Note: Descriptions are shown in the official language in which they were submitted.
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1 1~33~
PHN. 9644
The inven*ion.relates to an electric machine
with electronic commutation, having a rotor which at
least partly consist of:a permanent-magne-t material,
which rotor co-operates with at least two stationarily
arranged stator coils, which machine is equipped with at
least two magneto-sensiti~e elements arranged on a common
substrate, specifically Hall:elements, for supplying
signals which vary substantially.sinusoidally with the
rotor position in order to energize the stator coils as a
10 function of the rotor position.via an energizing circuit,
the magneto-sensiti~e elements being arranged at a
tangential angle re:lative to the rotor axis, which angle
is smaller than the phase difference y which is necessary
b.etween the energizing signa.ls :Eor the stator coils in
order to obtain a correct energization of said stator coils.
Such a machine is known from Applicant's
Canadian Patent 1,051,969.- issued April 3, 1979 (PHN.7940).
In conv:entional electronically commutating
machines the magneto-sensi*ive elements are arranged at an
20. angle y corresponding to.the phase angle of the machine,
i.e. electrically at 12~ in the case of a three-phase
machine and at 90 in the c~se of a two or four-phase
machine. In.accordance with the.said Patent Application
by the draw~acks of th:is,.:such.as mounting and intercon-
necting two separate parts,.are overcome moun.ting the twomagneto-sensiti~e elements.together on one substrate and
ha~ing this co-operate with a disk which is mounted on the
rvtor.shaft and is. pro~ided.~ith two concentric magneti-
cally coded tracks. ~ disa.d~antage of this is that , since
said tracks should.be arranged near each other, there is
.a substantially amount of leakage, so that the Hall elements
receive little flux
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1 1~331~
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PHN.9644 2 5,9.80
..
and should be mounted very closely to the disk~ bu-t so
as to ensure a free rotatlon of -the disk. Moreover, such
a magnetically-coded disk is highly disadvantageous from
an economic point of view.
It is the object of the invention -to provide
an electric machine wh:ch does not have this drawback
and to this end it is characterized in that -the energizing
circuit is provided with a combining circuit for linearly
cornbining the signals supplied by at least two magneto-
10 sensitive elements, in order to obtain at least two
energizing signals having a mutual phase difference
which is substantially equal to ~. `
; The invention is based on -the recognition that
from -two phase-shifted substantially sinusoidal signals
15 two signals with another phase difference can be derived
by linearly combining said signals and that this enables
-the magneto-sensi-tive elements to be arranged at compara-
tively small tangen-tial angles relative to the ro-tor axis.
A first ~referred ernbodiment of the invention
2~ concerns a two-phase or four-phase machine and is
characterized in tha-t the combining circuit supplies
a signal which is propor-tional to the sum of the signals
supplied by the two magneto-sensitive elements and a
signal which is proportional to the difference of the
25 signals supplied by the -two magneto-sensitive elements.
This embodiment has the advantage that the
phase difference between said combined signals is
independent of the -tangen-tial angle at which the two
magneto-sensitive elements are arranged.
In general, such a linear combination, which also
enables phase differences o-ther than 90 to be realized,
may be characterized in that the combining circuit supplies
a first signal C, which satisfies -the equation C = ~ ~ KB,
and a second signal D, which satisfies -the equa-tion
35 D = ~ - KB, where A is the signal supplied by a first one
of -the magneto-sensi-tive elements, B :is the signal supplied
by a second one of -the magneto-sensitive elernents,
and K is a predetermined cons-tan-t which is such
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P~N.~64~ 3 5.9.80
that the phase difference be-tween the signals C and D
is eaual to ~.
A drawback of -this combining method may he that
in general the amplitudes of the combination signals C
and D are not equal. An embodiment of the machine in
accordance with the invention which does not have said
drawback may be characterized in that the combining
circuit supplies a first signal C, which satisfies
the equation C _ A - kB, and a second signal D, which
satisfies the equation D = B - kA, where A is the signal
supplied by a first one of the magneto-se~i-tive elements,
B is the signal supplied by a second one of the magneto-
sensitive elements, and k is a predetermined constant
which is such that the phase difference between the
signals C and D is equal to ~.
