JPH05207783A - Driver for variable reluctance motor - Google Patents

Abstract

PURPOSE:To provide a driver for variable reluctance motor having simple constitution in which steep rising/falling of current can be realized even if the voltage to be applied on a phase winding is boosted over power supply voltage. CONSTITUTION:When the conduction of a phase winding La is started, a PNP transistor TR1a and an NPN transistor TR2a are simultaneously turned ON. Power is fed from a regenerative capacitor 7 (application of high voltage VH) so long as the voltage Vc of the regenerative capacitor 7 is higher than the voltage Vd of a DC power supply circuit 3 and then the transistor TR1a is turned OFF to switch power supply from the regenerative capacitor 7 to the DC power supply 3 (application of power supply voltage Vd) thus rising the phase winding current Ia steeply. Alternatively, the transistor TR1a is turned OFF while the transistor TR2a is turned ON (application of power supply voltage Vd) when conduction is started and the transistor TR1a is subsequently turned ON when the inductance begins to increase and the exciting current level begins to drop (application of high voltage VH) thus suppressing decrease of phase winding current Ia.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for a variable reluctance motor.

[0002]

2. Description of the Related Art A variable reluctance motor (hereinafter referred to as an SR motor) has an advantage that a large torque can be obtained because a stator and a rotor are made of iron and a magnetic flux density can be increased. On the other hand, since the inductance of the phase winding is large and it is difficult to rapidly increase or decrease the exciting current, it is often used as a motor for medium to low speed rotation rather than being used for high speed rotation. For example, it is used as a drive motor for electric vehicles.

In a variable reluctance motor having such characteristics, a DC power supply 1 is conventionally used as shown in FIG. 6, for example.
The drive device 100 is mainly configured by energization control circuits 110a, 110b, 110c for controlling the energization from 02 to the phase windings La, Lb, Lc. In the drive device 100 of this type, the rotor is continuously rotated by energizing the phase windings La to Lc in a predetermined circulation order to excite the magnetic poles (not shown) of the stator. For example, the two transistors 112a, 114a, 112b, ...
114b, 112c, 114c are simultaneously turned on-of
When F is set, the driving device 100 rotationally drives the SR motor. Further, diodes 116a, 118a, 116b, 118b, 116c connected to both ends of each of the phase windings La to Lc and the positive and negative electrodes of the capacitor 104, respectively.
118c forms a regenerative circuit. That is, the respective transistors 112a, 114a, 112b, 114
When b, 112c and 114c are turned off, the magnetic energy accumulated in the excited phase windings La to Lc is
The power loss is reduced by being regenerated as electric charge in the capacitor 104 and supplying the regenerated electric charge to the phase windings La to Lc to be subsequently energized.

[0004]

By the way, since the SR motor is made of iron, it has a characteristic that the inductance of the phase windings La to Lc is large, and the rise and fall of the phase winding current when energized is slow. become. In particular, it becomes slow at high speed rotation. As is clear from the following equation, S
When the rotation speed of the R motor is increased, the phase windings La to Lc
This is because the induced electromotive force generated in the power source becomes large and the induced electromotive force is generated in the opposite polarity to the power supply voltage during the period when the inductance increases.

E = -I × dH / dθ × ω e is the induced electromotive force, I is the instantaneous value of the phase winding current, H is the inductance of the phase winding, θ is the rotation angle of the rotor, and ω is the angular velocity. Therefore, the voltage applied to the phase windings La to Lc becomes lower than the power supply voltage, and the rising and falling of the phase winding current becomes slower. For example, in the case of high speed rotation as compared with medium and low speed rotation, the rising and falling edges thereof are delayed and the rising limit of the phase winding current is lowered. Further, at high speed rotation, the energization period becomes short, and the phase winding current does not flow sufficiently.

Therefore, the S by the conventional drive unit 100 is
In the operation of the R motor, the generated torque becomes smaller as the number of rotations increases, and there is a problem that the load cannot be increased at high speed operation. So, from the past, DC power supply 1
By increasing the output voltage of 02, the rise and fall of the phase winding current is made steep to improve the high-speed rotation characteristics of the SR motor. However, when the DC power supply voltage is set to a high voltage, an element or the like having a large withstand voltage is required, and there is a problem that the manufacturing cost thereof becomes high, so that it cannot be easily adopted.

