KR20080019105A - Apparatus and method for monitoring operating of synchronous electric motor - Google Patents

Abstract

An apparatus and a method for monitoring an operation of a synchronous electric motor are provided to simplify structure of the synchronous electric motor without an additional speed sensor by using a counter electromotive force of an exciting coil to detect rotation speed of the synchronous electric motor. An apparatus for monitoring an operation of a synchronous electric motor includes a control block(302), a switching block(312), a waveform shaping block(318), a counter, and a main control block(320). The control block monitors a magnetizing state of magnetic material and generates a selection signal to selectively switch output of counter electromotive force of an exciting coil(314) when detecting the normal magnetizing state of the magnetic material. The switching block is installed between a power supply block(304) and the exciting coil to switch the output of the counter electromotive force in response to the selection signal. The waveform shaping block shapes a waveform of the counter electromotive force outputted from the switching block into a pulse waveform. The counter counts the shaped pulse waveform to generate a count value. The main control block calculates a rotation speed of the synchronous electric motor based on the count value to monitor the operation of the synchronous electric motor based on the rotation speed.

Description

Operation monitoring device of synchronous motor and its method {APPARATUS AND METHOD FOR MONITORING OPERATING OF SYNCHRONOUS ELECTRIC MOTOR}

1 is a plan view of a typical synchronous motor,

2 is a block diagram of a typical synchronous motor drive device having a conventional driving monitoring device;

3 is a block diagram of a synchronous motor driving apparatus including a driving monitoring apparatus according to a preferred embodiment of the present invention;

4 is a flowchart illustrating a process of monitoring a driving state when a synchronous motor is driven according to a preferred embodiment of the present invention;

5A is a sine wave waveform of counter electromotive force output from an excitation coil, and 5B is a pulse waveform obtained by shaping a sine wave waveform into a square wave pulse.

<Brief description of the major symbols in the drawings>

302: control block 304: power supply block

306: first switching element 308: second switching element

310: main coil 312: switching block

314: excitation coil 316: sensor

318: waveform shaping block 320: main control block

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous electric motor, and more particularly, to an operation monitoring apparatus and method suitable for monitoring an operating state of a synchronous motor including an excitation pole, a stator with a plurality of teeth, and a rotor with a magnetic body. It is about.

As is well known, a typical synchronous motor, such as a written pole motor (WPM), generates a rotational force by synchronizing an input frequency with a rotational frequency. An example of such a synchronous motor includes a type as shown in FIG. It is mainly used as an electric motor for home appliances, such as an air conditioner and a refrigerator.

Referring to FIG. 1, a typical synchronous motor, which is roughly divided into a stator 102 and a rotor 112, has a stator 102 facing its inner wall side (ie, facing the rotor 112). Side, one female pawl 104 and a plurality of teeth 108 are formed, the female pawl 104 and each tooth 108 being spaced circumferentially along the inner wall of the stator 102. It has a structure that is formed to protrude. The synchronous motor of this structure is called an inner rotor type, and the excitation pole 104 is a soft low loss magnetic material.

In addition, an excitation coil 106 of the stator 102 is wound along a predetermined direction, and a main coil 110 is wound around each tooth 108 of the stator 102 along a predetermined direction. It is. Here, the excitation coil 106 and the main coil 110 are supplied with an excitation current and a driving current, respectively, to rotate the rotor 112 by the interaction (magnetic field) with the conductor 116 and the magnetic body 118. Generates torque.

On the other hand, the rotor 112 is fixed to the shaft 114 for transmitting the rotational force of the rotor 112 in the center, the magnetic body 118 of a certain thickness is fixedly mounted along the outer periphery. The magnetic body 118, for example, can be mounted in a ring shape on the outside of the rotor by attaching a magnetic operation in the form of a fragment to a certain shape, and has a high coercive force that can be remagnetized by an exciter during operation of the synchronous motor. It is possible to use a high energy ferrite ceramic magnetic material or a high energy rare earth magnetic material.

In addition, the conductors 116 having a structure spaced apart at regular intervals are formed between the inside of the rotor 112, that is, between the shaft 114 and the magnetic body 118 fixedly mounted along the outer circumference thereof. These are used to generate a start torque for the initial drive of the rotor 112.

