with the other devices.
Accordingly, there exists a need to provide a three phase induction motor with ultra-premium efficiency which overcomes the drawbacks of the conventional techniques.

Objects of the invention

An object of the present invention is to achieve ultra-premium efficiency of a three phase induction motor.

Another object of the present invention is to reduce energy consumption of the three phase induction motor.

Yet another object of the present invention is to reduce the losses in a motor for example core loss, stator copper loss, rotor copper loss, friction and windage loss, stray load loss and improve the efficiency of the motor.

Summary of the invention

Accordingly, the present invention provides a three phase induction motor (hereinafter, “the induction motor”). The induction motor comprises a shaft, a motor body, a stator, a rotor, a terminal box and a fan. The stator is fitted within the motor body and produces constant amplitude rotating magnetic field upon excited with an electric supply. Specifically, the stator is made of high grade silicon steel and a copper wire having a diameter from 5 SWG to 48 SWG. To reduce the stator copper losses, number of turns per slot is reduced wherein the number of slots is even integers based on number of poles. The rotor is arranged in a close vicinity of the stator and rotates in a same direction as the magnetic field produced therein. Specifically, the rotor is made of high grade silicon steel, copper bars and copper end rings. A slot area of the stator and the rotor is increased by increasing slot height and width. The shaft is rotatably coupled to the rotor. The shaft is configured with a driving end bearing located at a driving end shield and a non-driving end bearing located at a non-driving end shield. The terminal box is arranged on a top of the motor body. The terminal box is covered by a terminal box cover. The fan and a fan cover are mounted at one end of the shaft for cooling of the induction motor. In accordance with the present invention, increased stator rotor lengths along with increased stator lamination diameter improve the efficiency of the induction motor.

Brief description of the drawings

The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows an exploded view of a three phase induction motor, in accordance with the present invention;

Figure 2 shows a cutaway view of the three phase induction motor, in accordance with the present invention;

Figure 3 shows a cross sectional view of the three phase induction motor, in accordance with the present invention; and

Figure 4 shows a sectional view of a rotor part of the three phase induction motor, in accordance with the present invention.

Detailed description of the invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a three phase induction motor that achieves ultra-premium efficiency (IE5 efficiency) which further leads to reduce the energy consumption. The three phase induction motor of the present invention reduces all losses such as core loss, stator copper loss, rotor copper loss, friction and windage loss, stray load loss, and improves the efficiency of the motor.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in brackets in the following description and in the table below.
Table 1:
Component Name Reference Number Component Name Reference Number
Shaft 1 Rotor 10
Extension key 2 NDE bearing 11
Drive end shield 3 NDE shield 12
Driving end bearing 4 Fan 13
Terminal box 5 Fan cover 14
Terminal box cover 6 Silicon steel 15
Eye bolt 7 Copper bar 16
Motor body 8 Copper ring 17
Stator 9 Three phase
induction motor 100

Referring to figures 1-4, a three phase induction motor (100) (hereinafter ‘the induction motor’ (100)) in accordance with the present invention is shown. The induction motor (100) comprises a shaft (1), an extension key (2), a drive end shield (3), a terminal box (5), a motor body (8), a stator (9), a rotor (10) and a fan (13).

The shaft (1) is rotatably coupled to the rotor (10) to form a shaft-rotor assembly and the assembly is inserted inside the stator (9) that is fitted within the motor body (8). The stator (9) produces constant amplitude rotating magnetic field upon excited with an electric supply. The stator (9) is made of high grade silicon steel and a copper wire. The rotor (10) is arranged in a close vicinity of the stator (9) and rotates in the same direction as the magnetic field produced therein. The rotor (10) is made of high grade silicon steel (15), copper bars (16) and copper end rings (17) as shown in figure 4. The stator-rotor slot is designed in such a way as to reduce the core losses by using high grade steel as core. In accordance with the present invention, the stator and the rotor slot area is increased than the existing designs by increasing slot height and width. To reduce the stator copper losses, number of turns per slot is reduced and the copper wire diameter is increased. In an embodiment, the number of slots is even integers ranging from 12, 18, 24, 36, 48, etc. based on number of poles. In the context of the present invention, the number of turns is calculated first and then according to the stator slot size, the copper wire size to accommodate calculated number of turns is calculated. In an embodiment, the copper wire diameter is from 5 SWG to 48 SWG. However, it is understood here that the number of turns per slot and the copper wire diameter can be customized as per the intended application and design in other alternative embodiments of the present invention. The rotor finish outer diameter is grinded to reduce stray load losses. The smaller size fan (13) is used to reduce windage loss. The fan (13) along with a fan cover (14) is mounted at one end of the shaft (1) for the induction motor cooling purpose. Specifically, the fan (13) along with the fan cover (14) is arranged at the NDE shield (12) for the induction motor cooling. The extension key (2) is used for customer coupling fitment.

