FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Totally enclosed tube ventilated AC induction motor
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030,
Maharashtra, India, an Indian Company
INVENTOR
Khan Tabassum, Crompton Greaves Ltd, Machines M7 Division, D-5 Industrial Area,
MPAKVN, Mandideep - 462046, Madhya Pradesh, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to
be performed:

FIELD OF THE INVENTION
This invention relates to a totally enclosed tube ventillated AC induction motor.
BACKGROUND OF THE INVENTION
Totally enclosed tube ventillated (TETV) AC induction motors are heavy duty motors and are used in heavy duty equipments or apparatuses like sugar mills or cement machinery. A TETV AC induction motor comprises a rotor mounted on a shaft and rotatably disposed within a stator which is located in the motor housing. The shaft is rotatably held in a pair of endshields fitted at the ends of the motor housing. The ends of the shaft project outside the respective endshields. One end of the shaft is disposed in an air inlet duct mounted at one end of the motor housing and connected to the air inlet end of a heat exchanger mounted on the motor housing. The motor housing is connected to the heat exchanger through openings in the motor housing. An external fan is disposed in the air inlet duct and mounted on the said one end of the shaft. The external fan is usually made of mild steei. The motor also comprises a pair of internal fans each disposed in the motor housing at each end of the shaft and mounted on the shaft. Each of the internal fans is associated with an air guide mounted at the inner surface of the motor housing in the proximity of the respective internal fan. Each of the internal fans comprises a fan body having a pair of spaced apart circular side plates and a ring interconnecting the side plates. Each of the side plates is formed with a shaft hole at the centre thereof and mounting holes at the circumference of the shaft holes. The fan also comprises a plurality of fan blades mounted on the outer circumference of the ring in radially spaced apart relationship with one another and fixed to the side plates. The internal fans are usually made of mild steel. Drive is taken from the other end of the shaft.

During operation of the motor, the external fan and internal fans rotate with the shaft. Due to rotation of the external fan, atmospheric air is sucked into the air inlet duct and blown into the heat exchanger. Air from the heat exchanger enters the motor housing through the openings in the housing due to rotation of the internal fans. Air in the housing is blown onto the stator and rotor and circulated in the housing due to rotation of the interna] fans. Hot air in the housing rises up and enters the heat exchanger and escapes into the atmosphere through the outlet of the heat exchanger. The performance efficiency of the motor depends upon the cooling efficiency thereof. If the stator and rotor are not properly cooled, temperature in the motor housing increases and reduces performance efficiency of the motor. The insulation of the stator and rotor windings may also get damaged thereby damaging the windings and reducing the life of the windings. Therefore, it is very critical and important to maintain the temperature of the windings within the permissible limits. The cooling efficiency of the motor will depend upon the volume of air being swept and blown by the internal fans onto the windings and volume of air circulated in the motor housing. If the internal fans can be improved to increase the volume of air being swept and circulated by the fans, the cooling efficiency and performance efficiency of the motor can be substantially improved. Also damage to the insulation of the windings can be avoided and life of the windings can be increased. There is thus need for increasing the volume of air being swept and circulated by the internal fans in order to improve the cooling efficiency and performance efficiency of the motor.
OBJECTS OF THE INVENTION
An object of the invention is to provide a totally enclosed tube ventitlated AC induction motor,
which has increased cooling efficiency and performance efficiency.

Another object of the invention is to provide a totally enclosed tube ventillated AC induction motor, which is simple in construction and cost effective.
Another object of the invention is to provide a totally enclosed tube ventillated AC induction motor, which prevents damage to the stator and rotor windings and increases the life thereof.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a totally enclosed tube ventillated AC induction motor comprising a rotor mounted on a shaft and rotatably disposed in a stator which is located within a motor housing, the shaft being rotatably held in a pair of endshields, each fitted at each end of the motor housing, the ends of the shaft protruding outside the respective endshields, one end of the shaft being disposed in an air inlet duct communicating with a heat exchanger at the air inlet side of the heat exchanger, the heat exchanger being mounted on the motor housing and communicating with the motor housing through openings in the motor housing, an external fan disposed in the air inlet duct and mounted on the said one end of the shaft and a pair of internal fans each disposed within the motor housing at each end of the shaft and mounted on the shaft and a pair of air guides each disposed at each end of the housing in the proximity of the respective internal fan and mounted at the inner surface of the motor housing, each of the internal fans comprising a fan body having a pair of spaced apart circular side plates each having a shaft hole at the centre thereof and mounting holes at the circumference of the shaft hole, the side plates being interconnected with a ring and a plurality of main fan blades mounted on the outer circumference of the ring in radially spaced apart relationship with one another and

