JP3829236B2 - Brushless DC motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brushless DC motor, and more particularly to a brushless DC motor driven by a PWM inverter.
[0002]
[Prior art]
This type of brushless DC motor has an armature current control device that controls the current value supplied to the armature based on the output signal of the rotational position sensor that detects the rotational position of the rotor, and a PWM control unit and an inverter unit. However, there is known one provided with a driving device for supplying an armature current to the armature based on the current value.
[0003]
By the way, in a brushless DC motor designed for high-speed rotation, the intrinsic inductance of the armature inevitably becomes very small. When a brushless DC motor having a very small armature inductance is driven by a PWM inverter, a ripple component is included in the current flowing through the armature. For this reason, there arise problems that the rotor does not rotate smoothly or that the armature generates intense heat.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a brushless DC motor that solves the above problems, can reduce ripple current, and can rotate at high speed.
[0005]
[Means for Solving the Problems and Effects of the Invention]
The brushless DC motor according to the present invention includes armature current control means for controlling a current value supplied to the armature based on an output signal of a rotational position sensor for detecting the rotational position of the rotor, a PWM control section, and an inverter section. and includes a driving means for supplying the armature current to the armature based on the current value, the phase between the inverter unit and the armature, a large current smoothing inductance in comparison with the armature A brushless DC motor provided with a coil, wherein the armature current control means is provided with phase control means for advancing the phase of the armature current with respect to the output signal of the rotational position sensor , wherein the phase control means Current waveform data output means having storage means in which current waveform data representing a predetermined current waveform as a whole is stored at a series of addresses, and the series of addresses Address value control means for sequentially repeating the address value signal corresponding to the above and outputting it to the current waveform data output means, wherein the current waveform data output means corresponds to the address value signal output from the address value control means Current waveform data at the address of the storage means is output, and the address value control means outputs a pulse signal for phase control with a predetermined width in response to an external trigger signal, and the rotational position sensor A signal synchronizing means for synchronizing the start end of the output signal and the end of the phase control pulse signal and outputting a count pulse signal having a frequency higher than the output signal of the rotational position sensor, and the count pulse signal having a predetermined value Repeatedly counts and resets until the count value is the address value signal Output to the current waveform data output means and a count means for outputting a trigger signal to the pulse generation means when reset, and the phase of the current waveform represented by the current waveform data output from the current waveform data output means Outputs an address value signal so as to proceed with respect to the output signal of the rotational position sensor .
[0006]
Each phase between the inverter unit and the armature is provided with a current smoothing coil with a larger inductance than the armature, so the ripple component of the armature current is reduced and the smoothness of the rotor rotation is improved. In addition, the heat generation of the armature is reduced.
[0007]
By the way, if a current smoothing coil having a larger inductance than the armature is inserted in each phase between the inverter unit and the armature, the phase of the armature current is delayed, and high-speed rotation becomes difficult.
[0008]
However, since the armature current control means is provided with phase control means for advancing the phase of the armature current with respect to the output signal of the rotational position sensor, the phase delay of the armature current can be prevented. Then, by advancing the phase of the armature current with respect to the output signal of the rotational position sensor, that is, the position of the rotor, a demagnetizing action occurs, and high-speed rotation becomes smooth. Further, when the brushless DC motor is operated as a generator, the phase of the armature current is advanced with respect to the position of the rotor, thereby causing a magnetizing action and increasing the apparent capacity as the generator.
[0009]
Therefore, according to the brushless DC motor of the present invention, the ripple component of the armature current can be reduced, the smoothness of the rotation of the rotor can be improved, the heat generation of the rotor can be reduced, and high speed rotation is possible. It is.
[0011]
For example, a memory such as a PROM is used as the storage means of the current waveform data output means.
[0012]
When the address value signal is output from the address value control means, the current waveform data output means reads the current waveform data from the address of the storage means corresponding to the address value signal and outputs it. The address value signal corresponding to the series of addresses of the storage means is sequentially and repeatedly output from the address value control means, so that the current waveform data stored at the series of addresses of the storage means is sequentially and repeatedly output. Current waveform data representing a predetermined current waveform (for example, a sine waveform) as a whole is repeatedly output. The current waveform data output from the current waveform data output means is converted into an analog signal by an appropriate means such as a DA converter, and this analog signal is supplied to the drive means as an armature current value. Since the address value control means outputs the address value signal so that the phase of the current waveform represented by the current waveform data output from the current waveform data output means advances relative to the output signal of the rotational position sensor, it is supplied to the drive means. The armature current value and the phase of the armature current supplied from the driving means to the armature based on this value are advanced with respect to the position of the rotor.
