GB1575621A - Ac rotary solenoids or rotary or linear stepping motors - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO AC ROTARY SOLENOIDS OR ROTARY OR LINEAR STEPPING MOTORS (71) We, PARAFLUX LIMITED, a British Company of 39-40 Gay Street, Bath, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to rotary solenoids or linear or rotary stepping motors and is a modification of the rotary solenoid described in Patent No. 1485154.

In said patent there is described with reference to Figures 4a and 4b thereof, a doubleacting rotary solenoid comprising a stator having two windings in quadrature and a rotor carrying a plurality of short circuited windings. With one stator winding energised, the rotor is in a 'null' position with the rotor coil axis normal to the coil axis of said stator winding whilst energisation of the other stator winding will rotate the rotor through 90" to another 'null' position to bring the rotor coil axis normal to that of said other stator winding; the rotor thus taking up a position relative to the respective energised stator winding which minimises the flux linkage with the rotor short circuited windings. If both stator windings are energised, the rotor will tend to take up a position intermediate the two 'null' positions.

An object of the present invention is to provide a single phase or three phase rotary or linear solenoid or stepping motor in which, by variation of the relative phase or voltage applied to the stator windings, the rotor or linear equivalent member may be caused to rotate or move in either direction to any position, or to rotate or move continuously.

According to one aspect of the present invention there is provided a single phase or multi-phase a.c. rotary solenoid or rotary or linear stepping motor comprising two laminated ferro-magnetic members restrained to move relative to each other maintaining a constant air gap therebetween, one member carrying a plurality of armature step-phase windings per supply phase of nominally equal displacement, the other member having at least one planar short circuited winding and providing for a single phase supply or for each phase of a multiple phase supply, a path of low reluctance to the passage of alternating flux parallel to the plane of the short circuited winding or windings and of high reluctance in the perpendicular direction to thereby influence the reactance of the windings of said one member, and means for controlling the relative phase or magnitude of the voltage applied to adjacent armature step-phase windings to cause limited or continuous relative motion of the two members.

According to a further aspect of the invention there is provided a single phase or multiphase rotary solenoid or rotary or linear stepping motor including a stator having a plurality of windings per phase displaced by up to 120 electrical degrees from each other, and a rotor or linear equivalent member having at least one planar short circuited winding providing for the single phase or for each multiple phase, paths of low reluctance to the passage of alternating flux parallel to the plane(s) of the short circuited winding or windings and of high reluctance perpendicular to them to thereby influence the reactance of the stator windings, and means for controlling the phase and/or magnitude of the voltage applied to pairs of adjacent said stator windings to cause the rotor or linear equivalent member to be progressively stepped in either direction or to rotate or move linearly continuously.

According to another aspect of the invention there is provided a multi-phase rotary solenoid or rotary or linear stepping motor including a pair of similar stators having a plurality of step-phase windings displaced by up to 120 electrical degrees from each other and fed from separate supply phases, the pair of stators being connectable to the supply phases in a manner which would produce travelling fields in opposing directions with all windings energised, and a mechanically coupled pair of rotors or equivalent linear members or a common single rotor or linear equivalent having one or more planar short-circuit windings pro viding for a single-phase alternating field paths of low reluctance parallel to the plane of the short-circuit winding or windings and of high reluctance in a plane perpendicular to them, to thereby influence the relative reactance of the step-phase windings, and means for controlling the phase and/or magnitude of the voltage applied to pairs of adjacent step-phase windings in each stator simultaneously to cause the rotors or equivalent linear members to be progressively stepped in either direction or to move continuously.

The invention will now be described by way of example only with particular reference to the accompanying drawing wherein: Figure 1 is a winding diagram for a single phase machine having two step-phase stator windings in quadrature and showing the rotor in the 'null' position for one winding energised; Figure 2 is the equivalent 3-phase winding diagram of Figure 1 using a 3-phase rotor construction; (Figures 1 and 2 are the equivalent of Figure 4a, 4b of Patent No. 1485154).

Figure 3 illustrates 3-phase, 2-pole stator flux axes relating to a single phase rotor and Figures 4a and 4b show alternative star and delta switching means respectively.

Referring to the arrangement of Patent No.

1485154, where the rotor takes up a position intermediate the two extreme 'null' positions, upon energisation of both stator step-phase windings, the quadrant into which the rotor moves is determined by the relative phase relationship of the two windings. Thus, referring to Figure 1 of the accompanying drawing the rotor 1 is shown in the 'null' position for energisation of stator winding L, L1. If winding M, M1 is also energised from the same supply with a phase relationship such that flux is entering the rotor 1 at the 12 o'clock position while flux due to L, L1 is leaving at the 3 o'clock position, the rotor flux axis X will move to the 1.30 position. Conversely, if winding M, M1 were energised in the opposite phase sense so that flux entered at the 6 o'clock position while leaving at the 3 o'clock position, the rotor flux axis Y would move to the 10.30 position.

