JPH07118945B2 - Synchronous motor speed controller - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a speed control device for a synchronous motor using a permanent magnet as a rotor.

[Technical background of the invention and its problems]

Conventionally, a synchronous motor that uses a permanent magnet as a rotor is directly connected to a commercial power source and is driven in synchronization with the power source frequency, so variable speed cannot be achieved, and the rotation speed of the rotor is synchronized with the power source frequency. If this is not done, effective torque will not be generated, and there was the problem that starting would be difficult. In order to improve this, a cage coil and a hysteresis ring were provided separately from the permanent magnet of the rotor to perform the starting, but there was a problem that the configuration was complicated and the efficiency was deteriorated as it was expensive. .

However, recently, due to the development of the inverter,
A motor in which a motor is connected through an inverter and the power supply frequency is variably controlled by the above-mentioned inverter to control the rotational speed of the motor at a variable speed has come to be widely used.

This inverter drive system is effective for a three-phase induction motor, but for a synchronous motor, there is a possibility that a synchronous deviation may occur due to a sudden rotation speed change such as overload, start-stop, or so-called step-out. Have the problem of being.

On the other hand, a so-called brushless motor, which is formed so that the rotor position detector such as a Hall element detects the rotational position of the rotor of the permanent magnet, and is controlled by this detection signal, has a good controllability and high efficiency. It has come to be often used as a drive source for office automation equipment and audio equipment.

This brushless motor is a very effective means for small motors of several W or less integrated with the drive circuit because the rotor position is detected by an electronic circuit such as a Hall element.
In the motors that require the motor, the size of the drive circuit becomes large, making it difficult to integrate the motor with the motor. In particular, the heat generated by these motors has a large effect, and the drive circuit formed by an electronic circuit is used. When the parts are incorporated, there is a problem that the size becomes large and a malfunction occurs due to thermal stress, resulting in a decrease in reliability.

For this reason, generally, a method is used in which only the position detector is incorporated in the motor, and the drive circuit is so-called externally connected to the main circuit of the motor main body and the lead wire of the position detector.

However, in the case of such a configuration, (a) since the mounting member for the position detector is incorporated, a space is required for the motor main body, resulting in a large size and an increase in cost.

(B) When a Hall element is used for the position detector, the Hall element is vulnerable to heat, so heat generation in the motor must be suppressed in order to maintain reliability. Is it necessary to upsize the motor to improve heat dissipation? , Or the motor output must be reduced before use.

(C) There are many lead wires (for example, 8 to 11),
It takes a lot of time and labor for the processing, which causes a high cost.

(D) The output signal of the position detector is weak (for example, 50 mV to 100 mV in the case of Hall element), and if the lead wire is long, noise is likely to be picked up, reducing reliability and causing malfunction.

I have a problem.

[Object of the Invention]

The present invention has been made in view of the above-mentioned points, and is compact and highly efficient without adding a cage coil or a hysteresis ring and without incorporating a position detector such as a Hall element in the motor body. It is possible to precisely control the variable speed and drive the motor.

[Outline of Invention]

In order to achieve the above object, the present invention detects an induced voltage from a neutral point of a stator coil of a star connection of a synchronous motor connected to a variable DC power supply via an inverter circuit, thereby synchronizing the rotation of the motor. A pulse signal is generated, and it is determined whether or not the pulse signal is an optimum energization phase in the rotation direction of the rotor based on the polarity of a predetermined induced voltage, and the inverter circuit is conduction-controlled. Is.

Example of Invention

First, in order to facilitate understanding of the present invention, the voltage generated at the neutral point of the stator coil will be described.

Via a DC power supply, an inverter circuit in which transistors Q _u , Q _v , Q _w , Q _x , Q _y , and Q _z are connected in a bridge shape, the stator coils S _u , S _v , of a synchronous motor star-connected. When S _w is connected and the transistors Q _{u to} Q _z of the inverter circuit are sequentially turned on to drive the rotor of the permanent magnet, the stator coils S _u , S _v , and S _w are connected to each phase. Causes induced voltages E _u , E _v , and E _w , as shown in FIG. As can be seen from this voltage waveform, the conduction timing of the transistors Q _{u to} Q _z is 60 ° (electrical angle) before and after the maximum value of the induced (back electromotive) voltage.
It is ideal to energize at a total of 120 ° (second
Figure (a), (b)). Thus if the ideal power is performed, the stator coil S _u, S _v, neutral voltage V _N0 generated at the neutral point N ₀ of S _w is the stator coil S _u, S _v, S _w the voltage measured each phase of the induced voltage from the neutral point N _0, respectively E _u, E _v, E _w
When the resistance of the stator coil is R and the applied voltage of the inverter circuit is V _s , in the period (I) shown in FIG. 2C, the transistors Q _u and Q _y are turned on and other transistors are turned on. Since Q _v , Q _w , Q _x , and Q _z are off, the equivalent circuit at this time is shown in FIG. 3, and the neutral point voltage V _N0 at this time is obtained by first obtaining the current I. , Therefore, the above V _N0 can be expressed as V _N0 = RI−E _v (2), and if I is eliminated from the above equations (1) and (2), Can be shown as Therefore, the neutral point voltage V _N0 has a value independent of the resistance and current of the stator coil. The same can be said for the other periods (II) to (VI), and only the results will be as follows.

