WO2007073854A1

WO2007073854A1 - Device for obtaining information about the rotor position of electric machines

Info

Publication number: WO2007073854A1
Application number: PCT/EP2006/011880
Authority: WO
Inventors: Rolf Strothmann
Original assignee: Rolf Strothmann
Priority date: 2005-12-15
Filing date: 2006-12-09
Publication date: 2007-07-05
Also published as: EP1961108A1; DE102006046637A1

Abstract

The invention relates to a device for obtaining information about the condition of electric machines that can be used to supply said machines with current. According to the invention, the device is provided with a unit (6, 8), which evaluates a measuring signal to obtain the condition information, said signal being influenced by a modification of the inductance of pole winding phases (1-3) of the electric machine, caused by the current flow. The measuring signal can, for example, relate to the potential at the neutral point (4) of star-connected phases (1-3).

Description

DEVICE FOR OBTAINING INFORMATION ON THE ROTOR POSITION OF ELECTRICAL MACHINES

The invention relates to a device for obtaining information that can be used for controlling the flow of electrical machines about the state of the machines.

EP 1 005 716 B1 discloses a device for determining the rotor rotational position during engine operation by applying pulses to phase strands of, in particular, multi-pole electrical machines and by evaluating the neutral point potential. The possibility of being able to determine the rotor position in such a way is based on the fact that the inductance of the phase strands within the half magnetic period is an unambiguous function of the rotational angle φ of the rotor, as described in EP 1 005 716 Bl incorporated herein. Measuring voltage pulses can therefore generate a potential signal in the star point, which depends on the respective inductance of the phase strand and therefore is a measure of the position of the rotor within half the magnetic period.

The invention has for its object to provide a new device of the type mentioned, which extends the possibilities for controlling the energization of electrical machines and in particular can complement the above-mentioned device for determining the rotor rotational position advantageous.

The device for solving this object according to the invention is characterized by a device which evaluates a measurement signal for obtaining the state information, which is influenced by changing the inductance of Polwicklungsphasen- strands of the electric machine due to current flow through the phase strands. The measurement signal may be, for example, a voltage dependent on the phase-strand inductances, a current change or a phase angle.

The changes in the inductance of pole winding phase strands considered here are based on a weakening or strengthening of the magnetic field passing through the pole windings. For large, flowing through the electrical machine operating currents, the field strength change in the pole windings and thus their inductance change can be significant. Consequently, changes in inductance can provide information about the current status of the electrical machine.

In a preferred embodiment of the invention, the state information relates to the orientation of a selected phase strand to the north or south pole or, in multi-pole machines, the north poles or south poles of the magnetic field. Here, depending on the position of the rotor, current supplies either lead to an increase or decrease in the inductance of the relevant phase string, so that it is possible to conclude by evaluating a signal dependent on the changed inductance on the rotational position in front of a north or south pole.

The current which changes the inductance may be a current flowing in the context of the operating current of the electrical machine and / or a current generated separately by said device.

In the latter case, the device for generating the current is preferably provided in such a way that the generated current does not influence the torque of the electrical machine, ie forms a reactive current.

In particular, the current may be a component of a resulting current vector including a phase angle of 90 ° with a torque producing component of that current vector, based on the magnetic period. The former component thus does not contribute to the torque of the electric machine.

The measurement signal may be influenced by a change in the ratio of the inductance of the phase strands. Such an influence is present in particular when, according to a preferred embodiment of the invention, the measuring signal is the potential at the star point in the star-connected phase strands of the electrical machine. In the star point, there is always a division of the voltage across the phase strands, wherein in three-phase machines for the division of the inductive resistance of a strand and the parallel connection of the inductive resistors of the other two strands is authoritative.

Suitably, the device further comprises a device which applies voltage pulses to at least one of the Polwindlungsphasenstränge and evaluated to determine the rotational position of the rotor within half a magnetic period by the voltage pulses generated at the star point of the star-connected phase strands potential.

Such a position determination within half a magnetic period gives no information about whether half the magnetic period is formed by a north or south pole. The knowledge of the orientation of the selected phase strand to a north or south pole forms an advantageous supplement to this.

The invention will be explained in more detail below with reference to exemplary embodiments and the accompanying drawings relating to these exemplary embodiments. Show it:

Fig. 1 is a schematic representation of an electrical machine with a

FIG. 2 shows a diagram explaining the application of measuring voltage pulses to the phase strings of the electrical machine of FIG. 1, FIG. 3 shows a representation explaining the rotational position of the rotor, and FIG. 4 shows the relationship between the pole windings passing through Magnetic field H of the electric machine and the induction B in the PoI windings and the inductance L of the pole windings.

