JP2792122B2 - Drive device for variable reluctance motor - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to a variable reluctance motor driving apparatus which appropriately excites a multi-phase excitation winding of a variable reluctance motor according to a rotation angle of a rotor thereof. More particularly, the present invention relates to a variable reluctance motor drive device that modulates an exciting current flowing in an exciting winding to control a torque generated in a rotor to a predetermined value.

(Prior art) Conventionally, as a driving device of a variable reluctance motor,
The following technologies are known.

In order to drive the variable reluctance motor, the excitation windings of each phase are sequentially excited for an excitation period corresponding to the rotation angle of the rotor. Further, in order to control the output torque to a predetermined value, it is necessary to perform a so-called current pattern control for controlling the excitation current flowing through the excitation winding to a predetermined pattern during the excitation period. Therefore, conventionally, FIG.
Excitation winding of each phase of variable reluctance motor as shown in
Transistors Tr1 and Tr as switching elements at both ends of SL
2, and a switching signal obtained by PWM-controlling a desired current pattern as shown in FIG. 4 (B) is input thereto. Also, in FIG. 1A, each transistor Tr1, Tr
Diodes D1 and D2 connected in parallel to 2 and the excitation winding SL
When both of the transistors Tr1 and Tr2 are turned off by the switching signal, the electromagnetic energy stored in the exciting winding SL is regenerated to the smoothing capacitor CC of the power supply.

With the drive device for the variable reluctance motor, the effective value of the exciting current passed through the exciting winding SL of the variable reluctance motor approximates the target current pattern, and the output torque can be controlled.

(Problems to be Solved by the Invention) The following problems have not been solved in the conventional drive device. As described above, in the conventional driving device, in order to match the effective value of the exciting current to the target current pattern, the PWM of the exciting current is used.
Controls are employed. However, the control accuracy of the exciting current by the PWM control is extremely low, so that the output torque cannot be freely controlled.

In order for the effective value of the exciting current flowing through the exciting winding SL to completely match the target current pattern, the waveform of the exciting current flowing through the exciting winding SL is shown in FIG.
It is desirable that the pulse sequence coincides with the pulse train shown as the base signal of Tr2. That is, the rise time and the fall time of the exciting current flowing through the exciting winding SL are short, and it is necessary to instantaneously follow the ON / OFF control of the transistors Tr1 and Tr2.

However, the waveform of the current actually flowing through the exciting winding SL has a relatively smooth rising and falling characteristic as shown in the figure, and therefore differs from the target current pattern waveform. In particular, the fall characteristic of the exciting current is poor, and the exciting current continues to flow for a relatively long time even after the end of the exciting period. This is because the regenerative circuit shown by the dotted line in FIG. 4A formed at the time of regeneration of the electromagnetic energy at which the exciting current falls has a large time constant T. That is, the time constant T of the regenerative circuit is expressed by the following equation.

Here, Lm is the inductance of the exciting winding SL, and Rm is the electric resistance of the exciting winding SL. This resistance value Rm is a very small value, and therefore, the time constant T becomes a large value.

In addition, such a failure of the fall characteristic of the exciting current is as follows.
In the case of high load or high-speed rotation through a large exciting current, this has a more remarkable adverse effect, and depending on the configuration of the variable reluctance motor, a braking torque is generated due to the exciting current that continues to flow after the end of the exciting period, thereby reducing the electro-mechanical conversion efficiency. It induces various problems such as greatly lowering it.

The present invention has been made in order to solve the above-mentioned problems that have not been solved in the drive device of the variable reluctance motor, and has greatly improved the controllability of the exciting current flowing to the exciting winding, thereby reducing the output torque to a desired value. It is an object of the present invention to provide an excellent variable reluctance motor drive device that can be controlled to a value and can increase the electro-mechanical conversion efficiency of the variable reluctance motor.

