KR100242001B1 - Method and apparatus for restricting current in switched reluctance motor - Google Patents

Abstract

Disclosed is a current limiting method of a switched reluctance motor for limiting the flow of a large current and preventing breakage of the switching element by varying the current value for the speed of the motor, including braking the rotation of the motor. Relates to a device.

The present invention relates to a device for driving a motor by controlling a switching element having a motor consisting of a stator and a rotor of a multiphase, an encoder for detecting a rotational speed of the motor, and a difference between the detected rotational speed and position: Means for calculating a rotational speed of the motor obtained by the encoder; Current sensing means for sensing a drive current flowing through the stator windings; Current limit value determining means for variably determining a maximum allowable current limit value for each speed according to the calculated rotation speed; And current limiting means for inhibiting driving of the switching elements by calculating the maximum allowable current limit value for each speed and the detected driving current of the motor.

Therefore, when applying the brake to rotation, if the current flows more than the reference current for the rotational speed of the SR motor, the current value can be variably set and flowed through the switching device, and the current can be accurately limited regardless of the magnetic temperature of the switching device. The effect is provided.

Description

Current limiting device for switched reluctance motors {METHOD AND APPARATUS FOR RESTRICTING CURRENT IN SWITCHED RELUCTANCE MOTOR}

The present invention relates to the operation of a switched reluctance motor (abbreviated as " SR motor "), and more particularly, to continuous operation when braking (rotating brake function) of the rotation of the SR motor. As a way to prevent the switching device from generating heat or burn out by the flow of large current, it is possible to limit the continuous flow of large current by variably setting the current value for the rotational speed of the SR motor including braking. The present invention relates to an SR motor current limiting method and apparatus.

The internal structure of a typical SR motor is shown in FIG.

That is, the general SR motor 100 has a stator winding 103 or an armature coil wound around the core of the stator 102 disposed around the rotor 101 installed on the rotating shaft, and the stator winding Torque is generated by the suction force acting between the rotor 101 and the core of the stator 102 that is magnetized when energizing the three-phase current generated by the inverter circuit section 103. Thus, three-phase, i.e., again In other words, the rotor 101 is rotated by sequentially energizing the stator winding 103 of each of the R, S, and T phases.

On the other hand, Figure 2 shows a drive control circuit of the prior art for controlling the drive of the SR motor described above.

The driving control circuit changes the DC voltage generated from the converter unit (not shown in the drawing) into a three-phase power source according to the pulse width modulation signal PWM applied to the gate terminal, thereby changing the respective angles of the SR motor 100. Inverter section consisting of a pair of switching elements Q1, Q2, Q3, Q4, and Q5 and Q6 that control the current flowing through the stator windings 103c, 103b, and 103c. And a plurality of diodes D1 to D6 for current feedback, and each of the pair of switching elements Q1, Q2, Q3, Q4, and Q5 is a gate thereof. When the pulse width modulated signal PWM is input to the terminal, it is turned on and energizes each stator winding 103a, 103b, 103c by supplying a current in phase with the energized signal. The excitation state of the core is changed to control the operation of the SR motor.

The SR motor 100 rotates according to the relative position between the rotor 101 and the rotor 101 when the stator windings 103a, 103b, and 103c are energized to magnetize the core of the stator 102. Since this is determined and the rotor 101 can be rotated and stopped, it is important to detect the speed and position of the rotor 101. In general, as shown in FIG. An encoder 106 having two holes 105 drilled therein is coupled to the rotor 101, and an optical sensor (not shown) is installed to face the hole 105 so that the light receiving element and the light emitting element are paired. Since the light emitted from the light emitting element passes through the hole 105 of the encoder 106 and enters the light receiving element, a predetermined detection signal is generated, and thus the position and speed of the rotor 101 are detected based on this. I can do it.

Since the pulse width modulation signal PWM supplied to the drive control circuit is determined according to the position of the rotor 101 thus detected, as a result, the rotation direction of the SR motor 100 is determined or the rotor 101 rotates. And stop.

On the other hand, as the rotor 101 approaches a core having any phase among the cores of the stator 102, the inductance increases, and when the rotor 101 and the core having any phase coincide, the inductance is maximum. In addition, the inductance decreases as the rotor 101 moves away from the core having any phase.

In a typical case, the pulse width modulated signal PWM is designed to be constantly output at an advanced point from 0 ° to 7.5 ° based on the point of time when the inductance increases regardless of the rotational speed of the rotor 101. .

