KR20010011524A - The protection circuit of over current about switched reluctance motor - Google Patents

Abstract

PURPOSE: A circuit for protecting a switched reluctance motor from an over current is provided to reduce the manufacture cost of the switched reluctance motor and to save the installation space by substituting a current sensing part for three PTC thermistors. CONSTITUTION: A circuit for protecting a switched reluctance motor from an over current includes a current sensing part(28), a sensor(23), an inverter driving part(27), and a motor driving circuit. The motor driving circuit includes an inverter(22), a rotation sensing part(24), and a control part(26). The current sensing part(28) senses a current passing through motor windings. The current sensing part(28) determines whether the current passing through the motor windings is an over current or not, and outputs an interrupt signal when an over current passes through the motor windings. The inverter driving part(27) causes the inverter(22) to be stopped when the interrupt signal is inputted from the current sensing part(28).

Description

SRM's over current protection circuit {THE PROTECTION CIRCUIT OF OVER CURRENT ABOUT SWITCHED RELUCTANCE MOTOR}

In the present invention, in the driving of an N phase SRM (Switch Recession Motor), a temperature rise of a coil of a motor winding suddenly occurs when a current is continuously output by each fan due to a fan restraint or a microcomputer runaway. In order to prevent possible fires, instead of installing PTC thermistors in the motor's narrow motor, it is related to the overcurrent protection circuit of SLM that installs a simple overcurrent protection circuit, which is advantageous for space utilization. The present invention relates to an overcurrent protection circuit of SLM which is advantageous in terms of price using a current detector.

FIG. 1 is a block diagram of an over temperature protection circuit of a conventional SM. As shown in FIG. 1, the rectifier 11 rectifies the input AC power into a DC voltage and a DC voltage provided from the rectifier 11. An inverter 12 for converting the AC voltage back to drive the SM 19, a sensor 13 and a rotation detecting unit 14 for detecting the position and the rotational speed of the rotor when the SM 19 is driven; The input unit 15 outputs a signal corresponding to the air volume selected by the user, and the rotation detection unit 14 allows the motor to rotate in one direction according to the detection signal, and the air volume input from the input unit 15 A control unit 16 for outputting a matching signal, a drive unit 17 for turning on / off the switching element of the inverter 12 by the output of the control unit 16, and the motor winding of the SM 19 When the temperature rises, the current of the motor winding It consists of a PTC thermistor 18 to limit the temperature rise.

Looking at the prior art configured as described above is as follows.

The motor winding of the SM 19 is composed of La, Lb, and Lc in three phases, and an AC power source is applied to drive the motor windings.

The applied AC power is rectified by the rectifying unit 11 to a DC voltage and output to the inverter 12 for driving the SM 19.

Then, the inverter 12 converts the DC voltage back into AC power and supplies it to the SM 19 to drive it.

The SM 19 is composed of a stator and a rotor. The windings of each phase become the windings of the stator, and when the temperature rises to about 120 ° C., the resistance of the PTC thermistor 18 rises rapidly and the motor windings Limit the current to prevent temperature rise.

At this time, three PTC thermistors 18 to prevent the temperature rise is required to be connected in series with the motor windings La, Lb, and Lc in each phase.

When the SM 19 is driven and rotated, the sensor 13 detects the rotor position and the rotation speed of the motor and provides the rotation detection unit 14.

Then, the rotation detecting unit 14 transmits the detected rotor position and the number of rotations to the controller 16.

At this time, the input unit 15 transmits a signal corresponding to the air volume selected by the user to the controller 16.

Accordingly, the control unit 16 determines the motor speed by using the wind speed signal selected by the user and the position and the rotation speed of the rotor detected by the rotation detecting unit 14, and provides the corresponding driving signal to the driving unit 17. do.

Then, the driving unit 17 applies a switch control signal for driving the inverter 12 suitable for the characteristics of the SM to the inverter 12.

Accordingly, the switching element of the inverter 12 is turned on or off to rotate the motor by exciting current to the motor windings La, Lb, and Lc of the SM 19.

When the motor is constrained by some cause during the rotation of the SM 19 due to such an operation, the controller 16 sends a signal for increasing the current excitation time on each of the motors for the desired rotational speed. .

