Electric machine driving device

Abstract

PURPOSE: To provide a motor drive with a simple structure capable of reducing mechanical noises and vibrations. CONSTITUTION: In this motor drive which controls the rotational speed of a three-phase np (np: an even number more than or equal to 4) pole brushless DC motor, there are provided an DC-AC converting means for converting DC voltage into desired false AC voltage, a position detection means for detecting rotational phases obtained from the induced voltage of a three-phase armature winding of the brushless DC motor, and a duty control means for performing pulse width modulation(PWM) of the DC-AC converting means. The duty control means consists of a reference duty determining means for determining a reference duty value based on a frequency command value, a correcting means for correcting the reference duty value into an output duty value based on rotational speed for each angle range obtained by dividing a one-turn angle of the brushless DC motor into np portions, and an output means for outputting the output duty value.

Description

technical field [0001] The present invention relates to a motor drive for controlling the frequency of a brushless direct current (DC) motor. Background technique [0002] Such as Figure 7 As shown, a 120° excitation control (square wave excitation control) type motor drive device is known, which is used to control the number of revolutions of a three-phase np pole (np is an even number not less than 4) brushless DC motor. Such as Figure 7 As shown in , this known motor driving device includes a DC / AC converter 2 for converting a DC voltage into a pseudo AC voltage to output a pseudo AC voltage to the motor 1 and a magnetic pole position detection device for detecting the rotor position of the motor 1 Device 3. A pulse width modulation (PWM) duty controller 5' outputs an added voltage to the DC / AC converter 2 to control the number of revolutions of the motor 1, and outputs a duty signal to control the frequency and phase of the motor 1. The DC / AC converter 2 is composed ...

AI Technical Summary

Problems solved by technology

[0007] However, in case the load torque of the motor 1 is not constant with respect to the rotation angle of the motor 1, the residual torque caused by the difference between the output torque and the load torque makes the motor 1 The speed of the motor 1 changes constantly, so the speed control of the motor 1 is unstable

Therefore, the mechanical system should be made strong against noise and vibration, the occurrence of this problem greatly increases the production cost, and if the measures against noise and vibration are not very useful, the motor 1 and the mechanical system may break

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