Method for operating an electronically commutated synchronous machine, and actuation circuit

Abstract

A method for operating an electronically commutated synchronous machine with several phases, wherein an actuation circuit operates the synchronous machine, the actuation circuit having at least two switches for each phase and a degree of actuation for each phase being periodically ascertained by the actuation circuit, wherein the switch-on period, during which a supply voltage is applied to the respective phase by way of the associated switch, is determined for ascertaining the degree of actuation, wherein the following steps are carried out: measuring current by a single measurement resistor in at least two measurement windows and shifting one or more of the switch-on periods of the different phases relative to one another as soon as the difference between switch-on instants of at least two phases falls below a minimum period or the difference between the switch-on periods of at least two phases falls below twice the minimum period.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is the U.S. National Phase Application of PCT International Application No. PCT / DE2017 / 078414, filed Nov. 7, 2017, which claims priority to German Patent Application Ser. No. 10 2017 211 196.8, filed Jun. 30, 2017, and European Patent Application No. 16198509 filed Nov. 11, 2016 the contents of such applications being incorporated by reference herein.FIELD OF THE INVENTION[0002]The invention relates to a method for operating an electronically commutated synchronous machine, and also to an actuation circuit.BACKGROUND OF THE INVENTION[0003]Electronically commutated synchronous machines with permanent excitation, also known as brushless motors, have a stator with at least two, in particular three, phase windings and a rotor with at least one pole pair which is arranged perpendicularly to the rotation axis and is formed by one or more permanent magnets which are arranged in or on the rotor. A brushless motor is supplied with...

AI Technical Summary

Benefits of technology

The invention provides a method to reduce torque ripples in a motor. This is achieved by fixing measurement points and arranging the switch-on periods in a centered manner when there is a large difference in the phases. This arrangement expands the measurement region and allows for measuring currents for PWMs between zero and 100 percent. This helps to improve the motor's performance and reduce noise.

Problems solved by technology

Switching effects in the inverter of the actuation circuit are a leading source of line-bound interference phenomena which can result in malfunctions in electronic circuits by way of the on-board electrical system.

However, the prior art exhibits the disadvantage that, for the measurement, it is not possible by means of a single shunt to provide centering of the switch-on periods of the individual phases with a fixed measurement point or measurement window or shifted switch-on periods with a dynamic measurement point or measurement window.

Specifically, if, for example, centering of the switch-on periods is provided and two of the switch-on periods have the same values, it is not possible to measure the currents of the phases.

In addition, the measurement windows would have to change as soon as the duty cycle changes, but this is not readily possible in most microcontrollers.

For this purpose, for example, currents are fed into the motor, but said currents cause relatively high torque ripples and relatively poor NVH (noise vibration harshness) behavior.

This has the effect that a measurement is not possible in the full PWM period.

This likewise causes more torque ripple.

However, currents cannot be measured when there is a central arrangement and two PWMs have the same values.

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