CA1164032A

CA1164032A - Totally enclosed fan cooled motor

Info

Publication number: CA1164032A
Application number: CA000364811A
Authority: CA
Inventors: Rick D. Camps; Carlo Di Pietro
Original assignee: Westinghouse Canada Inc
Current assignee: Westinghouse Canada Inc
Priority date: 1980-11-17
Filing date: 1980-11-17
Publication date: 1984-03-20

Abstract

ABSTRACT OF THE DISCLOSURE
Heat transfer from heat producing parts to the exterior of totally enclosed fan cooled machines, is improved by exterior fans which move external air axially over the machine from both ends and a structure including a ribbed frame with an inner surface in essentially total contact with the stator core.

Description

TOTALLY ENCLOSED FAN COOLED MOTOR
BACKGROUND OF THE INVENTION
Field of the Invention:
The invention relates to improved cooling of dynamoelectric machines, particularly those of the totally enclosed fan cooled type.
Description of the Prior Art:
Totally enclosed machines are used where isolation between internal parts and the environment is desirable or necessary. Since there is no flow of external air through the machine, such machines, particularly in larger sizes such as several hundred horsepower and above, are in most cases temperature limited in their rating~ This is so even with external fan cooling.
Active machine parts of copper and magnetic steel are capable of developing much higher power than -the power that can be prod~ced continuously and still be cooled to a safe temperature. The maximum safe temperature is usually d0termined by the type of insulation in the machine. Notwith-stand~ng improvement in insulation, it is still desirable to improve the heat transfer from the acti~e parts to the exte~ior.
One of the most important heat transfer paths is that from the stator copper to the core, from the core to the 1 16~0:}~

frame, and from the frame to the outside air. The effectiYe-ness of this ~ath depends upon transfer of heat from the frame to the outside air.
SUMMARY OF THE~ NTION
An object of this invention is to provide an improYed exterior fan configuration, to improve transfer of heat from the frame to the outside air and also desirable for lowering the temperature of the rear bearing which is important for large motors.
Briefly, the improvements in accordance w~th this invention include a pair of similar exterior fans which move external air axially over the machine from both ends through hoods to cause an essentially equal flow over the machine from each end to the midpoint of the machine.
BRIEF DESCRIPTION OF THE DRA~INGS
_ Figure 1 is a longitudinal view, partly in elevation and partly in section, of a dynamoelectric machine in accordance with one embodiment of the invention; and Figure 2 is an en& view, partly in section of the machine of Fig. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention will be described with reference to an embodiment that is an ac motor of the totally enclosed fan cooled type. The embodiment described is one that has been made in ~arious sizes for operation in the range of from about 200 horsepower to about 600 horsepower.
Referring to Figs. 1 and 2, the motor in accordance with ~his invention includes a frame 10 that has a generally cylindrical configuration and within which is affixed the stator 1 ~64()~

core 12, such as one made of a plurali~y of stacked lamina-tions, with a winding 13 therearound. A rotor 1~, such as one also made of a stack of laminations, is mounted on a shaLft 16. End brackets 1~ and 19 (sometimes called end bells) cooperate with the cylindrical frame portion 10 to tot;ally enclose the rotor and stator. The shaft 16 extends through the end brackets 1~ and 19 and is rotatably supported by suitable bearings.
The frame 10 is characterized by a cylindrical wall 22 that is essentially unbroken and makes direct contact ~ith essentially all of the outer surface of the stator core 12.
The frame 10 is also characterized by a plurality of axially extending heat dissipating fins 23 extending radially there-from.
The machine in accordance with this invention comprises front and rear external fans 25 and 26, respectively, substantially identical but smaller than the normal single fan mounted on the shaft 16 each driving air axially over the end brackets and frame. The front external fan 25 is conventional in totally enclosed fan cooled motors. In accordance with this invention, a rear external fan 26 is added to assist motor cooling and is also helpful for cooling the rear bearing. The external fans 25 and 26 are partially enclosed within hoods 27 and 2~ which have vented end faces. The hoods 27 and 2~
engage the end portions of fins 23 but retain openings between them and the ~rame exterior for air flow as shown by arrows 42 and 44. The air from the fans 25 and 26 will therefore flow over and between the fins 23 on the frame outer surface providing improved heat transfer. The means for joining the It various members are not in themselves a part of ~his invention and are not shown in detail.
In an alternative arrangement, a barrier ~2 at the ce!ntre of frame 10, shown in dotted lines, prevents the can-ce!llation of air velocity at the centre of the frame 10 by deflecting both air streams radially outwards.
On a conventional totally enclosed fan cooled motor with a single external blower 25, the velocity of the external cooling air between the fins 23 decreases as the air moYes towards the rear end of the frame 10. This reduces heat dissipation at the rear end. The external blower 26 on the rear end of the motor effectively increases the heat dissipa-tion at the rear end by virtue of the high air velocity at this end. Thus, with equal heat dissipation at each end, a more even temperature distribution and higher horsepower rating is obtained. The construction has the additional advantage of permitting an equal cooling with reduced noise because of the smaller fan required or increased cooling with no increase of noise.
~hile the invention has been described in a single form only, it will be apparent that numerous changes may be made without departing from its true scope. Preferably, construction is such as to permit identical components such as fans and hoods at each end and also to conform to standard motor frame sizes.

Claims

We claim as our invention:

1. A dynamoelectric machine with improved cooling comprising a stator and rotor enclosed within a totally enclosed structure comprising a frame and two end brackets, a rotatable shaft supporting said rotor and extending through both of said end brackets, a fan mounted on said shaft exter-nal of and adjacent to, each of said end brackets, a perforate protective shroud enclosing each of said fans and directing the air from said fans axially along the external surface of said frame.

2. A dynamoelectric machine as claimed in claim 1 wherein the external surface of said frame includes a plurality of axial cooling fins extending radially from said surface.

3. A dynamoelectric machine as claimed in claim 2 wherein said shrouds engage the ends of said fins to cause the air from said fans to be directed axially between adjacent fins.

4. A dynamoelectric machine as claimed in claims 1 to 3 wherein said fans are substantially identical.

5. A dynamoelectric machine as claimed in claim 3 including barrier intermediate the ends of said frame sub-stantially perpendicular to said shaft closing the ducts formed between adjacent fins.