DE4036565C1 - Electronic drive system using variable reluctance electric motor - slows down variations in magnetic induction of stator by electronic control of winding current - Google Patents

Abstract

The electronic drive system uses a variable reductance electric motor (1) with one or more phases. The stator poles (5) have one or more windings (6, 7) for each phase, exhibiting an inductance which varies cyclically in dependence on the rotation of the rotor (3). The rapid variations in the magnetic induction of the stator (2), caused by the switching of the stator windings (6, 7) in dependence on the rotor position, are slowed by auxiliary electronic control of the winding current, for reducing the motor operating noise. Pref. the current variation rate is controlled in dependence on the motor revs. and the motor torque. ADVANTAGE - Reduced operating noise.

Description

The invention relates to an electronic drive system that an electric motor with variable reluctance with a pronounced bottom len exists on both the stator and the rotor, with one or more ren phases, with one or more per phase, on the poles of the Stator-arranged windings are present, their inductance changes cyclically with the movement of the rotor and with one Switching device that the coil current depending on the Turns rotor position on and off.

Such an electric motor with variable reluctance is already under the title "Ways to reduce noise on elec trischen Maschinen "by Dr. E. Lübcke and H. Plattner in the Siemens magazine, edition 1935, pages 157 to 164, described ben. Among other things, the report states that Geräu vibration caused by the electric motors tend to be caused by non-sinusoidal forces Rivers and rivers and through the interaction of harmonics stand. It is also stated here that the noise on Ma machines and transformers thanks to a low magnetic induc tion can be kept small.

From DE-29 44 355 A1 a stepper motor is described, the a control current controlled by a reference quantity is supplied to reduce noise in the engine. The current and therefore the river do not change suddenly.

A switched reluctance is also known from EP-03 97 514 A2 Motor known, the one for switching two phases, a switch  has direction, the one controls the phase current size and the other has a circulation path for the phase stream. This arrangement should reduce switching losses in particular be decorated.

Furthermore, from DE-39 40 569 A1 is a circuit arrangement for operating a multi-phase synchronous motor on a same Known voltage network, which is a switching device for successive Connecting the winding phases of the armature winding to the network DC voltage and a commutation logic for logical connection control the electronic switch of the switching device Switching signals in accordance with the rotor rotation position of the Has synchronous motor. To bring about a gentle commu to reduce noise and prevent radio interference the two switching signals for the commutate overlap the switches associated with the winding phases in time and are clocked in the overlap area such that the mean of the phase current in the emerging winding phase decreases in the commutating winding phase.

Furthermore, from the patent short description of the Japanese Patents 54-1 31 713 a stepper motor is known in which the Wick lungs are temporarily short-circuited after they have been switched off thus allowing the reduction in performance while holding lichen.

Furthermore, EP-01 93 708 A2 is an electric drive system for a variable reluctance motor known specifically refers to two-phase reluctance motors and in the first Line serves the starting behavior of the motor. Here are the Ro Goal extensions selected so that they interact with lead two adjacent stator poles.  

Finally, a reluctance motor is from DE-39 05 997 A1 knows, proposed measures for lining the rotor will. The rotor has no extensions. To the ver However, being able to anchor clothing becomes additional help here medium needed, especially at high speeds and long straight rotors are connected with great effort.

There is also an electronic drive system with a motor variable magnetic resistance from EP-03 43 845 A2 known. In such a controlled reluctance motor arise by the rapid change in magnetic induction when turning switch the individual phases in the stator iron noise, the ge compared to conventional electric motors, such as three-phase motors etc. are considerably louder. The cause of this is relatively ho hen engine noises are required to control the engine due to the switching operations that occurred during the whole Engine runtime are required. This leads in practice often that such electric motors are reluctant in electrical devices ten, especially in household machines, although they have a simple mechanical structure and a good one Have efficiency.

The object of the invention is therefore an electronic drive system with a variable magnetic resistance create, through the particularly uncomfortable Mo Gate noise can be greatly reduced without affecting the motor performance drops significantly.