[0014]
As the pulse generating means, for example, a monostable multivibrator is used. As the signal synchronization means, for example, a PLL (Phase Locked Loop) circuit or the like is used. As the counting means, for example, a counter is used.
[0015]
The count means outputs the count value as an address value signal to the current waveform data output means every time the counting pulse signal from the signal synchronization means is counted, and counts up to a predetermined value after the count means is reset. In the meantime, an address value signal corresponding to a series of addresses of the storage means is output from the counting means to the current waveform data output means, and as a result, current waveform data representing a predetermined current waveform as a whole is output from the current waveform data output means. Is done. Then, when the counting means repeats the operation of counting up and resetting the counting pulse signal to a predetermined value, current waveform data representing a predetermined current waveform as a whole is repeatedly output. The rest is the same as above.
[0016]
When the counting means counts up and resets, a trigger signal is output from the counting means to the pulse generating means, and a pulse signal for phase control is output from the pulse generating means to the signal synchronizing means. At the same time, the first address value signal is output from the counting means, and the first current waveform data is output from the current waveform data output means. Therefore, the phase of the series of current waveform data output from the current waveform data output means, that is, the phase of the armature current is synchronized with the reset of the count means, that is, the start end of the trigger signal. On the other hand, the signal synchronization means synchronizes the start of the output signal of the rotational position sensor and the end of the pulse signal for phase control, so that the phase of the output signal of the rotational position sensor is phase controlled with respect to the phase of the armature current. This is delayed by the width of the pulse signal for use. That is, the phase of the armature current advances by the width of the phase control pulse signal with respect to the phase of the output signal of the rotational position sensor.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
FIG. 1 schematically shows the overall configuration of a brushless DC motor. This electric motor is applied to, for example, a power storage flywheel device using a control type magnetic bearing. In this type of flywheel device, a rotor supported in a non-contact manner by a magnetic bearing in a vacuum in a casing is rotated at high speed by a built-in brushless DC motor.
[0019]
The electric motor includes an electric motor main body (1) and a control unit (2).
[0020]
The motor body (1) has the same configuration as that of a normal brushless DC motor, but only the rotor (3) on the rotor side and the armature (4) on the stator side are shown in FIG. It is shown. The armature (4) is provided with three-phase armature windings (5a) (5b) (5c). The windings are generically designated by reference numeral (5).
[0021]
The control unit (2) includes a rotational position sensor (6), an armature current control device (7) constituting armature current control means, and a drive device (8) constituting drive means. FIG. 3 shows an example of a signal of a required portion of the armature current control device (7).
[0022]
The rotational position sensor (6) detects the rotational position of the rotor (3). As shown by a signal A in FIG. 3, the motor body (1) is rotated while the rotor (3) rotates once. One or more pulses proportional to the number of poles are generated. The rotational position sensor (6) also serves as a sensor that detects the rotational speed of the rotor (3).
[0023]
The armature current control device (7) controls the armature current value based on the output signal (pulse signal) of the rotational position sensor (6) corresponding to the position of the rotor (3). A phase control device (9), a subtracter (11), an amplifier (12), and a multiplying DA converter (13) are provided. The phase control device (9) is for advancing the phase of the armature current with respect to the output signal A of the rotational position sensor (6), and is a current waveform data output device (10) constituting current waveform data output means. And an address value control device (22) constituting address value control means.
[0024]
The current waveform data output device (10) is provided with a PROM (23) that constitutes a storage means, and in a series of addresses of the PROM (23), a constant signal E (current value signal) as shown in FIG. Current waveform data representing a current waveform (in this example, a sine waveform) is stored. The PROM (23) stores current waveform data for three phases of the armature (4). The current waveform data output device (10) is stored in the address of the PROM (23) corresponding to the address value when an address value signal is output from the address value control device (22), as will be described later. The phase current waveform data is output to the DA converter (13).
[0025]
The address value control device (22) includes a PLL circuit (14) constituting a signal synchronizing means, a counter (15) constituting a counting means, and a monostable multivibrator (16) constituting a pulse generating means.
[0026]
The multivibrator (16) outputs a phase control pulse signal B having a predetermined width when a trigger signal C described later is input.
