DE113022C - - Google Patents

Description

IMPERIAL

^ PATENT OFFICE.

F ^ TENTSVHRIFT

CLASS 21 <T

Jf,

Patented in the German Empire from July 27th 189g.

It is a well-known fact that sparking occurs in current sources with carbon brushes is significantly smaller than those with metal brushes. The reason for this is known to be the greater resistance of coal compared to metal, although of course only the resistance in the The spark formation is reduced in the tangential direction, but that in the radial direction only causes an unnecessary loss of tension.

In order to increase the useful effect of the resistor even more, the invention according to the end of each commutation period between the brush and the bezw away from her current transmitter lamella. their connection point in the armature winding an appropriately dimensioned additional resistor is switched on. This resistance, the as just mentioned, is only introduced towards the end of the period of commutation and which as a result of this, the loss of tension in the armature is not or only extraordinary will increase little, on the one hand very quickly weakens the current in the supply line, which is just moving away from the brush, and on the other hand causing current paths in it a loss of voltage which manifests itself as a part of the total electromotive force of the machine with the same electromotive force that is generated by the brush short-circuited coil is induced as a result of the action of the commutation field. This loss of voltage enables a sparkless current reversal even with one relatively weaker fields. Since this loss of tension as the reversal process progresses becomes smaller and smaller, it can therefore only accelerate the turnaround, but never cause an overcurrent reversal.

The means which make it possible to achieve the above purpose are as follows described in more detail.

The current supplier is designed in such a way that over the entire circumference there is between every two lamellas of the usual arrangement one auxiliary lamella is used. Depending on the direction of rotation, the latter are connected to one of their neighboring lamellae (den Main lamellas) connected by a certain resistance.

The auxiliary lamellas can be weaker or stronger than the main lamella as required and two lamellas connected by the resistance can also be relatively weakly isolated from one another.

In Fig. Ι of the accompanying drawings, the scheme of the connections between the armature winding, the connecting wires v ¹ v ² , the additional resistors W ¹ W ^ and the current output lamellae (main lamellae I ¹ Z ² , auxiliary lamellae h ¹ h ² ) for three different brush positions is shown .

In FIG. 2, the connections are arranged for a direction of rotation opposite to the direction r in FIG. 1. In Fig. 3 the arrangement for reversible motors or the like is shown, in which case each main lamella or its Änschlufsstelle in the armature winding development on both sides with one auxiliary

lamelle is connected by a certain additional resistance. Fig. 4 illustrates an arrangement represents, in which each auxiliary lamella is replaced by two (or more) such lamellae; here must be the connection resistances the larger the further the auxiliary lamella is from its main lamella. In all these cases it is advantageous to make the brush tangentially so strong that it becomes is able to touch two main blades.

The process that takes place when the current is reversed is as follows:

When the brushes are in position I (FIG. 1), the current passes from the armature winding through the connecting wire v ² to the lamella Z ² . When transitioning ■ to position II, the intermediate ^{lamella / 1 2} is initially de-energized. The more the current transmitter moves to the right, the greater the contact resistance between the brush and the lamella / ² and the more current will therefore also reach the brush through w ² " and h ^2. In position III, the armature current can only pass through ν ² W ² Ii ^ on the one hand and through v ^l P on the other hand. The resistance of the first path has now become greater than that of the second path through the interposition of iv ^{2. The current that still flows through V 2} J ^ ² Zi ² , suffers a certain voltage loss. By the amount of this voltage loss that electromotive force is now greater, which accomplishes the current reversal in the coil s, whereby the duration of the current reversal is accelerated or, in the case of a weaker commutation field, a sparkless current reversal is made possible. The latter also means a increased machine efficiency.

The additional resistances w ^x w ² . . ., which circulate with the commutator, can also be omitted if one or a few completely insulated brushes are dragged on the commutator in such a way that they rest a little before the other brushes on the commutator. The same then take over the role of the circulating additional resistors and in some cases it will also be possible to omit the auxiliary lamellas.

All the arrangements described can of course be combined with one another.

Claims (2)

Patent Claims: 1. Device to reduce spark formation on the commutator of DC machines, characterized by additional resistances, which mean auxiliary lamellas arranged between the main lamellae at once or in stages between the brushes and the armature winding in this way At the end of each commutation, these resistances are introduced in the current paths emanating from the brushes Cause voltage losses, which change the current-reversing electromotive force Increase an amount corresponding to this voltage loss and thereby a Enable non-sparking commutation even with a relatively weak commutation field. 2. Device according to claim 1, characterized in that that instead of the co-rotating additional resistances, completely isolated auxiliary brushes are arranged in front of the main brushes will. 1 sheet of drawings.