JPH053694A - Driving method for synchronous motor - Google Patents

Abstract

PURPOSE:To obtain a highly efficient synchronous motor for driving vehicle having excellent operating characteristics by externally switching the windings between star-connection and delta--connection while shifting so that the current to be applied on the motor has synchronous phase when the rotor reaches a preset rotational speed. CONSTITUTION:Connection of unit windings 10 for respective phases of a synchronous motor 1 is switched through contactors A, B based on a switching command. A rotational angle detector 4 mounted at the end of rotor shaft of the synchronous motor detects a signal Sd which is converted through a polarity detector 24 into a pole position signal Sp of rotor. A phase shifter 25 then regulates the pole position signal Sp to be synchronous with the current being applied on each phase winding 10 of the synchronous motor according to star/delta connection and the rotational angle of rotor to produce an output signal Sf. When switching is made from star connection to delta connection, switching commands are delivered from a switching timing commander 5 to a winding switcher 3 and an inverter 2 at the time when a detected value Vs of actual speed matches with a preset speed level Vo.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a synchronous motor used in an electric vehicle or the like.

[0002]

2. Description of the Related Art Generally, the torque characteristic of an automobile using an internal combustion engine is preferably a constant torque characteristic in order to obtain a uniform acceleration characteristic from a low speed region to a high speed region. However, as shown in FIG. 7, the driving of automobiles using the currently popular internal combustion engine is switched from the low speed gear to the high speed gear sequentially in accordance with the vehicle speed in consideration of the driving characteristics such as fuel consumption and quietness. The engine speed and torque are selected and operated with constant output characteristics so that fuel consumption is good and proper acceleration can be performed. As a drive unit for future automobiles, practical application of an electric drive unit which is pollution-free, easy to maintain and lightweight is being studied. When driving by electric type, AC motors are more suitable than DC motors, and among them, synchronous motors are highly efficient and optimal, and there is a desire to omit the transmission gear by taking advantage of the characteristics of motor control that the speed control range is wide. strong. Generally, the size of the motor depends on the torque at base speed. Since the gears are continuously changed, when the synchronous motor is driven by an inverter, the output increases in proportion to the speed if the constant torque characteristic is used, and the capacity of the inverter device that drives the motor must be increased. On the other hand, if the high speed side of the base speed is made to have a constant output characteristic, it is possible to satisfy the required characteristics of currently popular automobiles without increasing the capacity of the inverter. FIG. 8 shows a basic torque-speed characteristic of a permanent magnet field type synchronous motor, which is an example of a synchronous motor and is suitable for driving an electric vehicle because of its high efficiency. When this motor is driven by an inverter, if the voltage drop and the iron loss due to the winding resistance of the motor are neglected in order to discuss the basic characteristics, it is assumed that the induced voltage becomes the power supply voltage V1 at the speed N1.
You can't go faster than that. To solve this, the voltage of the power supply may be increased or the number of turns of the electric motor may be decreased to increase the rated current, but the capacity of the inverter becomes large. In addition, as another solution, as shown in FIG. 9A, two sets of windings of the electric motor are mounted, and the connection of each winding is switched between series and parallel, so that it is shown in FIG. 9B. There is a method of obtaining such characteristics. However, with this method, the number of lead wires or terminals (12 for three-phase AC)
Pieces: Even if the neutral points are internally connected, the number is 10 and the number of contacts is also large (9 or more sets), which makes connection and connection complicated and is difficult to manufacture.

[0003]

SUMMARY OF THE INVENTION In order to solve such problems, the present invention provides a method for driving a synchronous motor for driving a vehicle such as an automobile, which is highly efficient, has excellent driving characteristics, and is easy to manufacture. It is a thing.

