Inverter device

Abstract

AN INVERTER APPARATUS INCLUDING A DC / AC CONVERTING DEVICE (4) WHICH INCLUDES A PLURALITY OF SWITCHING ELEMENTS AND CONVERTS A DC VOLTAGE IN A PSEUDO AC VOLTAGE BY CLOSING AND OPENING THE SWITCHING ELEMENTS SO AD TO OUTPUT THE PSEUDO AC VOLTAGE TO A THREE-PHASE BRUSHLESS DC MOTOR, A VOLTAGE DETECTING DEVICE (1) FOR DETECTING AN INDUCED VOLTAGE IN A DURATION WHEN AN ARMATURE CURRENT OF THE THREE-PHASE BRUSHLESS DC MOTOR ASSUMES ZERO BY LOWERING THE PSEUDO AC VOLTAGE, A PULSE WIDTH MODULATION (PWM) CONTROL DEVICE (3) FOR PERFORMING PWM CONTROL OF THE PSEUDO AC VOLTAGE OUPUTTED BY THE DC / AC CONVERTING DEVICE (4) AND A CURRENT WAVEFORM COMPENSATING DEVICE (2) WHICH SHAPES ON THE BASIS OF A PREDETERMINED CONDITION AN ARMATURE CURRENT WAVEFORM SUPPLIED TO THE THREE-PHASE BRUSHLESS DC MOTOR IN ACCORDANCE WITH INDUCED VOLTAGE DETECTION INFORMATION OF THE VOLTAGE DETECTING DEVICE (1) AND OUTPUT INFORMATION ON THE WAVEFORM SHAPING TO THE PWM CONTROL DEVICE.(FIG 1)

Description

technical field [0001] The present invention relates to an inverter device for controlling the frequency of a brushless direct current motor. Background technique [0002] In a conventional inverter device that controls the number of revolutions of a three-phase brushless DC motor, a 120° excitation control method and a 180° excitation control method are employed. A 120° excitation control method is disclosed in, for example, Japanese Patent No. 2642367, and a 180° excitation control method is disclosed in, for example, Japanese Patent Laid-Open Nos. 7-245982 (1995) and 7-337079 (1995). In the 120° excitation control method, the zero point of the induced voltage is directly detected by comparing the inverter phase voltage with the reference voltage, and the rectification signal is changed according to the zero point generated at intervals of 60° electrical angle. [0003] On the other hand, in the 180° excitation control method, the potential difference between the neutral ...

AI Technical Summary

Problems solved by technology

However, if the motor is operated by setting the excitation angle to about 150° in order to reduce motor noise and vibration during motor operation, the induced voltage can be continuously confirmed only during an electrical angle of only 30° per phase, so that even There is also a higher risk of loss of steps during normal operation of the motor, and instabilities such as oscillations are likely to occur

[0006] In addition, in the prior art 120° excitation control method, this defect makes it almost impossible to set the electrical angle at 180° or thereabouts

[0007] On the other hand, in the known 180° excitation control method, since the signal passes through the integrated circuit, the absolute value of the zero point of the induced voltage cannot be detected correctly, and the phase difference between the zero point and the rotational position detection signal depends on the operating state have changed so much that complex controls such as phase correction should be performed

However, it is difficult to adjust the phase correction, and the algorithm operation for controlling the phase correction becomes complicated

[0008] Meanwhile, in the conventional 180° excitation control method, since the motor requires a neutral output terminal and uses the third harmonic component of the induced voltage waveform, there arises a problem that the conventional 180° excitation control method cannot be applied to a motor employing sine wave excitation

Images