Having a plurality of secondary windings

There is disclosed an improved method and apparatus for operating an electric power station including a cycled transformer having a primary winding and a plurality of secondary windings, in a manner that includes the changing of the current permeability of a variable load component connected in parallel to one of the secondary windings for preventing the current flowing within the circuitry thereof from decreasing below a predetermined value during a no-load condition at the output terminal of such secondary winding, thus assuring that the widths of the direct current pulses admitted into the primary winding are maintained above a predetermined value and that the energy transfer to each of the secondary windings is sufficient.

The invention related to method and apparatus for operating an electric 
power station including a cycled transformer to maintain output voltages 
at a plurality of output terminals. 
BACKGROUND OF THE INVENTION 
The transformation of electric loads by the admittance of direct current 
pulses into the primary winding of a transformer is priorly known. Such 
transformers are commercially available, and are known as "cycled 
transformers". Such cycled transformers are often employed as power 
suppliers to consumer circuits, for example, telecommunications 
equipments. In various applications of such cycled transformers, the 
voltage values provided on the secondary windings output terminals must be 
maintained within restricted tolerances or limits and, consequently, 
voltage regulation is indispensable. In known cycled transformers such 
regulation was usually provided to the secondary windings which were 
designed for handling the larger output terminal loads. More particularly, 
such regulation was provided by changing the width of the direct current 
pulses admitted into the primary windings of the cycled transformers in 
accord with the magnitude of the load connected to the output terminals of 
the regulated secondary windings. 
The aforesaid regulation approach presented a problem to the prior art in 
that during the no-load condition of the regulated secondary windings only 
very narrow direct current pulses were admitted into the primary windings 
which resulted in satisfying only minimum energy transfers to the 
secondary windings. This often caused a breakdown in the voltage at the 
output terminals of the regulated secondary windings, as well as a 
breakdown of voltage at the output terminals of the other secondary 
windings, or at a minimum caused such output voltages to decrease below 
acceptable levels. To limit the consequences of such prior art problem, 
use limitations were stated on the various prior art cycled transformers 
as to the minimum load required for the output terminals of the regulated 
secondary windings. In other cases, the cycled transformers were limited 
to only one secondary winding each with concomitant expense and space 
requirements. 
OBJECTS OF THE INVENTION 
An object of the present invention is to provide a novel method and 
apparatus for operating an electric power station including a cycled 
transformer with a plurality of secondary windings which may be operated 
independent of the load condition associated with the secondary winding 
that is regulated. 
Another object of the present invention is to provide a novel method and 
apparatus for operating a cycled transformer wherein a plurality of 
secondary windings are operational, notwithstanding a low-load or no-load 
condition as to the secondary winding of such plurality which determines 
the width of direct current pulses admitted into the primary winding. 
Still another object of the present is to provide a novel method and 
apparatus for operating a cycled transformer having a plurality of 
secondary windings without being subject to restrictions as to low-load or 
no-load conditions on the output terminals of the secondary windings. 
SUMMARY OF THE INVENTION 
These and other objects of the present invention are achieved by a method 
and apparatus for operating an electric power station including a cycled, 
direct current, voltage transformer by changing the current permeability 
of a variable load component connected in parallel to a regulated one of a 
plurality of secondary windings. More particularly, the current 
permeability of such variable load component is changed in dependency upon 
the current flowing in the circuitry of the regulated secondary winding in 
a manner that such current does not decrease below a predetermined value. 
As a consequence of such variable load component, a minimum internal load 
condition is achieved in the circuit of the regulated secondary winding 
during a no-load condition at the output terminal of such secondary 
winding, and the widths of the direct current pulses admitted into the 
primary winding of the cycled transformer are maintained above a 
predetermined value. Thus, there is assured sufficient energy transfer to 
the secondary side of the transformer so that the secondary windings in 
addition to the regulated secondary winding are provided with the 
appropriate potentials.

Referring to FIG. 1, a direct current, electric power station 1 includes an 
input terminal E on its primary side to which, by way of example, a 60 
volt D.C. potential is applied. The secondary side of the electric power 
station 1 includes three output terminals A1, A2 and A3. By way of 
example, the output terminal A1 has a direct current potential of 95 
volts; the output terminal A2 a direct current potential of +5 volts; and 
the output terminal A3 a direct current potential of -5 volts. The three 
output terminals A1, A2 and A3 are connectable to a plurality of consumer 
circuits V by way of a plurality of switches 2, 3 and 4. The direct 
current potential provided at the output terminal A1 is regulated by 
influencing the primary side, internally generated, direct current pulses 
of the electric power station 1. In accordance with the principals of the 
invention, the number of output terminals may be two or more. Of such 
plurality of output terminals only one such plurality of output terminals 
need be regulated. The output terminal which is designed for handling the 
heaviest load is preferably selected for such regulation. In the exemplary 
embodiment, the voltage values at output terminals A1, A2 and A3 differ to 
a substantial degree. However, such voltages may differ in a less 
pronounce manner and, in specific cases, may have equal voltages at two or 
more output terminals. 
The circuitry of the direct current, electric power station 1, and its mode 
of operation will be understood from the following description with regard 
to FIGS. 2 and 3. 
Referring to FIG. 2, the electric power station 1 comprises a cycled , 
direct current, voltage transformer U indicated within the dash-dot border 
lines. The transformer U includes a primary winding 5 and three secondary 
windings 6, 7 and 8. The direct current potential on output terminal A1 
results from secondary winding 6, while the direct current potential on 
output terminal A2 results from secondary winding 7, and the direct 
current potential on output terminal A3 results from the secondary winding 
8. Further, the transformer U includes a core 9. As only the direct 
current potential at output terminal A1 is regulated, only the secondary 
winding 6 with its associated circuitry is illustrated, the circuitry 
associated with the secondary windings 7 and 8 are not shown for 
simplicity. 
The circuitry associated with the secondary winding 6 includes a rectifier 
10 connected between one side of the secondary winding 6 and an impedance 
element 11. Connected on each side of the impedance element 11, and to the 
other side of the secondary winding 6 are two capacitors 12 and 13. 
Connected in parallel to the capacitor 13 is a voltage divider formed by a 
pair of serially connected resistors 14 and 15. A connection point T 
between the resistors 14 and 15 is connected to a first input terminal of 
a comparison circuit 16, which preferably functions as an operational 
amplifier. To a second input terminal of the comparison circuit 16 there 
is applied a reference, direct current, potential designated