Note: Descriptions are shown in the official language in which they were submitted.
H. Landhult-2
~ 56 ~Revision)
FREQUENCY MULTIPLICATION
Background of the Invention
Through the use of semiconductor elements such
as diodes, thyristors, triacs, transistors, etc.,
there are a number of known circui~ configurations
for control and supervision of current or voltage
and for obtaining frequencies other than that of the
A.C. mains. The ability of these components, subject
to a control impulse, to utilize the whole or a part
of the period of the alternating current, may be used,
for example, in connections like whole wave rectifiers
with controlled values or triacs and antiparallel con-
nected thyristors for controlling of lights or soft
starters for motors. Circuits of this type are well
known.
It is also known that if windings are arranged
around a magnetic circuit such as in a single phase or
a multiple phase transformer, a current is obtained
in the secondary windings, the strength of which de-
pends on the current in the primary circuit and the
ratio between the number of windings in the secondary
and primary circuits respectively. The frequency on
the secondary side is the same as that of the primary
side.
Additionally, if an ml-phase A.C. mains is con-
nected toan ml-phase electric machine, an MMF wave is
obtained which rotates with the synchronous speed US
¦ which is determined by the frequency of the connected
frequency f and the pole number of the winding accord-~L
ing to the formula: q~P
,..
.,
H. Landhult-2
1~9~56 (Revision)
-- 2 --
u = 120 . f
s
Depending on the type, the rotor or the machine can
be forced to rotate with the same speed (synchronous)
or with a load dependent slip (asynchronous).
Objects of the Invention
It is an object of the invention to obtain an
integrated combination of semiconductor connections
with a transformer or an electric machine which is
provided with a special winding arrangement which uses
a minimum of semiconductor elements and a special wound
machine and provides in an efficient manner, another
frequency, another r.p.m. or another number of phases
than those of the A.C. mains.
Brief Description of the Invention
This is achieved according to the invention in that the
operation of an electric machine having at least one primary
winding including a plurality of separate primary winding
parts to which electric current is supplied from A.C. mains
to induce an alternating magnetic field in the electric
machine is controlled by selecting portions of the A.C. mains
voltages; and applying the selected portions of the A.C. mains
voltages to the primary winding parts at such intervals and in
such a sequence that the magnetic field induced in the electric
machine by the resultant electric current flow through the
primary winding parts has a frequency differing by a pre-
determined factor from that of the A.C. mains. Advantageously,
at least one switchable element which can be rendered con-
ductive by the application of external control signals thereto
is interposed between the A.C. mains and the respective
primary winding part; and the selection is achieved by supply-
ing the external control signals to the switchable elements
of the primary winding parts at the above intervals and in
the above sequence to render the switchable elements conductive
to the resultant electric current flow during the occurrence
of the selected portions of the A.C. mains voltages.
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H. Landhult-2
ll'~9~S6 ( Revision)
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By connecting the impulses from a system of semi-
conductor elements as described above to each respective
primary circuit of a transformer, a voltage is obtained
in the secondary circuit having a frequency which is
determined by the number of primary circuits and the
directions of the connected impulses. If for instance,
the positive part and the corresponding part of the
negative half period in each phase voltage and each main
voltage in a three phase system are used, a frequency
multiplying with the factor K, up to 6, could be obtained
in the secondary circuit. By alotting a suitable number
of such impulses to the same phase (or different phases
in a multiple phase system, i.e., a transformer or motor)
it is possible to build up a voltage at any desired frequency
which is a multiple of the frequency of the A.C. mains. The
factor K could be bigger or smaller or equal to one. This
also permits fractions of the A.C. mains frequency to be
obtained. If, in an m-phase wound machine (m -1, 2, 3, etc.),
each winding phase is arranged with n parallel circuits
which are magnetically equal and electrically isolated and
the n circuits and the m-phases are fed with suitably
chosen impulses,
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l~. L.lndhult-2
(Revision)
.~ S6
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an M.M.F. wave is obtained which rotates with a
synchronous speed decided by the pole number of
the winding and the frequency generated by the im-
pulses. It is then important that the impulses are
supplied in such a way that a symmetrical alternative
flux occurs. The result is that the synchronous
speed of the machine is the factor K times that corre-
sponding to pole number and A.C. mains frequency.
