TH25607B - A brushless DC motor that can start stably? - Google Patents

Abstract

In the synchronized operating condition, where the output voltage and frequency of the inverter increase during startup, when the differential voltage signal is determined not to be at the specified level by the differential voltage signal level determination section (41), or when the comparison result in the mode comparison section (42) indicates that the position signal and inverter mode are not correlated as specified, the V/F pattern adjustment section (44) outputs a voltage command signal to reduce the inverter output voltage to the PWM section (54). At the same time, when the differential voltage is determined to be at the specified level by the differential voltage signal level determination section (41), and when the position signal and inverter mode are correlated as specified, upon receiving the determination signal from the differential voltage signal level determination section (41) and the signal representing the comparison result from the mode comparison section (42), the position detection switch (43) switches the operating switch SW from the synchronized operating side to the position detection side.

Claims (13)

1. A brushless DC motor system consisting of a rotor (10) with pole magnets, a stator (1) with armature windings (1a, 1b, 1c) connected in a three-phase star configuration, a resistor circuit (2) connected in a three-phase star configuration in parallel with the armature windings (1a, 1b, 1c), a rotational position detection pathway (3) which detects the rotational position of the rotor (10) relative to the stator (1) on the basis of the voltage difference between the neutral points of the armature windings (1a, 1b, 1c) and the neutral point of the resistor circuit (2) to output a position signal, and an inverter section (20) which switches the voltage patterns of the armature windings (1a, 1b, 1c) on the basis of the position signal from the rotational position detection pathway (3); synchronous control methods (51,55,56,57) for outputting the voltage and frequency of the inverter output of the inverter section (20) on the basis of the specified initial pattern; The position detection control path (52) controls the inverter output of the inverter section (20) based on the position signal from the rotational position detection path (3); the decision path determines whether the position detection, using the position signal from the rotational position detection path (3), can be activated when the inverter section (20) is in synchronous operation by the synchronous control paths (51,55,56,57); and the switching paths (43,63,104,113) switch the control paths of the inverter section (20) from the synchronous control paths (51,55,56,57) to the position detection control path (52) when the decision path determines that the position detection can be activated; essentially, the voltage and frequency of the inverter output of the inverter section (20) are output based on the pattern specified by the synchronous control paths (51,55,56,57), and when the decision path determines that the position detection can be activated. Position detection cannot be enabled after the specified pattern has been sent. Synchronous control paths (51,55,56,57) reduce the V/F ratio and the voltage V to frequency F of the inverter output of the inverter section (20) until the decision path determines that position detection based on the position signal can be enabled. 2. A brushless DC motor system according to claim 1, where the decision path consists of level decision paths (34, 35, 36, 37, 41, 60, 61, 100, 101) to determine whether the voltage difference between the neutral point of the armature winding (1a,1b,1c) and the neutral point of the resistor circuit (2) is not less than the specified value, and will operate when the level decision paths (34, 35, 36, 37, 41, 60, 61, 100, 101) determine that the voltage difference is not less than the specified value in order to determine whether the position acceptance can be performed. 3. A brushless DC motor system according to claim 2, where the level determination method (34,41) consists of a rectifying method (15) for rectifying the signal representing the voltage difference between the neutral points of the armature windings (1a,1b,1c) and the neutral point of the resistor circuit (2), a smoothing method (16) for smoothing the signal rectified by rectifying method (15), and a smoothing comparison method (17) for comparing the signal smoothed by smoothing method (16) with a specified reference value (Eo), and will operate when the smoothing comparison method (17) compares the signal smoothed by smoothing method (16) with a specified reference value (Eo) and it appears that the smoothed signal exceeds the specified reference value (Eo) in order to determine that the voltage difference is not less than the specified value. 4. A brushless DC motor system according to claim 2, where the level determination path (35, 36, 60, 61) incorporates a differential voltage comparison path (18,19) for comparing the signal representing the voltage difference between the neutral point of the armature winding (1a,1b,1c) and the neutral point of the resistor circuit (2) with specified reference values (E1, E2, E3) and operates when the output signal of the differential voltage comparison path (18, 19) obtained from comparing the differential voltage signal with specified reference values (E1, E2, E3) is obtained, and the differential voltage comparison path (18, 19) has the specified pattern to determine that the voltage difference is not less than the specified value. 5. A brushless DC motor system according to claim 2, whereby the level determination devices (37, 100, 101) operate when the output signal of the hysteresis comparator (37), obtained by comparing the signal representing the voltage difference between the neutral points of the armature windings (1a, 1b, 1c) and the neutral point of the resistor circuit (2) with the specified reference values (E4, E5), based on the hysteresis characteristics of the hysteresis comparator (37), has the specified pattern to determine that the voltage difference is not less than the specified value. 