JPH07118943B2 - Synchronous motor speed controller - Google Patents

Description

The present invention relates to a speed control device for a synchronous motor used in an air conditioner or the like.

<Technical background of the present invention and its problems> Conventionally, a synchronous motor using a permanent magnet as a rotor has been designed to be directly connected to a commercial frequency power source for driving, but the variable speed cannot be achieved and the number of rotations of the rotor is low. Has a problem that starting is difficult because effective torque is not generated unless is synchronized with the power supply frequency.To improve this, a cage coil and a hysteresis ring are provided in addition to the permanent magnet of the rotor. Although it is formed to start the engine, there is a problem in that the structure is complicated, the cost is high, and the efficiency is poor.

However, due to the recent development of inverters, a motor is connected to a commercial frequency power supply via an inverter, and the power supply frequency is variably controlled by the above-mentioned inverter, so that the number of revolutions of the motor is variably and immediately controlled. Things have become popular.

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, etc., and so-called step-out may occur. Have the problem of being.

In addition, a so-called brushless motor formed so that the rotor position detector such as a Hall element detects the rotor rotation position of the permanent magnet and controls by this detection signal is a so-called brushless motor, which has good controllability and high efficiency. It has come to be often used as a drive source for machine 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 motors used for air conditioners, etc., where the drive circuit becomes large, it is difficult to integrate it with the motor, and the heat generated from these motors has a particularly large effect. Incorporating a drive section formed of an electronic circuit into the above-mentioned structure has a problem that the size becomes large and 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 of the motor is incorporated, 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 in 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) The number of lead wires is large (for example, 8 to 11), which requires a lot of labor and 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.

On the other hand, recent air conditioners are required to have more precise electronic controllability, and accordingly, motors are also required to have fine-tuned variable speed control, high efficiency, miniaturization, and cost reduction. Even a brushless motor equipped with a detector cannot sufficiently meet the above demand.

<Object of the present invention> The present invention has been made in view of the above points, without adding a cage coil or a hysteresis ring, and without incorporating a position detector such as a Hall element in the motor body, (EN) Provided is a device that can be precisely controlled and driven at a variable speed for downsizing and high efficiency.

<Summary of the present invention> In order to achieve the above object, the present invention provides an induction voltage generated in a stator coil from a neutral point voltage of a star-connected stator coil of a synchronous motor connected to a DC power supply via an inverter circuit. Detected, by this, to generate a pulse signal in synchronization with the rotation of the motor, by the pulse signal is configured to drive the motor by controlling the conduction of the inverter circuit, when starting the motor, instead of the pulse signal,
The ignition pulse signal is forcibly generated, the inverter is conduction-controlled by this, the motor is started, and after the start, the drive is automatically switched to the drive by the induced voltage.

<Examples of the Present Invention> First, in order to facilitate understanding of the present invention, a voltage generated at a neutral point of a stator coil will be described.