That is, the applied voltage is applied to the neutral point N ₀ of the stator coils S _u , S _v , S _w.
A voltage obtained by adding 1/2 of V _s and 1/2 of the induced voltage (for example, _Eu ) is generated, which is shown in FIG.

For the reasons described above, the neutral point from the point of 1/2 of the applied voltage V _s N
If it is configured to measure a voltage V _N0 of ₀ , that is, when the applied voltage V _s and the neutral point voltage V _N0 are voltage-compared, the comparison value V _CP is (However, E: E _u , E _v , and E _w are generic names), and the present invention detects the induced voltage E irrespective of the applied voltage V _s , as is apparent from the equation (4). It was made with a focus on what you can do.

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is an AC power supply of commercial frequency, 2 is connected to the power supply 1 described above, and a rectifier circuit that sends out a DC output that is single-phase rectified by a diode or the like, 3 is connected to the rectification circuit 2 It is a variable DC power supply circuit including a pulse width modulation type chip power supply, etc., in which an output voltage is varied and sent according to a command. This is because the Choket coil L and the capacitor C ₁ are inserted in series between the input terminals via the collector and the emitter of the control transistor Q ₁ ,
Insert the resistor R ₁ between the collector and the base of the Q _1, a diode D ₁ connected to cathode emitter of the transistor Q ₁
The anode of is connected to the negative side of the input terminal, resistors R ₃ and R ₄ are inserted in series between the terminals of the capacitor C ₁ , and the connection point of these resistors R ₃ and R ₄ is composed of an operational amplifier. It is connected to the inverting input terminal of the voltage error detector EA ₁ , and the output voltage corresponding to the motor speed is set to the non-inverting input terminal of this error detector EA ₁ , and this is sent as a speed command. Connect the output terminal of the speed setting circuit (not shown) to the error detector EA ₁
Diode with the output terminal of the cathode connected to the output terminal
The output terminal is connected via D ₂ to the inverting input terminal of the comparator CP ₁ consisting of an operational amplifier with an open collector, and the inverting input terminal of this comparator CP ₁ is connected to the current error detector consisting of an operational amplifier. Similarly to the above, the output terminal of EA ₂ is connected via the diode D ₃ having the cathode connected to the output terminal thereof, and the non-inverting input terminal of this error detector EA ₂ is connected between the constant voltage power supply V _C and the circuit ground. The connection point of resistors R ₅ and R ₆ inserted in series is connected, and the inverting input terminal of the error detector EA ₂ is connected to the output terminal of the current detector ID which is the resistor inserted in the negative side output circuit of the circuit 3. And connect the inverting input terminal of the comparator CP ₁ to the constant current source C
It is connected to the constant voltage power supply V _C via I, and the non-inverting input terminal of the comparator CP ₁ has a sawtooth pulse signal that oscillates at a constant frequency (for example, 30 KH _Z ) Connect the output terminal, connect the output terminal of this comparator CP ₁ to the base of the transformer Q ₂ whose emitter is connected to the negative side of the input terminal, and connect it to the constant voltage power supply V _C via the resistor R _7. and, connected to the base of the transistor Q ₁ to the collector of the transistor Q ₂ through a resistor R _2, sends out a terminal voltage of the capacitor C ₁ as the output voltage V _s, the resistance of the output voltage V _s It is input to the error detector EA ₁ via the voltage divider consisting of R ₃ and R ₄ to detect the error from the speed command, and the pulse width modulation signal (hereinafter referred to as the pulse width modulation signal sent from the output terminal of the comparator CP ₁ is detected by this detected value. the called PWM signal) variable and via the transistor Q ₂ with transistor Controls the on period of Q _1, and summer to deliver the output voltage V _s corresponding to the speed command. Further, the circuit 3 detects the error detector EA ₂ when the output voltage of the current detector ID tries to exceed the predetermined value (that is, the value corresponding to the overcurrent preset by the resistors R ₅ and R ₆ ).
Output voltage V _EA2 prioritizes the output voltage V _EA1 of the error detector EA ₁ (that is, in the relationship of V _EA2 <V _EA1 ) and controls the ON period of the transistor Q ₁ as described above to output the output voltage V _EA1.
Overcurrent can be suppressed by lowering V _s . In other words, it functions as an overcurrent limiter. Reference numeral 4 is an inverter circuit connected to the output terminal of the variable DC power supply circuit 3. This is to connect the emitters of three PNP type transistors Q _u , Q _v , and Q _{w to} the positive output terminal of the variable DC power supply circuit 3, and to connect the emitters to the collectors of these transistors Q _u , Q _v , and Q _w. The collectors of the three transistors Q _x , Q _y , and Q _z connected to the negative side output terminal of the variable DC power supply circuit 3 are respectively connected, and the transistors Q _u and Q _x , Q _v and Q _y , Q _w are connected to each other. With each connection point of Q _z as an output end, the transistors Q _{u to} Q _z are energized at appropriate times to convert the DC input voltage V _s into a three-phase AC voltage and supply it to the motor 5. Flywheel diodes D _{u to} D _z are inserted between the collectors and emitters of the transistors Q _{u to} Q _z . Then, the motor 5, as is well known, the rotor 5 _a which is permanently magnetized to multiple magnetic poles, stator coil S _u is opposed to the rotor 5 _a, S _v, stator (not shown) wound around the S _w And one end of the stator coils S _u , S _v , S _w is commonly connected to form a star connection with the neutral point N _0, and the other ends of the stator coils S _u , S _v , S _w are connected. Inverter circuit 4
Is connected to each output terminal of. 6 is to insert the resistors R ₈ and R ₉ in series between the input terminals of the inverter circuit 4, and input the input voltage V _s from the voltage dividing point (connection point of R ₈ and R ₉ ) to 1 /
