DE631785C - Single-phase core or shell transformer - Google Patents

Description

Single-phase core or shell transformer The invention relates to single-phase core or jacket transformers, in which by switching on a magnetic, Air gap-free, fixed current path shunt between the primary and secondary windings the currents are limited in the event of a short circuit. The invention aims to achieve a complete short-circuit protection, in a purely magnetic way. this will according to the invention achieved in that in or on the sheet metal stack without spreading web Sheets are arranged with a spreading bar and the entire spreading bar cross-section is only part of the secondary core cross-section. The sheets with air gap-free, fixed spreading bar are either provided with closed yoke pieces or only with pieces of yoke. If you want to reduce the no-load current at the same time cause, then the yoke piece approaches can also serve to reinforce the yoke.

To enable the windings to be connected in series or in parallel, according to the invention, not only these but also the fixed spreading ridges are subdivided.

There are already single-phase transformers known in which between the primary and secondary windings are a magnetic, air gap-free, fixed stray path shunt is switched on, on which a special auxiliary winding is arranged. at these known transformers, however, these three cores have the same cross-sections on, so that a control of the short-circuit safety only by means of the auxiliary winding is possible. In contrast, the invention solves the problem in a fundamentally different way and a simpler way, namely in a purely magnetic way, so that the one special Excitation circuit requiring auxiliary winding is dispensable, what for the production and the operation of the transformer is of considerable economic advantage, while disadvantages that result from any deficient excitation of the auxiliary winding can assert are completely excluded.

There are also transformers have been proposed in which the purpose Reduction of the short-circuit current strength, magnetic shunts are provided, some of which consist of an air route and the other part of an iron route, however, the air path determines the size of the force flow to be deflected is.

The invention differs from these known arrangements basically through the arrangement of a practically air gap-free, solid spreading web. The purpose thereby achieved. the achievement of a complete short-circuit protection is not possible in the known arrangements. In addition, the conditioned by the built-in air gap increased the primary flow an excessive amplification of the Primary winding, which makes the transformer considerably more expensive to build.

It is also known for multiphase transformers between to switch on the transformer plates, but to a completely different one Purpose, namely to achieve one of the distortion of the current curve preventive flow.

After all, it is known in welding transformers that reactance in a purely electrical way, namely by switching it on and off. of turns of two Winding groups, dei: - way of regulating that with constant no-load voltage the scattering ratios or reactance can be changed in the desired sense, with to reduce the additional scattering that occurs as a result, variable scatter ridges serve, which, however, are not free of air gaps.

In contrast, according to the invention, there is the fixed and constant scattering path completely independent of the type of winding or parts thereof and serves therefore for a completely different purpose.

The invention offers particular advantages in the construction of small transformers (Bell transformers, toy transformers, etc.), where a fuse of the Primary circuit because of the low primary short-circuit currents makes difficulties: But The invention is also of advantage for large transformers, especially in such Cases where short circuits are unavoidable during operation, such as electrical ones Welding machines, in elevator construction, for rectifiers, e.g. for radio systems, in signaling devices for railway operations and the like. This enables short-circuit protection a substantial reduction in warming.

Another advantage is that it allows simultaneous Reduction of the no-load current and consequently the no-load losses.

In the drawing, the invention is in various embodiments for single-phase jacket and core transformers with stray bar as a magnetic shunt and shown for different winding arrangements.

Fig. Z shows a schematic top view of a jacket transformer with spreading bar, the windings and the course of the power flows when the spreading sheets are arranged above and below the iron core and the yokes.

Fig. 2 shows the section of the cores, the yokes and the diffuser plates of the sheathed transformer if the. Scatter bars above and below the iron cores and the yokes lie.

Fig. 3 shows the section of the cores, the yokes and the diffuser plates of the sheathed transformer, if the spreading sheets to. Part between the core and the Yokes and on the other hand arranged above and below the core and the yokes are.

Fig.q. shows the schematic plan view of a core transformer Scatter bar between the cores and sheet metal approaches for the yoke reinforcement, if the spreading sheets are only above and below the yokes. Fig. 5 shows the section the cores, the yokes and the diffuser sheets of the core transformer, if the diffuser sheets are only above and below the yokes.