In this way, an increase in the current of the motor windings increases, and thus the temperature of the motor windings increases.

In addition, when the microcomputer is congested, that is, when the controller is congested due to some cause and the signal that excites the current on each motor is continuously turned on, the temperature may increase in the motor windings and a fire may occur.

In order to prevent this, PTC thermistors are installed in series with the motor windings inside the motor, so as to prevent the temperature rise and the fire by limiting the current of the motor windings as described above even if a signal for continuously turning on each phase of the motor occurs.

However, in the prior art as described above, the motor windings are wound separately for each phase of the stator, and the windings of each phase are independently controlled to excite the windings of each phase separately, so that each phase winding independently series PTC thermistors. Should have a configuration to have. Therefore, if SM has three phases, it must have three PTC thermistors. Therefore, since three PTC thermistors must be installed inside the motor, the mounting space is narrow, so that the mounting position is difficult, and three PTC thermistors must be installed, thereby increasing the price.

Accordingly, an object of the present invention for solving the conventional problems as described above is to provide an overcurrent protection circuit of the SM to install the current detector instead of the PTC thermistor to protect the overcurrent.

Another object of the present invention is to provide an overcurrent protection circuit of the SLM to enable the compactness of the motor because the current detection unit is installed on the PCB do not need to use the space inside the motor.

It is still another object of the present invention to provide an overcurrent protection circuit of SLM that can be designed at a much lower cost in terms of cost by not using a PTC thermistor.

1 is a block diagram of an over temperature protection circuit of a conventional SRM (SRM).

Figure 2 is a block diagram of an overcurrent protection circuit of the present invention SM.

Figure 3 is a detailed view of the overcurrent protection circuit of the present invention SM.

Figure 4 is another embodiment of the overcurrent protection circuit of the present invention SM.

5 is a characteristic diagram of a transfer function (hysteresis) of the current detection unit in FIG. 3;

***** Explanation of symbols for the main parts of the drawing *****

21: rectifier 22: inverter

23: sensor 24: rotation detection unit

25 input unit 26 control unit

27: drive unit 28: current detection unit

29: reset unit Buf1, Buf2, Buf3: buffer

Chys: Hysteresis Comparator

La, Lb, Lc: Motor Winding

In order to achieve the above object, the present invention converts a DC voltage output from the rectifying unit rectifying the input AC power back to AC power to drive an SM, and the rotor position of the SM to detect the rotor accordingly In the SM drive circuit comprising a sensor for outputting a position signal and a rotation detection unit, and a control unit for turning on and off the switch element of the inverter in accordance with the rotor position signal, the inverter detects the current in each phase to the motor winding And a current detector for outputting a driving stop signal when it is determined that an overcurrent flows, and a driver for stopping the operation of the inverter when the driving stop signal is input by the current detector.

Hereinafter, with reference to the accompanying drawings in detail as follows.

2 and 3 are schematic diagrams of the overcurrent protection circuit of the present invention, as shown in the rectifier 21 for rectifying the input AC power to a DC voltage, and the DC voltage at the rectifier 21. When supplied, N motor windings La, Lb, Lc connected in parallel with each other by the number of N phases, and switch elements Q1a, Q1b, Q1c connected in series with the motor windings La, Lb, and Lc (Q2a). Inverter unit 22 for converting AC power to Q2b and Q2c again to drive an SM, a sensor 23 and a rotation detecting unit 24 for detecting the position and the number of rotations of the rotor when the SM is driven. And an input unit 25 for outputting a signal corresponding to the air volume selected by the user, and allowing the motor to rotate in one direction according to the detection signal by the rotation detecting unit 24, and the air volume input from the input unit 25. A control unit 26 for outputting a signal conforming to the The drive unit 27 for controlling the switch element of the inverter unit 22 by comparing the signal with the reference signal, and the current detecting resistors Rs1, Rs2, which are connected in series to the lower switch element of the inverter unit 22, Rs3) detects the current flowing through the motor, converts it into a voltage value proportional to the detected current, outputs to the drive unit 27, and constitutes a current detection unit 28 that controls the operation of the drive unit 27 do.

Referring to the operation and effect of the present invention configured as described in detail as follows.

When AC power is input to drive the motor windings of La, Lb, and Lc constituted by three phases of the SRM, the rectifier 21 is inputted to rectify the DC voltage to the inverter 25.