[0004]

In order to solve the above-mentioned problems, in a variable speed drive method for switching winding connection of a synchronous motor by an inverter device applied to vehicle driving or the like, a rotation speed of a rotor of a motor is preset. Is set as the switching timing, and the phase of the electric current applied to the motor is shifted so as to synchronize with the magnetic pole position of the rotor as a reference, and the winding is connected to the star connection and delta connection in the low speed range and the high speed range. To achieve both high torque at low speed and high speed operation without increasing the capacity of the drive power supply.
It operates automatically with a constant output characteristic. Immediately before switching, the torque command is throttled to suppress the current surge at the time of switching the winding connection to extend the life of the contactor, and hysteresis is provided at the switching timing to provide more shockless gear shifting. It is a good one.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to FIGS.
Will be described. FIG. 1A is a block diagram of a control circuit of the present invention. FIG. 1B shows a winding switching device provided outside. Single winding 10 for each phase of the synchronous motor
In the same manner as the star / delta switching device normally used in the induction motor, the contactors A and B are used to switch the connection by a switching command. The torque command T commanded by the driver is input to the current command device 23. On the other hand, the signal Sd detected by the rotation angle detector 4 such as a resolver provided at the shaft end of the rotor of the synchronous motor 1 is converted by the magnetic pole detector 24 into the magnetic pole position signal Sp of the rotor, and further the phase shifter 25.
Then, at the timing as shown in FIG. 5, according to the star / delta connection, according to the rotation angle of the rotor, it is synchronized with the phase of the current applied to each phase (U, V, W) winding 10 of the synchronous motor. The output signal Sf adjusted to is output. Current command device 23
Then, the current command signal Ic having an amplitude proportional to the torque command T and having the same phase as Sf is output. Current command signal Ic
Is input to the current control amplifier 22 with a positive sign. on the other hand,
The output current Id of the inverter main circuit 21 is the current transformer 26.
Is detected in the current control amplifier 22 and fed back to the current control amplifier 22 with a negative sign, and as a result, (Ic-Id) is added to the current control amplifier 22. In the current control amplifier 22, (Ic-
When the drive command signal Vr corresponding to Id) is given to the inverter main circuit 21, the inverter main circuit 21 supplies a drive current to the AC synchronous motor 1 via the winding switching device 3. The output Sd of the rotation angle detector 4 is also input to the switching timing command device 5 and converted into the speed signal Vs by the pulse-speed converter 27, and then the preset reference speed command signal Vo (indicated by N1 in FIG. 2). When (Vs-Vo) becomes 0, the switching timing command device 5 commands the winding switching device 3 to send a star / delta switching timing signal. The comparator 28 has a hysteresis characteristic in order to stabilize the operation.
On the other hand, the output of the switching timing command device 5 is also input to the inverter device 2, and the inverter main circuit 2 at the time of winding switching
Control of drive command signal Vr of No. 1 and ON-OF of gate signal
Used for F. There are the following four cases of control when switching windings. (1) As shown in FIG. 2, when switching from the star connection to the delta connection, when the detected value Vs of the actual speed becomes equal to the preset speed level Vo (corresponding to the base speed N1),
The switching timing command device 5 gives a switching command between the star connection at low speed and the delta connection at high speed to the winding switching device 3 and the inverter device 2. At this time, if the torque command T is constant, the actual torque changes from the torque T1 at low speed to T2 at high speed. The torque T2 is maintained up to the maximum speed N2. At this time, N1: N2 = T2: T1 (=
1: √3), and when the operating points of N1 and N2 are compared, the constant output relationship is maintained. (2) As shown in FIG. 3, the winding command timing Tch is preceded by a preset time Tad, the torque command T is narrowed down by a function generator, etc. The gate signal of the circuit 21 is turned off to bring it into a non-energized state, the torque command is started again immediately after switching the winding, and the current surge at the time of switching the winding connection of the inverter circuit is suppressed. Actually, the time when the switching command is received may be set to Tch and delayed. (3) As shown in FIG. 4, when the detected value Vs of the actual speed exceeds the preset speed level Vo (corresponding to the base speed N1), the star connection is switched to the delta connection.
By setting the point at which the delta connection is switched to the star connection at a level Vo ′ that is slightly lower than Vo, hysteresis is provided in the switching characteristic and more stable operation is secured. (4) As shown in FIG. 6, the command torque is less than the base speed (0
(From N1 to N1), either star / delta connection can be selected, only delta connection is available between base speed N1 and maximum speed N2, and rapid acceleration is required in the rotation speed range from 0 to N1. , A so-called kick-down characteristic of switching from delta connection to star connection according to the amount of depression of the accelerator pedal (torque command) is provided. As another embodiment, constants of the motor stator, rotor, and control circuit are stored in advance, and the current control amplifier 22 is used.
There is a torque control method in which a control parameter is calculated using an equivalent circuit network or the like and the drive command signal Vr corresponding to the parameter is controlled. Furthermore, N1, N2, T1, and T may be changed according to the running state of the automobile, the state of the storage battery, and the change of the vehicle body weight.
The relationship between 2, Vo may be predicted and the setting of control parameters may be made variable. As another embodiment, two types of magnetic pole detectors, one for star connection and one for delta connection, are provided to control the shift amount of the applied current at the time of switching the windings so that the synchronization at the time of switching can be smoothly performed. Good.

