Field Measuring Apparatus for Uniformly Loaded Rotary Phase Current Systems.
Year: 1899

page_text: Date of Application, 15th Dec., 1899-Accepted, 19th May, 1900
COMPLETE SPECIFICATION.
Rotary Field Measuring Apparatus for Uniformly Loaded Rotary
Phase Current Systems.
We, SIEMENS BROTHERS & Co., LIMITED, of 12. Queen Anne's Gate, West-
minster, S.W,. Electrical Engineers, do hereby declare the nature of this inven-
tion (as communicated to use from abroad by Siemens & Halske Aktien
Gesellschaft, of Markgrafen Strasse, 94, Berlin, S.W., Germany, Electrical
Engineers) and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
-
For measuring the work done in a uniformly loaded rotary phase current
system, a rotary field measuring apparatus can be employed the current winding
of which has the current from one main lead of the network flowing through it
and its pressure winding connected across the other two main leads.
The disadvantages of this arrangement are:
1. That between the current and pressure windings of the same measuring
apparatus there exists a high potential difference at least 87 per cent. of the line
voltage.
°
2. That even with the inclusion of an amply sufficient induction-free resistance,
the self induction of the pressure windings cannot be compensated for, whereby
errors are caused.
3. That the continuous consumption of energy in the shunt circuit is very great.
The present invention relates to an arrangement which not only does away
with the disadvantages mentioned under (1) and (2), but which also enables the
continuous consumption of energy in the shunt circuit to be reduced to the
smallest possible amount.
Referring to the accompanying drawings Fig. 1 is a diagrammatic view of the
apparatus shewing the arrangement of the windings and electrical connections.
Fig. 2 is a plan of a meter constructed according to this invention. Fig. 3 is a
vertical section through the line 3-3 of Fig. 2 and Fig. 4 is a section through
the line 44 in Fig. 3. Referring to Fig. 1, if a coil kk, short circuited on
itself is placed near the main winding a a, a current will be induced in it which
will produce a difference of phase between the main current and the active
field. If the current in the pressure winding ee lags behind the potential differ-
ence at the terminals of this winding by an angle wo, then the field produced by
this winding will also lag behind the potential difference by an angle approxi-
mately equal to 20º.
With an induction-free load of the rotary-phase current system, the current
will precede the pressure by 30°.
In Figs. 2, 3 and 4 c is a laminated iron ring carrying the four pole pieces ff
99, the two former carrying the main current coils a and the latter the pressure
windings e. Between each pole piece 9 and its main coil a is the closed coil k.
The angle is advantageously so chosen that it is nearly 90°. In that
case will be nearly 30°, which can be readily effected by altering the resist-
ance of the short circuited winding kk, unless it be preferred to give the

page_text: angle a contant value and then to adjust the angle w by altering the electric
or magnetic constants of the induction coil d which is connected in series with
the pressure winding e e.
It should be stated that the angle w can also become negative, this being
effected by the employment of a condenser instead of the induction coil d. In
this case the angle o must be greater than 30° in order to insure as small a
consumption of energy in the shunt circuit as possible.
In place of the short circuited winding kk a non-inductive resistance con-
nected in parallel with the main current winding a a might be used. This would
however have to be of considerable size in particular for currents of great
strength, whereas the short circuited winding would not materially increase the
cost of the measuring apparatus.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, we declare that what
we claim is:-
Rotary field measuring apparatus for a uniformly loaded rotary phase current
system, wherein there is arranged co-axially with the main current winding a
short circuited winding with or without an external adjustable resistance, and
which can be acted on inductively by the main current winding while the shunt
winding has one of its terminals connected to the lead in which the main current
winding is inserted, while the other is connected to either of the other two leads,
such winding being arranged so that the current in it lags nearly 90° behind the
potential difference at its terminals, substantially as described.
Dated this 15th day of December 1899.
ABEL & IMRAY,
Agents for the Applicants.