Such mid-positions only apply if the voltage applied to the two stator step-phase windings are equal. If the relative voltages are varied, the rotor position will tend towards the stepphase with the highest voltage. Thus, by appropriate control of the relative phase and voltage, it is possible to cause the rotor to step in either direction to any position, or to rotate" continuoulsy. The equivalent arrangement using 3-phase stator step-phase windings and 3-phase rotor short-circuit loops shown in Figure 2 of the accompanying drawings and the rotor thereof can be made to step or move progressively in the same way.

It will be appreciated that the machine can be inverted in that the energising step-phase windings can be provided on the rotor and the short circuit loops in the stator, and equivalent linear machines of either type can be constructed.

While the description and illustrations have been given for windings in quadrature, it will be appreciated that the relative position of the resultant flux from two windings displaced by other than 90" can be varied in a similar manner by variation of the phase or voltage relationship of the two windings. For example, a single phase 2-pole machine having at least 3 energising step-phase windings displaced equidistantly from each other e.g. as shown in Figure 6a of Patent No. 1485154, can be controlled, so that the resultant alternating flux progressively rotates from the first to the second windings and then on to the third at any desired speed by progressive variation of the relative voltage or phase relationshps of these windings. With two windings only in quadrature, the relative phase relationships have to be reversed to obtain a complete revolution, while with 3 or more equally displaced windings unipolar switching can be used with advantage, i.e. one end of the said windings can be common, and phase control by suitably programmed bidirectional solid state switches applied at the other end of each winding.

Alternatively, where it is advantageous to utilise a three-phase supply, a similar pair of machines can be used with single-phase short circuit loops on one member.

The rotatable single-phase alternating field can be derived from a 3 phase supply to cause relative motion between the member carrying single-phase short circuit loops and the member carrying the armature windings at a speed dependent on the rate of transfer of a.c.

energisation from one step-phase of the winding to the next.

Considering initially a stator carrying conventional 3 phase 2 pole windings Al, B1 and C1 disposed at 1200 to each other and a rotor having short circuit loops parallel to the diameter, and switching means to energise each single phase separately, the rotor will tend to align itself at null positions corresponding to each of the three phasors Al, B1, and C1 in Fig. 3.

If the rotor is in the null position corresponding to energisation of Al, and phase B1 is then energised as well, the combination of phases Al and B1 will produce a resultant alternating flux equal in magnitude and opposite in direction to that produced by C, and represented by the phasor A1 +B1. The rotor will therefore tend to turn 60 clockwise to align itself with this intermediate position; it will however also be influenced by the travelling field and flux set-up by alternate energisation of the two phases, so that under two-phase conditions it will tend to produce continuous motion like a conventional induction motor.

This travelling field effect can be cancelled out by using an identical pair of machines mechanically coupled, with energising windings connected with opposite phase rotation, as shown. Equivalent machines with energising windings on the rotors and short-circuit loops in the stators, linear machines of either type, or of other numbers of phases or poles can readily be constructed using the same principle. Alternatively a common single rotor can be used.

It will be apparent that the 0 null position is achieved by energising Al and A2; energising B1 and C2 in addition will produce a new null position at 60". Rotor 1 will be influenced by the rotating field effect of Al and B1, but rotor 2 by A2 and C2, which will obviously be in the opposite direction. The two rotors will therefore tend to align with the 60 null position. Disconnection of Al and A2 will allow the rotors to take up the 1200 position, and so on. Simple on/off switching will produce a stepping action, while progressive voltage or phase control will produce progressive movement to the required position at the required speed.

Three phase windings can be star or delta connected as required, and Figures 4a and 4b show typical alterntive arrangements of triac switches, the gate firing circuits and sequence logic being omitted for simplicity, these being straightforward applications of known electronic art.

WHAT WE CLAIM IS:- 1. A single phase or multi-phase a.c.

rotary solenoid or rotary or linear stepping motor comprising two laminated ferromagnetic members restrained to move relative to each other maintaining a constant air gap therebetween, one member carrying a plurality of armature step-phase winding per supply phase of nominally equal displacement, the other member having at least one planar short circuited winding and providing for a single phase supply or for ecah phase of a multiple phase supply, a path of low reluctance to the passage of alternating flux parallel to the plane of the short circuited winding or windings and of high reluctance in the perpendicular direction to thereby influence the reactance of the windings of said one member, and means for controlling the relative phase or magnitude of the voltage applied to adjacent armature step-phase windings to cause limited or continuous relative motion of the two members.

2. A single phase or multi-phase rotary solenoid or rotary or linear stepping motor including a stator having a plurality of windings per phase displaced by up to 120 electrical degrees from each other, and a rotor or linear equivalent member having at least one planar short circuited winding providing for the single phase or for each multiple phase, paths of low reluctance to the passage of alternating flux parallel to the plane(s) of the short circuited winding or windings and of high reluctance perpendicular to them to thereby influence the reactance of the stator windings, and means for controlling the phase and/or magnitude of the voltage applied to pairs of adjacent said stator windings to cause the rotor or linear equivalent member to be progressively stepped in either direction or to rotate or move linearly continuously.