Alternatively, when it is difficult to increase the voltage to a high voltage because the DC power source is a battery and there are restrictions on the loading size and weight, as in an electric vehicle, the number of turns of the phase windings La to Lc is reduced to reduce the inductance. It is also considered to make the rise and fall of the current steep by making it small. However, in this case, a larger current is required to generate the same amount of torque, and the power-torque conversion efficiency deteriorates, and there is a limit to the current capacity of the switching element, and the energization amount must be increased. There is also a problem that the high speed rotation characteristics cannot be improved because there is a limit.

In view of the above, according to the present invention, the voltage applied to the phase winding is boosted above the DC power supply voltage by a simple structure without increasing the DC power supply voltage and reducing the number of turns of the phase winding, and the current rises. The object of the present invention is to provide a drive device of a variable reluctance motor that can make the fall steep.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a direct current power supply and energization control means for supplying power from the direct current power supply to each phase winding of a variable reluctance motor in a predetermined circulation order. A storage means for storing electric charge; a power regenerating means for regenerating the magnetic energy stored in the phase winding from the phase winding, which has been de-energized by the energization control means, into the storage means as a charge; A variable reluctance motor, comprising: selecting means for selecting one of the means and power supply switching means for supplying power to the energization control means from one of the DC power supply and the power storage means based on the selection result of the selecting means. On the device.

[0010]

According to the apparatus of the present invention constructed as described above, the energization control means is supplied with power from the DC power source to energize the respective phase windings of the variable reluctance motor in a predetermined circulation order. When the energization is cut off, the electric power regeneration means regenerates the magnetic energy accumulated in the phase winding as electric charges in the electricity storage means. Therefore, the voltage of the power storage means rises. At that time, the selecting means selects either one of the DC power source and the power storage means. For example, when the voltage of the power storage means exceeds the voltage of the DC power supply, the power storage means is selected, and when the voltage of the DC power supply is lower, the DC power supply is selected. Then, the power supply switching means supplies power to the energization control means from one of the DC power supply and the power storage means based on the selection result of the selection means. For example, while the voltage of the power storage means exceeds the voltage of the DC power supply, the power supply switching means supplies power from the power storage means to the energization control means instead of the DC power supply.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 is an electric circuit diagram showing a drive device of a variable reluctance motor to which the present invention is applied, and FIG. 2 is an explanatory diagram showing a structure of the variable reluctance motor.

As shown in the figure, a drive device 1 of a variable reluctance motor (hereinafter referred to as an SR motor) having a three-phase configuration (A phase, B phase and C phase) comprises a DC power supply circuit 3 and a DC power supply circuit 3. Each phase winding La, Lb, L of the SR motor SRM
energization control circuits 5a, 5b, 5c for controlling energization to c
, A regenerative capacitor 7 for storing regenerative charges from the phase windings La to Lc, a voltage dividing resistor circuit 9 for detecting the voltage of the regenerative capacitor 7, and a current flowing through the phase windings La to Lc. The current detection resistor 11 for this purpose is configured as a main part.

The DC power supply circuit 3 is composed of a battery 3a and a smoothing capacitor 3b for removing a pulsating component and stabilizing an output voltage (hereinafter referred to as power supply voltage) Vd. A well-known rectifier circuit that generates direct current from alternating current may be used as the direct current power supply circuit 3. The energization control circuits 5a to 5c include PNP transistors TR1a, TR1b and TR1c provided on the positive side of the phase windings La to Lc, NPN transistors TR2a, TR2b and TR2c also provided on the negative side, and the phase winding La. ~ Lc commutation diodes Da1, Db1, Dc1 provided in series between the negative electrode side and the regenerative capacitor (positive electrode) 7.
And the backflow prevention diodes Da2, Db2, Dc2 provided in series between the power bus DCBus (+) from the DC power supply circuit 3 and the phase windings La to Lc (positive side).