fixed to the side plates, each of the internal fans further comprising a plurality of supplementary fan blades mounted at the outer face of the outer side plate in radially spaced apart relationship with one another, each of the supplementary fan blades being radially aligned with each of the main fan blades, each of the side plates having air circulation openings at the circumference of the shaft hole therein communicating with the respective shaft hole.
The following is a detailed description of the invention with reference to the accompanying drawings, in which :
Fig 1 is a crosssectional view of a totally enclosed tube ventillated AC inductor motor according to an embodiment of the invention; and
Figs 2 and 3 are isometric views of an internal fan of the motor of Fig 1 from opposite sides thereof.
The totally enclosed tube ventillated AC inductor motor 1 as illustrated in Fig 1 of the accompanying drawings comprises a rotor 2 mounted on a shaft 3 and rotatably disposed in a stator 4 describing a clearance with the stator. The clearance between the rotor and stator is not marked but can be seen in Fig 1. The stator is located in a motor housing 5 and the shaft is rotatably mounted in a pair of endshields 6, 7 each fitted at each end of the motor housing. The ends of the shaft protrude outside the respective endshields. One end of the shaft is disposed in an air inlet duct 8 communicating with the air inlet side 9 of a heat exchanger 10 mounted on the motor housing. The heat exchanger and motor housing communicate with each other through

openings 11 in the motor housing. Air outlet side of the heat exchanger is marked 12. 13 is a external fan disposed in the air inlet duct and mounted at the said one end of the shaft. The external fan comprises a fan body 14 and a plurality of blades 15 mounted on the body. A pair of internal fans 16 are disposed in the motor housing at each end of the shaft and mounted on the shaft. A pair of air guides 17 are disposed in the motor housing at each end thereof in the proximity of each of the internal fans and mounted at the inner surface of the motor housing. As illustrated in detail in Figs 2 and 3 of the accompanying drawings, each of the internal fans comprises a fan body IS having a pair of spaced apart circular side plates 19, 19 and a ring 20 interconnecting the side plates. Each of the side plates is formed with a shaft hole 21 at the centre thereof and mounting holes 22 at the circumference of the shaft hole. A plurality of main blades 23 are mounted on the outer circumference of the ring in radially spaced apart relationship with ope another and fixed to the side plates. A plurality of supplementary fan blades 24 are mounted at the outer surface of the outer side plate in radially spaced apart relationship with one another. Each of the supplementary fan blades is radially aligned with each of the main fan blades. A plurality of air circulating openings 25 are provided in the side plates at the circumference of the shaft holes communicating with the shaft holes. The internal fans are engaged over the motor shaft through the shaft holes therein with the outer side plate facing the respective endshie)d. The internal fans are fixed to the motor shaft with bolts (not shown) tightened in the mounting holes 22 in the side plates and corresponding mounting holes (not shown) in the shaft. During operation of the motor, the internal fans and the external fan rotate with the motor shaft. Air is swept and blown onto the windings of the stator and rotor and also circulated in the motor housing by the main blades of the internal fans. Additional volume of air is also swept and blown onto the windings of the stator and rotor and also circulated in the motor housing by the

supplementary fan blades. The air circulating openings 25 in the side plates also facilitate circulation of air in the motor housing. As a result of all this, the total volume of air being swept and blown by the internal fans and circulated by the internal fans is substantially increased correspondingly increasing the cooling efficiency and performance efficiency of the motor. Preferably the external fan and the internal fan are made of mild steel. Preferably the external fan is made of mild steel and internal fan body is made of mild steel and the blades of internal fans are made of plastics. According to the invention the cooling efficiency and performance efficiency of the motor are substantially increased. Because of the increased cooling efficiency, damage to the insulation of the stator and rotor windings is avoided and life of the windings is increased. Further the fan is simple in construction in that the supplementary blades can be easily made and fitted on the outer side plate. The supplementary blades do not significantly add to the cost and weight of the motor. Therefore, the motor is also cost effective and its weight remains almost the same. Preferably the supplementary blades are rectangular and their outer ends corners are tapered as seen in Fig 2 so as to further improve the air cutting and sweeping efficiency of the supplementary blades.

We claim :
1) A totally enclosed tube ventillated AC induction motor comprising a rotor mounted on a shaft and rotatably disposed in a stator which is located within a motor housing, the shaft being rotatably held in a pair of endshields, each fitted at each end of the motor housing, the ends of the shaft protruding outside the respective endshields, one end of the shaft being disposed in an air inlet duct communicating with a heat exchanger at the air inlet side of the heat exchanger, the heat exchanger being mounted on the motor housing and communicating with the motor housing through openings in the motor housing, an external fan disposed in the air inlet duct and mounted on the said one end of the shaft and a pair of internal fans each disposed within the motor housing at each end of the shaft and mounted on the shaft and a pair of air guides each disposed at each end of the housing in the proximity of the respective internal fan and mounted at the inner surface of the motor housing, each of the internal fans comprising a fan body having a pair of spaced apart circular side plates each having a shaft hole at the centre thereof and mounting holes at the circumference of the shaft hole, the side plates being interconnected with a ring and a plurality of main fan blades mounted on the outer circumference of the ring in radially spaced apart relationship with one another and fixed to the side plates, each of the internal fans further comprising a plurality of supplementary fan blades mounted at the outer face of the outer side plate in radially spaced apart relationship with one another, each of the supplementary fan blades being radially aligned with each of the main fan blades, each of the side plates having air circulation openings at the circumference of the shaft hole therein communicating with the respective shaft hole.

2) The AC induction motor as claimed in claim 1, wherein the internal fans and the external fans are made of mild steel.
3) The AC induction motor as claimed in claim 1, wherein the external fan is made of mild steel and the internal fan body is made of mild steel and the main blades and the supplementary blades are made of plastics.
4) The AC inductor motor as claimed in any one of claims 1 to 3, wherein the supplementary blades are rectangular and their outer end corners are tapered.