This is a voltage divider circuit that outputs the divided output voltage V ₆ to 2. Numeral 7 compares the neutral voltage V _N0 of the stator coils S _u , S _v , S _w of the motor 5 with the output voltage V _{6 of the} voltage dividing circuit 6 to detect the induced voltage, and outputs a pulse signal synchronized with this. It is a synchronizing pulse generating circuit that is generated. This is because the non-inverting input terminal of the comparator CP ₂ which is an operational amplifier is connected to the neutral point N _0.
, The inverting input terminal of the comparator CP ₂ is connected to the output terminal of the voltage dividing circuit 6, and the output terminal of the comparator CP ₂ is configured to send a one-shot pulse signal at the rising edge of the input signal. Both input terminals of a first pulse generator MB ₁ consisting of a stable multivibrator and a second pulse generator MB ₂ consisting of a monostable multivibrator which sends a one-shot pulse signal at the falling edge of the input signal. Connected to the output terminals Q of both pulse generators MB ₁ and MB ₂ to prevent malfunction due to spike voltage superposed on the induced voltage when switching the transistors Q _{u to} Q _z. Voltage V _N0 and output voltage V ₆
The pulse signals synchronized with the zero point of the voltage difference (V _N0 −V ₆ ) from and are transmitted respectively. 8 is a drive circuit,
The output terminal O ₀ sends out an "H" level output signal when the control power is applied, and the output terminal O ₁ → O ₂ → O ₃ → O ₄ → O ₅ → O ₀ is output each time the input signal rises. has between six binary counter CU which is adapted to sequentially sends the "H" level of the output signal in order, the transistor Q _u to Q _z as many Orr circuit OR _u ~OR _z, input Orr circuit OR _u At the end the counter CU outputs O ₀ and O
₅ , OR _z inputs to outputs O ₁ and O ₁ , OR _v inputs to outputs O ₁ and O ₂ , OR _x inputs to outputs O ₂ and O ₃ , OR _w Outputs O ₃ and O ₄ are connected to the input of and output O ₄ and O are connected to the input of OR _y.
5, is formed from a divider DEV connected respectively, and summer to deliver base drive signals respectively from the output terminal of the Orr circuit OR _u ~OR _z to the base of the transistor Q _u to Q _z. 9 is connected from the output end of the synchronous pulse generation circuit 7 and the output end of the counter CU of the drive circuit 8 so that the pulse signals of the pulse generators MB ₁ and MB ₂ depend on the polarity of the predetermined induced voltage. It is a synchronizing pulse discriminating circuit which discriminates whether or not to transmit a synchronizing pulse signal. This is at the output Q of the pulse generators MB ₁ and MB ₂ ,
The output terminals of the OR circuit OR ₂ connected to the output terminals O ₁ , O ₃ , O ₅ of the counter CU of the drive circuit 8 by connecting the input terminals of the _first and _second AND circuits AND ₁ , AND ₂ respectively. Connection point between the resistor R ₁₂ and the capacitor C ₄ inserted in series between the capacitor and the circuit ground (point a)
Is connected to the input terminal of the AND circuit AND ₁ and is connected to the input terminal of the AND circuit AND ₂ via the not circuit N ₁ to output the “H” level output signal of the AND circuits AND ₁ and AND _2. Is transmitted as a periodic pulse signal via the OR circuit OR ₁ . That is, this periodic pulse discrimination circuit 9
The stator coil S _u of the motor 5, S _v, when energized phase with S _w, by connexion energization polarity of the induced voltage generated at the neutral point N ₀ is in the direction of rotation of the powered electrode and the rotor 5 _a coil Paying attention to the points that are determined for each, for example, the output terminals O ₀ , O of the counter CU
_2, O ₄ of the "H" level positive polarity induced voltage on the output signal of the negative polarity of the induced voltage on the output terminal O _1, O _3, of O ₅ "H" level of the output signal By predetermining that, when the output signal of the output terminal O ₁ is at “H” level, the pulse signal sent from the synchronous pulse generating circuit 7 when the induced voltage changes from negative to positive is determined to be normal, The pulse signal is sent as a synchronizing pulse signal, and the pulse signal input when the induced voltage changes from positive to negative is not sent. Reference numeral 10 is connected from the synchronizing pulse discriminating circuit 9 and forcibly sends an ignition pulse signal when the motor 5 is started in a stopped state such as when the power is turned on or when the lock is complete, and the synchronizing pulse signal is synchronized. The ignition pulse generating circuit is adapted to send the synchronizing pulse signal of the synchronizing pulse discriminating circuit 9 when in the state. This is because the input ends of the NOR circuit NOR ₁ and the OR circuit OR ₃ are connected to the output end of the OR circuit OR ₁ of the synchronizing pulse discrimination circuit 9, and the cathode of the diode D ₄ is connected to the output end of the NOR circuit NOR _1. Is connected to the anode of the diode D ₄ and the connection point (point b) between the resistor R ₁₁ and the capacitor C ₃ inserted in series between the constant voltage power supply V _c and the circuit ground is connected. Point) is connected to the input end of a _third pulse generator MB ₃ consisting of a multivibrator which sends a one-shot pulse signal at the rising edge of the input signal, and the output end Q of this pulse generator MB ₃ is connected to the above. NOR circuit NOR ₁ and OR circuit O
The output end of the OR circuit OR ₃ is connected to the input end CK of the counter CU of the drive circuit 8 by connecting to the input end of R ₃ and the output of the OR circuit OR ₁ of the sync pulse discrimination circuit 9 is synchronized with When a pulse signal is received (when the motor 5 is being driven), this is sent to the drive circuit 8 via the OR circuit OR ₃ , and when a synchronous pulse signal is not received (at the time of startup, etc.), the capacitor is sent. When the potential at the point b reaches the threshold level of the pulse generator MB ₃ due to the rise of the charging voltage of C ₃ , the one-shot pulse sent by the pulse generator MB ₃ is sent to the drive circuit 8 as an ignition pulse signal. It is about to do. The pulse width of the pulse signal of the pulse generator MB ₃ is the same as that of the pulse generators MB ₁ and MB ₂ and MB ₃ >>
It is set to the relationship of MB ₁ = MB ₂ . 11 is the rectifier circuit 2
Is a constant voltage power supply circuit that is inserted between the output terminals of the constant voltage power supply V _C as a control power supply to each circuit.