The respective commutation diodes Da1 to Dc1 are NP
When the N-transistors TR2a to TR2c and the PNP transistors TR1a to TR1c are turned off, the magnetic energy accumulated in the phase windings La to Lc is used as an electric charge to charge and discharge the line P.
The circuit is configured to regenerate the regeneration capacitor 7 via L.

The energization timing by the energization control circuits 5a-5c is determined by the NPN transistors TR2a-TR2c or PNP.
A switching pulse P for each phase generated on the basis of the transistors TR1a to TR1c on the basis of a detection signal from a magnetic pole sensor (both not shown) in the drive signal generation circuit.
It is determined by inputting a, Pb, and Pc.

The energization control circuits 5a and 5b correspond to energization control means, the regenerative capacitor 7 corresponds to a storage means, and the commutation diodes Da1 to Dc1 correspond to power regenerating means. The detection signal Idet from the current detection resistor 11 is the SR motor SR.
Although it is used for torque control in a control system (not shown) of M, it is not an essential part of the present invention, and therefore its explanation is omitted.

The SR motor SRM is a well-known three-phase motor having a stator S having a 6-pole structure and a rotor R having a 4-salient pole structure, and the stator poles Pa1 and Pa2 form opposite poles A.
The stator magnetic poles Pb1 and Pb2 form opposite phases to form a B phase, and the stator magnetic poles Pc1 and Pc2 form opposite phases to form a C phase. The salient rotor pole is the stator pole Pa1 · P
In the section approaching a2 to Pc1 and Pc2, the phase windings La to Lc
When the rotor salient pole faces the stator magnetic poles Pa1, Pa2 to Pc1, Pc2, the inductance becomes maximum. On the other hand, the salient rotor pole is the stator pole Pa1.
In the section away from Pc2 to Pc2, the inductance of the phase windings La to Lc decreases, and when the rotor salient pole is at the center position of the mechanical angle (60 degrees) of the SR motor (the center of two adjacent magnetic poles). The inductance of the phase windings La to Lc becomes the minimum.

The drive device 1 drives the SR motor SRM having such a configuration. That is, when the switch SW is turned on and the power is turned on, the regenerative capacitor 7 is charged and boosted to the power supply voltage Vd, and then the switching pulses Pa to Pc are input, the A phase → B phase → The SR motor SRM is driven by exciting the phase in the period in which the inductance increases with time in the circulation sequence of the C phase → A phase.

As shown in FIG. 3, a positive torque is generated by shifting the energization timing of each phase by an electrical angle of 2π / 3 to drive the SR motor SRM in the normal direction. For example, when the electrical angle is 0, energization is started and stopped near the electrical angle of 2π / 3, and a positive current is generated during the energization period, and during the period when the inductance decreases from the maximum, the winding current Ia,
The energization period is adjusted so that Ib and Ic hardly flow and negative torque is not generated.

Next, the energization control operation of the drive unit 1 will be described. FIG. 4 is an explanatory diagram of the energization mode. When the drive device 1 is powered on, the drive device 1 operates in a normal mode, a high voltage mode,
The SR motor SRM is driven by operating by selecting one of the three energization modes of the through mode. Although each energization mode will be described by taking the A phase as an example, the operations in the respective energization modes are the same for the B phase and the C phase.

First, in the normal mode, the PNP transistors TR1a to TR1c are kept in an open state of always OFF, and
The NPN transistors TR2a to TR2c are turned on and off (the switching pulse Pa is input) to drive the SR motor SRM. In this mode, since the PNP transistors TR1a to TR1c are in the open state, when the NPN transistor TR2a is turned ON, the DC power supply circuit (positive electrode) 3
→ Power bus DCBus (+) → Reverse current blocking diode Da2 →
Phase winding La → NPN transistor TR2a → Power bus DC
A current Ia flows through the path of Bus (-) → DC power supply circuit (negative electrode) 3 to excite the magnetic poles Pa1 and Pa2. Then N
When the PN transistor TR2a is turned off, the magnetic energy accumulated in the phase winding La of the excited magnetic poles Pa1 and Pa2 is discharged as electric charges in the direction in which the current Ia continues to flow. That is, as shown in the column (A) of FIG. 4, the current Ia flows in the path of the phase winding La → commutation diode Da1 → charge / discharge line PL → regenerative capacitor 7 and becomes the charging current ic to become the regenerative capacitor 7. Is charged and the voltage Vc is boosted. Since the capacity of the regenerative condenser 7 is small, it is charged rapidly,
The voltage VC between the terminals quickly becomes a high voltage VH. Therefore, the current Ia rapidly decreases, the voltage across the phase winding La also rapidly decreases, and falls below the voltage VC of the regenerative capacitor 7. Then, the current tries to flow backward from the regenerative capacitor 7, but is blocked by the commutation diode Da1.
The voltage VC of the regenerative capacitor 7 is maintained at the high voltage VH.