As described above, in driving a general SR motor, the current limit value is usually set (or set a little less) that the switching element can flow at a maximum, and a normal switching element may flow according to its own temperature. Since the current value is different, the temperature rises, and in order to heat the temperature, a heat sink is typically used to manage the temperature of the switching element.

However, the drive control circuit of the related art for controlling the driving of the general SR motor described above can be protected to some extent by dissipating heat generated by the switching element by using a heat sink when driving the SR motor. However, especially when the SR motor is braked, a large continuous current is applied to the switching element, and if such operation is continuous, the temperature of the switching element cannot be covered with only the heat sink itself. As a result, the switching element generates heat. It can be seen that the broken.

Therefore, there is a problem in that a current cannot flow beyond the reference current determined by the switching element.

Therefore, in the above-described conventional technique, the switching element is damaged due to the large current continuously applied when braking the SR motor of the drive control circuit of the SR motor, and the current exceeds a predetermined reference current. As one aspect of the present invention, the current limiting method of the SR motor to limit the continuous flow of a large current by varying the maximum current value for the rotational speed including braking is excluded. And to provide a device.

In another aspect of the present invention, when the braking is applied to flow over the reference current for the rotational speed of the SR motor, the current value is set variable to allow the flow through the switching element.

As another aspect of the present invention, the object is to accurately limit the current regardless of the magnetic temperature of the switching element.

1 is a cross-sectional view showing a general switched reluctance motor.

2 is a prior art drive control circuit diagram for controlling the drive of a switched reluctance motor;

3 is an exemplary view showing an encoder coupled to the rotor of the switched reluctance motor of FIG.

4 is a block diagram showing a preferred embodiment of a current limiting device of a switched reluctance motor according to the present invention;

5 is a waveform diagram of current flowing through a winding of the switched reluctance motor of FIG. 4;

Figure 6 is a waveform diagram showing the current limit value for the speed of the switched reluctance motor according to the present invention when applying braking to the rotation of the motor.

<Description of the symbols for the main parts of the drawings>

104: inverter section 106: encoder

200: current sensing unit 201: microcomputer

202: current limiting unit 203: speed detecting unit

204: position sensing unit 205: current limit value determining unit

206: subtractor 207: waveform determination unit

The current limiting device of the switched reluctance motor according to the present invention for achieving the above objects, each phase for switching the excited state of each phase of the stator in accordance with the position of the rotor relative to the stator of the polyphase In a switched reluctance motor comprising a switching element,

An encoder for generating position detection pulses discretely by light optically penetrating each of the slits of the concentric slits group as the rotor is coupled to the rotation axis of the rotor;

A speed sensing unit for counting and detecting the rotational speed of the rotor by counting the position detection pulses detected during a unit time;

A position sensing unit for sensing the relative position of the rotor with respect to the multi-phase stator with a predetermined angular resolution, which is varied by the rotation of the rotor;

A current sensing unit sensing a driving current flowing through the stator winding wound around the stator;

The maximum allowable current limit value for each speed is applied as the rotation speed is applied from the speed sensor in a state where the maximum allowable current limit value for each speed proportional to the detected rotation speed is stored as a look-up table in the upper and lower limits. A current limit value determining unit for determining and outputting a pulse width modulated signal; And

A switching element of each phase when the detected driving current of the stator winding exceeds the determined maximum allowable current limit value for each speed as a result of comparing the determined maximum allowable current limit value for each speed with the detected driving current of the stator winding. It is preferable that it consists of a current limiting part which suppresses the drive of a.

The current limiting unit may include: a low pass filter configured to analog-to-digital convert a maximum allowable current limit value for each speed in the form of a pulse width modulation signal output from the current limit value determiner to output the maximum allowable current limit value for each speed in an analog form;

A comparator configured to receive a maximum allowable current limit value for each speed in an analog form from the low pass filter unit, and to perform a comparison operation by receiving a drive current of the stator winding detected by the current sensing unit;

As a result of the comparison of the comparator, it is preferable that the on / off switching unit grounds the current applied to the switching element of each phase when the sensed driving current of the stator winding exceeds the determined maximum allowable current limit value for each speed. .

In addition, it is preferable that the current sensing unit is a resistance element, one end of which is coupled to the stator winding of one of each phase through a current feedback diode, and the other end of which is connected to the negative side of the power supply terminal.

And, there may be a plurality of embodiments of the present invention, hereinafter will be described in detail with respect to the most preferred embodiment.

This preferred embodiment makes it possible to better understand the objects and advantages of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the current limiting device of the switched reluctance motor according to the present invention.

