Abstract
A monitoring device for a reluctance machine includes a vector rotator for rotating a space phasor of the reluctance machine that depends on a voltage in a coordinate system that rotates with a negative fundamental frequency, a low-pass filter filtering the rotated space phasor and producing an output signal, and a signal evaluation device evaluating the output signal. A DC value of the produced output signal in the rotating coordinate system is monitored, and an error in operating the reluctance machine is identified when the DC value is above a predefined threshold value.
Claims
1. A monitoring device for a reluctance machine, comprising: a vector rotator for rotating a space phasor of the reluctance machine that depends on a voltage into a coordinate system that rotates with a negative fundamental frequency, a low-pass filter filtering the rotated space phasor and producing an output signal, and a signal evaluation device evaluating the output signal.
2. The monitoring device of claim 1, wherein the space phasor is a voltage phasor.
3. The monitoring device of claim 1, wherein the signal evaluation device comprises an absolute-value generator and a threshold comparator.
4. A method for monitoring a reluctance machine, comprising: transforming a space phasor for a flux that depends on a voltage, into a coordinate system that rotates with a negative fundamental frequency; producing an output signal by low-pass-filtering the transformed space phasor; monitoring a DC value of the produced output signal in the rotating coordinate system; and identifying an error in operating the reluctance machine when the DC value is above a predefined threshold value.
5. The method of claim 4, further comprising generating the DC value of the produced output signal with a low-pass filter.
6. The method of claim 4, wherein the reluctance machine is operated without an encoder.
7. The method of claim 4, wherein the reluctance machine is operated with open-loop control.
8. The method of claim 4, wherein the reluctance machine is monitored with a monitoring device configured to: rotate with a vector rotator the space phasor of the reluctance machine that depends on the voltage into a coordinate system that rotates with a negative fundamental frequency, filter the rotated space phasor with a low-pass filter and producing the output signal, and evaluate the output signal with a signal evaluation device to detect the DC value signal of the output signal.
Description
(1) The invention as well as further embodiments of the invention are described in greater detail below with reference to exemplary embodiments in the figures, in which:
BRIEF DESCRIPTION OF THE DRAWING
(2) FIG. 1 shows a plate section of a rotor of a reluctance machine;
(3) FIG. 2 shows a reluctance machine with a closed-loop current controller;
(4) FIG. 3 shows a phasor diagram during normal operation;
(5) FIG. 4 shows a phasor diagram in the fault scenario (locking-up or rattling of the rotor or the shaft); and
(6) FIG. 5 shows a monitoring device.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
(7) The representation according to FIG. 1 shows a rotor plate section 1 of a reluctance machine. Further shown are a pole 2 and a pole gap 3 together with the axes d and q of the flux on the basis of the Park transform. The d axis relates to the flux-forming component and the q axis relates to the moment-forming component of the overall flux. The rotor plate section 1 is a typical exemplary example of a rotor of a reluctance machine. Also shown alongside the pole 2 and the gap 3, which represent the d axis and the q axis accordingly, is the flux ψ.sub.d and the flux ψ.sub.q.
(8) The representation according to FIG. 2 shows a reluctance machine 4 with a closed-loop current controller 14. A simplified block diagram of the closed-loop control of the reluctance machine 4 is therefore produced. The reluctance machine 4 has a stator 5 with stator slots 6, into which stator windings are inserted. Further shown is a rotor 7, the plate section of which is Indicated. The reluctance machine 4 has a three-phase current connection 8. In order to measure a current or a voltage for the phases of the current connection 8, a three-phase measured value recorder 9 is provided. The recorded measured values are processed in an actual value processor 10. The actual value processor 10 produces an actual current value I. This actual current value I is an input value of the closed-loop current controller 14. A further input value of the closed-loop current controller 14 is the target current value I.sub.target 12. The closed-loop current controller 14 additionally has a link to a motor model 13. An output value of the closed-loop current controller 14 is the target voltage value U 15. The target voltage value U 15 is an input variable of an open-loop inverter controller 16. The open-loop inverter controller 16 has actuation signals 17 as output variables, which are supplied to an inverter 18. The inverter 18 is used to feed electrical energy to the reluctance machine 14.
