FR2584544A1 - Device for cooling a DC electric motor with permanent magnets, whose magnets have a low thermal conductivity - Google Patents

Abstract

The subject of the invention is an electric machine equipped with magnets arranged outside the armature within which are arranged interpole pieces enabling the power of the machine to be increased very notably. Device essentially efficacious for closed or open machines without forced ventilation.

Description

 The subject of the invention is a direct current electric motor fitted with ferrite magnets, to which is added a device making it possible to reduce very significantly the heating of its wound armature and therefore to increase the power of this motor in the reverse ratio. Essentially effective process when the engine is closed or possibly opened without internal ventilation.

 A DC motor with permanent magnets of the ferrite type of conventional construction comprises a steel carcass (2) fitted with ferrite magnets (3) bonded to this carcass. The wound armature (5) is internal and its coils are powered by by means of a collector himself receiving his electrical supply from the outside by his brushes.

 This type of magnet, efficient and inexpensive allows performance that is never achieved because of the heating of the inner product.

 The calories created by the losses of the engine must cross several barriers before being dissipated by the external metal carcass by radiation.

 They must pass through an air gap under the magnets, the magnet itself, which has a very low thermal conductivity, of the order of a hundred times lower than that of aluminum, the thickness of the adhesive film which still creates a temperature gradient and finally the carcass good thermal conductor which diffuses calories by radiation.

 The invention consists in placing non-magnetic parts (I) in the inter-polar space having good thermal conductivity playing the role of heat pump for the armature.

 The air gap under the magnets being in general progress -sifth), these interpolar parts have with the armature, a constant air gap.

The distance of these parts to the armature is less than or equal to the distance from the magnet to the armature od it is the most reduced it is
to say in the axis of the pale.

These parts (I) include openings (6)
used to hold the ferrites in place without bonding. Thus with return screws (9) we apply both the parts (I) and the ferrites (3) against the carcass (2) which has the advantage of eliminating the bonding operation and consequently removing the film of bad conductive glue tbermi
Finally, the device is shock and vibration proof. Last
quality which will be highly appreciated when the engine is on board any vehicle. These parts being made of non-ferrous metal such as
copper or an aluminum alloy also have the property of reducing the
demagnetization due to a transverse reaction of the armature. Their length is at least equal to that of the magnets.

The cooling capacities are further improved.
-ement of the device by having longitudinal holes (7) and (8) in which any coolant circulates.

With this extremely simple device
to achieve from the point of view of sealing it is possible to cool very effectively a closed or open motor without ventilation of a completely conventional design.

 It is thus possible either to maintain an engine at a reduced temperature rise which reduces the significant flux drift with this type of magnets, or to make it work at the limit of the chosen temperature class. In all cases the mass power is greatly increased .

 The simplified device fig. 2 does not include the method of fixing the magnets, nor the circulation of fluid. The element (I) is used for the passage of the assembly rods. The assembly can be carried out differently} the part then no longer has a recess. The magnets count the interpolar parts are glued to the carcass and between them.

 This device is of course generalizable to motors comprising several pairs of poles.

 This device is applicable to any motor comprising magnets having a low conductivity.

A conventional engine without this 55 mm diameter device and 130 mm in length off the shaft, verified the previous allegations. The engine being closed supplied with
Volts direct current develops a power of 60 Watts useful at 3000 revolutions per minute. Its induced temperature rise is 85 degrees centigrade.

 By adding the simplified device (-fig.fi) the useful power on the shaft becomes 105 Watts for a comparable induced heating, or 85 degrees centigrade.

Claims (5)

CLAIMS I / Device intended for electric machines equipped with magnets with low thermal conductivity, arranged outside the armature.Essentially applicable to closed or open motors without forced venti-latoon.Characterized by non-magnetic metal parts of good thermal conductivity, of length at least equal to that of the magnets. Device which aims to pump the calories from the internal armature to bring them back onto the carcass.  20 / Device according to claim (I) is used to hold the magnets in place without wiring.  30 / Device according to claims I and 2 made of non-magnetic metal electrically conductive and the consequence of which is to reduce the effects of the transverse reaction of demagnetizing armature.  40 / Device according to I, 2,3 used with circu -lation of a fluid in order to extract the calories even more efficiently without heating of the outer carcass.  50 / Device according to I, 2,3,4 making it possible to limit the drift in the flux of the magnets which are particularly sensitive to the rise in temperature.  60 / Device according to I, 2,3,4,5 produced by extrusion or by molding of a non-ferrous metal.  7 / Simplified device according to I, 3,5,6 (fig.F)  80 / Simplified device according to 1.5 produced in non-magnetic laminated mind with the profile of fig. 2.  90 / Device according to I, 2.3,, 5.6, T, 8.9 which can be: used for motors comprising several pairs of poles.