A very simple embodiment of the last-mentioned
machine may further be charact;erized in that the ener-
gizing circuit comprises a first comparator, of which
a first input is connec-ted to a first one of -the magneto-
sensitive elements, of which an output is connected tothe series connection of a first one of -the stator coils
and a first resistor, and of which a second input is
connected to the junction between said first stator coil
and said firs-t resistor, a second comparator, of Irhich
` 25 a first input is connec-ted to a second one of the magneto-
- sensi-tive elements, of which an output is connected to
the series connec-tion of a second one of the stator coils
and a second resis-tor, and of which a second input is
connected to the junction be-tween the second stator coil
and said second resistor, and a third resistor, which is
included be-tween the junction of the firs-t stator coil
and the first resistor and the junction of the second
sta-tor coil and the second resistor.
A preferred embodiment of a three-phase machine
in accorctance with -the invention may further be character-
ized in that the firs-t resistor is a variable resistor.
The invention will now be described in more
de-tail with reference to -the drawing, in which
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P~IN. 9644 4 5.9.80
Figure 1 is a ashematic elevation of a three-
phase electronically commutating motor which is equippecl
with a ~Iall-element in a conventional manner,
Figure 2 represents a sectional view of the
motor Or ~igure 1 in more detail,
Figure 3 shows the arrangement of the ~all
elements in accordance with the invention in a motor as
shown in Figure 1,
~ igure 4 is a vector diagram to illustrate the
use of the invention in a two-phase motor,
~ igure 5 is a vector diagram -to illustrate
a first general embodiment of a mo-tor in accordance wi-th
the invention,
Figure 6 is a vector diagram to illu.strate a
preferred ambodiment of a motor in accordance with the
i.nven-tion,
Figure 7 is a vector diagram to illustrate
an alternative o~ the embodiment described with re~erence
to Figure 6,
2~ Figure 8 is a circuit for realizing the linear
combination described with re~erence to Figure 4,
~igure 9 represents a circuit ~or realizing
-the linear combination described with re~erence to
Figures 6 and 7,
Figure 10 is a vec-tor diagram to il]ustrate
the linear combination in the case of a three phase motor,
Figure 11 represents a preferred embodiment
~or realizing the combination me-thod descri.bed wi-th
reference to Figure 10, and
~igure 12 represents a combination method
in accordance with -the invention with -triangular signals.
Figure 1 is a schematic elevation o~ a three-
phase electronically commutating motor which is equipped
wi-th ~lall elemen-ts in a conventional manner and Figure 2
in a greater detail represents a sectional view o~ the
motor o~ Fig~ure 1 -taken on the line II. The motor com-
prises a sha~-t 1 on which a bell-shaped rotor housing 2
is secured, which on the inner circumference is provicled
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PHN.9644 5 5.9.80
;~t~
wi-th an annular permanent magnet ~. The stator body L~
carries a lamination assembly 5 on which three stator
coils 6,7 and 8 are arranged. On the stator body L~ a
support 9 is mounted on which the Hall elements 10 and 11
are arranged at an angle of 120 , which elemen-ts detect
the field o~ the permanent-magnet ring ~ and, via a circuit
which is also mounted on said support, energize the s-tator
coils 6, 7 and 8 as a function of the rotor position.
Figure 3 illustrates a solution for the arrange-
lO ment of the Hall elements 10 and 11 in accordance with
the invention in a mo-tor in accordance with Figures 1
and 2. For the sake o~ simplicity only the stator
lamination assembly of this motor is shown. The two Hall
elements 10 and 11 are arranged closely to each other
l5 - at an angle ~ relative to -the rotor axis - so that by
means of ~ilm techniques they can be accommodated on one
substrate -together with the required electronics or they
can even be incorporated in one integrated circuit together
with the required electronicsO Nevertheless it is found
20 possible to realize the correct phase differences between
the ener~izing signals ~or the stator coils by generating
linear combinations of the signals from the Hall elements
10 and 11, provided with said signals are substantially
sinusoidal.
This is illustrated in Figure ~ by means o~ -
a vector diagram ~or a t~o-phase (or four-phase) motor.
The signals A and B from the Hall elements 10 and 11
respec-tively, the sum C of -these signals A and B and the
difference D of saicl signals A and B are represented
30 as vectors in this Figure. It is ~ound that generating
the linear combinations:
C = A~B
and D = A-B
yields two signals with a phase clifference o~ 90 .
35 For these combinations, t~is is inclependent of the
angle ~ between the Hall elements. In general it is
possible to generate any phase difference between the
signals C and D by means o~ the li~ear combinations:
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- PHN.9644 6 5.9.80
C _ A~KB
and D = A-EB
where ~ is a constant factor which depends on the angle
and the desired phase difference between the signals
C and D.