3. A multi-phase rotary solenoid or rotary or linear stepping motor including a pair of similar stators having a plurality of step-phase windings displaced by up to 120 electrical degrees from each other and fed from separate supply phases, the pair of stators being connectable to the supply phases in a manner which would produce travelling fields in opposing directions with all windings energised, and a mechanically coupled pair or rotors or equivalent linear members or a common single rotor or linear equivalent having one or more planar shortcircuit windings providing for a single-phase alternating field paths of low reluctance parallel to the plane of the short-circuit winding or windings and of high reluctance in a plane perpendicular to them, to thereby influence the relative reactance of the step-phase windings, and means for controlling the phase and/or magnitude of the voltage applied to pairs of adjacent stepphase windings in each stator simultaneously to cause the rotors or equivalent linear members to be progressively stepped in either direction or to move continuously.

4. A single or multi-phase rotary solenoid or rotary or linear stepping motor as claimed in claim 1 in which the short-circuited winding or windings are wound on the stationary member(s) and the energising step-phase windings on the moving member(s).

5. A single or multi-phase rotary solenoid or linear or rotary stepping motor as claimed in Claim 1 wherein the direction of motion is determined by the relative phase and/or voltage relationships of adjacent step-phase windings.

6. A single or multi-phase a.c. rotary solenoid or rotary or linear stepping motor substantially as hereinbefore described and as shown in Figure 3 or 4 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. two-phase conditions it will tend to produce continuous motion like a conventional induction motor. This travelling field effect can be cancelled out by using an identical pair of machines mechanically coupled, with energising windings connected with opposite phase rotation, as shown. Equivalent machines with energising windings on the rotors and short-circuit loops in the stators, linear machines of either type, or of other numbers of phases or poles can readily be constructed using the same principle. Alternatively a common single rotor can be used. It will be apparent that the 0 null position is achieved by energising Al and A2; energising B1 and C2 in addition will produce a new null position at 60". Rotor 1 will be influenced by the rotating field effect of Al and B1, but rotor 2 by A2 and C2, which will obviously be in the opposite direction. The two rotors will therefore tend to align with the 60 null position. Disconnection of Al and A2 will allow the rotors to take up the 1200 position, and so on. Simple on/off switching will produce a stepping action, while progressive voltage or phase control will produce progressive movement to the required position at the required speed. Three phase windings can be star or delta connected as required, and Figures 4a and 4b show typical alterntive arrangements of triac switches, the gate firing circuits and sequence logic being omitted for simplicity, these being straightforward applications of known electronic art. WHAT WE CLAIM IS:-

1. A single phase or multi-phase a.c.

rotary solenoid or rotary or linear stepping motor comprising two laminated ferromagnetic members restrained to move relative to each other maintaining a constant air gap therebetween, one member carrying a plurality of armature step-phase winding per supply phase of nominally equal displacement, the other member having at least one planar short circuited winding and providing for a single phase supply or for ecah phase of a multiple phase supply, a path of low reluctance to the passage of alternating flux parallel to the plane of the short circuited winding or windings and of high reluctance in the perpendicular direction to thereby influence the reactance of the windings of said one member, and means for controlling the relative phase or magnitude of the voltage applied to adjacent armature step-phase windings to cause limited or continuous relative motion of the two members.

2. A single phase or multi-phase rotary solenoid or rotary or linear stepping motor including a stator having a plurality of windings per phase displaced by up to 120 electrical degrees from each other, and a rotor or linear equivalent member having at least one planar short circuited winding providing for the single phase or for each multiple phase, paths of low reluctance to the passage of alternating flux parallel to the plane(s) of the short circuited winding or windings and of high reluctance perpendicular to them to thereby influence the reactance of the stator windings, and means for controlling the phase and/or magnitude of the voltage applied to pairs of adjacent said stator windings to cause the rotor or linear equivalent member to be progressively stepped in either direction or to rotate or move linearly continuously.

3. A multi-phase rotary solenoid or rotary or linear stepping motor including a pair of similar stators having a plurality of step-phase windings displaced by up to 120 electrical degrees from each other and fed from separate supply phases, the pair of stators being connectable to the supply phases in a manner which would produce travelling fields in opposing directions with all windings energised, and a mechanically coupled pair or rotors or equivalent linear members or a common single rotor or linear equivalent having one or more planar shortcircuit windings providing for a single-phase alternating field paths of low reluctance parallel to the plane of the short-circuit winding or windings and of high reluctance in a plane perpendicular to them, to thereby influence the relative reactance of the step-phase windings, and means for controlling the phase and/or magnitude of the voltage applied to pairs of adjacent stepphase windings in each stator simultaneously to cause the rotors or equivalent linear members to be progressively stepped in either direction or to move continuously.

4. A single or multi-phase rotary solenoid or rotary or linear stepping motor as claimed in claim 1 in which the short-circuited winding or windings are wound on the stationary member(s) and the energising step-phase windings on the moving member(s).

5. A single or multi-phase rotary solenoid or linear or rotary stepping motor as claimed in Claim 1 wherein the direction of motion is determined by the relative phase and/or voltage relationships of adjacent step-phase windings.

6. A single or multi-phase a.c. rotary solenoid or rotary or linear stepping motor substantially as hereinbefore described and as shown in Figure 3 or 4 of the accompanying drawings.