The change amount ΔVc of the capacitor voltage Vc is determined by the magnitude of the magnetic energy accumulated in the phase winding La. Assuming that the capacity of the regenerative capacitor 7 is c, the phase winding current at the moment when the energization is stopped is I, and the magnitude of the inductance of the phase winding La is H, the magnitude of the magnetic energy accumulated in the phase winding La is Is [1/2 × H × (I) ² ], and this magnetic energy is accumulated in the regenerative capacitor 7 as electric charges, so that the following equation holds.

½ × H × (I) ² = 1/2 × c × (ΔVC) ^{2 In the} high voltage mode, the NPN transistors TR2a to TR2c and the PNP transistors TR1a to TR1c are turned on at the same time to turn on the SR motor. Drive the SRM. In this mode, N
While the PN transistor TR2a and the PNP transistor TR1a are both ON, two paths to the phase winding La are formed. That is, DC power supply circuit (positive electrode) 3 → power supply bus DC
Bus (+) → backflow blocking diode Da2 → phase winding La, regenerative capacitor 7 → charge / discharge line PL → PN
A path from the P transistor TR1a to the phase winding La is formed respectively. Regenerative capacitor voltage Vc and power supply voltage Vd
One of them is selected as the power feeding path depending on the level of For example, when the regenerative capacitor voltage Vc is higher than the power supply voltage Vd, the reverse current blocking diode Da2 blocks the power supply from the DC power supply circuit (positive electrode) 3. Therefore, the regenerative capacitor 7 supplies power to the phase winding La. .. When power supply is started, the regenerative capacitor voltage Vc decreases, and when the regenerative capacitor voltage Vc becomes lower than the power source voltage Vd,
The backflow prevention diode Da2 becomes conductive and power is supplied from the power supply voltage Vd.

Since the circuit operation is as described above, one way to execute the high-voltage mode is to execute the high-voltage mode at the start of energization and then to the normal mode in the middle, as shown in column (B) of the figure. Take the switching method. That is, at the start of energization, the PNP transistor TR1a and the NPN transistor T
R2a and R2a are turned on at the same time, and the PNP transistor TR1a is set before the regenerative capacitor voltage Vc falls below the power supply voltage Vd.
Is turned off to switch the applied voltage from the high voltage VH to the power supply voltage Vd. As described above, when the high voltage VH is applied at the beginning of the energization period, that is, while the inductance is small, the rising in the normal mode (shown by a chain line in the figure)
The phase winding current Ia rises sharper than that of (indicated by the solid line in the figure).

As another method of executing the high pressure mode,
As shown in column (C) of the figure, a method of executing the normal mode at the start of energization and switching to the high-voltage mode for a certain period in the middle is adopted. That is, the PNP transistor TR1a is turned off, only the NPN transistor TR2a is turned on, and then the PNP transistor TR1a is turned on and turned off before the regenerative capacitor voltage Vc falls below the power supply voltage Vd, and the power supply voltage Vd → high voltage VH → The power supply voltage Vd and the applied voltage are switched. In this way, when the inductance increases and the current level begins to decrease, the high voltage VH is applied to suppress the decrease in the phase winding current Ia.