If it is required - for example when the two
Hall elements 10 and 11 are disposed symmetrically
relative -to the centre between two stator poles, as is
shown in Figure 3 - that the vector C is situated
exactly between the vectors A and B in view of the correct
commutation ins-tants, then it is for example possible
to generate the following linear combinations:
C = A+B
D = A-KB
Figure 5 shows such a vector diagram for a
phase difference of 120 between the signals C and D.
This diagram is sel~-explana-tory.
In the case of the combination methods described
with re~erence -to the vector cliagrams o~ Figures L~ and 5
,LO the amplitudes of the signals C and D are not equal when
the amplitudes of the signals A and B are equal.
When the signals C and D solely switch the stator
excitation at their zero passages, this is not a problem.
~oweverJ if the signals C and D are employed as energizing
signals for the stator coils, as the case may be after
amplification, then i-t may be necessary to amplify the
two signals to the same amplitude by adapting the gain
factors o~ said ampli~ier~ A combina-tion method which
does not have this drawback is described with reference
to Figure 6.
Figure 6 represents the vector diagram
associated with the following linear combinations:
C = B-KA
D = A-~B
In -the case of this linear combina-tion -the ampli-tudes
of -the signals C ancl D are equal i~ the amplitudes of
-the signa:Ls A and B are also equal. In the vec-tor diagram
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PHN.964~ 7 5.9~80
of ~igure 6 the factor K has been selected so tha-t when
the vec-tors A and B are situated at -2'~ and ~2'~ respec-
-tively~ the vectors C and D are situated at ~120 and +2L~o
respectively. The third phase-signal E for a three-phase
rnotor is obtained in known manner by inverting the sum
of the signals C and D (E = -C-D). It is also possible
to employ the attenuated sum of the signals A and B.
~ igure 7 represents the vector diagram of
an alternative method of realizing the combination
described with reference -to ~igure 6 in order ot obtain
a three-phase signal. The factor K is then selected so
that the vectors C and D are situated at 60 and 300
respectively and the vec-tor ~ = -(C~D) is consequently
- situated at -180.
The linear combinations described can simply
be realized by means of operational amplifiers, which may
be integrated together wi-th the Hall elements 10 and 11.
Figure 8 shows an example of a circuit for
realizing the linear combination described with reference
to ~igure l~. The circuit comprises a summing amplifier 12
having a gain factor G1~ to which the sign~ls A and B from
the Hall elements 10 and 'I 1 are applied. The output signal
G1 (A+B) may be applied directly across a stator coil 6'
of a two-phase motor. The signals A and B are furthermore
applied to a differential amplifier ~ with a gain factor
G2. The output signal G2 (A-B) is then 90 out of phase
with the output signal G1 (A~B) and may be applied directly
to the other stator coil 7'. By a sui-table adjustment of
the gain factors G1 and G2 relative to each other -the
amplitudes of the two ou-tput signals can be equalized.
The amplitude ratio of the signals G1 (A~B)
and G (A-B) is of less significance when these signals
are employed as switching signals, ~or e~ample when the
outputs of the amplifiers 12 and 17 are connected to the
sta-tor coils 6' and 7' via switching -transistors T1 and T2
respectively instead of direc-tly~ as is represented by the
dashed connections in ~igure 8.
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PHN.9644 8 5.9.80
By means of the circuit of Figure 8 it is also
possible to realize other linear combinations of the
signals A ancl B in order to realize phase differences
other than 90 between the output signals, employing -the
linear combinations discussed with re~erence to Figures 4
and 5. For this purpose the factors K may for example
be realized in the amplifiers 12 and 17 for example by
means of operational amplifiers known from analogue
computing technology~
Figure 9 shows an example of a circuit for
reali7ing the linear combinations A KB and B-KA discussed
with reference to Figures 6 and 7. It comprises an
operational amplifier 18, which amplifies the signal A
by a factor G and the signal B by a factor -KG, so that
an output signal G(A-KB) is obtained, which may be applied.
directly to a stator coil 6 of a three-phase motor.
A second operational amplifier 19 amplifies the signal B
by a fac-tor G and the signal A by a factor -KG, so that
a signal G(B-KA) - which in the case of a suitable choice
of the factor ~ differs 120 in phase with the signal
G(A-B) - is obtained, whichmay be applied directly to the
coil 7 o~ the three-phase motor. The third phase can be
obtained by inverting -the sum of the output signals,
which yields -the signal G(1-k~(A+B). This signal - as is
shown in Figure 9 - can also be realized by means of a
third amplifier 20 having a gain factor (k-1)G, to which
the signals A and B are applied. The output signal may
then be applied directly to the third stator coil 8.
