# US 11,876,477 B2 · Position observer for electrical machines

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- Number: US 11,876,477 B2
- Document ID: US11876477B2
- Status: Granted
- Kind: B2
- Application number: 17/268,586
- Filed: 2019-08-15
- Published: 2021-11-11
- Granted: 2024-01-16
- Earliest claimed: 2018-08-15
- Assignees: Technelec Ltd
- Applicants: Technelec Ltd
- Inventors: Charles Pollock; Helen Pollock
- Web page: https://patentgrep.com/patent/US11876477B2

## CPC

- H02P 6/181: {using different methods depending on the speed}
- G01R 15/181: {using coils without a magnetic core, e.g. Rogowski coils}
- H02P 6/182: using back-emf in windings
- H02P 6/185: using inductance sensing, e.g. pulse excitation
- H02P 21/0021: {using different modes of control depending on a parameter, e.g. the speed}
- H02P 21/0025: {implementing a off line learning phase to determine and store useful data for on-line control}
- H02P 21/141: {Flux estimation}
- H02P 21/18: Estimation of position or speed
- H02P 21/24: Vector control not involving the use of rotor position or rotor speed sensors
- H02P 21/28: Stator flux based control
- H02P 2203/05: Determination of the rotor position by using two different methods and/or motor models
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A control system for an electrical motor comprises a rotor, a stator having a plurality of phase windings, and an inverter for applying voltage to the plurality of phase windings by connecting individual phase windings to a first or second voltage level. The control system is configured to measure a first rate of change of current in a first phase winding, of said plurality of phase windings, connected to the first voltage level, to measure a second rate of change of current in a second, different phase winding connected to the first voltage level, and to calculate a difference between the first and second rate of change of current. The control system is further configured to use the calculated difference to obtain data related to a position of the rotor.

## Claims

### Claim 1

A control system for an electrical motor comprising a rotor, a stator having a plurality of phase windings, and an inverter for applying voltage to the plurality of phase windings by connecting individual phase windings to a first or second voltage level, the control system configured:
a) to measure a first rate of change of current in a first phase winding, of said plurality of phase windings, connected to the first voltage level;
b) to measure a second rate of change of current in a second, different phase winding connected to the first voltage level;
c) to calculate a difference between the first and second rate of change of current to obtain a first signal, A;
d) to repeat steps a) to c) for one of (i) the first and a third phase windings or (ii) the second and third phase windings when both phase windings are connected to the same first or second voltage level to obtain a second signal, B;
e) to use the first, second and third signals, A and B, to obtain data related to a position of the rotor and to use the data related to the position of the rotor to determine the position of the rotor relative to the stator;
f) to operate the motor in a low speed regime; and
g) while operating in the low speed regime, to measure a stator current in the phase windings of the stator arising from an application of a stator voltage, and to calculate a motor characteristic of the electrical motor from positions of the rotor, the stator voltage, the stator current, and a resistance of the phase windings.

### Claim 2 (depends on 1)

The control system of claim 1, wherein the system is further configured to use the determined position of the rotor relative to the stator to control operation of the electrical motor.

### Claim 3 (depends on 1)

The control system of claim 1, wherein the system is configured to measure the first and second rates of change of current substantially simultaneously.

### Claim 4 (depends on 1)

The control system of claim 1, further comprising at least one sensor coil located in proximity to said first and second phase windings, wherein the system is configured to measure a voltage in the at least one sensor coil to determine the first and second rates of change of current.

### Claim 5 (depends on 4)

The control system of claim 4, wherein the at least one sensor coil is a Rogowski coil arranged such that a current in said first phase winding passes through the Rogowski coil in a first direction and a current in said second phase winding passes through the Rogowski coil in a second direction opposite to the first direction to calculate the difference between the first and second rate of change of current.

### Claim 6 (depends on 1)

The control system of claim 1, comprising:
a first Rogowski coil arranged such that the current in the first phase winding passes through the first Rogowski coil;
a second Rogowski coil arranged such that the current in the second phase winding passes through the second Rogowski coil; and
a first differential amplifier connected to the first and second Rogowski coils to calculate the difference between the first and second rate of change of current.

### Claim 7 (depends on 6)

The control system of claim 6, further comprising:
a third Rogowski coil arranged such that the current in the third phase winding, passes through the third Rogowski coil to measure a third rate of change of current; and
a second differential amplifier connected to the first and third Rogowski coils to calculate the difference between the first and third rate of change of current.

### Claim 8 (depends on 7)

The control system of claim 7, wherein the system is configured to measure the third rate of change of current when the third phase winding is connected to the first voltage level.

### Claim 9 (depends on 7)

The control system of claim 7, comprising a third differential amplifier connected to the second and third Rogowski coils to calculate the difference between the second and third rate of change of current.

### Claim 10 (depends on 9)

The control system of claim 9, wherein each differential amplifier is an operational amplifier.

### Claim 11 (depends on 2)

The control system of claim 2, wherein the control system is further configured to control the electrical motor by synchronising currents in the plurality of phase windings based on the determined position of the rotor relative to the stator.

### Claim 12

A control system for an electrical motor comprising a rotor, a stator having a plurality of phase windings, and an inverter for applying voltage to the plurality of phase windings by connecting individual phase windings to a first or second voltage level, the control system configured:
to measure a first rate of change of current in a first phase winding, of said plurality of phase windings, connected to the first voltage level;
to measure a second rate of change of current in a second, different phase winding connected to the second voltage level;
to measure a third rate of change of current in a third, different phase winding connected to the second voltage level;
to calculate a difference between the first rate of change of current and a sum of the second and third rates of change of current to obtain an improved measurement of the first rate of change of current;
to use the improved measurement to obtain data related to a position of the rotor and to use the data related to the position of the rotor to determine the position of the rotor relative to the stator;
to operate the motor in a low speed regime; and
while operating in the low speed regime, to measure a stator current in the phase windings of the stator arising from an application of a stator voltage, and to calculate a motor characteristic of the electrical motor from positions of the rotor, the stator voltage, the stator current, and a resistance of the phase windings.

### Claim 13 (depends on 1)

An electrical motor comprising the control system of claim 1.

### Claim 14 (depends on 1)

The control system according to claim 1, wherein the control system is further configured to repeat steps a) to c) for the other one of (i) the first and the third phase windings or (ii) the second and the third phase windings when both phase windings are connected to the same first or second voltage level to obtain a third signal, C, and to use the third signal, C, together with the first and second signals A and B to obtain the data related to the position of the rotor.

### Claim 15 (depends on 14)

The control system according to claim 14, wherein the data related to the position of the rotor comprises a first phase signal (Alpha) and a second phase signal (Beta), wherein
Alpha
=
Signal
⁢
⁢
A
-
(
Signal
⁢
B
+
Signal
⁢
C
2
)
Beta
=
3
⁢
(
Signal
⁢
⁢
B
-
Signal
⁢
⁢
C
2
)
.

### Claim 16 (depends on 15)

The control system according to claim 15, wherein the position of the rotor relative to the stator comprises a rotor angle, and wherein the rotor angle is calculated by the Arc Tangent of Beta/Alpha.