[0027]
The output signal A of the rotational position sensor (6) and the pulse signal B from the multivibrator (16) are input to the PLL circuit (14). The PLL circuit (14) synchronizes the start (rising) of the signal A and the end (rising) of the signal B, and generates a counting pulse signal having a frequency higher than the frequency of the signal A by the division ratio of the counter (15). Output to the counter (15).
[0028]
The counter (15) repeats the operation of counting and resetting the counting pulse signal from the PLL circuit (14) to a predetermined value, and the current value is output as an address value signal D each time counting is performed (23 ) And a trigger signal C is output to the multivibrator 16 when reset.
[0029]
The output signal of the rotational position sensor (6) is converted into an analog rotational speed signal by appropriate means such as a monostable multivibrator (not shown). In the subtractor (11), the difference between this rotational speed signal and a preset speed set value is calculated, and the output of the subtracter (11) is converted into a DA converter (13 as a speed difference signal via the amplifier (12). ).
[0030]
The DA converter (13) converts the current waveform data for three phases from the current waveform data device (10) into an analog value each time and converts the result into a speed difference signal from the amplifier (12). Is output to the drive device (8) as a current value signal E for three phases.
[0031]
The drive device (8) includes three subtractors (17a) (17b) (17c) corresponding to the three-phase armature windings (5), a PWM control circuit (18) constituting the PWM control unit, and an inverter unit. (19) is provided. The subtractor is generically designated by reference numeral (17). The current value signal E for three phases from the DA converter (13) of the armature current control device (7) is input to the corresponding subtracter (17). Each armature winding (5) is provided with current detectors (20a), (20b) and (20c), and these voltage outputs are respectively input to the corresponding subtracters (17). The current detector is generically designated by reference numeral (20). Also, between the inverter section (19) and each armature winding (5), a current smoothing coil (inductor) (21a) (21b) (21c) having a larger inductance than the armature winding (5). Is provided. A coil is named generically by the code | symbol (21). The PWM control circuit (18) outputs a PWM control signal of a corresponding phase to the inverter unit (19) based on the output of each subtracter (17). The inverter unit (19) supplies an armature current to the armature winding (5) of each phase based on the PWM control signal. The PWM control circuit (18) and the inverter unit (19) can adopt a known appropriate configuration.
[0032]
In the armature current control device (7), the counter (15) uses the count value as the address value signal D each time the count pulse signal from the PLL circuit (14) is counted, and the current waveform data output device (10). The address value signal D corresponding to a series of addresses of the PROM (23) is output from the counter (15) to the current waveform data until the counter (15) is reset and counted up to a predetermined value. Output to the device (10). When the address value signal D is output from the counter (15), the current waveform data is read from the address of the PROM (23) corresponding to the address value signal D in the current waveform data output device (10). It is output to the DA converter (13). By sequentially outputting an address value signal corresponding to a series of addresses of the PROM (23) from the counter (15), the current waveform data stored in the series of addresses of the PROM (23) is repeatedly outputted. As a result, the current waveform data representing a constant current waveform like the signal E in FIG. 3 as a whole is repeatedly output to the DA converter (13). The current waveform data output from the current waveform data output device (10) is converted by the DA converter (13) into an analog current value signal E proportional to the speed difference signal from the amplifier (12). E is supplied to the driving device (8) as an armature current value.
[0033]
Each phase between the inverter section (19) and the armature (4) is provided with a coil (21) having a larger inductance than the armature winding (5), reducing the ripple component of the armature current. Thus, the smoothness of the rotation of the rotor (3) is improved, and the heat generation of the rotor is reduced. However, since there is a coil (21) having a large inductance in each phase between the inverter (19) and the armature (4) in this way, the armature current phase is delayed as it is, and high-speed rotation becomes difficult. However, in the above-described electric motor, the phase control device (9) advances the phase of the armature current with respect to the output signal of the rotational position sensor (6), as will be described below. Can be prevented and high-speed rotation becomes possible.
[0034]
The operation of the phase control device (9) when the multivibrator (16) is not provided in the address value control device (22) is as follows (see FIG. 2).