Next, the operation will be described with reference to FIGS. 4 and 5.

(A) Startup at power-on Now, when all the transistors Q _{u to} Q _z are off and no speed command is given, a power switch (not shown) is turned on (at time t _{0 in} FIG. 4). The AC power supply 1 is supplied, and the constant voltage power supply V _c is supplied from the constant voltage power supply circuit 11 to each circuit via the rectifier circuit 2 as a control power supply. As a result, in the variable DC power supply circuit 3, since the output signal of the comparator CP ₁ becomes “H” level, the transistor Q ₂ turns on and the transistor Q ₁ does not send the output voltage V _s until it turns off. On the other hand, by the supply of the control power source, the ignition pulse generating circuit 10
, The output signal of the NOR circuit NOR ₁ becomes “H” level, the diode D ₄ becomes non-conductive, the capacitor C ₃ is charged through the resistor R ₁₁ at the time determined by the CR time constant, and the potential at the point b becomes This is the threshold of the pulse generator MB ₃
When the hold level V _th3 is reached, pulse generator MB ₃
Sends a one-shot pulse as an ignition pulse signal through the OR circuit OR ₃ and also sends it to the NOR circuit NOR ₁ to invert its output signal to the “L” level and turn it on to the diode.
When D ₄ is turned on, the capacitor C ₃ discharges through the diode D ₄ , the potential at the point b is dropped and the pulse generator MB ₃ is reset, and when the above one-shot pulse transmission is stopped,
As above, charge the capacitor C ₃ to generate the pulse generator MB ₃
The operation of sending out the ignition pulse signal is repeatedly performed at regular intervals.

The counter CU of the drive circuit 8 receiving this sends out an output signal of "H" level from its output terminal O ₀ by the supply of the control power source, and the OR circuits OR _u and OR _{z of} the distributor DEV receiving this output signal.
The output signal of "H" level is sent from the output terminal of the inverter to the bases of the transistors Q _u and Q _z of the inverter circuit 4 as a base drive signal, but the inverter circuit 4 does not receive the input voltage V _s. Does not start and then repeats at regular intervals and receives a firing pulse signal.
The CU counts at the rising edge of the ignition pulse signal, and sequentially outputs "H" level output signals from its output terminals O _{1 to} O _5, from which the distributor DEV outputs transistors Q _z and Q _v , Q _v. When
The base drive signal is sequentially sent to Q _x , Q _x and Q _w , and Q _w and Q _y , but the motor 5 remains stopped.