The list below shows possible values for the
factor K defined as the relationship of the secondary
voltage frequency to the A.C. mains frequency in a
transformer or the relationship between actual,motor
r.p.m. which could be obtained by help of the princi-
ples of the invention and the synchronous r.p.m. ob-
lS tained by the pole number of the motor and the A.C.mains frequency. For the highest X-values the igni-
tion angle must be chosen high, e.g.,(150), and the
possibilities to obtain multiple phased secondary
voltage are limited, i.e.,
K = 6, 5, 4, 3, 1,5,'3/4, 3/5, 1/2 etc.
Brief Description of the Drawings
~ .... ~
Figure 1 illustrates a transformer connected
in accordance with the invention.
Figures 2 and 3 illustrate current flow in
the primary,windings of the transformer of Figure 1.
Figure 4 illustrates a 3-phase transformer.
Figure 5 illustrates the current in the trans-
former of Fig. 4.
Figures 6a and 6b illustrate circuitry for
conversion of a 3-phase signal to a 3-phase signal
having a higher frequency.
' Figure 7 illustrates the location and intercon-
nection of primary and secondary windings in the
, circuit shown in Figures 6a and 6b.
Figure 8 illustrates the line voltages in the
circuit of Figures 6a, 6b and 7.
Figure 9 illustrates an alternative circuit
, arrangement to that of Figure 6a.
.
H. Landhult-2
~Revision)
3L1'~ 56
-4-
Figure 10 illustrates the interconnection of
primary and secondary windings in the circuit of
Figure 9.
Fig. 11 illustrates the pulses existing in
S the circuit of Fig. 10.
Fig. 12 illustrates the order of windings in
an electric motor.
Fig. 13 illustrates the interconnection of
the windings of Figure 12.
Fig. 14 illustrates the pulses in the windings
of Figure 13.
Fig. 15 illustrates a circuit arrangement for
converting a 3-phase signal to a single phase signal.
Fig. 16 illustrates the line voltages in the
circuit of ~ig. 15.
Figures 17aand 17b illustrate a circuit and
its interconnections for obtaining a number of
different frequency alterations.
Figures 18 and 19 illustrate various pulses
contained in the circuit of Figs. 17a and 17b.
Figure 20 illustrates a circuit for varyinq
the frequency.
Dbscription of the Preferred Embodiments
..
In order to appreciate the present invention,
examination of the following exa~ples will be most
illustrative.
Example 1
The principle according to this invention is
to achieve an alternating flux by letting current
pulses flow in different windings in such a direction
that one pulse in one winding and the other pulse
in another winding gives a flux of the same magni-
tude but in opposite directions.
In Figure 1, the positive half-cycle gives a
positive flux in winding A and the negative half-
cycle gives a negative flux in winding B. This
principle will ~e put to use in this invention.
Fig. 2 shows how the current i + flows in wind-
ing A from 0 to T/2 inducting the positive flux ~ +
._~ . ~ t . .
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H. Landhult-2
(Revision)
-5-
which is directed upwards. In Fig. 3 is shown how
the current i - flows in winding B from T/2 to 1
inducting the flux ~ -. The average value of the
~lux during the whole period equals 0.