As described above, in the high voltage mode, by making the rising of the current steep or by suppressing the sudden decrease of the current level, the amount of electricity supplied during the energization period is increased while controlling the current waveforms respectively. Increase torque. In addition, by adjusting the period TH of the high voltage mode to be short or long and adjusting the execution timing of the high voltage mode, the current I
The waveform of a is controlled to suppress the fluctuation of the output torque, and the SR motor is smoothly driven to rotate.

In the through mode, the regenerative capacitor voltage Vc is increased when the regenerative capacitor voltage Vc greatly increases during driving of the SR motor SRM in the normal mode or the high voltage mode.
This is a mode for preventing overcharging and overvoltage of the. That is, while keeping the NPN transistors TR2a to TR2c in the OFF open state, the PNP transistors TR1a to TR1c are turned ON so that the phase winding current Ia is phase winding La → commutation diode Da1 → PNP transistor TR1a → phase winding La. It continues to flow in the loop and is consumed in output torque and heat generation.
Therefore, no charge is regenerated in the regenerative capacitor 7 and the voltage V
c also does not rise.

For example, the divided voltage V from the voltage dividing resistor circuit 9
DV is proportional to the regenerative capacitor voltage Vc and is input to the control system (not shown) of the SR motor SRM, and when the regenerative capacitor voltage Vc exceeds a predetermined limit voltage, the energization mode or the high voltage mode is passed. Switching to the mode prevents abnormal heat generation and damage due to overvoltage.

SR motor S
The SR motor SRM is selected by the control system according to the rotation speed of the RM and driven. For example, when the medium-low speed rotation is performed, the normal mode is driven, when the high-speed rotation is performed, the high-speed mode is driven, and when the overvoltage is applied, the through mode is driven.

As described above, in the present embodiment, when the regenerative capacitor voltage Vc is higher than the power source voltage Vd, the regenerative capacitor 7 supplies power to the phase windings La to Lc, so that the current flowing through the phase windings La to Lc. The rising edges of Ia to Ic can be made steep. Alternatively, the currents Ia to I
It is possible to suppress a sharp decrease in c. Therefore, sufficient currents Ia to Ic can be supplied even during high-speed rotation to generate a large torque, and high-speed operation can be performed even with a larger load. Further, when the energization is cut off, the magnetic energy is regenerated in the regenerative capacitor 7 as an electric charge, so that the current Ia flowing through the phase winding La rapidly decreases, and the current Ia disappears during the period when the inductance is reduced, so that a negative torque is generated. Can be prevented.

In this way, the output characteristic (rotation speed-torque characteristic) at high speed rotation can be improved. Conventionally, the amount of current is insufficient to generate sufficient torque at the time of high-speed rotation because the current rises slowly, but negative torque is generated because the current Ia remains even during the period when the inductance is reduced. Then, the output characteristic was deteriorated, but this problem is overcome in the present embodiment.

Further, the method of reducing the number of turns of the phase windings La to Lc to make the rising and falling of the phase winding currents Ia to Ic steep is not adopted. Therefore, the output characteristics can be improved without lowering the power-torque conversion efficiency. Further, since the drive device 1 boosts the applied voltage with a simple circuit configuration without using a high-voltage output DC power source, it can be manufactured at low cost without using a high breakdown voltage element.

In addition, the current waveform can be adjusted by arbitrarily selecting the energization mode according to the rotation speed of the SR motor SRM. Therefore, an appropriate torque can be output at the time of rotation at medium and low speeds and at the time of high speed rotation, or torque fluctuations can be suppressed and smooth driving can be performed. That is, the drive state of the SR motor SRM can be optimally adjusted.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is an electric circuit diagram showing a driving device of a three-phase variable reluctance motor. As shown in the figure, the drive device 20 of the present embodiment has a configuration in which an overcurrent prevention circuit is added to the configuration of the first embodiment. That is, the DC power supply circuit 23,
The energization control circuits 25a, 25b, 25c, the regenerative capacitor 27, and the current detection resistor 29 are main components, and a protection circuit 40 for preventing overcharge during braking operation is added.