Fig. 1 shows phase strands 1 to 3 of the pole winding circuit of a not shown otherwise 3-phase electric machine. In the considered embodiment, the machine has a plurality of magnetic periods formed by permanent magnets on the rotor, which correspond to a rotational angle ΔΦ, which is substantially smaller than 360 ° and is for example 12 °. The phase strands 1 to 3, which are connected to one another in a star point 4, are each connected at their end remote from the star point to a voltage supply circuit 5 through which the electric machine is operated according to the pulse width modulation method.

The star point 4 is connected to a potential or the voltage U at the star point 4 detecting means 6, which in turn communicates with a control device 7, which u.a. controls the power supply of the electric machine by the circuit 5.

The means 6 for detecting the neutral point potential is connected on the output side to a device 8 which, controlled by the device 7, forms differences M between voltage values U, which the voltage detection device 6 supplies as output values.

Voltage difference values determined by the difference-forming device 8 can be supplied to a comparison and classification device 9 which determines from the voltage difference values M a rotational angle interval (i) decisive for the rotational position of the rotor of the electric machine within a half magnetic period ΔΦ / 2.

A calculation device 10 connected to the devices 8 and 9 then determines the exact rotational position of the rotor within the interval (i) of half the magnetic period.

According to FIG. 2, operating voltage pulses 1 1 to 13, e.g. a battery voltage UB in each modulation cycle (or in selected modulation cycles) by Δt time-delayed applied to the respective phase strands 1 to 3. During the period .DELTA.t applied by the circuit 5, from the operating voltage pulses 1 1 to 13 separate Meßspannungs- pulses 14 to 16 are mutually offset in time. The time interval .DELTA.t is so small that the rotational position of the rotor practically does not change within this interval.

The measuring voltage pulses 14 to 16 generate correspondingly time-offset voltage signals U 1, U 2 and U 3 at the neutral point 4, which detects the device 6 activated simultaneously with the generation of the measuring voltage pulses 14 to 16 by the control device 7. According to a (explained below) dependency of the inductance of the pole windings of the phase strands 1 to 3 of the rotation angle Φ within a half magnetic period .DELTA.Φ / 2 results depending on the rotation angle Φ within the half magnetic period for the voltage signals Ul, U2 and U3 each have a periodic , approximately sinusoidal course, wherein the three voltage signals are mutually phase-shifted by 120 °.

From the voltage signals Ul, U2 and U3, the device 8 forms differences Ml = U1-U2, M2 = U2-U3 and M3 = U3-U1. Three further possible differences differ from these differences only in the sign.

The dependence of these differences on the angle of rotation Φ is shown in FIG.

The approximately sinusoidal periodic curves M1 (Φ), M2 (Φ) and M3 (Φ) shown in FIG. 3 are also phase-shifted by 120 ° relative to one another. One full period of these curves corresponds to half a magnetic period each.

As can also be seen from FIG. 3, twelve intervals i = 1 to 12 result within a full period of the curve M 1, for which the following applies:

i = l: Ml positive, M2 negative, M3 positive, Ml smaller M3 i = 2: Ml positive, M2 negative, M3 positive, Ml larger M3 i = 3: Ml positive, M2 negative, M3 negative, M2 smaller M3 i = 4: Ml positive, M2 negative, M3 negative, M2 greater M3 i = 5: Ml positive, M2 positive, M3 negative, Ml greater M2 i = 6: Ml positive, M2 positive, M3 negative, Ml smaller M2 i = 7: Ml negative, M2 positive, M3 negative, Ml greater M3 i = 8: Ml negative, M2 positive, M3 negative, Ml smaller M3 i = 9: Ml negative, M2 positive, M3 positive, Ml greater M3 i = 10: Ml negative , M2 positive, M3 positive, Ml smaller M3 i = 1 1: Ml negative, M2 negative, M3 positive, Ml less M2 i = 12: Ml negative, M2 negative, M3 positive, Ml greater M2.

By determining the sign of three determined difference values Ml, M2 and M3 and by comparing these values with one another, the comparison and classification device 9 can determine the rotation angle interval (i) in which the rotor is currently located. The exact calculation of the rotational position within the intervals (i) by the device 10 is based on aresin or / and arctan functions, which are preferably applied to differences in the potential profiles. The phase change and thus the continuation of the intervals can be determined by monitoring switching states that occur in the normal Nutzbestromung or can be generated by slight modification (time-delayed switching on and off).