Then, the inverter 22 converts the DC voltage back into the AC power and supplies it to the SM to rotate.

Accordingly, the sensor 23 and the rotation detector 24 detect the position of the rotor and provide it to the controller 26.

At this time, if the user selects the air volume through the input unit 25, the control unit 26 is a signal for driving the motor according to the air flow rate input through the input unit 25 and the rotor position input through the rotation detection unit 24 Is outputted to the drive unit 27 through its output ports Port1, Port2, and Port.

Signals output through the output ports Port1, Port2, and Port of the controller 26 are input to the non-inverting input terminals (+) of the buffers Buf1, Buf2, and Buf3 in the driver 27.

A reference voltage set by the resistors R51 and R52 is input to the inverting input terminals (−) of the buffers Buf1, Buf2, and Buf3.

Accordingly, the buffers Buf1, Buf2, and Buf3 compare the reference voltages input to the inverting input terminal (-) and the voltages input to the non-inverting input terminal (+), respectively, so that the lower switches Q2a, Q2b, Q2c).

For example, when the control unit 26 generates a signal to turn on the A phase, when the voltage input to the non-inverting input terminal (+) of the buffer Buf1 is input to the inverting input terminal (-), the voltage is higher than the reference voltage. The lower switch Q2a on a of the inverter 22 is turned on.

At this time, as the control unit 26 generates a signal to turn off the B and C phases, the voltage input to the non-inverting input terminal (+) of the buffers Buf2 and Buf3 is input to the inverting input terminal (-). Lower, the lower switches Q2b and Q2c on b and c of the inverter 22 are turned off, respectively.

The upper switch Q1a is turned on when the base voltage of the upper switch Q1a becomes a threshold voltage at which the lower switch Q2a of the a phase is turned on.

Then, the current flows through the winding La of the motor, and the A phase of the stator generates the magnetic flux. Therefore, the rotor is accompanied and the current must be flowed to the next phase for continuous rotation, so that the controller 26 passes the winding La to its output port Port1. Outputs a signal that prevents current from flowing through.

Accordingly, the buffer Buf1 outputs a low signal to turn off the lower switch Q2a.

At this time, the magnetic flux induced in phase A must be removed, and the magnetic flux is removed by the freewheel diodes D1a and D2a.

Subsequently, the buffer Buf2 of the driving unit 27 outputs a high signal under the control of the control unit 26, which turns on the lower switch Q2b on the b phase of the inverter 22 and accordingly the upper switch Q1b. On, current flows in the motor winding Lb.

The current flows through the motor winding Lb, and the B phase of the stator generates magnetic flux, so that the rotor comes with the winding Lb from the control unit 26 to its output port Port2 to flow current in the next phase for continuous rotation. When outputting a signal to prevent current from flowing, the buffer Buf2 outputs a low signal to turn off the lower switch Q2b on b.

At this time, the magnetic flux induced on phase B is removed by the freewheel diodes D1b and D2b.

Under the control of the control unit 26, the buffer Buf3 of the driving unit 27 outputs a high signal, which turns on the lower switch Q2c of the c phase of the inverter 22 and thus the upper switch Q1c. On, current flows in the motor winding Lc.

The current flows through the motor winding Lc, and the phase C of the stator generates magnetic flux, so that the rotor comes with the winding Lc from the control section 26 to its output port Port3 to flow current in the next phase for continuous rotation. When outputting a signal that prevents current from flowing, the buffer Buf3 outputs a low signal to turn off the lower switch Q2c of c phase.

At this time, the magnetic flux induced on C is removed by the freewheel diodes D1c and D2c.

As described above, the magnetic flux is induced in the motor windings La, Lb, and Lc sequentially to rotate the SM.

In order to detect the current applied to the motor windings La, Lb, and Lc, the current detecting resistors Rs1, Rs2, in series between the emitters of the lower switches Q2a, Q2b, Q2c in the inverter 22 and ground. Rs3) is installed to detect positive voltage.

The voltage value proportional to the current detected by the current detection resistors Rs1, Rs2, and Rs3 provided in this way is removed by noise through the high frequency filters R2 and C3 of the current detection unit 28.

