METHOD FOR DETERMINING A MOTOR TYPE OF AN ELECTRIC MOTOR AND MOTOR CONTROL APPARATUS

Abstract

A method for determining a motor type of an electric motor includes several phases, wherein two or more pulses are applied to the motor, respective currents are measured and the motor type is determined based on the pulses. Further, a motor control apparatus is configured to perform such a method.

Claims

1. A method for determining a motor type of an electric motor having several phases, the method comprising the following steps: applying two or more pulses to the motor, each pulse representing a vector with respect to the phases, measuring respective time-resolved currents while applying the pulses, analyzing at least some of the currents, and determining the motor type based on the currents.

2. The method according to claim 1, wherein analyzing the currents comprises determining a pulse with highest peak current and a pulse with lowest peak current.

3. The method according to claim 2, wherein a saliency indicator is calculated as a ratio between the highest peak current and the lowest peak current.

4. The method according to claim 1, wherein analyzing the currents comprises determining a pulse with highest peak current and a pulse opposite thereto.

5. The method according to claim 4, further comprising the following step: fitting a respective function to the pulse with highest peak current and to the pulse opposite thereto.

6. The method according to claim 5, wherein the function is a third order polynomial function with coefficients a, b, c, and d:
y=a x{circumflex over ( )}3+b x{circumflex over ( )}2+c x+d.

7. The method according to claim 6, wherein, for both the pulse with highest peak current and the pulse with lowest peak current, the coefficients are classified into one of four classes: Class A: if a has positive sign, b has positive sign, c has positive sign, Class B: if a has positive sign, b has negative sign, c has positive sign, Class C: if a has negative sign, b has positive sign, c has positive sign, Class D: if a has negative sign, b has negative sign, c has positive sign.

8. The method according to claim 7, wherein determining the motor type comprises performing a shape-based determination of the motor type, wherein ASM or SRM is detected if the coefficients of the pulse with highest peak cur-rent are classified in class C, and if the coefficients of the pulse with lowest peak current are classified in class C, SPM or IPM is detected if the coefficients of the pulse with highest peak current are classified in class B, and if the coefficients of the pulse with lowest peak current are classified in class B, and PMaSynRM is detected if the coefficients of the pulse with highest peak current are classified in class B, and if the coefficients of the pulse with lowest peak current are classified in class C.

9. The method according to claim 4, wherein the current of the pulse opposite to the pulse with highest peak current is scaled to the current of the pulse with highest peak current.

10. The method according to claim 4, wherein a sum of square errors is calculated between the current of the pulse with high-est peak current and the pulse opposite thereto.

11. The method according to claim 3, wherein determining the motor type comprises performing a calculation-based determination of the motor type based on predefined sectors in a diagram having the saliency indicator on one axis and the sum of square errors on the other axis, wherein each predefined sector corresponds to one motor type.

12. The method according to claim 8, wherein the shape-based determination is used for disambiguation if the calculation-based determination yields two different possible motor types.

13. The method according to claim 1, wherein a pulse with highest current derivative is identified, and wherein a magnetization direction is calculated based on the pulse with highest current derivative.

14. The method according to claim 1, wherein the method comprises applying a positive pulse and a negative pulse to each phase.

15. The method according to claim 1, wherein the pulses have equal magnitude in voltage.

16. The method according to claim 1, wherein the motor has three phases.

17. Motor A motor control apparatus being configured to perform the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will now be further described with respect to the accompanying drawings, wherein:

[0044] FIG. 1 shows a motor control apparatus and a motor,

[0045] FIG. 2 shows a flow diagram, and

[0046] FIG. 3 shows a two-dimensional diagram with sectors.

DETAILED DESCRIPTION

[0047] FIG. 1 shows schematically a motor control apparatus 10 and a connected electric motor 20. The motor 20 has three phases u, v, w that are connected to the motor control apparatus 10. The phases are connected to each other at a central point. The motor control apparatus 10 is typically configured to provide electric power to the electric motor 20 and also to perform certain control and surveillance functions.

[0048] When a motor is connected to the motor control apparatus 10, or at any other point in time when it is required, the motor control apparatus 10 may perform a method as shown in FIG. 2.