The angle of rotation Φ of the rotor can be determined by counting the number of half magnetic periods passed through.

The above-mentioned change in the inductance of the pole windings of the phase strands 1 to 3 is based on the relationship shown in FIG. 4a between the magnetic field H of the rotor passing through the pole windings of the phase strands and the induction field B resulting in the iron-containing pole windings. Depending on the rotational position of the rotor within half a magnetic period, the B-field generated by the H-field of the permanent magnets of the rotor changes in the pole windings of the phase strands. With the change of the B-field, the slope dB / dH, which is proportional to the inductance of the phase strands, also changes. FIG. 4b shows the inductance L. as a function of the H-field. FIG.

At the neutral point, the pulse voltage U B applied to one of the phase strands 1 to 3 is divided, whereby, depending on the rotational position of the rotor, different division ratios and thus different potentials result at the position. Decisive for the division ratio are the inductive resistance of each acted upon by the voltage UB phase strand and the inductive resistance of the parallel connection of the other two phase strands. Due to the symmetry of the curve L (H) with respect to the L-axis, however, it can not be distinguished whether half the magnetic period, within which the

Rotordrehlage was determined, is formed by a north pole or a south pole.

In order to determine whether half the magnetic period relates to a north or south pole, in the embodiment described here, starting from the knowledge of the rotational position within half the magnetic period, the electric machine is energized by pulse width modulation such that the voltage resulting from the phase current flows, field vector H or B ^* generated by the totality of the pole windings, a first, exactly to the middle, between two poles of the rotor field directed component and a second, directed to one pole of the rotor field component is formed. Based on the magnetic period of the rotor field, the two components thus include a phase angle of 90 °. Thus, only the first component generates a torque, the second component, which represents a reactive current, provides no contribution to the torque of the electrical machines.

However, the additional reactive current causes a change of the H-field and thus also of the B-field in the pole windings of the phase strands. Assuming that the pole windings of a selected phase strand of the rotor are in front of a north pole, the second current component may be e.g. be generated so that the pole winding passing through H-FeId is weakened and the inductance L of these pole windings increases accordingly, if this assumption applies. The "operating point" then moves to the left in the positive part of the curve L (H) in Fig. 4b. If the assumption was wrong and the pole windings are actually in front of a south pole, this leads to an increase in the amount of the field passing through the pole windings. The "working point" then moves to the left in the negative part of the curve L (H). The inductance L decreases.

The decrease or increase of the inductance causes the resulting from the signals Ml to M3, rotating with the angle Φ pointer increases or decreases in length. From the change in length can be close to a north or south pole.

The observation of a variable-length pointer could be carried out in the context of normal operation current by pulse width modulation without separate measurement voltage pulses 14 to 16.

Claims

claims:

1. Apparatus for obtaining the control of the energization of electrical

Machine usable information about the state of the machines, characterized by a device which evaluates to obtain the state information by changing the inductance of Polwindlungsphasen- strands of the electric machine as a result of current flow through the phase strands affected measurement signal.

2. Device according to claim 1, characterized in that the inductance of the Polwicklungsphasenstränge (1-3) changing current is a current flowing in the context of the energization of the electric machine or a generated by said means, separate stream.

3. A device according to claim 2, characterized in that the means for generating the current is provided such that the current does not affect the torque of the electric machine.

4. The device according to claim 3, characterized in that the current is a component of a resulting current vector, which includes a torque-generating component of this current vector, based on the magnetic period, a phase angle of 90 °.

5. Device according to one of claims 1 to 4, characterized in that the measuring signal is influenced by a change in the ratio of the inductances of the Polwindlungsphasenstränge (1-3).

6. Apparatus according to claim 5, characterized in that the measuring signal is the potential at the neutral point in the star-connected phase strands (1-3).

7. Device according to one of claims 1 to 6, characterized in that the state information relates to the orientation of a selected phase strand to the north or south pole or, in multi-pole machines, the north or south pole of the magnetic field.

8. Device according to one of claims 1 to 7, characterized by a further device which voltage pulses to at least one of the Polwicklungsphasenstränge (1-3) applies and for determining the rotational position of the rotor of the electric machine within half a magnetic period by the voltage pulses (14 -16) evaluates the potential generated at the star point in the star-connected phase strands (1-3).