Configuration of the Invention (Means for Solving the Problems) In order to solve the above problems, the means of the present invention is provided at both ends of an exciting winding of a variable reluctance motor,
A switching element that cuts off connection between the excitation winding and a power supply based on a switching signal, or permits excitation by energization in only one direction, a switching element provided at both ends of the excitation winding, one of the excitation windings, A first diode that is connected in parallel to the first switching element and forms a parallel circuit that allows conduction in the direction opposite to the conduction direction of the one switching element; and the other of the switching elements provided at both ends of the excitation winding and the excitation winding. A second diode that is connected in parallel with the second switching element and forms a parallel circuit that allows conduction in the direction opposite to the conduction direction of the other switching element. An excitation timing control circuit that adjusts a current to set a predetermined value to a rotational torque generated in the variable reluctance motor. In the drive device for a reactance motor, a resistor having a value corresponding to a withstand voltage of each switching element is connected in series to a parallel circuit formed by the first diode and a parallel circuit formed by the second diode. The gist of the present invention is a variable reluctance motor driving device.

(Operation) A drive device for a variable reluctance motor according to the present invention includes a parallel circuit formed by a first diode and a second diode provided to constitute a regenerative circuit that regenerates electromagnetic energy accumulated in an exciting winding. In the parallel circuit formed by
Each is configured by connecting resistors in series. Accordingly, the time constant T of the regenerative circuit is reduced and improved according to the sum of the resistance values of the resistors.

For this reason, the fall characteristic of the exciting current becomes good, and the followability to the ON / OFF control of the switching element is improved.

Further, the resistance value of the resistor connected in series to each of the parallel circuits is selected to a value corresponding to the withstand voltage of the switching element. Therefore, the durability of the switching element is not reduced, and the reliability as a driving device is secured as in the related art.

However, since the time constant T of the regenerative circuit is determined based on the sum of the resistance values of the resistors, even if each resistance value is suppressed according to the withstand voltage of the switching element, it can be made sufficiently small, and the rise of the exciting current can be reduced. There is no deterioration of the falling characteristics.

Hereinafter, the present invention will be described more specifically with reference to examples.

(Embodiment) FIG. 1 is a block diagram showing a circuit configuration of a driving device of a variable reluctance motor 10 according to an embodiment. For simplicity, the control system shown in the figure shows only a part that controls the excitation current of the one-phase excitation winding 12, and the control system describes only the current feedback loop, and other position and velocity feedback The loop is omitted. So in practice,
The control system shown in FIG. 1 with a position and speed feedback loop added is provided by the number corresponding to the number of phases of the exciting windings of the variable reluctance motor 10.

As shown, transistors 14 and 16 are connected as switching elements between both ends of the exciting winding 12 of the variable reluctance motor 10 and the power supply. Further, a parallel circuit in parallel with the excitation winding 12 and the transistor 14 includes:
It is constituted by a series connection of a diode 18 and a resistor 19 having a resistance value R1 described later. Similarly, a parallel circuit of the exciting winding 12 and the transistor 16 is configured by connecting a diode 20 and a resistor 21 having a resistance value R2 described later in series. The current supplied to the exciting winding 12 is controlled by the transistors 14, 16 and the diodes 18, 20 and the resistors 19, 21.However, in order to detect what kind of exciting current is actually flowing, the transistor 14 A current detection coil 22 is attached to a connection line between the motor and the exciting winding 12. Further, in order to detect how the variable reluctance motor 10 is actually rotated by such an exciting current, the output shaft of the variable reluctance motor 10 has an encoder 24 for detecting a rotation direction and a rotation angle, and a rotor. And a pole pulse sensor 26 for detecting a phase relationship between the stator and the stator.

In order to control the conduction state of the transistors 14 and 16 at a predetermined timing, the base of each transistor is connected to the transistor drive circuits 30 and 32. Here, when a timing signal described later is input to the transistor drive circuits 30 and 32, the transistor 1
It generates a base signal that makes the 4 and 16 conductive, and is composed of a TTL circuit or the like.

In the present embodiment, the following circuit is used as a circuit for generating the timing signal.

