Automatic Transformer-switch Apparatus.
Year: 1897

page_text: Date of Application, 24th July, 1897-Accepted, 9th Oct., 1897
Automatic Transformer-switch Apparatus.
I, ALFRED SCHLATTER, of V Vairi út No. 76, Budapest, Hungary, Professor, do
hereby declare the nature of this invention and in what manner the same is
to be performed to be particularly described and ascertained in and by the
following statement:-
An alternating current system which distributes electrical energy to the consumers
by means of transformers suffers, as is known, from the disadvantage that the
transformers are connected with the primary network also when the consumer does
not require current, and there is consequently a useless consumption of energy, as the
work of magnetisation going on entails a waste of energy which in most cases is not
inconsiderable, causing a dead load at the central station.
This waste of energy can, according to the present invention, be reduced considerably,
when the consumer does not require current, by either automatically transferring the
nagnetising work of the working transformer, which necessarily contains a great deal
of iron, to an auxiliary or switch-transformer having a minimum quantity of iron,
or by entirely cutting out the working transformer.
In both cases the putting in circuit of the working transformer at the moment
when the consumer requires a current supply can be effected by the switch-
transformer.
I effect this by means of an apparatus which I will describe with reference to the
accompanying diagrammatic drawings, Figures 1, 2 and 3. It consists of a greater
or less number of component parts, according as it is to be applied to single
transformers, or to groups of transformers.
The arrangement of parts constituting an apparatus serving to control the working
of a single transforiner, as also the connection thereof with the network are shewn at
Figure 1. Here P1 P2 and S1 S2 designate the primary and secondary networks, T is
the working transformer, ta controlling or switch-transformer whose primary coil
either directly or indirectly (in series with the primary coil with the working
transformer) connected with the primary network. W1 W2 are differently wound
electro magnets, having different self induction, whose armatures are rigidly connected
to switch-levers M' M² with contact forks; n is a hook carried by the lever M¹ of the
magnet Wand capable of engaging with the catch when the armature of magnet H
is not attracted. A, B, D, are mercury cups, G, G1, G2, are balance weights, N is a
glow-lamp in the circuit of the magnet H; F is the shunt coil of the electricity
meter, if such is provided; iii are current consuming devices connected to the
secondary network.
The electrical connections of these several parts are shewn in the drawing and need
not be further explained.
The drawing shews a transformer station consisting of a single working transformer,
the parts being in the position corresponding to a cessation of the consumption. In
this condition a minimum primary current pass both through the coil of the working
transformer T and through that of the switch transformer t; the dimensions and
windings of the latter are so chosen that the greater part of the primary potential
difference is consumed in this device and that the iron core of the working transformer

page_text: Is only slightly excited, so that the work of magnetising is transferred to the
controlling transformer.
According to the second before mentioned arrangement, the minimum current only
passes through the primary coil of the controlling or switch transformer t, while the
working transformer is entirely without current.
The secondary potential difference of the switch-transformer is advantageously
kept higher than the norinal working pressure.
The action is as follows:-
If a current consuming device i is put in circuit, then in consequence of the
increased potential difference of the transformer t, a current proportionate to the
requirement of the device passes through the numerous windings of the magnet W¹,
which is thereby so strongly excited that it can set in motion its armature and con-
sequently the switch lever M¹. By this means the secondary circuit of the switch
transformer is at the same time broken at u, the working transformer is connected
at A directly to the primary network and the magnet W' is cut out of the circuit of
the switch-transformer and inserted into the circuit of the working transformer.
As the working current now passes also through the coil of the magnet W¹ the
working transformer remains included so long as a consuming device is connected to
the secondary network, that is to say, so long as a current excites the magnet W¹.
On cutting out the last named object, the balance weight, G moves the lever M¹ back
into the position shewn.
The course of the secondary current is, during the first described position,
t S1 S2 W¹ ut and after the change, T S1 S2 W¹ B W² T.