Thus, a typical synchronous motor having the structure as described above, the rotor 112 by generating a drive torque by supplying a drive current to the main coil 110 wound on each tooth 108 of the stator 102 during the initial drive Induces an initial rotation of the magnet, and then magnetizes the remagnetizable magnetic body 118 by supplying an exciting current to the excitation coil 106 wound on the excitation pole 104, and the excitation coil when the magnetization of the magnetic body 118 is completed. It cuts the supply of current to the 106 and drives through the driving current supplied to the main coil 110.

FIG. 2 is a block diagram of a conventional driving device for driving a typical synchronous motor having a structure as described above, that is, a typical synchronous motor driving device having a conventional driving monitoring device, and a control block 202. Block 204, first switching element 206, second switching element 208, main coil 210, excitation coil 212, first sensor 214, second sensor 216 and main control block 218 and the like.

At this time, in the synchronous motor drive device having the above-described configuration, as a constituent member constituting the operation monitoring device, the magnetic body 118 of the rotor 112 by the exciting current supplied through the exciting coil 212. Is completely magnetized and based on the rotation speed detected by the second sensor 216 and the second sensor 216 to detect the rotation speed (rotation rpm) when the rotor 112 of the synchronous motor maintains a normal operating state. The main control block 218 checks whether the synchronous motor is normally operated at a predetermined target rpm and provides the result to a monitor (not shown).

Referring to FIG. 2, the first switching element 206 is turned on in accordance with a switching control signal (on control signal or off control signal) provided from the control block 202 through lines L21 and L23 at the time of initial driving. The second switching element 208 is maintained in the off state, so that the current output from the power supply block 204 is supplied only to the main coil 210, not to the excitation coil 212.

Here, the main coil 210 is, for example, wound around each tooth 108 of the stator 102 as shown in FIG. 1 to drive the rotor 112 based on the drive current supplied to it. Perform the function. Therefore, based on the driving (starting) torque caused by the induced electric power generated between the main coil 210 wound on each tooth 108 of the stator 102 and the conductor 116 of the rotor 112 shown in FIG. The rotor 112 is rotated.

Thereafter, the second switching element (in response to the switching control signal provided from the control block 202 through the line L23 at a predetermined suitable time (for example, several to several tens of millimeters since the initial driving current is supplied to the main coil). When the 208 is turned on, the exciting current is supplied to the exciting coil 212. As a result, a magnetic exciting field is generated, and the magnetic body 118 of the rotor 112 is magnetized (N / S alternating magnetization).

Here, the excitation coil 212 is, for example, the outer side of the rotor 112 on the basis of the excitation current (square wave drive current) is wound on the excitation pole 104 as shown in FIG. For example, it performs a function of magnetizing (N / S alternating magnetization) the magnetic body 118 fixed to the outside of the rotor 112 by an adhesive method or the like.

At this time, the first sensor 214 detects the rotation frequency (rotation rpm) of the synchronous motor of the rotor 112 and provides it to the control block 202. In the control block 202, the rotation frequency is approximately 70 of the synchronous speed. When the magnetic material 118 of the rotor 112 is completely magnetized when it is about 80% to about 80%, a corresponding switching control signal (off control signal) is generated to the second switching element 208 through the line L23. As a result, the power supply to the excitation coil 212 is cut off by turning off the second switching element 208.

Therefore, after that, the motor is driven by the power (drive current) supplied to the main coil 210 wound around each tooth 108 of the stator 102 through the first switching element 206 (ie, the rotor). 112 is rotated).

On the other hand, when the magnetic material of the rotor is completely magnetized through a series of control processes as described above, when the rotor rotates, that is, the synchronous motor is driven, the second sensor 216 detects the rotational speed of the rotor, The rotation speed of the detected synchronous motor is transmitted to the main control block 218. Here, the second sensor 216 is a speed sensor mounted at a specific position of the synchronous motor and detecting the rotational speed thereof.

In response, the main control block 218 compares the rotational rpm transmitted from the second sensor 216 with a target rpm (including an allowable error range) previously stored in the internal memory so that the operation state of the synchronous motor is normal. It checks whether it is an operating state or an abnormal operation state, and transmits and displays the check result (normal operation state or abnormal operation state) to the monitor side not shown in figure. Accordingly, the user (worker) may determine and confirm (monitor) whether the corresponding synchronous motor is operating normally by looking at the check result displayed through the monitor.