# 'ZFig. 6 shows the section of the cores, the yokes d of the diffuser plates of the core transformer, if the scattering plates are partly between the yokes and the other part are arranged above and below the yokes.

Fig. 7 shows the schematic top view of a jacket transformer with subdivided secondary winding and several spreading bars, if the spreading plates either just above and below the cores and yokes or partially between Core and yokes and above and below the core and yokes are arranged.

Fig. 8 shows the schematic top view of a core transformer subdivided windings and associated spreading bars if the spreading sheets are either are arranged between the yokes or above and below the yokes.

The sheathed transformer shown consists of the core k of the same thickness for the primary and secondary windings and the yokes i, which are composed of stamped or cut transformer sheets b. On the actual iron core, two windings are arranged in such a way that the primary winding Py is on one side and the secondary winding Sek is on the other. Over the yokes and the core, punched or cut sheets for the spreading webs St are inserted transversely to the core at the top and bottom. If the primary winding is applied to an alternating voltage, this generates an alternating force flow Otl in the iron core, which closes mainly over the secondary part of the iron core and over the yokes and, even when idling, gives off a small scattering force flow Osp over the scattering webs St according to the scattering web cross-section.

If the secondary winding is loaded to the point of short circuit, it is urgent the flow through the secondary winding part of the primary main power flow into the magnetic shunt of the scattering web until the flux of force Ot ... in the Secondary winding to that $ s in the stray bar in the inverse proportion of the magnetic Resistances of these two shunts and the number of ampere turns of both Circles are equal to each other. The secondary current can therefore only be so large up to this steady state is reached, so that by an appropriate choice of Scattering cross-sections and the paths of the lines of force as well as the arrangement of the scattering plates over, under and between the cores and yokes in the event of a short circuit in the secondary circuit each desired size of the secondary current can be set can. at With this arrangement, the yokes can be reinforced at the same time, as the case may be the scattering plates are arranged, which also reduces the no-load current and the no-load power is reduced, which is extremely important in small transformers The arrangement of the stray bars f to reduce the short-circuit currents is practically applicable for all jacketed transformers of any power, but with increasing Power a subdivision of the windings is required, so that accordingly two or a multiple of two spreading bars must be attached, as shown in Fig. 7 is shown.

The core transformer shown consists of the two cut or punched cores k and the side yokes i, which are composed of transformer sheets b. The primary winding Pr is accommodated on one iron core and the secondary winding Sek is accommodated on the other. In the case of the core transformers, the diffuser plates can then be inserted into the yokes or they can be provided with diffuser plate attachments V, so that here too the diffuser core cross-section is composed of the diffuser plates arranged above, below or between the yokes. With this type of transformer, when loaded up to a short circuit, a part of the primary main power flow is diverted from the secondary winding after the stray web as a magnetic shunt due to the flooding of the secondary winding.

When the transformer is idling, flows according to the cross-section of the scattering core a stray force flow Oso, which when loaded up to the short circuit to the maximum value Oso increases, with which the short-circuit current can be reduced to the desired level can. The size of the maximum possible secondary current is therefore also determined here an expedient choice of the iron cross-section of the spreading web and the arrangement the diffuser itself is determined above, below or between the yokes, and at the same time, the yoke reinforcement can lead to a reduction due to the spreading plate approaches the no-load current and the no-load power can be achieved.

This arrangement of the stray bars to reduce the short-circuit currents is practically applicable to all core transformers of any power, whereby However, with increasing power a subdivision of the windings according to the type of Fig. 8 is required and thus also brings with it a subdivision of the spreading ridges.

Claims (1)

PATENT CLAIMS: Single-phase core or shell transformer in which, by switching on a magnetic, air gap-free, fixed current path shunt the currents are limited between the primary and secondary winding in the event of a short circuit, characterized in that sheets with in or on the sheet metal stack without spreading web a spreading bar are arranged and the entire spreading bar cross-section only a part of the secondary core cross-section. z. Single-phase core or shell transformer according to claim z, characterized by a subdivision of the windings and the fixed ones Scatter bars to enable the windings to be connected in series and in parallel (Fig. 7 and 8).