W2
The apparatus bere described can, in its simplest form (with magnet W¹ only), be
used in all cases where the consumption of current is small, and the secondary net-
work is comparatively of large dimensions, so that the loss of pressure in the same
only differs slightly with a weak and a full load. For rendering the apparatus also
applicable for more extended working and at the same time to equalize the lamp
pressure between certain limits, notwithstanding a variable loading of the network,
there may be provided in the apparatus in addition to the magnet W₁ other magnets
W in the same circuit. These may be made of such dimensions that the
potential of the feeding points of a net of many branches will be kept at a constant
value corresponding to practical requirements, notwithstanding variations of the
load. Assuming for example, a domestic installation of 200 glow lamps with a total
consumption of current of 100 ampères. This installation is assumed to be fed from
a transformer between the secondary terminals of which there is (as is usual in
parallel working) a constant potential of 105 volts. The supply lead is assumed to
be of such dimensions that the loss of potential at the feeding points with full
consumption by the installation, is 5 volts. In this case, the potential of each lamp,
that is, the lamp potential, will conveniently be 100 volts; and at this potential
the lamps are assumed to be worked at their normal rate.
If it is now desired that the lamps in the installation shall burn with the same
potential 100 volts-in case of partial consumption, there must be included in series
with the supply lead a resistance which can be varied in amount in constant ratio to
the current strength passing at each instant through the supply lead, the arrangement
being such that the product of the current strength multiplied by the resistance
shall always have the same numerical value, the constant loss of potential (in this
case 5 volts).
This resistance would have to be gradually diminished on increase of the load,
and would have to be gradually increased on decrease in current strength.
I produce this desired result by introducing into the current circuit by means of
magnets W1 W2
W successive steps of an induction-resistance which must be
greatest at sinall load on the net or system, and must be smallest at full load. The
regulation of the constant "lamp-potential" takes place automatically in dependence
on the current strength.
This method is carried out in Figure 1 with two stages.
The magnets W¹ and W2 are so wound that W² only attracts its lever M² when, in

page_text: consequence of increasing load and of the winding of magnet W₁, the pressure in
the secondary network up to the lamps sinks below the normal value.
The winding of WI is then short circuited at D; in this case care must be taken
that the switch lever M' of the magnet W1, which is now without current, is held in
its attracted position by mechanical means, which can be easily effected in various
simple ways by means of the switch lever M².
The holding of the lever M' when W₁ is short circuited is however also effected by
the catch carried by the armature of the magnet H. This armature which was
attracted after the connection of the working transformer (in consequence of the
direct connection of the magnet H with the transformer T) falls back and its catch k
engages with the hook n as soon as the circuit of the magnet H is broken at u² in
consequence of the motion of lever M². This magnet H has however to perform
another function beside the above; it is required to render innocuous the concussions,
that are unavoidable when the working transformers are switched into circuit, by
mechanically holding for a short time the drawn-down switch lever M¹ by means of
the hook n and catch as above described. To effect this the magnet is so arranged
that it attracts its armature somewhat after the switching in of the working
transformer; for this purpose a resistance is included in the circuit of magnet H the
value of which is decreased on the passage of the current, in consequence of heating,
thus allowing only a gradual increase of current. A suitable material for this purpose
is the carbon filament of a glow lamp, which is indicated by N on the diagram.
The connection of this magnet H in such manner that the current which excites it
must first pass through the magnet W₁ is also of importance in this arrangement.
I have, namely, in this case employed this circuit for reducing the residual
magnetism of the magnet W₁ (which would prejudicially influence the action of the
apparatus on cutting out a larger consuming device) to such an extent that the
transformer T will always be cut out with certainty when the secondary network is
without current.
The above described transformer switch apparatus can be employed as independent
apparatus in all cases where the distributing stations consist of single transformers,
or where several thereof are to be included or cut out simultaneously.
