Device for determining a position of a rotor of an electric motor

Patent metadata

Field	Value
Publication number	US-9628005-B2
Application number	US-201314778620-A
Country	US
Kind code	B2
Filing date	Mar 28, 2013
Priority date	Mar 28, 2013
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

A device for determining a rotor position in a polyphase electric motor has a power control unit for applying drive voltages according to a pulse width modulation scheme so as to synchronously drive the motor. A measurement unit is arranged for measuring a voltage value on a respective phase by determining a zero-crossing interval where the phase current is around zero, disconnecting the phase from the respective drive voltage during the zero-crossing interval, and measuring the voltage value when the drive voltage of a first other phase is the supply voltage and the drive voltage of a second other phase is the zero voltage. A position unit is arranged for determining the rotor position based on the voltage value.

First claim

The invention claimed is:

1. A device for determining a rotor position in a polyphase electric motor having stator coils comprising three phases, the device comprising:
a power control unit configured to apply drive voltages on each of the three phases, wherein the drive voltages comprise drive pulses alternating between a zero voltage and a supply voltage according to a pulse width modulation scheme so as to generate sinusoidal phase currents in each of the phases for synchronously driving the motor;
a measurement unit arranged for measuring a voltage value on a respective phase by
determining a zero-crossing interval where the respective phase current is around zero,
disconnecting the respective phase from the respective drive voltage during the zero-crossing interval,
determining at least one measurement interval in the zero-crossing interval where the drive voltage of a first other phase is the supply voltage and the drive voltage of a second other phase is the zero voltage, and
measuring the voltage value during the measurement interval;

a position unit configured to determine the rotor position based on the voltage value,
wherein the measurement unit is arranged for initiating the zero-crossing interval based on detecting the respective phase current being below a predetermined threshold.

2. The device as claimed in claim 1 , wherein the measurement unit is arranged for determining the measurement interval based detecting that the drive voltage on the first other phase is the supply voltage, while the drive voltage on the second other phase is the zero voltage.

3. The device as claimed in claim 1 , wherein the measurement unit is arranged for initiating the measurement interval based on the drive voltage on the first other phase alternating to the supply voltage, while the drive voltage on the second other phase is the zero voltage.

4. The device as claimed in claim 1 , wherein the measurement unit is arranged for initiating the measurement interval based on the drive voltage on the first other phase being the supply voltage, while the drive voltage on the second other phase is alternating to the zero voltage.

5. The device according to claim 1 , wherein the position unit is arranged for determining a speed of rotation by determining a multitude of consecutive rotor positions.

6. The device according to claim 1 , comprising a memory unit adapted to register a position value of the rotor for maintaining the rotor position value while the rotor is not rotating.

7. An integrated circuit comprising at least one device according to claim 1 .

8. A device for determining a rotor position in a polyphase electric motor having stator coils comprising three phases, the device comprising:
a power control unit configured to apply drive voltages on each of the three phases, wherein the drive voltages comprise drive pulses alternating between a zero voltage and a supply voltage according to a pulse width modulation scheme so as to generate sinusoidal phase currents in each of the phases for synchronously driving the motor;
a measurement unit arranged for measuring a voltage value on a respective phase by
determining a zero-crossing interval where the respective phase current is around zero,
disconnecting the respective phase from the respective drive voltage during the zero-crossing interval,
determining at least one measurement interval in the zero-crossing interval where the drive voltage of a first other phase is the supply voltage and the drive voltage of a second other phase is the zero voltage, and
measuring the voltage value during the measurement interval;

a position unit configured to determine the rotor position based on the voltage value,
wherein the measurement unit is arranged for initiating the zero-crossing interval based on the drive voltages of both other phases being the zero voltage.

9. A device for determining a rotor position in a polyphase electric motor having stator coils comprising three phases, the device comprising:
a power control unit configured to apply drive voltages on each of the three phases, wherein the drive voltages comprise drive pulses alternating between a zero voltage and a supply voltage according to a pulse width modulation scheme so as to generate sinusoidal phase currents in each of the phases for synchronously driving the motor;
a measurement unit arranged for measuring a voltage value on a respective phase by
determining a zero-crossing interval where the respective phase current is around zero,
disconnecting the respective phase from the respective drive voltage during the zero-crossing interval,
determining at least one measurement interval in the zero-crossing interval where the drive voltage of a first other phase is the supply voltage and the drive voltage of a second other phase is the zero voltage, and
measuring the voltage value during the measurement interval;

a position unit configured to determine the rotor position based on the voltage value,
wherein the measurement unit is arranged for initiating the zero-crossing interval based on the respective drive voltage of the respective phase being the zero voltage.

10. A device for determining a rotor position in a polyphase electric motor having stator coils comprising three phases, the device comprising:
a power control unit configured to apply drive voltages on each of the three phases, wherein the drive voltages comprise drive pulses alternating between a zero voltage and a supply voltage according to a pulse width modulation scheme so as to generate sinusoidal phase currents in each of the phases for synchronously driving the motor;
a measurement unit arranged for measuring a voltage value on a respective phase by
determining a zero-crossing interval where the respective phase current is around zero,
disconnecting the respective phase from the respective drive voltage during the zero-crossing interval,
determining at least one measurement interval in the zero-crossing interval where the drive voltage of a first other phase is the supply voltage and the drive voltage of a second other phase is the zero voltage, and
measuring the voltage value during the measurement interval;

a position unit configured to determine the rotor position based on the voltage value,
wherein the measurement unit is arranged for determining the measurement interval by controlling the drive voltage of the second other phase to the zero voltage, and wherein the controlling the drive voltage of the second other phase comprises the measurement unit arranged for suppressing the drive voltage of the second other phase to alternate to the supply voltage.

11. The device as claimed in claim 10 , wherein the controlling the drive voltage of the second other phase comprises the measurement unit arranged for connecting the second other phase to the zero voltage.

12. A device for determining a rotor position in a polyphase electric motor having stator coils comprising three phases, the device comprising:
a power control unit configured to apply drive voltages on each of the three phases, wherein the drive voltages comprise drive pulses alternating between a zero voltage and a supply voltage according to a pulse width modulation scheme so as to generate sinusoidal phase currents in each of the phases for synchronously driving the motor;
a measurement unit arranged for measuring a voltage value on a respective phase by
determining a zero-crossing interval where the respective phase current is around zero,
disconnecting the respective phase from the respective drive voltage during the zero-crossing interval,
determining at least one measurement interval in the zero-crossing int

Assignees

• Lovas Ivan
• Bobek Viktor
• Nxp Usa Inc

Inventors

• Lovas Ivan
• Bobek Viktor

Classifications

• H02P6/182 Primary

  using back-emf in windings · CPC title

• H02P29/021

  Electricity · mapped topic

• H02P6/185 Primary

  using inductance sensing, e.g. pulse excitation · CPC title

• H02P29/0241

  the fault being an overvoltage · CPC title

• H02P29/024

  Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load · CPC title