6. A brushless DC motor system according to claim 1, where the decision path consists of the position signal mode comparison paths (42, 62, 102, 111) for comparing the position signal from the rotational position detection path (3) with the inverter output of the inverter section (20) to determine whether the position signal and the inverter output are related as specified and will operate when the position signal mode comparison paths (42, 62, 102, 111) compare the position signal with the inverter output and show that the position signal and the inverter output are related as specified to determine whether the position detection can be operated. 7. Brushless DC motor system according to claim 1, where the decision path includes the position signal cycle comparison path (103, 112) for comparing the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output signal frequency with the specified value to determine whether the absolute value is not greater than the specified value and will operate when the position signal cycle comparison path (103, 112) determines that the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output frequency is not greater than the specified value to determine whether position acceptance can cause operation. 8. A brushless DC motor system according to claim 7, where the rotation position detection path (110) is composed of a voltage differential detection path (31) to detect the voltage differential between the neutral points of the armature windings (1a, 1b, 1c) and the neutral point of the resistor circuit (2) to output a voltage differential signal, an integration path (32) to integrate the voltage differential signal from the voltage differential detection path (31) to output an integral signal, and a hysteresis comparator (38) which has hysteresis properties and will compare the integral signal from the integration path (32) with specified reference values (E8,E7) to output a position signal. 9. A brushless DC motor system according to claim 1, where the decision path consists of at least two of the following parts: the level decision path (34, 36, 36, 37, 41, 60, 61, 100, 101) for determining whether the voltage difference between the neutral point of the armature winding (1a, 1b, 1c) and the neutral point of the resistor circuit (2) is not less than the specified value, and will operate when it is determined that the voltage difference is not less than the specified value, in order for the decision path to determine that the position detection can cause operation; the position signal mode comparison path (42, 62, 102, 111) for comparing the position signal from the rotation position detection path (3) with the inverter output of the inverter section (20) for determining whether the position signal and the inverter output are related as specified, and will operate when the position signal and the inverter output are related as specified, in order for the decision path to determine that the position detection can cause operation; and the position signal cycle comparison path. (103,112) For comparing the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output frequency and the specified value, and will operate when the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output frequency and the specified value is not greater than the specified value, in order to make the decision path determine that the position detection can cause operation. 10. A brushless DC motor system according to claim 1, where the decision path consists of level decision paths (34, 35, 36, 37, 41, 60, 61, 100, 101) to determine whether the voltage difference between the neutral of the armature winding (1a, 1b, 1c) and the neutral of the resistor circuit (2) is not less than the specified value, and will operate when the level decision paths (34, 35, 36, 37, 41, 60, 61, 100, 101) determine that the voltage difference is not less than the specified value, in order to determine whether the position detection can cause operation. 11. A brushless DC motor system according to claim 1, where the decision path consists of the position signal mode comparison paths (42, 62, 102, 111) for comparing the position signal from the rotational position detection path (3) with the inverter output of the inverter section (20) to determine whether the position signal and the inverter output are related as specified and will operate when the position signal mode comparison paths (42, 62, 102, 111) compare the position signal with the inverter output and it appears that the position signal and the inverter output are related as specified to determine that the position detection can cause operation. 12. Brushless DC motor system according to claim 1, where the decision path consists of the position signal cycle comparison path (103, 112) for comparing the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output frequency with the specified value to determine whether the absolute value is not greater than the specified value and will operate when the position signal cycle comparison path (103,112) determines that the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output frequency is not greater than the specified value to determine whether position acceptance can cause operation. 13. A brushless DC motor system according to claim 1, where the decision path consists of at least two of the following parts: the level decision path (34, 35, 36, 37, 41, 60, 61, 100, 101) for determining whether the voltage difference between the neutral point of the armature winding (1a, 1b, 1c) and the neutral point of the resistor circuit (2) is not less than the specified value, and will operate when it is determined that the voltage difference is not less than the specified value, in order for the decision path to determine that the position detection can be activated; the position signal mode comparison path (42, 62, 102, 111) for comparing the position signal from the rotational position detection path (3) with the inverter output of the inverter section (20) for determining whether the position signal and the inverter output are related as specified, and will operate when the position signal and the inverter output are related as specified, in order for the decision path to determine that the position detection can be activated; and the position signal cycle comparison path. (103,112) For comparing the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output frequency and the specified value, and will operate when the absolute value of the difference between the position signal cycle value and the corresponding position signal cycle value on the basis of the inverter output frequency and the specified value is not greater than the specified value, in order to make the decision path determine that the position detection can cause operation.