In this state, when an output voltage corresponding to a predetermined number of revolutions is given as a speed command from a speed setting circuit (not shown), the error detector EA ₁ of the variable DC power supply circuit 3 which receives it receives the other input (OV). Output the voltage V _EA1 that detected the error. Since the summer the relation of V _EA1 <V _EA2 the error detector EA ₁ of the output voltage V _EA1 and the output voltage V _EA2 of the error detector EA ₂ at this time,
The diode D ₂ is conducting (the diode D ₃ is non-conducting), and the comparator CP ₁ compares the level of the above V _EA1 with the sawtooth output signal of the pulse generator OSC, and the output signal of the pulse generator OSC is _Sends an output signal that is at "H" level for a period that is higher than V _EA1 . As a result, the transistor Q ₂ is turned off while receiving the “L” level input signal, and the transistor Q ₁ is turned on during this off period to charge the capacitor C ₁ through the chain coil L, and the charged voltage is the output voltage. It is sent to the inverter circuit 4 as V _s (time t _{1 in} FIG. 4). In response to this, the inverter circuit 4 sends the base drive signal of the drive circuit 8 to, for example, the bases of the transistors Q _u and Q _{z according to} the firing pulse signal sent from the firing pulse generating circuit 10 at regular intervals. When has been to apply an input voltage V _s between the transistors Q _u, a stator coil of the motor 5 Q _z are turned on S _u to S _w. This stator salient poles are magnetized to N or S pole, the attraction force between the magnetic poles of the rotor 5 _a, by the action of repulsion is generated a rotational torque to rotate the rotor 5 _a. At this time, the rotor 5 _a of not generated by connexion rotational torque to the stop position, when the rotor 5 _a has failed to rotate, then ignition pulse to be sent from the firing pulse generating circuit 10, for each period of time The counter CU of the drive circuit 8 counts at its rising edge in response to the signal, for example, outputs an “H” level output signal from the output terminal O ₁ , and the distributor DEV receiving this outputs the output signal from the OR circuits OR _v and OR _z. The base drive signal is sent (the output signal of OR _u is inverted to the “L” level), the transistor Q _u of the inverter circuit 4 is turned off, Q _v is turned on, and between the stator coils S _{v and} S _{w of the} motor 5. There is magnetized salient poles of a stator (not shown) is energized, the rotor 5 _a to generate a rotational torque between it and the rotor 5 _a pole that starts to rotate, to start (Fig. 4 t ₂ time).

In this way, when the motor 5 is started, the pulse generator MB ₃ of the ignition pulse generator circuit 10 repeatedly discharges at regular intervals by the charging / discharging circuit of the capacitor C ₃ provided at its input end. By the pulse signal, the base drive signal is sequentially transmitted to the bases of the transistors Q _{u to} Q _z of the inverter circuit 4 via the drive circuit 8, and the transistor
Since Q _u to Q _z forcibly sequentially switched are you summer to energize the motor 5, regardless of the stop position of the rotor 5 _a, can be accurately started without causing fatal.

In this case, since the induced voltage is zero or very small, the stator coil S _u of the motor 5, S _v, the current flowing through the S _w is intends to become very large, this current Yotsute the current detector ID Error detector EA of variable DC power supply circuit 3 detected and output voltage variable
₂ and the error detector EA ₂ tries to make this input voltage larger than the other input voltage, the output voltage V _EA2 is changed from the output voltage V _EA1 of the error detector EA ₁ to V _EA1 > V _EA2 . Since the diode D ₃ is conducting (D ₂ is non-conducting), the output of the error detector EA ₂ is sent to the comparator CP ₁ in preference to the output of EA ₁ for comparison. The device CP ₁ outputs the pulse width of the “H” level output signal so as to be wider than that of the other input signal and prolongs the ON period of the transistor Q ₂ , so that the ON period of the transistor Q ₁ is increased. Shorten the output voltage V _s to prevent current above a certain level from flowing. That is, it functions as an overcurrent limiter.