Here, the main control block 218 is composed of, for example, a microprocessor, etc. to control the overall operation of the synchronous motor, for example, a control block 202 for selectively controlling the power supply to the main coil 210 and the excitation coil 212. Control for the operation in the control panel).

However, the conventional drive device which detects the rotational speed of the synchronous motor using the speed sensor as described above, and monitors the operating state of the synchronous motor based on the detection result, is a separate method for detecting the rotational speed of the synchronous motor. Since the speed sensor must be installed, the hardware structure of the synchronous motor becomes complicated, and this problem eventually leads to an increase in manufacturing man-hours and an increase in manufacturing cost of the synchronous motor.

The present invention is to solve the above problems of the prior art, it is possible to detect the rotational speed of the synchronous motor by using the counter electromotive force generated from the excitation coil without employing a hardware means for detecting the rotational speed of the synchronous motor It is an object of the present invention to provide an apparatus and a method for monitoring the operation of a synchronous motor.

Another object of the present invention is to provide an apparatus and a method for monitoring operation of a synchronous motor capable of realizing a simplified hardware structure of the synchronous motor by detecting the rotational speed of the synchronous motor using the counter electromotive force generated from the exciting coil.

The present invention according to one aspect for achieving the above object, the excitation coil is supplied through the excitation coil from the power supply and the stator equipped with a plurality of teeth each winding the excitation coil and the main coil is wound A device for monitoring the operation of a synchronous motor having a rotor having a magnetic body selectively magnetized by an electric current, the apparatus for monitoring the magnetization state of the magnetic body, and when the normal magnetization of the magnetic body is detected, Means for generating a selection signal for selective switching of an output, a switching means provided between the power supply source and the excitation coil, for switching the output of the counter electromotive force in response to the generated selection signal, and an output through the switching means. Pulse shaping to shape a waveform of the counter electromotive force into a pulse waveform Means for counting the shaped pulse waveform to generate a count value, and calculating the rotational speed of the synchronous motor based on the generated count value, and operating state of the synchronous motor based on the calculated rotational speed. It provides a driving monitoring apparatus of a synchronous motor comprising a means for monitoring.

According to another aspect to achieve the above object, the present invention provides an excitation supplied through the excitation coil from a power supply and a stator equipped with at least one excitation pole wound with an excitation coil and a plurality of teeth wound with a main coil, respectively. A method for monitoring the operation of a synchronous motor having a rotor having a magnetic body selectively magnetized by an electric current, the method comprising: detecting a counter electromotive force of a sine wave generated in the exciting coil when a normal magnetization of the magnetic body is detected; Shaping the detected counter electromotive force waveform into a square wave pulse; counting the converted square wave pulse; calculating a rotation speed of the synchronous motor based on the count result; Monitoring the operating state of the synchronous motor based on speed; It provides a way to monitor operation of the synchronous motor.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a key technical aspect of the present invention, unlike the above-described conventional method of mounting a speed sensor to the synchronous motor and thereby detecting the rotational speed of the synchronous motor to monitor the driving state, the exciting coil wound on the excitation pole of the stator Switches back electromotive force of sine wave generated from the outside and outputs the outside electromotive force by shaping square wave pulse, and counts the pulse value to detect rotation speed of synchronous motor, and based on the detection result, operation state of synchronous motor By monitoring this, it is possible to easily achieve the object of the present invention through this technical means.

3 is a block diagram of a synchronous motor driving apparatus including a driving monitoring apparatus according to a preferred embodiment of the present invention, the control block 302, the power supply block 304, the first switching element 306, the second The switching element 308, the main coil 310, the switching block 312, the excitation coil 314, the sensor 316, the waveform shaping block 318, the main control block 320, and the like.

At this time, in the synchronous motor driving apparatus having the above-described configuration, as a constituent member of the driving monitoring apparatus of the present invention, the magnetic body of the rotor 112 is caused by the exciting current supplied through the exciting coil 314. A switching block 312 which outputs the counter electromotive force generated by the excitation coil 314 to the outside based on the switching switching signal at a time when 118 is fully magnetized (for example, about 70 to 80% of the synchronous speed); Waveform shaping block 318 and main control block 320 may be mentioned. Each function of these components will be described in detail later.