(9) The representation according to FIG. 3 shows a phasor diagram for the reluctance machine, wherein the voltage phasors are not specifically shown in the phasor diagram. The voltage phasor is produced from the temporal derivation of the flux and rotated by 90° with respect to the flux phasor. The phasor diagram is based on the representation of the d axis 26 and the q axis 27. Shown are the current phasor I, the flux ψ.sub.I, the flux ψ and the flux ψ.sub.I*. The space phasors move, as shown, with the electric rotor angular velocity ω.sub.r. With regard to the values shown, the following equations are produced:
ω.sub.r=ω
Ψ.sub.I=L.sub.R.Math.I
Ψ.sub.I*=L.sub.Im.Math.I*
(10) The representation according to FIG. 3 shows the phasor diagram of the reluctance machine during normal operation. In an operating state of the reluctance machine according to FIG. 3, no rattling or locking-up of the rotor is produced. On the basis of the equations
Ψ=Ψ.sub.d+jΨ.sub.q
Ψ=(L.sub.ΣI+L.sub.Δ.Math.I*)
L.sub.Σ=0.5.Math.(L.sub.d+L.sub.q)
L.sub.Δ=0.5.Math.(L.sub.d−L.sub.q)
it can be seen that the d axis also rotates, as does the complex conjugate component of the flux.
(11) The representation according to FIG. 4 shows a further phasor diagram with the axes d 26 and q 27. Further shown are the current phasor I with the angular velocity ω and the phasor Ψ.sub.I running thereon, as well as the phasor Ψ.sub.I* which has been displaced by −ω in relation thereto. Unlike the representation according to FIG. 3, the representation according to FIG. 4 does not show a normal operating state, but rather the fault scenario, in which the shaft or the rotor is locked up, i.e. rattles. The flux phasor Ψ.sub.I rotates with the angular velocity ω. The phasor Ψ.sub.I* rotates with the angular velocity −ω. The phasors Ψ.sub.I and Ψ.sub.I* therefore rotate in opposing directions. This produces a DC component, which can be detected.
(12) The representation according to FIG. 5 shows a monitoring device 19. The monitoring device 19 serves to monitor the reluctance machine. The monitoring device has input signals 21 and 25. The input signal 21 is a space phasor, in particular a stator-fixed voltage phasor U.sub.ab (terminal voltage of the motor). The input signal 25 is a negative angular frequency 2π(−f.sub.fund). Here, the fundamental frequency f.sub.fund is negated by the minus sign. The negative angular frequency 25 is sampled by means of a sampling with the sampling frequency T.sub.ab. For a vector rotator 20, an integration of the input signal 25 takes place over the sampling time by means of an angular integration 24. The output signal of the angular integrator 24 is supplied to the vector rotator 20, which rotates the space phasor 21. The space phasor 21 rotated with the negative angular frequency is guided through a low-pass filter 22. The output signal of the low-pass filter 22 is further processed in a signal evaluation 23. The signal evaluation 23 is, for example, an absolute-value generator, wherein in the present case an absolute-value generation of the components of the voltage phasor |U.sub.XV| in the rotating coordinate system is performed. In the fault scenario, the component L.sub.ΣI always rotates in the positive direction, as in the normal scenario. The component L.sub.ΔI* rotates in the negative direction in the fault scenario. In the normal scenario, the component L.sub.ΔI* also rotates with a positive frequency. It is therefore the case that in the fault scenario, as in the normal scenario, the component L.sub.ΣI rotates in the positive frequency (direction of rotation), the conjugate component L.sub.ΔI* rotates in the positive direction in the normal scenario, but in the fault scenario the direction of rotation changes and it rotates in the negative direction.