The shaft (1) is further configured with a driving end bearing (DE) (4) and a non-driving end (NDE) bearing (11) and located at driving end (DE) end shield (3) and non-driving end (NDE) end shield (12) respectively. The terminal box (5) is arranged on a top of the motor body (8) and stator lead wires are connected to the terminal board in the terminal box (5). The terminal box (5) is covered by a terminal box cover (6). An eye bolt (7) is fixed on the motor body (8) for lifting purpose.

Again referring to figures 1-4, in an operation of the induction motor (100), upon provided with a three phase supply to the stator (9), a rotating magnetic field is produced which rotates at synchronous speed. The rotor (10) stands stationary in an initial stage. When the rotor (10) cuts the rotating magnetic field and as per Faraday’s Law, an electromotive force is generated in the rotor (10) which produces the current. According to Lenz’s Law, the direction of this current is to oppose the vary cause of its production. The vary cause of its production is the difference in its relative speed i.e. rotating magnetic field and stationary rotor. So the rotor (10) starts rotating in the direction of the rotating stator magnetic field and tries to achieve the same speed. As the magnetic field rotates at synchronous speed, the rotor (10) rotates at speed less than synchronous speed.
In accordance with the present invention, design details of the induction motor (100) with comparison to motor having IE2 efficiency is provided in the following table:
Table 2: Design details of a three phase motor having a specifications 3.7 Kw 2P.
Parameter IE2 The induction motor (100) (IE5)
Stator Lamination OD (mm) 155 188
Stator Lamination ID (mm) 84 98
No. of Stator Slots 24 24
Rotor Lamination OD (mm) 84 98
Rotor Lamination ID (mm) 37.7 37.7
No. of Rotor Slots 20 28
Stator / Rotor Core Length (mm) 110 140
No. of Turns 64 52
Wire Size 2 x 0.65 mm 0.76 mm and 0.90 mm
Cooling Fan OD (mm) 154 134.5
Core Loss 150.09 91.21
Stator Copper Loss 257.20 86.12
Rotor Loss 168.30 61.4
Friction and Windage Loss 43.51 40.51
Stary Load Loss 95.90 40
Total Losses 715 319.20
Efficiency as per IS 12615 85.5 (-2.2) 91.6 (-1.26)
Achieved Efficiency 84.4 91.55
Temperature Rise (°C) 70 21.5

The design details of the induction motor (100) provided in the above table are to be interpreted merely as an illustration and they are in no way to be construed as a limitation and it is understood here that these specifications can be varied in other alternative embodiments of the present invention as per the intended application.

Advantages of the invention

1. The induction motor (100) achieves ultra-premium efficiency by using copper rotor and high grade electrical steel which further leads to reduce the energy consumption.
2. The increased stator rotor lengths along with increased stator lamination diameter and the modified stator rotor slot design improve the efficiency of the induction motor (100).
3. The usage of high grade electrical steel in the core and by adjusting the core lengths of stator and rotor the induction motor (100) reduces the core loss and achieves higher efficiency. By this way, the induction motor (100) also reduces all the losses such as core loss, stator Cu loss, rotor Cu loss, friction and windage loss and stray load loss, and increases the efficiency.
4. The induction motor (100) is easy to manufacture and has lesser overall motor cost.
5. The induction motor (100) does not require additional devices like invertor, VFD, etc. for operation thereof.
6. The induction motor (100) does not require synchronization and is free from humming noises.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention. ,CLAIMS:We claim:

1. A three phase induction motor (100) comprising:
a stator (9) fitted within a motor body (8), the stator (9) produces constant amplitude rotating magnetic field upon excited with an electric supply;
a rotor (10) arranged in a close vicinity of the stator (9) and rotates in a same direction as the magnetic field produced therein, wherein a slot area of the stator (9) and the rotor (10) is increased by increasing slot height and width;
a shaft (1) rotatably coupled to the rotor (10), the shaft (1) configured with a driving end bearing (4) located at a driving end shield (3) and a non-driving end bearing (11) located at a non-driving end shield (12);
a terminal box (5) arranged on a top of the motor body (8), the terminal box (5) being covered by a terminal box cover (6); and
a fan (13) and a fan cover (14) being mounted at one end of the shaft (1) for cooling thereof,
wherein, increased stator rotor lengths along with increased stator lamination diameter improve the efficiency of the induction motor (100).

2. The three phase induction motor (100) as claimed in claim 1, wherein the stator (9) is made of high grade silicon steel and a copper wire having a diameter from 5 SWG to 48 SWG.

3. The three phase induction motor (100) as claimed in claim 1, wherein to reduce the stator copper losses, number of turns per slot is reduced, the number of slots is even integers based on number of poles.

4. The three phase induction motor (100) as claimed in claim 1, wherein the rotor (10) is made of high grade silicon steel (15), copper bars (16) and copper end rings (17).