AU642397B2 - Electric motor cooling - Google Patents

Description

642397 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-62 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Application Number: Class Int. Class Lodged: Complete Specification Lodged: Accepted: Published: Priority: Relatud Art: TO BE COMPLETED BY APPLICANT Name of Applicant: F.F. SEELEY NOMINEES PTY. LTD.

Address of Applicant: 1-11 Rothesay Avenue, St Marys, South Australia, Australia Actua: Inventor: ANTHONY DAVID COLLIVER Address for Service: Care of R.K. Maddern Associates, 345 King William Street, Adelaide, South Australia, Australia Complete Specification for the invention entitled: '"LECTRIC MOTOR COOLING" The following statement is a full description of this Invention, including the best method of performing It known to me.

us.

Aoo'-14/? I PATENT, TRADE MARKS DESIGNS SUB.OFFICE 14 NOV 1989 SOUTH AUSTRALIA FQ lti 2M This invention relates to the cooling of electric motors, and particularly to the cooling of electric motors that are used to drive centrifugal fans.

It is known that the operating temperature of an electric motor effects the motor's efficiency, copper increasing in resistance about 10% for a 30*C temperature rise. Thus for the same power output, heating of the motor will increase about 10%. There is also a small decrease in magnetisation as o 10 temperature rises. Running an electric motor at an elevated temperature for an extended period of time reduces the life of the motor, since the insulation deteriorates.

With any particular device that is driven by an electric motor, if more output is required from the device, the motor will draw a greater amperage and therefore run at a higher temperature. If a larger motor is installed, the copper resistance is reduced and the heating is consequently also 0e 0 0 reduced.

In many instances, overloading a motor is unsatisfactory due to the reduced life of a motor running at higher operating temperatures. In addition many motors are enclosed and are therefore much more difficult to cool. However to instal a oee* 5 larger motor will have a cost disadvantage.

One example of the difficulty associated with sizing and cooling of motors relates to the use of electric motors with fans. In the case of air conditioning systems axial fans are generally cooled directly by the air flow. This advantage does not occur with centrifugal fans, wherein motors are mounted externally. In such situations there is little or no opportunity to create an air flow around the motor which will provide effective cooling.

It is an object of this invention to provide a means whereby greater output from a centrifugal fan can be achieved 2 without increasing the size of the electric motor, by effectively cooling the motor.

In its broadest form, the invention consists of cooling means for cooling an electric motor mounted on or adjacent a volute of a centrifugal fan, comprising an aperture through the wall of the volute, a deflector tube opening at one end within the volute and extending outwardly through said aperture and terminating at its other end adjacent said motor, the deflector rube being so inclined with respect to the wall as to intercept some of the air when swirling within the volute and deflect it onto the motor.

An advantage of this invention is that it creates a forced flow of air over the motor which then passes away from the motor. The air is not recycled, and there is a continuous flow f fresh air onto the motor.

An embodiment of this invention is described hereunder with reference Fig, 1 is a partly sectioned side elevation of a centrifugal fan and motor, 0:4' 20 and Fig. 2 is a part-plan of Fig. 1.

4 In this embodiment an electric motor 10 drives a centrifugal fan 11, 25 being'mounted on the external surface of the fan volute 12. The centrifugal fan wheel 13 is driven via driving and driven pulleys 14 and 15, and V-belts 16.

This is a conventional arrangement.

Such centrifugal fans receive air at the centre of the volute and the air changes direction to swirl within the volute before discharging from the outlet of the volute. Therefore, it can be seen that the electric motor 10 which is used to drive a fan wheel 13 will have very little or no air movement for cooling purposes when attached to a centrifugal fan. In addition, it is often quite difficult to obtain fresh air that can be directed onto the motor for effective cooling, and the fans incorporated within electric motors normally recirculate the air immediately cadjacent the motor which results in inefficient cooling.

This invention relates to providing a means for directing the air from the fan to the motor. A tube 17 extends through an aperture 18 in the wall of the volute 12 so as to direct air from within the fan onto the motor. The tube 17 has a first end 19 within the volute 12 which is so inclined to the wall of volute 12 as to interrupt air which swirls within the volute 10 and cause a portion of air tn exit the volute via the tube.

The exit end 20 of the tube 17, which is outside of the volute, is adjacent to, and directed at, the motor Therefore, the motor receives a constant flow of fresh air for cooling purposes when running, which enables a much cooler running temperature to be maintained. As a result, the motor is able to run at more efficient temperatures.

In addition, it will ta recognised that any chamber that the motor is encapsulate- within will require a vent so as to allow the cooling air to exit from the motor chamber. In the case where the centrifugal fan is housed within a protective cover with no duct leading into the centre of the volute the air flow path from the cooling means will be back to the intake 25 of centrifugal fan. Where the air is not able to re-enter the air flow circuit of the fan, then venting away from the motor will be required.

In a further aspect of this invention, the motor may be provided with a shroud that surrounds it, and is used to duct the air from one end of the motor to the other. In this example, the cooling means would direct the air into the shroud, and the shroud would then control the movement of the air over the external surface of the motor thereby providing a greater degree of cooling efficiency.

1II In the above embodiment, it is intended that the tube 17 comprising the air cooling means is affixed by gluing or other similar means within the volute of the centrifugal fan.

However, it will be recognised that the volute may be moulded with the required air cooling means incorporated within the volute moulding. In such an example, the entrance and the exit of the tube may be shaped so as to have a low drag coefficient, together with the maximum efficiency of air movement therethrough.

S*

Although the deflector is herein described as the inclined tube 17, it can equally as well be comprised by one or more louvres in the wall of the volute 12. There are some locations around the volute where a deflector is not required at all, and an aperture through the volute wall will suffice.

From a brief consideration of this invention, it will be obvious to a person skilled in the art that the invention provides a novel means of cooling a motor which is attached to a fan, thereby allowing a greater output from the motor without any reduction in the working life of the motor.

Claims (2)

1. Cooling means for cooling an electric motor mounted on or adjacent a volute of a centrifugal fan, comprising an aperture through the wall of the volute, a deflector tube opening at one end within the volute and extending outwardly through said aperture and terminating at its other end adjacent said motor, the deflector tube being so inclined with respect to the wall as to intercept some of the air when swirling within the volute and deflect it onto the motor.

2. Cooling means substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. DATED this 10th day of June 1993 F F SEELEY NOMINEES PTY LTD By its Patent Attorney KEN MADDERN *ego g* *oo