First, the current pattern generation circuit 40 receives the torque command T and the positive and negative signals TS of the torque from a speed control system (not shown), and the current rotation state of the variable reluctance motor 10 is controlled by the encoder 24 and the pole pulse sensor 26. Detect from output signal. Then, based on the information, a current pattern (see FIG. 2 (A)) required to generate a target torque with a phase suitable for the angular position of the rotor is determined, and a predetermined rotation of the rotor is determined. The current pattern signal is output in synchronization with the angle.

In order to pass the exciting current conforming to the current pattern to the exciting winding 12, it is necessary to perform PWM control on the connection between the voltage source having the constant voltage Vp and the exciting winding 12. Therefore, the current pattern signal output from the current pattern generation circuit 40 is PW
Input to the M circuit 42. At this time, in order to improve the control accuracy of the excitation current, the current pattern signal and the current detection coil 22 are used.
, And compares the result with the proportional / integral controller (Pl
After the responsiveness is improved through the controller 44, the signal is input to the intended PWM circuit 42. With this PWM circuit 42,
As is known from FIG. 2 (A), a comparison is made between the target current pattern of the excitation current and the triangular wave carrier for PWM. Based on the comparison result, the conduction as the final target as shown in FIG. 2 (B) is performed. A timing signal is obtained. The conduction timing signal created in this way is the transistor described above.
The signals are input to the transistor drive circuits 30 and 32 for the 14 and 16 and the target excitation current PWM control is achieved.

According to the variable reluctance motor driving device of the present embodiment configured as described above, the following exciting current flows during the exciting period of the exciting winding 12, the control accuracy of the PWM control is improved, and the variable reluctance motor is 10 output torque can be adjusted arbitrarily.

An exciting current and a regenerative current as shown in FIG. 3 flow through the exciting winding 12 by the driving device of the variable reluctance motor of this embodiment. During the period in which the conduction timing signal is output and the transistors 14 and 16 are in the conduction state, a closed circuit of “power supply → transistor 14 → exciting winding 12 → transistor 16 → ground” is formed and is shown by a dashed line in FIG. An exciting current flows, and the exciting winding 12 enters an exciting mode, in which magnetic energy is stored.

Also, based on the conduction timing signal, the transistors 14,1
During the period when 6 is OFF, “Ground → Resistor 21 → Diode
A closed circuit of 20 → excitation winding 12 → diode 18 → resistor 19 → power supply is formed, and a regenerative current shown by a dotted line in FIG. 3 flows. That is, during this period, the electromagnetic energy stored in the excitation winding 12 is regenerated to the power supply side. Then, the regenerative current decreases while being converted into thermal energy by the diodes 18 and 20 which are the resistance components of the regenerative circuit, the internal resistance of the power supply, and the resistors 19 and 21. The following equation is visually obtained from the circuit diagram of FIG. 3 as the time constant Tc of this regenerative circuit.

As is clear from the right side, the resistance of the regenerative circuit is
With the addition of the resistors 19 and 21, the time constant Tc becomes smaller than the conventional time constant T, and the fall characteristic of the exciting current is improved. Therefore, if the exciting current flowing through the exciting winding 12 by the drive circuit of FIG.
The waveform is as shown in FIG. 2 (C), and at a glance it can be understood that it is closer to the target current pattern than the conventional excitation current waveform (FIG. 4 (B)).

As described above, since the falling characteristics of the exciting current are improved by the resistors 19 and 21, the resistance values R1 and R2 are desirably large. However, on the other hand, during this regeneration mode, the transistor 14 has a voltage VR (= Vp + Vr) equal to the sum of the power supply voltage Vp applied to the excitation winding 12 and the voltage drop Vr due to the resistance of the diode 18 and the resistor 19.
Is applied, and the voltage VR increases with an increase in the resistance value R1 of the resistor 19. Therefore, the upper limit of the resistance value R1 of the resistor 19 is determined by the breakdown voltage characteristics of the transistor 16.
Similarly, the upper limit of the resistor 21 is determined by the withstand voltage characteristics of the transistor 14.