The protection circuit 40 is a circuit for preventing overcharging and overvoltage of the regenerative capacitor 27, and includes a heat dissipation resistor 42.
, And a normally-closed contact relay 44, which is provided in series between the commutation diodes Da1, Db1, Dc1 and the regenerative capacitor (positive electrode) 27. In the protection circuit 40, when the contact of the relay 44 is closed, both ends of the heat radiation resistor 42 are short-circuited and no current flows through the heat radiation resistor 42.

When the SR motor is brake-operated, the phase is excited to generate a negative torque to brake the SR motor SRM during a period in which the inductance decreases, so that the SR motor is accompanied by a power generation action. The induced electromotive force E [W], the phase winding current I [A] when the energization is cut off, and the rotation speed N of the SR motor
The relation of the following formula is established between [rpm].

E = k.NI ² where k is a predetermined constant. Therefore, when the current I increases and the induced electromotive force E increases, positive feedback may be applied to overcharge the regenerative capacitor 27.

When the SR motor is braked, the stator rotates against the reluctance (magnetic resistance) to gradually decrease the load inertia and reduce the rotation speed. Magnetic energy is accumulated in the phase windings La to Lb according to the gradual decrease. The magnetic energy accumulated in the phase windings La to Lc increases, and the voltage Vc of the regenerative capacitor 27 increases.

Therefore, during braking operation, the current sensor H
The charging current ic of the regenerative capacitor 27 is detected by S (for example, a current sensor using a magnetoelectric conversion element), and the relay 44 is operated when the charging current ic exceeds a predetermined level based on the detection signal IDET ( Open the contacts). Then, since the charging current ic flows through the heat dissipation resistor 42, the charging current ic is limited and the inertia energy is consumed as heat. Therefore, the regenerative capacitor 2
The voltage increase of 7 is suppressed.

As described above, in this embodiment, in addition to the same effects as the first embodiment, it is possible to prevent overcharging and overvoltage of the regenerative capacitor 27 during braking operation.

[0041]

As described in detail above, according to the present invention, either the DC power supply or the power storage means is selected as the power supply and the phase winding is energized, so that the voltage of the power storage means exceeds the power supply voltage. When the voltage is high, the power storage means can supply power to the phase winding.

Therefore, the rising of the current flowing through the phase winding is
The fall becomes steep, sufficient current is supplied even at high speed rotation, and a larger torque can be generated, so that the output characteristics at high speed rotation can be improved. Furthermore, since the method of reducing the number of turns of the phase winding to make the rise of the phase winding current steep is not adopted, the output characteristics can be improved without lowering the power-torque conversion efficiency.

Further, since the applied voltage is boosted with a simple circuit structure without using an expensive high-voltage DC power supply, the manufacturing can be performed at low cost.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a drive device of a variable reluctance motor that is a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a structure of a variable reluctance motor.

FIG. 3 is an explanatory diagram of inductance of a phase winding and energization timing.

FIG. 4 is an explanatory diagram showing the inductance and current change characteristics of the phase winding.

FIG. 5 is an electric circuit diagram showing a drive device of a variable reluctance motor according to a second embodiment.

FIG. 6 is an electric circuit diagram showing a drive device of a conventional variable reluctance motor.

[Explanation of symbols]

1, 20 ... Drive device 3,
23 ... DC power supply circuit 5a, 5b, 5c ... Energization control circuit 25a, 25b, 25c ... Energization control circuit 7,27 ... Regenerative capacitor SRM ... Variable reluctance motor La, Lb,
Lc ... Phase winding Da1, Db1, Dc1, Dd1 ... Commutation diode Da2, Db2, Dc2 ... Reverse current blocking diode

Claims (1)

[Claims] 1. A direct current power supply, an energization control means for energizing each phase winding of a variable reluctance motor supplied from the direct current power supply in a predetermined circulation order, a storage means for accumulating electric charges, and the above energization. Select one of the electric power regenerating means for regenerating the magnetic energy stored in the phase winding from the phase winding, which has been de-energized by the control means, to the power storing means, and the DC power source and the power storing means. A driving device for a variable reluctance motor, comprising: a selection unit that performs a power supply switching unit that supplies power to the energization control unit from one of the DC power supply and the power storage unit based on a selection result of the selection unit.