[0049] At first, motor type detection is started.

[0050] In step 1, a pre-estimate of inductances L.sub.d, L.sub.q is performed. The d-axis inductance L.sub.d and the q-axis inductance L.sub.q may especially be estimated by using a tuning sequence.

[0051] In step 2, a pulse time is pre-estimated by multiplying the d-axis inductance L.sub.d with a saturation current I.sub.sat and by dividing the value by the DC voltage U.sub.dc.

[0052] In step 3, a pulse generation is performed. In detail, pulses denoted as 001, 110, 010, 101, 001 and 110 are applied. Each triple of numbers represents a pulse, wherein a 0 represents that no voltage is applied to a respective phase in the order uvw and a 1 indicates that a voltage is applied to the respective phase. The corresponding sectors may be named as sectors 0, 1, 2, 3, 4, and 5.

[0053] In step 4, a sampling is performed during each pulse and the respective samples are stored in respective arrays of I.sub.u+, I.sub.u−, I.sub.v+, I.sub.v−, I.sub.w+, I.sub.w−. Those samples correspond to the sectors mentioned in step 3 and the corresponding generated pulses.

[0054] In step 5a, the sectors which have the highest and lowest peak currents are determined and are named I.sub.max and I.sub.min. In step 5b, the sector opposite to the I.sub.max and corresponding array is named I.sub.max_opp The number of samples available from those both arrays is n.sub.max.

[0055] A current I.sub.max is defined as the maximum peak current of the pulse with highest peak current. A further current I.sub.max_opp is defined as the maximum current of the opposite pulse.

[0056] In step 6, a curve fit is performed. Especially, a cubic curve fit may be performed and coefficients a, b, c and d for both I.sub.max and I.sub.max_opp may be found.

[0057] In step 7, an extrapolation is performed. The array I.sub.max_opp is extended until reaching the peak value of the pulse with highest current peak or until linear increase by using the formula I=at.sup.3+bt.sup.2+ct+d. The number of samples is noted.

[0058] If the array I.sub.max_opp is completely extrapolated at some current level of array I.sub.max, the common peak current value is the end index value I.sub.max.

[0059] In step 8, a saliency ratio is calculated by dividing the maximum current through the minimum current.

[0060] In step 9, a curve fit is performed and cases a, b, c, d are identified as described above.

[0061] In step 10, the sum of square errors is calculated in order to have an indication of the sum of square errors between the two pulses.

[0062] For example, the following formula can be used:

[00001]$\mathrm{MeanSquareError}=\frac{{.Math.}_1^{N\mathrm{samples}}{\left(\frac{\left(\frac{\mathrm{di}}{\mathrm{dt}}\right)\max -\left(\frac{\mathrm{di}}{\mathrm{dt}}\right)\mathrm{opposite}}{\left(\frac{\mathrm{di}}{\mathrm{dt}}\right)\max }\right)}^2}{N_{\mathrm{sample}}}.Math.100$

[0063] The value Nsamples is the maximum number of samples, and it is a current which is denoted as relating to the pulse with maximum peak current (max) and the opposite pulse (opposite).

[0064] After all these calculations, the saliency rate and the sum square error are put into a diagram as shown in FIG. 3. The diagram is split into four sectors, which in principle may overlap, but do not overlap in the present case. Each motor yields a combination of saliency ratio and sum square error which can be identified in the diagram and can be seen as being in one of the sectors.

[0065] The lowermost sector, comprising values of the saliency ratio up to a value SR1, corresponds to an asynchronous motor (ASM). The vertically middle sector, comprising values of the saliency ratio of more than the value SR1 and up to a value SR2, corresponds to a surface permanent magnet motor (SPM). The upper left sector, comprising values of the sum square error of up to a value SSE1, corresponds to a synchronous reluctance motor (SRM). The upper right sector, comprising values of the sum square error of more than the value SSE1, may correspond to an interior permanent magnet motor (IPM) or to a permanent magnet assisted synchronous reluctance motor (PMaSynRM). Both upper sectors comprise values of the saliency ratio of more than the value SR2. A disambiguation between the last two types can be made by using coefficients that can be calculated out of the samples as described above.

[0066] While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.