Figure 4 is a block diagram showing a preferred embodiment of the current limiting device of the switched reluctance motor according to the present invention.

A preferred embodiment of the current limiting device of the switched reluctance motor according to the present invention is an SR motor composed of a stator and a rotor of a multiphase, as shown in Figure 4, coupled to the rotor of the SR motor of the SR motor A sense of speed that calculates the current speed of the SR motor and the position of the current rotor from the encoder 106 for detecting the rotational speed and the electrical signal built into the microcomputer 201 corresponding to the rotational speed detected by the encoder 106. Subtractor 206 for generating a difference value between the current rotation speed of the SR motor and the position of the current rotor calculated by the branch unit 203 and the position detecting unit 204 and the speed detecting unit 203 and the position detecting unit 204. And a pulse width modulation signal is determined according to the difference value obtained by the subtractor 206, and each switching element Q1, Q2, Q3, Q4, Q5, Q6 of the inverter unit 104 is determined. ) Is turned on and off so that each phase wound on the stator of the SR motor Waveform determination unit 207 for energizing the direct current of the power supply terminal Vdc to the child windings 103a, 103b, and 103c, and one end of the current feedback diode D1 of the inverter unit 104. Connected to the stator winding 103a and the other end connected to the negative of the power supply terminal Vdc, and the current sensing unit 200 as a resistor for detecting the drive current of the SR motor, and the speed sensing unit 203 The speed limit determined by the current limit value determining unit 205 and the current limit value determining unit 205 which variably determine the maximum allowable current limit value for each speed previously stored according to the rotation speed of the SR motor and output the result as a pulse width modulation signal. The maximum allowable current limit value of each pair and the driving current of the SR motor sensed by the current sensing unit 200 are compared, and the pair of switching elements Q1, Q2, Q3, Q4 (Q5) consists of a current limiting section 202 that controls the driving of (Q6), The same reference numerals are given to the same parts as the above description, and the operation thereof will be omitted below.

As described above, the current limiting device of the switched reluctance motor of the present invention having the structure performs the following operation with respect to the case where the maximum current to the rotational speed of the SR motor is continuously applied, including when braking is applied.

Hereinafter, with reference to FIG. 5, FIG. 6, it demonstrates more concretely.

First, the current sensing unit 200 such as a resistor senses the motor driving current flowing through the stator windings of the stator windings 103a, 103b, and 103c wound on the stator of the SR motor, and will be described later. The current limiting unit 202 is provided.

On the other hand, each pair of switching elements Q1, Q2, Q3, Q4, and Q5 of the inverter unit 104 by the pulse width modulation signal of the waveform determination unit 207 incorporated in the microcomputer 201. When Q6 is turned on, the stator windings 103a, 103b, and 103c of the above-described phases, as shown in FIG. 4, are energized by flowing the current of the power terminal Vdc in phase with the energized signal. Rotor of will rotate.

In FIG. 5, a represents a current flowing in each phase in a normal state, and b shows an example of a current flowing in each phase in applying braking, which will be described later.

Subsequently, when the rotor of the SR motor rotates, the encoder 106 senses the rotational speed of the SR motor, and the speed detecting unit 203 and the position detecting unit built in the microcomputer 201 are detected by the electric signal corresponding thereto. 204.

The speed detector 203 calculates the rotational speed of the current SR motor with the electrical signal input from the encoder 106, and the position detector 204 calculates the current position of the rotor.

The calculated position value is provided to the subtractor 206 and the rotational speed value is provided to the current limit value determination unit 205.

The current limit value determination unit 205 determines the maximum allowable current limit value I10 for each speed as shown in FIG. 6 stored in the lookup table according to the current rotation speed of the SR motor calculated by the speed detection unit 203, and determines the pulse width. The modulation signal PWM is provided to the current limiting unit 202.

In other words, as shown in FIG. 6, the limit value of the current to be applied to the stator windings 103a, 103b, and 103c of each phase is determined and output with respect to the rotational speed (rpm) of the SR motor during braking.

The current limiter 202 includes a low pass filter 202a, a comparator 202b, a resistor R1 and a control element 202c such as a transistor.

Accordingly, the low pass filter 202a converts the pulse width modulated signal PWM from the current limit value determiner 205 of the microcomputer 201 into an analog signal, thereby inverting the negative terminal of the comparator 202b. Will be provided as a reference value.