Then, _a rotational torque is generated due to the positional relationship between the salient poles of the stator (not shown) magnetized by the current flowing between the stator coils S _{v and} S _w and the magnetic poles of the rotor 5 _a , and the rotor 5 _a
Moves to a predetermined position, an induced voltage is generated, and a neutral point voltage V _N0 including a spike voltage is generated at the neutral point N ₀ (input of CP ₂ in FIG. 4 (non-inverting input voltage)) . The comparator CP ₂ of the synchronizing pulse generating circuit 7 which receives this is the voltage dividing circuit 6
Of the output voltage V ₆ V _s / 2) of the output signal of the output signal and outputs an output signal that is at "H" level to the first and second pulse generators MB ₁ and MB ₂ for the period of V _N0 > V ₆ Yes (output of CP ₂ in Fig. 4). Upon receiving this, the pulse generator MB ₁ generates a _one- shot pulse signal having a constant pulse width at the rising edge of the input (fourth
Figure (MB ₁ ). The AND circuit AND ₁ of the synchronous pulse discrimination circuit 9 which receives this outputs the output terminal O ₁ of the counter CU of the drive circuit 8.
The OR circuit OR ₂ receiving the “H” level output signal inverts the output signal to the “H” level, and the capacitor C ₄ is charged through the resistor R ₁₂ at the time determined by the CR time constant and the potential at the point a. And when this potential reaches the _threshold level V _th1 of the AND circuit AND ₁ (at time t _{3 in} FIG. 4),
The output signal is inverted to the "H" level (AND _{1 in} Fig. 4), and this is fed via the OR circuit OR ₁ to the NOR circuit NOR ₁ and the OR circuit O.
Send to R ₃ . At this time, the output signal of the AND circuit AND ₂ is inverted to the “L” level and the output signal of the not circuit N ₁ is also inverted to the “L” level due to the potential increase at the point a.

The OR circuit OR _{3, which} has received the “H” level output signal from the OR circuit OR ₁ , has already received the pulse signal of the pulse generator MB ₃ and has sent it out as an ignition pulse signal. The output of Fig. MB ₃ ) and the logical sum of this output are sent (OR _{3 in} Fig. 4). Also, the pulse generator MB ₃ generates a one-shot pulse signal to invert the output signal of the NOR circuit NOR ₁ to the “L” level,
As a result, the diode D ₄ becomes conductive, the capacitor C ₃ is discharged through the diode D _4, and the potential at the point b drops to zero potential. That is, the pulse generator MB ₃ is reset.

Induced voltage above the rotor 5 _a is by connexion occurs by rotating the zeros negative when aerodrome cross from the positive (i.e. neutral voltage V _N0 is pressed halving the applied voltage of the stator coil Since the output signal of the comparator CP ₂ is inverted to the “L” level (at time t _{4 in} FIG. ₄ ) when the voltage changes from high to low compared to the voltage V ₆ , the pulse generator MB ₂ falls at the falling edge. It will generate a one-shot pulse signal and send it to the AND circuit AND ₂ .
Since the output signal of the NOT circuit N ₁ is at the “L” level, the AND circuit AND ₂ does not output the synchronizing pulse signal, since the output signal remains at the “L” level. That is, the synchronizing pulse discriminating circuit discriminates that the pulse signal received from the pulse generator MB ₂ at the time point t 4 in FIG. ₄ is not the polarity of the predetermined induced voltage and does not send the synchronizing pulse signal. In other words,
It will send a sync pulse signal to determine the optimum conduction phase with respect to the rotational position of the rotor 5 _a. Then, when the induced voltage zero point of the rotor 5 _a further O connexion generated to rotate and about to aerodrome cross from the negative contrary to the above, (Fig. 4 t ₅ point), the synchronization pulses Since the comparator CP ₂ of the generating circuit 7 inverts its output signal to the “H” level, the pulse generator MB ₁ sends out a pulse signal at the rising edge of its input. Upon receiving this, the AND circuit AND ₁ inverts the output signal to the “H” level, and sends this out as a synchronizing pulse signal via the OR circuit OR ₁ . The counter CU that receives this through the OR circuit OR ₃ counts at the rising edge of its input and inverts the output signal of the output terminal O ₂ to “H” level (output terminal
The output signal of O ₁ is inverted to “L” level, the output signal of the OR circuit OR _X of the distributor DEV is inverted to “H” level (the output signal of OR _z is inverted to “L” level), the base drive signal is sent to the base of the transistor Q _x which is turned on by a (Q _z is off, Figure 4 Q _x, Q _z), S energization phase of the stator coil from S _v → S _{w v} → S _Switch to _u and apply current to the rotor
5 the rotational torque to accelerate given to _a, into the so-called synchronized operation.

At this time, a spike voltage due to commutation is superimposed on the induced voltage generated at the neutral point N ₀ due to the switching from the transistor Q _z → Q _x , and the neutral voltage V _N0 instantly drops from V ₆ (V _N0 <V ₆ )
As a result, the output of the comparator CP ₂ is inverted to the “L” level, and the pulse generator MB ₂ also outputs a pulse signal at this falling edge, but the capacitor C ₄ has a CR time constant through the resistor R ₁₂ and has a CR time constant. Since it is discharged, the output of the NOT circuit N ₁ is at the “L” level, and the output of the AND circuit AND ₂ is at the “L” level.

If placed in a synchronous operation, since the induced voltage also increases, the current decreases and functions as an overcurrent Rimitsuta is released, the rotor 5 _a of the motor 5 at a commensurate ivy speed to the output voltage V _s corresponding to the speed command to rotate .

