DESC:
Field of the invention

The present invention relates to an electric motor assembly and more particularly, to a totally enclosed fan cooled (TEFC) motor and dissipation of heat generated therein for maintaining the motor temperature within a specified temperature rise limit thereby ensuring a safe and reliable operation thereof.

Background of the invention

Totally Enclosed Fan Cooled (TEFC) motors are electric motors with enclosures that do not permit outside air to freely circulate through the interior of the motor. The fans employed for cooling TEFC motors are purely radial type centrifugal fan as shown in figure 1. The heat generated inside the electric motor needs to be dissipated to maintain the temperature within the specified temperature rise limit of the motor and to ensure safe and reliable operation. In case of the cooling arrangement using traditional radial fan, the air is sucked axially from the center of perforated fan cover on non-driving end (NDE), and then gets pushed radially outward by the moving radial blades due to centrifugal force imposed by the fan. At the exit of the fan blade, the cover blocks the flow in radial direction. As a result, a pressure gradient and turbulence within the fan cover is created. The air eventually leaves the cavity because of the pressure gradient and flows out over the straight longitudinal/axial fins over the motor body and leaves the motor in longitudinal direction.

As the air flow path is not smooth and the air flow changes directions several times, aerodynamic noise and vibration are generated and this makes the cooling arrangement of the traditional TEFC motor inefficient.
Further, at present there is no means to cool the driving end (DE) side surface bearings of an end bell in the TEFC motors other than natural conduction and radiation. This is because the coolant leaves the motor body axially without travelling over the DE side surface. Thus, the cooling of the DE side of the end bell is not achieved and the DE side bearing having a higher temperature than non-driving end (NDE) side bearings have reduced life.

Accordingly, there exists a need for an electric motor with new geometry of fan and over all air flow path that overcomes the above mentioned drawbacks of the prior art.

Objects of the invention

An object of the present invention is to provide a smooth air flow path in an electric motor for improved cooling thereof.

Another object of the present invention is to reduce, power consumption, aerodynamic noise and vibration and improve overall motor performance.

Summary of the invention

Accordingly, the present invention provides an electric motor assembly. The electric motor assembly comprises a housing, a fan, a cover and a deflector. The housing is adapted for enclosing a motor therein. The motor is a totally enclosed fan cooled electric motor. The housing includes a plurality of fins configured on an external surface thereof and a motor shaft protruding centrally out on either ends thereof. The plurality of fins is skewed fins. The plurality of fins is skewed in a horizontal direction to minimize entry losses at a starting portion. The plurality of fins is skewed/placed at an angle more than 0 degrees with the axis to impose minimum obstruction to the air coming out of the fan for flowing smoothly thereon.

The fan is fitted to the motor shaft on one end of the housing. The fan is an axial fan causing the air to enter and exit in an axial direction. The fan includes a plurality of blades arranged over a periphery thereof to blow air/coolant over the housing for cooling the motor and thus dissipating heat therefrom. The plurality of blades is of aero foil shape to blow the air in the axial direction with a required pressure.

The cover is adapted for covering the fan. The cover includes a plurality of perforations configured on a periphery thereof. The plurality of perforations on the cover, the plurality of blades of the fan and openings at a fan inlet and a fan outlet are configured in alignment with each other to cause the air to enter freely/minimum resistance through the plurality of perforations over the cover to the plurality of blades of the fan in the axial direction as well as to exit freely from the fan by passing over the plurality of fins on the housing in the same axial direction without changing the air flow path.

The deflector is fitted to the motor shaft on another end of the housing. The deflector is adapted to guide the air/coolant over the housing towards a driving end side surface of an end bell to cool driving end side bearings.

Brief description of the drawings

The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
Figure 1 shows an electric motor cooled by radial fans, in accordance with a prior art;
Figure 2 shows a perspective view of an electric motor assembly from a non-driving end thereof, in accordance with the present invention;

Figure 3 shows an exploded view of the electric motor assembly along with geometry of cooling arrangement thereof and an air flow path there over, in accordance with the present invention; and

Figure 4 shows skewed fins of the electric motor assembly of figure 2.

Detailed description of the invention

The foregoing objects of the 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 embodiment.

The present invention provides an electric motor assembly. The electric motor assembly of the present invention provides a smooth air flow path for improved cooling of an electric motor. The electric motor assembly provides an improved overall performance due to reduced power consumption, aerodynamic noise and vibration.

Referring to figures 2 - 4, an electric motor assembly (100) in accordance with the present invention is shown. The electric motor assembly (100) comprises a housing (20), a fan (40), a cover (60) and a deflector (80).

The housing (20) encloses a motor (not shown) therein. Specifically, the motor is a totally enclosed fan cooled electric motor. The housing (20) includes a plurality of fins (10) and a motor shaft (15). The plurality of fins (10) (herein after ‘the fins (10)’) is configured on an external surface (not numbered) of the housing (20). Particularly, the fins (10) are skewed fins. More particularly, the fins (10) are skewed in a horizontal direction (refer figures 2-4) to minimize entry losses at a starting portion thereof. The fins (10) are skewed/placed at an angle more than 0 degrees with the axis. The angle of skew varies between 5 to 40 degrees depending upon the power rating and no. of pole of the motor. The angle of skew of the fins (10) imposes minimum obstruction to the air coming out of the fan (40) for flowing smoothly thereon. The cumulative effect of smoother and efficient flow path results into lower aerodynamic noise and vibration. The motor shaft (15) is adapted to protrude centrally out on either ends (not numbered) of the housing (20).