This object is achieved according to a first embodiment of the invention tion solved in that occurs when switching off the coils tendency to rapid changes in the magnetic induction in the stator  through an additional electronic control of the coil current be slowed down, the rate of current drop by one temporary short-circuiting of the coil winding after switching off of these windings is affected. It has been shown that the sole reduction in the current drop rate to considerable noise reduction with almost unchanged engine performance of the engine. This embodiment leads to the special advantage that they are in conventional reluk dance motors without major changes and at low cost can be used in a simple manner.

In a development of the invention it is provided that the Control the rate of current change depending on the speed and torque of the rotor. This tax tion is necessary to find a compromise between the noise damping (long switch-on and switch-off times) and good efficiency (short switch-on or switch-off time).

According to a second embodiment of the invention, in which the poles have projections on the front side at their edge region, as seen in the direction of rotation of the rotor (EP 01 93 708 A2), the mo gate noise can also be reduced by the lengths of the Projections in the circumferential direction be about 10 to 20% of the pole width wear and that the thickness of the projections in the radial direction un dangerous three to five times that between the rotor and the stator located air gap, the coil current so is set that the protrusions go into saturation. By A special rotor geometry is achieved that the Magnetic flux not building up in the iron of the rotor and the stator abruptly, but gradually increases, resulting in a noticeable Noise reduction leads. This could be done, for example, by a Oblique grooving on the rotor and on the stator can be achieved. Such Oblique grooves are all for reducing torque fluctuations commonly known in electric motors; but they are in their hearts position complex and associated with additional costs.  

This simpler and less expensive training contributes to ver slow the rate of change of the magnetic induct tion at. Due to the special training of the poles, the night part, namely that the engine has a lower torque holds, kept within certain limits and it becomes a very good torque with optimal engine noise reduction reached.

Due to the advantageous cover, the higher speed occurring wind noise in addition to those mentioned above th noise due to changes in induction greatly reduced. The Projections offer without additional fastening required medium a good and firm hold against the cover, all the more so to be able to withstand the centrifugal forces.

Several embodiments of the invention are in the drawing shown and are explained in more detail below.

Show it

Fig. 1 cross section through a three-phase, generally known from the prior art reluctance motor, in which the winding only one phase schematically and in which the Ver course of the magnetic field lines are shown both in the stator and in the rotor, the course of the magnetic field lines corresponds to the position of the rotor shown in this figure.

Fig. 2 block diagram of a switching device for one phase of the electric motor shown in Fig. 1.

Fig. 3 is a block diagram as in FIG. 2, but with the additional integrated according to the invention to the switching device electronic control,

Fig. 4 temporal variation of the current for one phase of the electric motor of FIG. 1 and the control pulses to the electro-African switches corresponding to FIG. 2,

FIG. 5 to FIG. 4, however, with additional pulses after switching off the coil L 1 according to the inventive circuit according to Fig. 3

Fig. 6 Detail view of the additional electronic circuit shown in Fig. 3 for generating pulses for speed and torque-dependent short-circuiting of the winding after turning off the same after the first inven tion and

Fig. 7 partial cross section through the rotor and stator of an electric motor according to the second invention.

In Fig. 1, a 3-phase reluctance motor is shown schematically in cross section, which consists essentially of a stator 2 and a rotor 3 rotatably mounted in the stator 2 . The stator 2 has six evenly distributed on the circumference and aligned to the center 4 of the reluctance motor 1 stator poles 5 , each of which is surrounded by a winding. For the sake of simplicity, only the two perpendicular stator poles 5 are provided with windings 6 , 7 in FIG. 1. The rotor 3 has four rotor poles 8 distributed uniformly on the circumference, the outer surfaces 9 of which run at a short distance (characterized by the gap width 1 according to FIG. 7) to the outer surfaces 10 of the stator poles 5 . The outer surfaces 9 , 10 of the rotor and stator poles 8 , 5 each lie on a circle with the diameters d 1 and d 2 that is concentric with the center 4 . The difference between d 2 and d 1 forms twice the gap width 1 between the poles 5 , 8 . The diametrically opposite windings 6 , 7 formed on the stator poles form a phase of the reluctance motor shown in FIG. 1.