In the variable reluctance motor driving apparatus according to the above-described embodiment, the distortion characteristic of the excitation current waveform is felt to increase as shown in FIG. 2 (C) by improving the fall characteristic of the excitation current. This is because the drawing is performed by lowering the frequency f of the triangular wave carrier in the PWM control for the sake of explanation. By increasing this frequency f, the excitation current has a less distorted waveform and further approaches the target current pattern. It is.

According to the variable reluctance motor driving device of the present embodiment configured as described above, the waveform of the current flowing through the exciting winding 12 exhibits a characteristic very similar to the target current pattern. Therefore, the output torque of variable reluctance motor 10 can be completely controlled to a desired value. In addition, since unnecessary excitation is not performed after the elapse of the excitation period, unexpected braking torque is not generated, and the electro-mechanical conversion efficiency of the variable reluctance motor can be increased.

Also, the time constant Tc is the combined resistance value of the resistors 19 and 21 (R1 + R
Although improved according to 2), the reverse voltage of each of the transistors 14 and 16 remains a small increase based only on the resistance R1 or R2 of each of the resistors 19 and 21. Therefore, an element having a relatively low reverse breakdown voltage and a high switching speed, for example, a power MOS-FET, can be used as the transistors 14 and 16, and the frequency f of the triangular wave carrier of the PWM control can be easily increased.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment at all, and may be embodied in various forms without departing from the gist thereof.

As described above in detail with reference to the embodiments, the variable reluctance motor driving device according to the present invention includes a switching circuit including a regenerative circuit formed by a first diode formed by a first diode and a parallel circuit formed by a second diode. In this configuration, resistors having values corresponding to the withstand voltages of the elements are connected in series.

In this case, the time constant of the regenerative circuit decreases according to the sum of the resistance values of these resistors. For this reason, despite the fact that the resistance value is limited by the withstand voltage of the switching element,
The time constant can be reduced.

Therefore, the fall characteristic of the exciting current flowing through the exciting winding is improved, and the control accuracy of the current pattern control is improved.
Thus, the output torque can be easily adjusted to a desired value. Further, since the unnecessary exciting current does not continue after the end of the exciting period, there is also an effect of increasing the electromechanical conversion efficiency of the variable reluctance motor.

[Brief description of the drawings]

FIG. 1 is an electric circuit block diagram of a driving device for a variable reluctance motor according to an embodiment of the present invention.
(B) and (C) are current waveforms of various parts in the embodiment, FIG. 3 is a view for explaining a mode of a current flowing through an exciting winding in the embodiment, and FIGS. FIG. 2 is an explanatory diagram of an electric circuit of a reluctance motor driving device and a current waveform of each part. 10 Variable reluctance motor, 12 Excitation winding 14, 16 Transistor 18, 20 Diode, 19, 21 Resistor 22 Current detection coil 24 Encoder 26 Polar pulse sensor 30, 32 transistor drive circuit 40 current pattern generator circuit 42 PWM circuit 44 proportional / integral controller

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-191300 (JP, A) JP-A-62-272851 (JP, A) Japanese Translation of PCT International Publication No. 3-501320 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H02P 7/05 H02P 5/05 H02P 8/00-8/42

Claims (1)

(57) [Claims] A switching element provided at both ends of an exciting winding of a variable reluctance motor, for disconnecting a connection between the exciting winding and a power supply based on a switching signal, or permitting excitation by energization in only one direction; A first diode that is connected in parallel to one of the switching elements provided at both ends of the excitation winding and the excitation winding and forms a parallel circuit that allows conduction of the one switching element in a direction opposite to the conduction direction; A second diode that is connected in parallel to the other of the switching elements provided at both ends of the excitation winding and the excitation winding, and forms a parallel circuit that allows conduction in the direction opposite to the conduction direction of the other switching element; A rotating torque generated in the variable reluctance motor by controlling an operation of the switching element to adjust an exciting current flowing through the exciting winding; The drive device for a variable reluctance motor having a excitation timing control circuit for a click with a predetermined value, a parallel circuit formed of the first diode and the second
A resistor having a value corresponding to the withstand voltage of each switching element is connected in series to a parallel circuit formed by the diode.