The fan (40) is fitted to the motor shaft (15) on one end of the housing (20). The fan (40) is an axial type fan that pushes/causes the air/coolant (herein after ‘the air’) to enter and exit in an axial direction as illustrated in figure 2 such that the air does not have to change direction of flow path thereof while passing though the fan (40) as opposed to traditional way of cooling. However, it is understood that any other suitable type of the fan can be used as per various alternate embodiments of the present invention.

The fan (40) includes a plurality of blades (30) (herein after ‘the blades (30)’) arranged over a periphery (not numbered) thereof. The blades (30) are adapted to blow the air over the housing (20) for cooling the motor and thus dissipating heat therefrom. In an embodiment, the blades (30) are of aero foil shape adapted to blow the air over the housing (20) in an axial direction with a required pressure for cooling the motor and thus dissipating heat more quickly. The angle of the blades (30) decides the angle of the fins (10). Further, the angle of blades (30) depends on the rate of flow and an operating speed of the motor for a particular motor rating.

The fan (40) is covered by a cover (60). The cover (60) includes a plurality of perforations (50) (herein after ‘the perforations (50)’) configured on a periphery (not numbered) thereof. The perforations (50) on the cover (60), the blades (30) of the fan (40) and openings (not numbered) at a fan inlet (not numbered) and a fan outlet (not numbered) are all aligned with each other. Such alignment causes the air to enter freely or with minimum resistance in the axial direction through the perforations (50) over the cover (60) to the blades (30) of the fan (40) as well as to exit freely in the same axial direction from the fan (40) by passing over the fins (10) on the housing (20) without changing the air flow path as illustrated in figure 3. Thus, such an alignment causes the air to experience minimum resistance while passing from the cover (60) to the fan blades (30).

The deflector (80) is fitted to the motor shaft (15) on another end of the housing (20). The deflector (80) is adapted to guide the air after travelling over the housing (20) towards a driving end (DE) side surface of an end bell to cool DE side bearings.

Advantages of the invention

1. The electric motor assembly (100) is designed with a new geometry of the flow path to provide smooth and blockage free flow path of air and thus efficient cooling.
2. The electric motor assembly (100) due to smooth air flow path results in lesser aero dynamic noise and vibration.
3. The fan (40) of the electric motor assembly (100) consumes lesser power for cooling than traditional radial fans thereby increasing over all motor performance.
4. Longer bearing life due to effective cooling.
5. The air pushed axially by the fan (40) does not have to change direction of flow path thereof while passing though the fan (40). There is no abrupt change in the air flow path due to alignment of the blades (30) and the openings at the inlet and the outlet.

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.
,CLAIMS:We claim:

1. An electric motor assembly (100) comprising:
• a housing (20) adapted for enclosing a motor therein, the housing (20) having a plurality of fins (10) configured on an external surface thereof and a motor shaft (15) protruding centrally out on either ends thereof, the plurality of fins (10) being selected from skewed fins;
• a fan (40) fitted to the motor shaft (15) on one end of the housing (20), the fan (40) having a plurality of blades (30) arranged over a periphery thereof to blow air/coolant over the housing (20) for cooling the motor and thus dissipating heat therefrom, the fan (40) being an axial fan causing the air to enter and exit in an axial direction;
• a cover (60) adapted for covering the fan (40), the cover (60) having a plurality of perforations (50) configured on a periphery thereof, the plurality of perforations (50) on the cover (60), the plurality of blades (30) of the fan (40) and openings at a fan inlet and a fan outlet being configured in alignment with each other to cause the air to enter freely/with minimum resistance through the plurality of perforations (50) over the cover (60) to the plurality of blades (30) of the fan (40) in the axial direction as well as to exit freely from the fan (40) by passing over the plurality of fins (10) on the housing (20) in the same axial direction without changing the air flow path; and
• a deflector (80) fitted to the motor shaft (15) on another end of the housing (20), the deflector (80) adapted to guide the air/coolant over the housing (20) towards a driving end side surface of an end bell to cool driving end side bearings.

2. The electric motor assembly (100) as claimed in claim 1, wherein the motor is a totally enclosed fan cooled electric motor.

3. The electric motor assembly (100) as claimed in claim 1, wherein the plurality of fins (10) is skewed in a horizontal direction to minimize entry losses at a starting portion.

4. The electric motor assembly (100) as claimed in claim 1, wherein the plurality of fins (10) is skewed/placed at an angle more than 0 degrees with the axis to impose minimum obstruction to the air coming out of the fan (40) for flowing smoothly thereon.

5. The electric motor assembly (100) as claimed in claim 1, wherein the plurality of blades (30) are of aero foil shape to blow the air in the axial direction with a required pressure.