[0007]

The present invention has the following effects by being configured as described above. (1) Since the connection of the single winding of the synchronous motor is switched externally, the structure of the motor is simplified without increasing the number of lead wires or terminals. (2) Since the base speed N1 and the maximum speed N2 have a constant output characteristic relationship, it is not necessary to increase the synchronous motor, the inverter device, and the power supply capacity. (3) Various commands before and after winding changeover can be handled smoothly during actual operation, so the driver does not feel uncomfortable.

[Brief description of drawings]

1A is a block diagram of a control circuit showing an embodiment of the present invention, and FIG. 1B is a winding switching device (star / star) used in the present invention.
Delta) schematic.

FIG. 2 is a graph showing the relationship between the rotation speed and the command torque according to the embodiment of this invention.

FIG. 3 is a timing chart showing the relationship of switching timing according to the embodiment of the present invention.

FIG. 4 is a graph showing hysteresis of command torque according to the embodiment of the invention.

FIG. 5 is a chart showing the output of the rotation angle detector according to the embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a rotation speed and a torque command having kickdown characteristics according to an embodiment of the present invention.

FIG. 7 is a graph showing a relationship between a rotational speed and a driving force due to gear shifting of an automobile using an internal combustion engine.

FIG. 8 is a graph showing torque characteristics of a general permanent magnet type synchronous motor.

9 (a) is a circuit diagram of a conventional winding switching device (parallel / series), and FIG. 9 (b) is a graph showing the relationship between its rotation speed and command torque.

[Explanation of symbols]

1 is a synchronous motor, 2 is an inverter device, 3 is a winding switching device, 4 is a rotation angle detector, 5 is a switching timing command device, 10 is a winding of an electric motor, 21 is an inverter main circuit, 2
2 is a current control amplifier, 23 is a current command device, 24 is a magnetic pole detector, 25 is a phase shifter, 26 is a current transformer, 27 is a pulse-speed converter, and 28 is a comparator.

Claims (7)

[Claims] 1. In a variable speed drive method in which a driver gives a torque command and switches winding connection of a synchronous motor by an inverter device applied to drive a vehicle or the like, a rotational speed of a rotor of an electric motor reaches a preset value. Time is the switching timing, and the phase of the electric current applied to the motor is shifted so as to synchronize with the magnetic pole position of the rotor, and the winding is switched externally between star connection and delta connection in the low speed range and the high speed range. , A method of driving a synchronous motor characterized by achieving a large torque at a low speed and a high speed operation at the same time without increasing the capacity of the drive power source, and performing an automatic operation 2. Immediately before switching between the star connection and the delta connection, the torque command is throttled, and then the inverter main circuit is put into a non-current state to suppress current surge at the time of switching the winding connection and to shorten the life of the contactor. The method for driving a synchronous motor according to claim 1, wherein the method is extended. 3. The shift between the star connection and the delta connection is compared with a detected value of an actual speed and a preset speed level, and a hysteresis generation circuit or the like provides a hysteresis at a switching timing to shift gears in a shockless manner. 3. The method for driving a synchronous motor according to 1 or 2. 4. The method for driving a synchronous motor according to claim 1, wherein the applied current of the electric motor is controlled by a control parameter determined from the circuit constants of the stator, the rotor and the inverter device. 5. The phase shift of the applied current of the electric motor
5. The method of driving a synchronous motor according to claim 1, wherein the method is performed by switching output signals of two types of magnetic pole detectors, one for star connection and the other for delta connection. 6. The method for driving a synchronous motor according to claim 1, wherein the driving is normally performed at a high speed, and the operating speed is rapidly switched by a kickdown operation when a low speed operation is required. 7. The method of driving a synchronous motor according to claim 1, wherein the automatic operation is normally performed, and the operation mode is switched to the manual operation if necessary.