Then, when the motor 5 enters the synchronous operation, the synchronous pulse generation circuit 7 detects the induced voltage generated at the neutral point N ₀ of the stator coils S _u , S _v , S _w , and sends out a pulse signal. The received sync pulse discrimination circuit 9 discriminates the input pulse signal from the output signal of the counter CU, and detects the sync pulse signal from the drive circuit 8.
Therefore, the ignition pulse generating circuit 10 discharges the capacitor C ₃ without the potential at the point b (charging voltage of the capacitor C ₃ ) against the threshold level of the pulse generator MB _3. Then, the generation of the ignition pulse signal transmitted from the circuit 10 is blocked.

That is, the motor 5 sequentially switches the transistors Q _{u to} Q _z of the inverter circuit 4 by the ignition pulse signal that is forcibly sent out at regular intervals even if the rotor 5 _a is located at an arbitrary position. given a rotational torque to _a, the rotor 5 _a begins to start, thereby sends out a sync pulse signal after one cycle of the induced power generated in synchronization, upon entry into the synchronous operation, the transistor Q _u of the inverter circuit 4 The switching of ~ Q _z is automatically switched from the ignition pulse signal to the base drive signal by the synchronization pulse signal, and the rotor 5 _a
Will be rotated.

(B) Steady operation The output voltage V _s corresponding to the speed command is applied from the variable DC power supply circuit 3 to the stator coils S _u , S _v , S _w of the motor 5 via the inverter circuit 4 to generate this voltage. motor 5 is driven at a commensurate ivy speed V _s, enters the so-called steady-state operation (Figure 4 t ₅ times).

To further explain the operation in this steady operation, the transistors Q _{u to} Q _z of the inverter circuit 4 are sequentially switched by the pace drive signal of the drive circuit 8 to cause the commutation spike of the transistor to the neutral point voltage V _N0. Are superimposed, the comparator CP ₂ of the synchronizing pulse generating circuit 7 operates and sends an output signal. That is, as shown by the input of CP ₂ in FIG. 5, the transistors Q _{u to} Q _z are applied to the neutral voltage V _N0.
This is because the spike voltage V _sp due to the switching of is overlapped and crosses the level of the output voltage V ₆ (V _s / 2) of the voltage dividing circuit 6, and after detecting the necessary induced voltage detection points g and h. The pulse that is generated is unnecessary, and it is necessary to mask this pulse to prevent malfunction. Therefore, the pulse width of the pulse signals output from the first and second pulse generators MB ₁ and MB ₂ provided at the output end of the comparator CP ₂ is set wider than the pulse width of the spike voltage V _sp. The first pulse generator MB ₁ is used for the positive half-wave of the sex-point voltage V _N0 , and the second pulse generator MB ₂ is used for the negative half-wave to superimpose the one-shot pulse signals. And a synchronous pulse discriminating circuit which receives the pulse signals of the first and second pulse generators MB ₁ and MB ₂ described above to prevent malfunction due to a spike voltage V _sp generated when switching the transistors Q _{u to} Q _z. The AND circuits AND ₁ and AND ₂ of 9 discriminate according to the potential of the point a charged / discharged by the output signal of the counter C _u and send the synchronization pulse signal to the motor 5 in synchronization with the motor 5 via the OR circuit OR _1. Therefore, the counter CU counts this at the rising edge of the input. To, by a combination of sending successively "H" level of the output signal from the output terminal O ₀ ~ O _5, distributor DEV input signal response, sequentially from the output end of Orr circuit OR _u ~OR _z base Transistor Q _u that sent drive signal and received it
〜 Q _z is, for example, turned on in the order of Q _u → Q _z → Q _v → Q _x → Q _w → Q _y , and supplies the input voltage V _s to the motor 5 as three-phase AC power to drive it. It will be.

(C) Variable Speed Control Next, in the steady operation state, the speed of the motor 5 is changed by changing the speed command (output voltage) of a speed setting circuit (not shown). That is, the PWM signal sent from the collector of the transistor Q ₂ is changed by changing the speed command to a voltage corresponding to the speed at which deceleration or acceleration is desired, and the ON period of the transistor Q ₁ is controlled. Output voltage V _s of the motor 5 is increased (accelerated) or decreased (decelerated), and the stator coils S _u , S _v , S _{w of the} motor 5 are
The induced voltage generated at the neutral point N ₀ of the
Comparator and by connexion detected CP _2, pulse generator MB ₁ for transmitting respectively the rising and falling of the output signal of the comparator CP ₂ of
The pulse signal of MB ₂ is discriminated by the synchronizing pulse discriminating circuit 9 and sent to the driving circuit 8 as a synchronizing pulse signal, and the base drive signal of this discriminates the transistors Q _{u to} Q _z to conduct at appropriate times, and the inverter circuit 4 _Will convert the input voltage V _s into a three-phase AC voltage and apply it to the motor 5,
The speed of the motor 5 is variably controlled by following the rotation speed of the motor 5. In addition, the follow-up to the rotation speed of the motor 5 detects the induced voltage every 1/6 cycle (60 °), so that the output voltage V _s of the variable DC power supply circuit 3 and the load torque can be obtained without causing step-out. The motor 5 is rotated at a suitable rotation speed.

