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Method of determining the rotor position of a permanent-magnet motor

A permanent magnet motor, phase current technology, applied in the direction of electronic commutator, single-phase motor control, AC motor control, etc., can solve the problem that the back electromotive force cannot always be reliably determined

Active Publication Date: 2017-11-03
DYSON TECH LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, since the magnitude of the back EMF is proportional to the speed of the rotor, the transition in the polarity of this back EMF cannot always be reliably determined at lower speeds

Method used

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  • Method of determining the rotor position of a permanent-magnet motor
  • Method of determining the rotor position of a permanent-magnet motor
  • Method of determining the rotor position of a permanent-magnet motor

Examples

Experimental program
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Embodiment Construction

[0014] figure 1 A permanent magnet motor 1 includes a rotor 2 , a stator 3 and a control system 4 .

[0015] The rotor 2 includes quadrupole permanent magnets 5 fixed to a shaft 6 . The stator 3 includes a pair of cores 7 having four salient poles, and a phase winding 8 wound around the cores 7 .

[0016] The control system 4 includes an inverter 10 , a gate driver module 11 , a controller 12 and a current sensor 13 .

[0017] Inverter 10 includes a full bridge of four power switches Q1-Q4 coupling phase winding 8 to a voltage rail of a power supply (not shown).

[0018] The gate driver module 11 drives the opening and closing of the switches Q1 - Q4 in response to control signals output from the controller 12 .

[0019] The controller 12 is responsible for controlling the operation of the motor 1 and generates three control signals DIR1, DIR2 and FW#. The control signal is output to the gate driver module 11, which drives the opening and closing of the switches Q1-Q4 in r...

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Abstract

The present invention provides a method of determining the position of a rotor of a brushless permanent-magnet motor, the method comprising: exciting and freewheeling a phase winding of the motor, wherein the phase winding is freewheeled when a phase current exceeds an upper threshold and freewheeling comprises one of: (i) freewheeling for a fixed period of time, and (ii) freewheeling until the phase current falls below a lower threshold. The method further comprises measuring a parameter corresponding to one of: (i) the magnitude of the phase current during or at the end of freewheeling when the phase winding is freewheeled for the fixed period of time, and (ii) the time interval between the start and end of freewheeling or the start and end of excitation when the phase winding is freewheeled until the phase current falls below the lower threshold. The measured parameter is used to define a saturation threshold. The phase winding is sequentially excited and freewheeled in the same way and the parameter is measured in the same way. The method then comprises comparing the measured parameter against the saturation threshold; and determining that the rotor is at a predetermined position when the measured parameter is less than the saturation threshold.

Description

technical field [0001] The invention relates to a method of determining the rotor position of a permanent magnet electric machine. Background technique [0002] Knowledge of rotor position is critical to commutating the phase windings of a brushless motor at the right time. Permanent magnet motors often include Hall effect sensors that output signals indicative of rotor position. Although the component cost of the sensor is relatively cheap, integrating the sensor within the motor often complicates the design and manufacture of the motor. Additionally, the signal output by the sensor is often susceptible to electromagnetic noise generated within the motor. [0003] Sensorless solutions for indirectly determining the position of a rotor are known. For permanent magnet machines, the transition in the polarity of the back EMF within the phase windings can be used to determine rotor position. However, since the magnitude of the back EMF is proportional to the speed of the ro...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02P6/18
CPCH02P6/186H02P6/18H02P6/26H02P6/182H02P27/06H02P6/16
Inventor 郑立波
Owner DYSON TECH LTD
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