The voltage value from which the noise is removed is again supplied to the non-inverting input terminal (+) of the hysteresis comparator (Chys) by filtering voltages of 5 V or more and 0 V or less through the diodes D2 and D3.

In this case, the reference voltage input to the inverting input terminal (−) of the hysteresis comparator (Chys) is determined by the resistors Ri and R1, and the hysteresis width is determined by the resistors Rf and Rp.

When the voltage input to the inverting input terminal (-) of the hysteresis comparator (Chys) does not exceed the input voltage Vu, as shown in FIG. 5, the output of the hysteresis comparator (Chys) becomes 0V, thereby turning on the transistor Q2. By turning off, the buffer of the driving unit 27 is operated normally.

When the voltage input to the inverting input terminal (-) of the hysteresis comparator (Chys) exceeds the input voltage Vu (or when an overcurrent flows) as shown in FIG. 5, the output of the comparator (Chys) becomes 5V. Turn on transistor Q2.

As the transistor Q2 is turned on, the reference voltages of the buffers Buf1, Buf2, and Buf3 in the driver 27 are set to 5V.

Therefore, the outputs of the buffers Buf1, Buf2, and Buf3 do not output 5V.

Therefore, the lower switches Q2a, Q2b, and Q2c of the inverter 22 are all turned off so that current does not flow through the current detecting resistors Rs1, Rs2, and Rs3, which are again input to the hysteresis comparator (Chys). The voltage capable of turning off the comparator again shows an operating characteristic that is not turned off unless the power is reset by setting VL to a negative voltage as shown in FIG.

By doing so, when the motor is constrained for some reason while the motor is rotating, the controller 26 increases the current excitation time for each phase of the motor for the desired number of revolutions, thereby increasing the amount of increase in the current resulting in the motor winding temperature. Rises, or the microcomputer (controller 26 in the present invention) may run out for some reason, and a signal may be continuously turned on to excite a current in each motor motor. The occurrence that can occur can be prevented.

And as another method, as shown in Fig. 4, the reset section 29 is provided.

Therefore, an overcurrent flows to the inverter 22, and the hysteresis comparator (Chys) outputs a high signal to turn on the transistor Q2.

At this time, the transistor Q2 is not connected to the buffer of the driver 27, but is connected to the reset unit 29.

Therefore, when the transistor Q2 is turned on and a high signal is applied to the reset unit 29, the reset unit 29 resets the control unit 26 to protect the circuit from overcurrent.

As described in detail above, the present invention installs a current detector for overcurrent protection instead of a PTC thermistor, so that the motor can be installed in a PCB without using a space inside the motor, and thus the motor can be made compact, compared to a PTC thermistor. In terms of price, it is possible to design at a much lower price.

Claims (5)

Inverter which converts the DC voltage output from the rectifying unit rectifying the input AC power to AC power to drive the SM, and the sensor and the rotation detecting unit which detects the rotor position of the SM and outputs the rotor position signal accordingly. And a control unit for turning on and off the switch element of the inverter according to the rotor position signal, wherein the inverter detects the current of each phase to determine whether the current flowing through the motor winding is a normal current or an overcurrent. And a current detecting unit for outputting a driving stop signal when judged to be an overcurrent, and a driving unit for stopping the operation of the inverter when the driving detection signal is input from the current detecting unit. The current detecting unit of claim 1, wherein the current detecting unit senses a current flowing in each phase in the inverter, converts the current into a voltage value proportional to the detected current, and outputs the current detecting resistor, and the voltage value output from the current detecting resistor. A high frequency filter for filtering out the effects of noise, a filter for filtering the output of the high frequency filter to a voltage of 5 V or more and 0 V or less, and comparing the output voltage and the reference voltage of the filter to each phase of the inverter. And a comparator for determining whether the current is an overcurrent or a steady current, and an output control transistor for controlling the output of the driver in accordance with the output of the comparator. The over-current protection circuit of SM, characterized in that the current detection resistor is installed between the emitter of the lower switch of each phase of the inverter and the ground to detect a positive voltage. 3. The overcurrent protection circuit of SLM according to claim 2, wherein the comparator is a hysteresis comparator. The overcurrent protection circuit of claim 1, further comprising a reset unit for resetting the operation of the controller when the driving stop signal is input by the current detection unit.