The operation of such a reluctance motor 1 , as shown in Fig. 1 and as it has long been known from the prior art, is based on the mutual attraction of the trained on the rotor 3 and the stator 2 poles 8 , 5 , the are strongly pronounced because they protrude radially outwards or radially inwards on the rotor 3 or the stator housing 2 . When current flows in an associated one of the stator pole 5 phase, for example in the through those shown in Figs. 1 and perpendicular stator and rotor poles 5, the magnetic forces generated in Fig. 1 by the magnetic lines 11 try the rotor 3 align so, that both the rotor and stator poles 3 , 5 are directly opposite. This is shown in FIG. 1 using the example of a 3-phase reluctance motor 1 . But it is of course also possible to use a 1-, 2-, 3- or multi-phase reluctance motor, which then works on the same principle. In the rotor position shown in Fig. 1, there is a torque counterclockwise when current is flowing in the windings 6 , 7 of a phase. Since the one shown in Fig. 1 3-phase switched reluctance motor 1 has long been known, for simplicity not mentioned more details.

In Fig. 2 is a schematic diagram of a switching device for one phase of the electric motor shown in Fig. 1 is shown. For the windings formed on the other four stator poles 5 , which are not shown in the drawing, two further switching devices are required, which have the same schematic circuit diagram as shown in FIG. 2. In Fig. 2, the switching device consists of two terminals 12 , 13 which are connected to a DC voltage source not shown in the drawing Darge. The connections 12 , 13 are also connected to one another via a smoothing capacitor 14 . About the two electronic switches T 1 and T 2 who the in Fig. 1 connected in series windings 6 , 7 , which are summarized in Fig. 2 in L 1 , with the connections 12 , 13 connected ver. The two electronic switches T 1 and T 2 are designed in FIG. 2, for example, as IGBTs (Insulated Gate Bipolar Transistor).

In series with the lower switch T 1 is a measuring resistor R, at which the actual current value is taken off via line 15 . Via the coil L 1 and the two electronic switches T 1 and T 2 , a free-wheeling diode D 1 and D 2 is connected each time. As already mentioned above, for the reluctance motor 1 according to FIG. 1 according to the circuit diagram just described, there is still one analog strand each for the coils L 2 and L 3 . Each of the electronic switches T 1 and T 2 is controlled by a driver 16 , 17 . The driver 16 is connected via a line 19 to the control connection 18 , which in turn is connected to a superordinate control electronics of the reluctance motor 1 , not shown in the drawing. The driver 17 is connected via a line 20 to a block 21 which, with the aid of pulse width modulation, takes over the current regulation according to the current setpoint at connection 22 . The connection 22 is connected to the higher-level motor control of the reluctance motor 1 . Line 15 forms the third input to block 21 . Drivers 16 , 17 and those to block 21 are also required again for each further phase of a reluctance motor.

In order to use the reluctance motor 1 to operate, is fed a request signal for turning on the phase L 1 via the control terminal 18 to the position shown in FIG. 2 switching means of the superordinate control electronics of FIG. 2. At the same time, a current setpoint is entered into the connection 20 by the higher-level switching device. In the first moment, both electronic switches T 1 and T 2 are switched on at the time t 1 , as clearly shown in FIG. 4. Now the current in the coil L 1 increases in accordance with the curve shape 23 according to FIG. 4. When the current setpoint value present at connection 22 is reached according to FIG. 2, the upper electronic switch T 2 is switched off (see t 2 according to FIG. 4) . The coil L 1 is short-circuited via T 1 and D 2 . As a result, the current dissipates slowly in the coil L 1 (see the sawtooth curve 43 ). With a fixed cycle (see curve 44 in FIG. 4), which is generated in block 21 , the upper switch T 2 is switched on until it reaches the limit value present at the connection 22 again. In this way, the coil current in L 1 is kept constant until it is switched off again at time t 3 ( FIG. 4) at the control terminal 18 at the instigation of the higher-level control electronics. After the conventional union control method, as shown in FIGS . 2 and 4, both electronic switches T 1 and T 2 are now switched off and remain in this switched-off position until the next cycle. According to FIG. 4, the current builds up through the inductor L 1 to t 3 relatively quickly, as shown in the curve 24th