Example 2
,
Fig. 4 shows a coupling where the primary winding
on a transformer is split into three separate windings
which are connected between the phases on a three
phase A.C. mains. In each part there is a pair of
anti-parallel thyristors with a firing angle of
120 degrees. This thyristor pair may be replaced by
one triac. That means that the impulses 1 and 4 shown
in Figure 5 from the line voltage UR S are fed to
winding A. Impulses 3 and 6 come from line voltage
Us T and are fed to winding B, while impulses 2 and 5
from line ~oltage UT R are fed to winding C. As shown
in Figure 5, the impulses 1, 2, 3, 4, 5, 6 are directed
in respective order to the windings A, C, B, A, C, B,
where every second pulse is negative and alternate
pulses are positive. As seen in Figure 6, the frequency
of the impulses is three times that of the applied
frequency. The frequency in the load winding will
therefore be 150 Hz if the line frequency is 50 Hz.
With a circuit arranged as in Figure 5, a three-phase
voltage with the frequency f, yieIds a single-phase
voltage with the frequency 3 x f or a ~lux in the magnetic
circuit with the frequency 3 x f,
Example 3
In the connection shown in Figs. 6a, 6b and 7
a three-phase voltage having the frequency f is trans-
; ferred to a three-phase voltage having the frequency
2 x f. Firing angles for the thyristors are 120 degrees.
A, B and C are 3 SCR bridges with the AC-mains
connected to 1 and 2 and the DC terminais, 3 and 4, con-
nected to the windings. The AC-mains, R, S, and T are
connected as shown in Figure 6a. Each primary winding
of the phase transformer is split into two separate
parts. Windings Xl and X2, Yl and Y2 al g
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Il. L~ndhult:-2
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.ll~ S6
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and Z2 are the two circuits in each phase X, Y, and
Z. Wl, W2, and W3 are the secondary windings.
As illustrated in Figure 7, the A3 terminal of
the SCR A is connected to the input terminal of
Xl. The output terminal on Xl is connected to the
output terminal of Y2. The input terminal of Y2 is
connected to A4.
In the same fashion, the SCR bridge terminal B3
is connected to the input of terminal Yl whose out-
put terminal is connected to the output of Z2 The
output of Yl is connected to the output of Z2 whose
input is connected to B4.
The SCR bridge C is connected in the same fashion
to Zl which is connected to X2.
The diagram in Figure 8 shows how the three-phase
secondary voltages are built up from pulses from the
SCR bridges. The frequency of the secondary windings
is twice that of the AC mains and the voltages are dis-
placed 120 electrical degrees from each other.
It should be noticed that all the positive pulses
come from Xl, Yl, and Zl and all the negative pulses
come from X2, Y2, and Z2
The SCR bridges A, B and C can also be connected
to the phase voltages as shown in Figure 9, while the
connection of the DC terminals is the same as in
Figure 7. The elementary diagram in Figure 8 remains
the same except that the line voltage UR-S is changed
into UR 0 Us_T into Us_O and UT_R T-0
Example 4
Conversion of a 3-phase system of the frequency
f into a 2-phase system of the frequency 2 x p.
In figure 10, one transformer is connected via
anti-parallel thyristors (or triacs) to the line
voltages and the other transformer is connected in the
same way but to the phase voltages. The reason for
this arrangement is to obtain a higher frequency and
also to get 90 degrees between the secondary voltages.
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~ ~ ~I. Landhult-2
~ 56 ( Revision)
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The firing angle should be approximately 120 de-
grees. As shown in Figure 11, the pulses in Y are
30 de~rees ahead of the pulses in X, if 360 degrees
is the period of the AC-mains. Since the frequency
of the windings of the secondary side is three times
higher, the angle between the voltages in Xs and Ys is
in a motor application where the two transformers
according to Fig. 10 are replaced by the stator of a
two-phase motor where each winding phase has three
parallel circuits Xl, X2, X3 and Yl, Y2, Y3 respectively
geographically displaced 90 electrical degrees. According
to electro machine theory, a rotating flux will occur
which has asynchronous speed depending on the A.C. main8
frequency and the pole number of the stator winding.
lS This means that the motor obtains normal starting
conditions like all three-phase motors.
Example 5
A motor for 9000 rpm (2 poles-50 Hz) and connected
to all phase and line voltages may be made pursuant to
this invention.