But if the transformers constitute groups of two or more transformers connected in
parallel either as regards the primary or the secondary circuits, and if the problem is
to be solved that each transformer is to be separately included or cut out, according
to the momentary requirements, the above described apparatus must be supplemented
by a new element. This element is shewn separately at Figure 2. It consists of a
simple maximum switch apparatus, an electromagnet which, with a certain strength
of current attracts its armature, and thereby includes the transformer in the circuit.
This electromagnet, according to Figure 3 (where the first transformer T is, for the
sake of clearness assumed to be continuously attracted), is included in circuit and
operates, that is to say, includes the transformers T2 T3 &c. when those previously
included are loaded to the limit of their maximum capacity. The cutting out of
course takes place in the reverse sequence as soon as the total load has sunk to such
an extent that an element of the group can be dispensed with.
Although this method appears very simple, yet in the practical carrying out thereof
certain difficulties are encountered.
The main difficulty consists in that a maximum switch apparatus made in the form
of an electromagnet must be so adjusted that its armature after being attracted by a
certain maximum strength, will still remain attracted with certainty when the current
has decreased to balf its strength, otherwise the lever system remains in a continual
state of oscillation which would produce inconvenient fluctuations of pressure, as also
cause the rapid wear of the contacts.
To prevent these inconveniences I construct the vibrating lever of the tumbler
kind, by increasing or decreasing the load, and thereby the moment, of the weighted
lever according to its position. A tube Q partially filled with liquid such as mercury,
which is attached to the lever in addition to the balance weight G, effectually serves
for this purpose.

page_text: By this means the pull of the electromagnet can in' no position (i.e. neither in
including or in cutting out the transformer), hold the load of the opposite lever arm
in balance; in other words, on including the transformer, the continuously increasing
magnetic pull preponderates, and in cutting out, the continuously increasing moment
of the weighted lever arm preponderates. Without this condition the oscillatory
motion of the parts cannot be prevented:
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. Switch apparatus for reducing the magnetising work either of a single alternate
current transformer, or the first member of a group of transformers, consisting of the
combination with the said transformer of a controlling or switch-transformer t arranged
and operating in such manner in conjunction with an electromagnet W that the
winding hereof is included alternately in the secondary circuit of the working
transformer and in that of the switch-transformer, according to the position of the
armature lever M', and that on the inclusion of a consuming device the said magnet
attracts the armature lever and holds it during the duration of consumption,
substantially as described.
2. In switch apparatus such as is referred to in the first claim, the use of two or
more electromagnets W1 W2 W" connected in series and having different self
inductions, whose powers of attraction are so graduated that with an increasing load
they attract their armatures in succession and at the same time short circuit the
windings of the preceding ones, the armature levers of the short circuited magnet
being mechanically held, substantially as and for the purposes described.
3. In an automatic transformer-switch apparatus, the use of an auxiliary magnet, H,
whose armature is provided with a catch k for holding the switch lever M', and
whose circuit is so arranged that the current which excites this magnet also passes
through the magnet WI, a resistance being included in the said circuit of such a
nature that its action is reduced on heating substantially as and for the purposes
described.
4. For a transformer station consisting of two, three, or more transformers
connected in parallel, the use in addition to the apparatus shewn at Figure 1, or
arranged as at Figure 3, of one or more switch magnets arranged as shewn at Figure 2
serving to effect the successive inclusion or cutting out of the separate transformers,
the windings of which switch magnets are successively included in the secondary
circuit of the preceding transformer which has already been included, and whose
moveable part is provided, in addition to the switch lever, with a tube containing
liquid, which serves to gradually decrease the moment of the loaded lever arin on
including a transformer, and to gradually increase the same on cutting out a
transformer, substantially as described.
5. In an automatic switch apparatus serving to reduce the magnetising work of an
idle alternate current transformer, the use of a controlling or switch-transformer, whose
secondary circuit is so arranged as to start the working of a consuming device when
this is included in the secondary network, substantially as described.
This outh to of T.1. 1007
Dated
this 24th day of July
1. 1902
ABEL & IMRAY,
Agents for the Applicant.
ABEL & IMRAY,
Agents for the Applicant.