The switching device shown in Fig. 3 agrees with the switching device shown in Fig. 2 with the exception of the two blocks 25 , 26 , which make up the actual invention in connection with the switching device. To avoid repetition, the same reference numerals have therefore been chosen for the same components according to FIG. 2 in FIG. 3.

According to FIG. 3, a switch 25 is inserted into the line 20 , which is connected to the control connection 18 via an additional control line 27 . The switch 25 has two switch positions, of which the switch position shown in FIG. 3 establishes the connection from the block 21 to the driver 17 . The second switching position, not shown in FIG. 3, connects the output 28 of the additional electrical circuit 26 to the driver 17 when the higher-level electronics on the control connection 18 switch off the coil L 1 . The additional electrical circuit 26 is connected to the block 21 via the line 29 . In addition, the additional electrical circuit 26 is connected via line 30 to terminal 22 . Furthermore, the circuit 26 is connected via an input 31 to a signal which represents the actual speed value of the reluctance motor 1 ( FIG. 1).

In Fig. 6, the additional electronic circuit 26 is shown in De tail so that the same reference numerals have been chosen for the same components. The additional electronic circuit 26 consists of a monostable multivibrator (mono flop) 32 , a comparator 33 and a setting controller 34 . The comparator 33 compares, via its two inputs 35 , 36, a speed predetermined at the setting controller 34 with the actual speed value at the input 31 . The output of the comparator 33 is connected via line 37 to the reset input R of the monoflop 32 .

The block diagram shown in Fig. 3 represents only one possibility to implement the invention. It is also possible to solve the object of the invention differently, for. B. by integrating a working according to the invention switching device in the higher-level control electronics.

The operation of the switching device according to the invention is ge according to FIGS . 3, 5 and 6 the following:
Between the times t 1 and t 3 ( FIG. 5), the superordinate electronics on the control connection 18 turns on the coil L 1 . Since in this period the switch 25 conducts the line 20 according to FIG. 3 in the same way as in FIG. 2, the time profile of the coil current in FIG. 5 during this period is exactly the same as in FIG. 4. At time t 3 , the higher-order Electronics switch off coil L 1 . At first, as shown in FIG. 2, the two electronic switches T 1 and T 2 are opened. The clock generated in block 21 (position number 44 in FIGS. 4 and 5) is now fed to the additional electronic switching device 26 via line 29 according to FIG. 3.

The timing of the clock signal 44 is also shown in FIG. 5, just as in FIG. 4. This clock 44 is now used to turn on the electronic switch T 2 for a certain time. Thus, the coil L 1 is short-circuited via the freewheeling diode d1. During this time, the current in the coil L 1 is reduced much more slowly than by reversing the polarity, as would be the case with the open electronic switches T 1 and T 2 . This is repeated cyclically until the current in the coil L 1 is reduced to zero, which corresponds to the time t 5 according to FIG. 5. From Fig. 5 it is seen that in the time range t 3 to t 5, the slope 38 of the current degradation in the middle is much lower than is the case at 24 in Fig. 4 (period t 3 to t 4).

The length of the switch-on times of the electronic switch T 2 is indirectly proportional to the current setpoint on the line 30 and the actual speed value at the input 31 according to FIG. 6. The comparator 33 compares the actual speed signal present at the input 31 with a fixed value given on the setting controller 34 Limit. At higher speeds, the comparator 33 completely prevents the electronic switch T 2 from being switched on cyclically by permanently resetting the monoflop 32 via the control input R.