As is known, a three-phase motor may also be
energized by three signals having a phase dif~erence of
relative to each other instead of by three signals
having a phase difference of 120 rela-tive to each o-ther,
if one of the stator coils is energized with opposite
polarity or, viewed from the winding sense, from the
opposi-te direction~ which in -the diagram of Figure 7
for exarnple means that the vector E is shifted through
180, so -that the vectors C, D anc1 E are situated at 60
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PHN.9644 ~ 5 9 oO
relative -to each other. If, as :is illustra-ted by -the vector
diagram of Figure 10, two signals C ancl D with a phase
difference of 60 are generated by a sui-table choice of
the factor K, the third phase E is obtained by taking
the difference E = D - C of the signals D and C.
If in the circuit of Figure 9 the factor K is selected
so that a phase difference of 60 exists between the
output signals o~ amplifiers 18 and 19, the third stator
coil 8 may be energized with the third phase E by including
it between the outputs of the amplifiers 18 and 19, as is
represented by the dashed line in Fi~ure 9. Amplifier 20
may then be dispensed with. Stator coil 7 should then be
ellergized (or wound) in a reverse sense in comparison
with the situation with the signals at 120 .
l5The linear combinations C = B-XA and D = A-KB
can simply by realized by allowing cross-talk with a
factor K to occur between an amplifier for -the signal A
; and an amplifier for -the signal B. This is utilized in
the circuit of Figure 11. In this circuit the current
` 20 through the stator coil 6 or 7 is sensed by including
a resistor 21 and 22 respectively, both for example having
a resistance value Ro. The current through the stator coil
6 or 7 is controlled by an amplifier 23 and 24 respectively,
which compared the signals A and B, in -this case a vol-tage,
with the voltage across the resistors 21 and 22 respec-
tively. The curren-ts through -the coi]s 6 and 7 are -then
A/Ro and B/Ro respectively, which when the E~all elements
10 and 11 are arranged in a conven-tional manner (Figure 1)
e~hibi-t a phase difference of for e~ample 120 . If a phase
difference of 60 is selected, the third sta-tor coil ~
may simply be included between the outputs of the ampli-
fiers 23 and 24. However, if -the Hall elements 10 and 11
are arranged at a smaller angle ~ (Figure 3), the phase
difference between the currents -through the coils 6 and 7
can still be made 60 (or, if desired, 120 or other
phase di~`ferences) by combining -the signals A and B,
in the present case very simply by :including a cross-talk
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PIIN.~644 10 5.9.80
resistor 25 with a resistance value R1 between the
junction of the coil 6 ancl resistor 21 and -the junc-tion
of coil 7 and resistor 22. Through resistor 21 a current
A/Ro flows, through resistor 22 a current B/Ro, and
through resistor 25 a current (A-B~R, so that through
stator coil 6 a current I6 = P(A KB) flows and through
stator coil 7 a current I7 = P(B-KA), where
P = (Ro +Rl )/~oR1 and K = ~o/(Ro + R1 ) O By a suitable
choice of ~, which can be determined by e~periment, for
examp]e by using a variable resistor for -the resistor 25,
i-t is again possible toobtain the correct phase difference.
In particular when the signals from the Hall
elements are used for switching, instead of for analogue
energization (as is for example shown as an alternative
in Eigure 8), the waveform of the signals A and B generated
by the lIall elements 10 and 11 less critical. This can be
demonstra-ted by means of ~igure 12, in which Eigures 12a
and 12b represent the signals A and B as triangular
voltage waveforms. ~igure 12c represents the sum of said
20 signals A and B and Eigure 12d the difference of said
signals A and B. It is found that also in this case the
zero passages of the combinations A+B and A-B are shifted
through a quartero~ the period of the signals A and B,
i.e. through 90, relative to each other~ Other shifts
are possible with other combinations.
Especially when the signals from the Hall
elements 10 and 11 and the linear combinations thereof
are employed as analogue energizing signals for the
stator coils, it may occur in practice that the form
and/or the streng-th of the magnetization of the permanent-
magnet rotor is not suitable -to produce suitable signals
in the Hall elements. A sui-table solution is -then to
arrange an additional magnetic disk on the ro-tor shaft,
with which disk the Hall elements co-operate. The advantage
that -the two elements can be arranged near each other
is then maintained, whils-t the drawback of the known
mo-tor with magnetically-coded disk mentioned in -the
introduction does not occur.