[0035]
When the counter (15) counts up and resets, the trigger signal C is output from the counter (15), and if the multi-vibrator (16) is not provided in the address value control device (22), the trigger signal C is changed to PLL. Input directly to circuit (14). At the same time as the trigger signal C is output from the counter (15), the address value signal D corresponding to the first address of the PROM (23) is output from the counter (15), and the current waveform data output device (10). First current waveform data is output. Therefore, the phase of the series of current waveform data output from the current waveform data output device (10), that is, the phase of the current value signal E is synchronized with the reset of the counter (15), that is, the start of the trigger signal C. On the other hand, in the PLL circuit (14), since the start end of the output signal A of the rotational position sensor (6) and the start end of the trigger signal C are synchronized, the phase of the current value signal E, that is, the phase of the armature current is determined by the rotational position sensor. Of the output signal A.
[0036]
On the other hand, the operation of the phase control device (9) in FIG. 1 is as follows (see FIG. 3).
[0037]
When the counter (15) counts up and resets, the trigger signal C is output from the counter (15) to the multivibrator (16), and the phase control pulse signal B is output from the multivibrator (16) to the PLL circuit (14). Is done. At the same time, the address value signal D corresponding to the first address of the PROM (23) is output from the counter (15), and the first current waveform data is output from the current waveform data output device (10). Therefore, the phase of the series of current waveform data output from the current waveform data output device (10), that is, the phase of the current value signal E is synchronized with the reset of the counter (15), that is, the start of the trigger signal C. On the other hand, in the PLL circuit (14), since the start of the output signal A of the rotational position sensor (6) and the end of the phase control pulse signal B are synchronized, the phase of the output signal A of the rotational position sensor (6) is The phase of the current value signal E is delayed by the width (a) of the phase control pulse signal B. That is, the phase of the current value signal E, that is, the phase of the armature current advances by the width (a) of the phase control pulse signal B with respect to the phase of the output signal A of the rotational position sensor (6). . This phase advance (a) is determined so as to be optimum in consideration of the characteristics of the motor, etc. If the period of the armature current is 360 degrees, it is, for example, 15 degrees or less.
[0038]
The configuration of the brushless DC motor, the configuration of the armature current control device (7), the drive device (8), and the like are not limited to those of the above-described embodiment, and can be changed as appropriate.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a brushless DC motor showing an embodiment of the present invention.
FIG. 2 is a time chart showing signals of respective parts of the address value control device when a monostable multivibrator is not provided in the address value control device of the phase control device;
FIG. 3 is a time chart showing signals of respective parts of the address value control device of the phase control device in the embodiment of FIG. 1;
[Explanation of symbols]
(3) Rotor
(4) Armature
(6) Rotation position sensor
(7) Armature current control device (armature current control means)
(8) Drive device (drive means)
(9) Phase control device (phase control means)
(10) Current waveform data output device (current waveform data output means)
(14) PLL circuit (signal synchronization means)
(15) Counter (counting means)
(16) Monostable multivibrator (pulse generation means)
(18) PWM control circuit (PWM controller)
(19) Inverter section
(21a) (21b) (21c) Current smoothing coil
(22) Address control device (address control means)
(23) PROM (storage means)

Claims (1)

Armature current control means for controlling the current value supplied to the armature based on the output signal of the rotational position sensor for detecting the rotational position of the rotor, and a PWM control section and an inverter section, and based on the current value Drive means for supplying an armature current to the armature is provided, and a current smoothing coil having a larger inductance than that of the armature is provided in each phase between the inverter unit and the armature. A brushless DC motor provided with phase control means for advancing the phase of the armature current with respect to the output signal of the rotational position sensor in the current control means ,
The phase control means sequentially repeats a current waveform data output means having storage means in which current waveform data representing a predetermined current waveform as a whole is stored in a series of addresses, and an address value signal corresponding to the series of addresses. Address value control means for outputting to the current waveform data output means is provided, and the current waveform data output means has current waveform data at the address of the storage means corresponding to the address value signal output from the address value control means. Wherein the address value control means outputs a pulse signal for phase control with a predetermined width in response to an external trigger signal, the starting end of the output signal of the rotational position sensor and the phase control pulse. Synchronize the end of the signal and count pulse signal with higher frequency than the output signal of the rotational position sensor. The signal synchronizing means for outputting the signal and the operation of counting and resetting the counting pulse signal up to a predetermined value are repeatedly outputted to the current waveform data output means and reset as the address value signal every time counting is performed. Includes a counting means for outputting a trigger signal to the pulse generating means, and addresses so that the phase of the current waveform represented by the current waveform data output from the current waveform data output means advances relative to the output signal of the rotational position sensor. A brushless DC motor characterized in that it outputs a value signal .

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