The comparator 202b of the current limiting unit 202 detects the current corresponding to the driving current of the SR motor sensed by the current sensing unit 200 and input to its non-inverting terminal (+) and the maximum allowable current limit value for each speed. In comparison, when the driving current of the SR motor is high, that is, at this time, as shown in FIG. 5, the maximum current b for the rotational speed of the SR motor continuously including the braking is performed. Through the resistor R1, a high potential is generated in the gate of the control element 202c such as a transistor to conduct the control element 202c.

Accordingly, the pulse width modulated signal of the waveform determination unit 207 inputted to the gates of the switching stations of the inverter unit 104 is bypassed through the control element 202c, and as a result, the switching element of the inverter unit 104. Are blocked, and the operation of the SR motor is stopped.

On the contrary, if the drive current of the SR motor is lower than the maximum allowable current I10 for each speed, the switching elements Q1, Q2, Q3, Q4, and Q5 and Q6 of the inverter unit 104 continue. To drive.

The pulse width modulated signal applied to the gates of the switching elements Q1, Q2, Q3, Q4, and Q5, Q6 may be a speed value calculated by the speed detector 203 and a position detector. The position value calculated at 204 is generated by the difference value subtracted through the subtractor 206 in the microcomputer 201.

Here, when it is necessary to flow the current to the stator windings 103a, 103b, and 103c of the SR motor to the maximum, that is, when it is necessary to flow about 15A, the current limit value determining unit 205 is shown in FIG. Likewise, the maximum allowable current limit value I10 for each speed may be set to about 10A.

The reason why the comparator 202b is provided is to compare whether the pulse width modulated signal determined from the waveform determination unit 207 is properly input to the switching element of the inverter unit 104.

As a result, according to the present invention, it can be seen that the breakdown of the switching elements is prevented by variably setting the maximum current value for the rotational speed, including when braking is applied, to restrict the continuous flow of a large current.

As described above, in the present embodiment, when the braking is applied when the current flows above the reference current for the rotational speed of the SR motor, it is possible to variably set the maximum allowable current limit value and flow it through the switching element.

In addition, according to the above application, it can be seen that the braking is prevented from being burned out by the heat generation of the switching elements generated by applying a large current continuously, and the flow of the large current can be further improved, thereby improving the reliability of the system.

In addition, while specific embodiments of the present invention have been described and illustrated above, it is obvious that the present invention may be variously modified and implemented by those skilled in the art.

Such modified embodiments should not be individually understood from the technical spirit or the prospect of the present invention, and such modified embodiments should fall within the appended claims of the present invention.

It is clear from the above description that the current limiting device of the switched reluctance motor of the present invention prevents the switching element from being generated and burned out by the continuous large current flow when braking the SR motor. In addition, by setting the current value for the rotational speed of the SR motor variably, there is an effect that can flow more than the reference current value to the SR motor.

Claims (3)

In a switched reluctance motor comprising a switching element of each phase for switching the excited state of each phase according to the position of the rotor relative to the stator of the polyphase and the rotational speed of the rotor, A current sensing unit sensing a driving current flowing through the stator winding wound around the stator; The maximum allowable current for each speed corresponding to the rotation speed of the rotor detected at this time in the state that the maximum allowable current limit for each speed proportional to the rotational speed of the rotor is stored as a look-up table in the upper limit and the lower limit. A current limit value determination unit which determines and outputs a limit value; And A switching element of each phase when the detected driving current of the stator winding exceeds the determined maximum allowable current limit value for each speed as a result of comparing the determined maximum allowable current limit value for each speed with the detected driving current of the stator winding. A current limiting device of a switched reluctance motor, characterized in that it comprises a current limiting unit for suppressing the driving of. The method of claim 1, wherein the current limiting unit, A low pass filter outputting the maximum allowable current limit value for each speed in analog form by analog-to-digital converting the maximum allowable current limit value for each speed in the form of a pulse width modulation signal output from the current limit value determination unit; A comparator configured to receive a maximum allowable current limit value for each speed in an analog form from the low pass filter unit, and to perform a comparison operation by receiving a drive current of the stator winding detected by the current sensing unit; As a result of the comparison of the comparator, it characterized in that the on / off switching unit for grounding the current applied to the switching element of each phase when the sensed drive current of the stator winding exceeds the maximum allowable current limit value for each speed Current limiting device for switched reluctance motors. The method of claim 1, wherein the current sensing unit, A current limiting device of a switched reluctance motor, wherein one end is a resistance element coupled to a stator winding of one of each phase through a current feedback diode and the other end connected to a negative side of a power supply terminal.

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