Referring to FIG. 3, the control block 302 is a control chip for selectively controlling power supply to the main coil 310 and the excitation coil 314 according to the control from the main control block 320. In response to a control signal, various detection signals, etc. from the 320, a function such as on / off control of the power supply and switching control of the current output is performed, that is, a control signal for power supply is generated to the power supply block 304. Providing on / off switching control signals for switching the power output (i.e. drive current output, excitation current output) at power supply block 304 to switch the first and second via lines L31 and L33, respectively. And providing the elements 306 and 308, respectively.

In addition, the control block 302 determines whether the rotation frequency (rotation rpm) provided from the sensor 316 to be described later, that is, the rotation frequency of the rotor, becomes about 70 to 80% of the preset target synchronization speed, for example, the synchronization speed. When the detected rotation frequency reaches the preset target synchronous speed of the synchronous speed, a switching select signal is generated through the line L35 and provided to the switching block 312, whereby the counter electromotive force generated in the excitation coil 314 is generated. A function of controlling the output to the waveform shaping block 318 to be described later is performed.

Next, the power supply block 304 selectively provides an AC power supply to provide driving power (power) to the synchronous motor, which is output in response to the power supply control signal from the control block 302. AC power is output through the terminal, and the output current is transmitted to the first and second switching elements 306 and 308, respectively.

Meanwhile, the first switching element 306 is switched on / off in response to the switching control signal provided from the control block 302 through the line L31, thereby selectively supplying a driving current to the main coil 310. As such a switching element, for example, a transistor, a relay, or the like can be used.

Here, the main coil 310 is wound around each tooth 108 of the stator 102 as shown in FIG. 1 as an example to drive the rotor 112 based on the drive current supplied to it. Perform the function.

In addition, the second switching element 308 is switched on / off in response to a switching control signal provided from the control block 302 through the line L33, thereby selecting an excitation current for magnetic magnetization formed in the rotor 112. The output switching is provided to one side of the variable contact (b) of the switching block 312, the off-switching control signal provided from the control block 302 through the line L33 when the magnetic body 118 of the rotor 112 is fully magnetized It switches to off state based on. As the second switching element 308, as in the first switching element 306, a transistor, a relay, or the like can be used.

Next, the switching block 312 is, for example, a relay having a bidirectional output contact, etc., with one fixed contact a and two variable contacts, whose outputs are connected to the excitation coil 314, that is, the second switching. A variable contact (b) connected to the output of the element 308 and a variable contact (c) connected to the input of the waveform shaping block 318, which switching block 312 is connected to the control block (line L35). In response to the switching select signal provided from the 302, when the exciting current is supplied to the exciting coil 314, the contact ab is connected, and the contact ac is connected when the magnetic body 118 of the rotor 112 is completely magnetized. The counter electromotive force of the sine wave (sine wave as shown in FIG. 5A as an example) generated in the excitation coil 314 is output to the waveform shaping block 318 through the connection of the contact ac.

Here, the excitation coil 314 is wound on the excitation pole 104 of the stator 102 as shown in FIG. 1 as an example, the outer side of the rotor 112 based on the excitation current supplied to itself, For example, the magnetic body 118 is fixed to the outside of the rotor 112 by an adhesive method or the like. In other words, the excitation coil 314 functions as a magnetizing coil for generating a magnetic excitation field. In this case, the magnetization means that the magnetic body is magnetized by the excitation current, and when the magnetic body loses the magnetization, it is called demagnetization. The magnetic body 118, for example, can be mounted in a ring shape on the outside of the rotor by attaching a magnetic operation in the form of a fragment to a certain shape, and has a high coercive force that can be remagnetized by an exciter during operation of the synchronous motor. It is possible to use a high energy ferrite ceramic magnetic material or a high energy rare earth magnetic material. In addition, the excitation pole 104 is a soft, low loss magnetic substance.

In addition, the sensor 316 detects the number of revolutions of the rotor 112 shown in FIG. 1, generates it as a rotation frequency, and provides the same to the control block 302. On the basis of the rotation frequency provided from) to determine whether the power supply to the excitation coil 314 (that is, whether to control the on / off of the second switching element 308).

On the other hand, the waveform shaping block 318 shaping the waveform of the back EMF generated from the excitation coil 314 by the rotation of the rotor 112 and output through the contact ac of the switching block 312, that is, as an example, Figure 5a A sinusoidal waveform as shown in FIG. 5 is shaped into a square wave pulse as shown in FIG. 5B, and the waveform shaped square wave pulse is transmitted to the main control block 320.