At this time, even if the speed command is suddenly changed to suddenly change the output voltage V _s of the variable DC power supply circuit 3, the synchronous pulse generating circuit 7 detects only the induced voltage. The change in _s is not erroneously detected as a change in induced voltage, and the synchronization state is determined by the synchronization pulse determination circuit 9 even when a disturbance occurs. The speed can be variably controlled.

(D) At the time of overload When a load torque that locks the rotation of the motor 5 is applied and the current is about to increase, the output voltage V _EA2 of the error detector EA ₂ of the variable DC power supply circuit 3 causes the error detection EA ₁ a of less than the output voltage V _EA1 connexion (V _EA2 <V _EA1), the output voltage V _EA2 of the error detector EA ₂ is delivered to the comparator CP _1, was narrow Maxi pulse width from the collector of the transistor Q ₂ PWM With the signal being sent to the base of transistor Q ₁ ,
The output voltage V _s of the variable DC power supply circuit 3 is lowered in preference to the speed command to suppress overcurrent.

If the cycle of the sync pulse signal sent from the sync pulse discrimination circuit 9 becomes longer than the cycle of the firing pulse signal sent from the firing pulse generation circuit 10 due to the drop of the output voltage V _s, the firing pulse is generated. Since the transistors Q _{u to} Q _z are sequentially switched through the drive circuit 8 by the ignition pulse signal of the circuit 10, even when the motor 5 is locked due to load torque or the like, the stator coil of a specific phase is overheated. There is no inconvenience, and when only a specific transistor is overheated, no inconvenience occurs.

Moreover, if the load torque that causes locking is released, the operation is performed in the same manner as at the start-up described above, and the synchronous operation is automatically started.

In the embodiment, the variable DC power supply circuit that varies the output voltage according to the speed command and sends the output voltage has been described as a tipper system, but the present invention is not limited to this, and the output voltage is varied and sent according to the speed command. Of course, other methods that can be applied are also applicable.

〔The invention's effect〕

According to the present invention, the induced voltage generated in the motor itself is determined by the polarity with respect to the neutral point of the stator coil as the zero point, and it is determined whether or not it is the optimum energization phase in the rotation direction of the rotor to generate the synchronization pulse signal, As a result, the inverter circuit can be conduction-controlled so that the energized phase is optimal for the rotational position of the rotor, and the induced voltage generated when the motor is started is reduced to 1%.
It is possible to synchronize in a cycle, and it is possible to perform variable speed control freely over a wide range from low speed to high speed even though it is a synchronous motor.

Moreover, the variable speed can be automatically driven at a driving frequency suitable for the load condition of the motor by simply changing the voltage applied to the inverter circuit, and the configuration can be simplified.

In addition, even when the number of rotations of the motor suddenly changes due to the load, the induced voltage is detected and tracked every 1/6 cycle (60 °), so it is possible to respond to sudden changes in the load. Also, the followability can be further improved and synchronization can be achieved without step out.

Moreover, since it is not necessary to detect the position of the rotor by the position detection element, there is no need to accommodate and arrange a printed circuit board for position detection in the motor body, and no heat dissipation means is required, so the motor can be made smaller and reliability is further improved. The improved product can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams of position detection by induced voltage in FIG.
FIG. 2 is a time chart, and FIG. 3 is an equivalent circuit diagram when the motor U-V phase is energized. 4 and 5 are time charts for explaining the operation of the motor shown in FIG. 1 at the time of starting and in a steady state. 3: Variable DC power supply circuit, 4: Inverter circuit 5: Synchronous motor, 6: Divider circuit, 7: Synchronous pulse generation circuit, 8: Drive circuit, 9: Synchronous pulse discrimination circuit, 10: Firing pulse generation circuit MB ₁ , MB ₂ , MB ₃ : 1st, 2nd, 3rd pulse generator, CU: Counter

Claims (1)

[Claims] 1. A variable direct-current power supply circuit which variably outputs an output voltage according to a speed command, and a synchronous motor which is connected to an output terminal of the variable direct-current power supply circuit through an inverter circuit and which has a star-shaped stator coil and a permanent magnet rotor. A synchronous pulse generating circuit for transmitting a pulse signal synchronized with the rotation of the synchronous motor by an induced voltage detected from a neutral point of the stator coil, and the inverter circuit is timely conducted via the drive circuit by the pulse signal. In what I did,
The synchronizing pulse generating circuit is a comparator connected from the output terminal of the voltage dividing circuit for dividing the input voltage of the inverter circuit into 1/2 and the neutral point of the stator coil, and the input connected to these output terminals. The first and second pulse generators output pulse signals at the rising and falling edges of
Rotation of the rotor from the polarity of the induced voltage between the output terminal of the second pulse generator and the input terminal of the drive circuit by the pulse signals of the first and second pulse generators and the output signal of the drive circuit. 1. A speed control device for a synchronous motor, comprising: a synchronous pulse judging circuit for judging an optimum energized phase in a direction and transmitting a synchronous pulse signal.