The generated by the additional electronic switching device 26 he pulse chain is fed to the electronic switch T 2 via the switch 25 until the higher-level electronics at the control connection 18 turns the coil L 1 on again ( FIGS. 3 and 5). These additional pulses have after the decay of the coil current, according to curve 38 in Fig. 5, but no longer function.

The 3-phase reluctance motor 1 shown partially in cross section in FIG. 7 corresponds essentially to the motor shown in FIG. 1. To avoid repetition, the same reference numerals have therefore been used for corresponding, identical item numbers. The windings surrounding the stator poles 5 are not shown here for the sake of simplicity.

The difference compared to the reluctance motor shown in Fig. 1 is only in Fig. 7 that at the radially outer ends of the rotor poles 8 in the circumferential direction and in the edge region projections 39 are formed so that these in normal operation of the reluctance motor 1 in the magnetic saturation. According to Fig. 7, the projections d by the thickness and the width b defined. A width b of the jumps 39 of approximately 10 to 20% of the pole width p and a thickness d which is approximately three to five times the air gap 1 , which is between the outer surfaces of the rotor poles 8 and the outer surfaces 10, are favorable the stator poles 5 results.

Due to the salient rotor poles 8 8 spaces 40 are formed as shown in FIG. 7 between the rotor poles. So that these spaces cannot form a storage space for the air when the rotor 3 rotates, the spaces between covers 41 are closed radially to the outside. The projections 39 engage behind the end regions 42 of the covers 41 in such a way that they cannot fly radially outward due to the centrifugal forces occurring on the covers 41 when the rotor 3 is rotated. On the other hand, the jumps 39 also serve as attachment of the covers 41 .

As shown in Fig. 7, the covers 41 are formed by circular annular disks. However, it is also possible to use covers 41 which fill the entire space 40 . However, it is advantageous if these covers 41 are then made of a particularly light but nevertheless stable material. The outer diameter of the covers 41 are dimensioned in their radial dimensions so that they form a uniform cylindrical surface with the outer surface 9 of the rotor poles 8 .

Claims (4)

1. Electronic drive system, which consists of an electric motor ( 1 ) variable reluctance with pronounced poles ( 5 , 8 ) both on the stator ( 2 ) and on the rotor ( 3 ), with one or more phases, one or more phases per phase the poles ( 5 ) of the stator ( 2 ) are arranged windings ( 6 , 7 ), the inductance of which changes cyclically with the movement of the rotor ( 3 ) and with a switching device which switches the coil current as a function of the rotor position - And switches off, characterized in that the rapid changes in the magnetic induction in the stator ( 2 ) which occur when the coils (L 1 ) are switched off are slowed down by an additional electronic control ( 25 , 26 ) of the coil current, the current drop-out speed being caused by a temporary short circuit the coil winding ( 6 , 7 ) is affected after switching off these windings. 2. Electronic drive system according to claim 1, characterized in that the control of the current change speed in dependence on the speed and the torque of the motor ( 1 ). 3. Electronic drive system according to the preamble of Pa tent Claim 1, wherein the poles at their edge region, seen in the direction of rotation of the rotor ( 3 ), have projections ( 39 ) on the front, characterized in that the lengths of the projections ( 39 ) in the circumferential direction about 10 to 20% of the pole width (P) and that the thickness (d) of the projections in the radial direction is approximately three to five times the air gap ( 1 ) between the rotor ( 3 ) and the stator ( 2 ), where the Spu lenstrom is set so that the projections ( 39 ) go into saturation. 4. Electronic drive system according to claim 3, characterized in that the cavity ( 40 ) formed between two adjacent poles (B) is closed radially outwards by a cover ( 41 ) and that the projections ( 39 ) cover ( 41 ) reach radially from the outside.