Next, the main control block 320 is composed of, for example, a microprocessor to perform overall operation control of the synchronous motor. In order to realize the present invention, a waveform shaping is performed using a built-in counter (or software). A square wave pulse provided from the block 318 is counted, and the rotation speed of the synchronous motor is calculated based on the pulse count value, and the calculated rotation speed and the target rpm (tolerance error range) which are preset and stored in the internal memory. And monitors and alarms, not shown, to determine whether the operation state of the synchronous motor is in a normal operation state or an abnormal operation state and to visually notify the outside of the determination result (normal operation state or abnormal operation state). Each function is output as

For example, when it is determined that the calculated rotational speed of the synchronous motor is out of a predetermined target rotational speed (including an error tolerance range), the main control block 320 may allow an operator to recognize that the operation is in an abnormal state (abnormal state). An alarm message (visual alarm message) for display on the monitor is generated and transmitted to the monitor side, and an alarm, which is not shown, is controlled to generate an intermittent sound to warn of abnormal operation.

Therefore, in the case of the present invention, the driving performance of the synchronous motor may be automatically applied to the case where the synchronous motor is manufactured and then the driving performance is tested.

On the other hand, in the preferred embodiment of the present invention, the waveform shaping block 318 and the main control block 320 is described as a separate component for the convenience of explanation and enhancement of understanding, the present invention is limited to a separate component Of course, these two components can be configured as one one-chip processor, depending on the need or use.

Next, a series of processes for monitoring the operation state by using the synchronous motor drive device of the present invention having the above-described configuration will be described.

4 is a flowchart illustrating a process of monitoring a driving state of a synchronous motor according to a preferred embodiment of the present invention.

Referring to FIG. 4, when an operator operates driving of the synchronous motor while the synchronous motor performs the standby mode (steps 402 and 404), the main control block 320 generates a control signal for starting the motor corresponding thereto. Power is supplied to the main coil 310 via the first switching element 306 by generating a switching control signal through the line L31 in the control block 302 in response thereto. It is rotated and the excitation current is supplied to the exciting coil 314 through the contact ba of the second switching element 308 and the switching block 312 by generating a switching control signal on the line L33 again with a certain time difference (step 406 ).

At this time, the sensor 316 detects the rotation frequency (rotation rpm) of the rotor 112 and provides it to the control block 302. In the control block 302, the sensor 316 rotates based on the rotation frequency provided from the sensor 316. It is checked whether the magnetic body 118 of the electron 112 is completely magnetized (step 408). Here, the control block 302 may be set to determine, for example, when the rotation rpm is about 70 to 80% of the preset synchronous speed as the magnetization completion point of the magnetic body 118.

As a result of the check in step 408, if it is determined that the magnetic body 118 of the rotor 112 is completely magnetized, the control block 302 generates a switching selection signal on the line L35, and as a result, the switching block ( As the connected state of 312 is switched from the contact ab to the contact ac state, the counter electromotive force of the sine wave generated in the excitation coil 314 is output to the waveform shaping block 318 through the contact ac of the switching block 312 (step 410). ). At this point the second switching element 308 is switched off based on the off switching control signal provided from the control block 302 via line L33.

In response, at the waveform shaping block 318, as an example, the counter electromotive force of a sine wave as shown in FIG. 5A is shaped into a square wave pulse as shown in FIG. 5B as an example and transmitted to the main control block 320. (Step 412).

Therefore, the main control block 320 calculates the rotational speed of the synchronous motor based on the count value obtained by counting the square wave pulses (steps 414 and 416), and the calculated rotational speed is preset and stored in the internal memory. It is checked whether the operation state of the synchronous motor is normal by comparing the target rpm (including the allowable error range) (step 418). For example, the main control block 320 determines that the operating state of the synchronous motor is normal when the calculated rotational speed is within a preset target rpm range having an error tolerance range, and the calculated rotational speed is outside the preset target rpm range. It is determined that the operation state of the synchronous motor is abnormal.

As a result of the check in the step 418, when the calculated rotation speed is within the preset target rpm range, the main control block 320 determines that the synchronous motor is in a normal operating state, and generates a corresponding visual guidance message. The control signal for generating a guide sound for audibly notifying that the monitor is transmitted to the monitor side, which is not shown, and is generated is transmitted to the alarm unit, which is not shown, (step 420).