This motor is wound as a two-phase motor with the
phases displaced 90 degrees. Each phase is split into
three separate windings equally placed in the slot.
The windings in one phase are called Xl, X2, and X3 and
the other Yl, Y2, and Y3.
The diagram in Figure 12 shows how the motor is wound.
By help of the principles according to the invention,
a pair of anti-parallel thyristors are connected in each
phase. The flux in each phase is then displaced 90 elec-
trical degrees. The frequency of the flux is three
times that of the AC-mains, which means that the flux
will rotate with 9000 rpm at 50 Hz and 10800 rpm at 60 Hz.
Phase X is connected to the line voltages and phase Y is
connected to the phase voltages.
The diagram of these connections is shown in
Figure 13.
The thyristors are turned on at 120 degrees.
Figure 14 shows how the impulses in the phase X
. __.. . .. \ ~ .... . . . . . .
Il. L.u~ lt-2
. ~l~cv ision
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and Y are achieved. It also shows that the frequency
of the applied voltage is three times greater than the
frequency of the power supply and that the impulses in
X and Y are displaced 90 electrical degrees.
S Example 6
Symmetric load on a three-phase A.C. mains by a
single-phase load.
It has been indicated in the patent application
how a lower frequency can be obtained by sending current
pulses through separate windings in the same phase.
~igure 15 shows how three pairs of anti-parallel
thyristors (firing angle 120) connected to separate
primary windings on a transformer, convert a three-
phase voltage to a single-phase voltage. Figures 4
lS and S illustrate the connections for multiplying the
frequency by 3, and the principle has been previously
explained. In Figure 15, one winding is connected in
the opposite way compared to Figure 4. This winding
should have a smaller number of turns in order to give
a stronger pulse. This will result in a voltage wave-
form of the secondary side,that is closer to a sine
wave.
Figure 16 illustrates this principle.
Example 7
General couplings with a possibility to chose or
control the frequency (speed).
The principle of the patent i8, as previously
described, to supply the winaings with a suitable number
of phase and/or line voltages. It is required that the
primary winding in ~he transformer or motor is split
into a suitable number of separate windings. This
number depends on the desired frequency.
The following describes some examples where it
is possible to obtain different frequencies, both higher
and lower than the frequency of the AC-mains. The
multiplication factor K described previously, can be an
integer for example 1, 2, 3 etc., or a fraction, for
examples 3/2, 3f4, 3/5, 1/2 etc. The principle is
explained wi~h two examples.
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H. Landhult-2
(Revision)
~ 9~S6
_g
One way of arranging the windings is shown in
Figure 17. Six SCR bridges are connected to separate
windings. Three of the SCR bridges should be con-
nected so that they give a positive flux and the other
three so that they give a negative flux. To make it
easier, a single phase transformer has been described.
As an example, two different firing angles are
used ~20 and 60 degrees. The table shows the firing
order of the SCR bridges used to obtain the desired
value of K.
................ ,.... ............ . ...... ~
..: . ; ~ Firin an le 120 de rees Pactor K
+ g g _ _ g :
: Firing order R T S R T S : 3 `
_ . n _ R + S R T S 3/2
_ _ + T S R T S 13/4
etc. R T S R T+ S 3/5
i, ' ' ' ',
. .. .................. .. .. . ... . .. .. .. ..
. ........ ..... . . ......... . ..... ,. ..
~iring angle 60 degrees ~ K
l _
Firing order R S T R S+ T 3/2
20. _ n _ R 5 T R S T 3/4
etc R S T R S T
Example 8
Using SCR bridges and power transistors of a
suitable kind, a continuous variable frequency can
be obtained. The winding is split into two parts here
- also. One gives the positive flux and the other the
negative flux. The transistor is switched by a control
circuit which gives the desired frequency.
It should be noted that a multiple phase system
can be obtained by building up more phases.
TNT:mmg
March 5, 1980