Therefore, the operator will be able to recognize that the guidance message output through the monitor and alarm, that is, the operation of the synchronous motor is in a normal state.

Meanwhile, as a result of the check in the step 418, when the calculated rotation speed is out of the preset target rpm range, the main control block 320 determines that the synchronous motor is in an abnormal operating state, and a visual alarm message corresponding thereto. To generate and transmit to the monitor not shown, and generate a control signal for generating an alarm sound (eg, intermittent sound, etc.) to audibly notify that the abnormal state (step 422). .

Therefore, the operator can recognize that the operating state of the synchronous motor is abnormal through an audiovisual alarm message (that is, an alarm message indicating that the operating state of the synchronous motor is abnormal) provided from the monitor and the alarm, and follow up therefor. You will be able to prepare for such troubles.

On the other hand, in the preferred embodiment of the present invention has been described as having only one excitation pole in the stator, this is merely an illustrative presentation for convenience of description and the present invention is not necessarily limited to this, it is necessary or necessary As a result, a plurality of excitation poles may be configured in the stator, and in this case, it is preferable to mount the excitation poles in an opposite direction to each other.

In addition, in the preferred embodiment of the present invention described as being applied to the inner rotor (inner rotor) method, the present invention is not necessarily limited to this, if one skilled in the art the present invention the outer rotor (outer rotor) method It will be clear that the same can be applied to.

In the foregoing description, the present invention has been described with reference to preferred embodiments, but the present invention is not necessarily limited thereto. Those skilled in the art will appreciate that the present invention may be modified without departing from the spirit of the present invention. It will be readily appreciated that branch substitutions, modifications and variations are possible.

As described above, according to the present invention, unlike the aforementioned conventional method of mounting a speed sensor to the synchronous motor and detecting the rotational speed of the synchronous motor, thereby monitoring the driving state, the excitation coil wound on the excitation pole of the stator The counter electromotive force of the generated sine wave is switched and output to the outside, and the output counter electromotive force is shaped into a square wave pulse, the pulse value is counted to detect the rotational speed of the synchronous motor, and the operation state of the synchronous motor is determined based on the detection result. By monitoring, the hardware structure of the synchronous motor can be simplified compared with the prior art which requires the installation of a separate speed sensor, thereby simplifying the manufacturing process of the synchronous motor and reducing the manufacturing cost.

Claims (6)

At least one excitation pole wound with an excitation coil and a stator equipped with a plurality of teeth wound around the main coil, and a rotor having a magnetic body selectively magnetized by an excitation current supplied through the excitation coil from a power source. A device for monitoring the operation of a synchronous motor, Means for monitoring a magnetization state of the magnetic material and generating a selection signal for selectively switching the output of back EMF generated from the exciting coil when a normal magnetization of the magnetic material is detected; Switching means installed between the power supply source and the excitation coil, for switching the output of the counter electromotive force in response to the generated selection signal; Pulse shaping means for shaping the waveform of the counter electromotive force output through the switching means into a pulse waveform; Means for counting the shaped pulse waveform to generate a count value; Means for calculating a rotational speed of the synchronous motor based on the generated count value, and monitoring the operating state of the synchronous motor based on the calculated rotational speed Driving monitoring device of the synchronous motor comprising a. The method of claim 1, The device, And a means for visually and alarming when the driving state of the synchronous motor is in an abnormal driving state. The method of claim 1, The switching means is a driving monitoring device for a synchronous motor, characterized in that the relay. The method according to any one of claims 1 to 3, And the pulse shaping means, the count value generating means and the monitoring means are constituted by a one-chip processor. At least one excitation pole wound with an excitation coil and a stator equipped with a plurality of teeth wound around the main coil, and a rotor having a magnetic body selectively magnetized by an excitation current supplied through the excitation coil from a power source. As a method of monitoring the operation of a synchronous motor, Detecting a counter electromotive force of a sine wave generated in the exciting coil when the normal magnetization of the magnetic material is detected; Shaping the waveform of the detected counter electromotive force and converting the waveform into a square wave pulse; Counting the converted square wave pulses; Calculating a rotational speed of the synchronous motor based on the count result value; Monitoring the operation state of the synchronous motor based on the calculated rotation speed Operation monitoring method of a synchronous motor comprising a. The method of claim 5, wherein The method, And when the driving state of the synchronous motor is determined to be an abnormal driving state, visually alarming the driving state of the synchronous motor.

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