The stator coils S _u , S _v , of star-connected synchronous motors are connected to a DC power supply via an inverter circuit in which transistors Q _u , Q _v , Q _w , Q _x , Q _y , Q _z are connected in a bridge shape. 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 first obtains the current I. When, 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 a DC power supply, 2 is a connection terminal for the DC power supply 1
This is a pulse width modulation type power supply circuit connected via P and N so as to change and output the output voltage. This is the connection terminal P, between N, the control transistor Q via the inter _first collector-emitter, insert the Chiyokukoiru L and capacitor C ₁ in series, the resistance R ₁ between the collector and base of the transistor Q ₁ , The anode of the diode D ₁ having the cathode connected to the emitter of the transistor Q ₁ is connected to the connection terminal N, and the resistors R ₃ and R ₄ are inserted in series between the terminals of the capacitor C ₁ . The connection point of these resistors R ₃ and R ₄ is connected to the inverting input terminal of the voltage error detector EA ₁ consisting of an operational amplifier, and the non-inverting input terminal of this error detector EA ₁ corresponds to the motor speed. The output terminal of a speed setting circuit (not shown) that sets the output voltage set as above and sends it as a speed command is connected, and the output terminal of the error detector EA ₁ is connected to the diode D ₂ whose cathode is connected to the output terminal. Output end is open via Connected to the inverting input terminal of the comparator CP ₁ consisting selector and summer were an operational amplifier, the comparator CP ₁
The output terminal of the current error detector EA ₂ consisting of an operational amplifier is connected to the inverting input terminal of the above through the diode D ₃ whose cathode is connected to the output terminal as described above.
Connect the connection point of resistors R ₅ and R ₅ inserted in series between the constant voltage power supply V _C and circuit ground to the non-inverting input terminal of EA ₂ , and connect the circuit to the inverting input terminal of error detector EA _2. Connect the output end of the current detector ID consisting of the resistor inserted in the negative side output circuit of 2,
The inverting input terminal of the comparator CP ₁ is connected via a constant current source CI to a constant voltage source V _C, to the non-inverting input terminal of the comparator CP _1, a pulse signal of a saw wave constant frequency (e.g. 30KH
_Z ), connect the output terminal of the pulse generator OSC, connect the output terminal of the comparator CP ₁ to the base of the transistor Q ₂ that is connected to the emitter circuit ground, and connect it via the resistor R _7. It is connected to the voltage power supply V _C , the collector of the transistor Q ₂ is connected to the base of the transistor Q ₁ via the resistor R _2, and the voltage across the terminals of the capacitor C ₁ is sent as the output voltage V _s. The output voltage V _s is input to the error detector EA ₁ via the voltage divider composed of the resistors R ₃ and R ₄ to detect the error with the speed command, and this detection value is sent from the output terminal of the comparator CP _1. Transistor via transistor Q ₂ with variable pulse width modulation signal
The ON period of Q ₁ is controlled to output the output voltage V _s according to the speed command. Further, the circuit 2 detects the error detector EA ₂ when the output voltage of the current detector ID exceeds a predetermined value (that is, a 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. The current can be suppressed by lowering V _s . In other words, it functions as an overcurrent limiter. A so-called 120 ° energization type inverter circuit 3 is connected to the output terminal of the chip power supply circuit 2 and supplies electric power to a three-phase synchronous motor (hereinafter simply referred to as a motor) 4. This is the three PNP type transistors Q _u , Q _v , Q at the positive output end of the power supply circuit 2 of the chip.
Connect the emitter of _w, this transistor Q _u, Q _v, to the collector of Q _w, 3 pieces of a transistor circuit grounded emitter
The collectors of Q _x , Q _y , and Q _z are connected to each other, and the connection points of the transistors Q _u and Q _x , Q _v and Q _y , Q _w and Q _z are used as output terminals, and the transistors Q _{u to} Q _{z are connected.} The DC input voltage V _s is converted into a three-phase AC voltage and supplied to the motor 4 by energizing the motor for 120 °. The above transistor
Flywheel diodes D _{u to} D _z are inserted between the collectors and emitters of Q _{u to} Q _z , respectively. Then, the motor 4, as is well known, the rotor 4 _a which is permanently magnetized to multiple magnetic poles, stator coil S _u is opposed to the rotor 4 _a, S _v, stator (not shown) wound around the S _w Consists of
One ends of the stator coils S _u , S _v , S _w are commonly connected to form a star connection, and the other ends of the stator coils S _u , S _v , S _w are connected to the output ends of the inverter circuit 3, respectively. ing.
5 is that the resistors R ₈ and R ₉ are inserted in series between the input terminals of the inverter circuit 3, and the input voltage V _s is divided in half from the voltage dividing point (connection point of R ₈ and R ₉ ). It is a voltage dividing circuit adapted to deliver the output voltage V ₅ . 6 is a stator coil of the motor 4
Synchronous pulse generated by comparing the neutral point voltage V _{N0 of} S _u , S _v and S _w with the output voltage V _{5 of the} voltage dividing circuit 5 to detect the induced voltage and generating a pulse signal in synchronization with this. It is a generation circuit. This is because the non-inverting input terminal of the comparator CP ₂ composed of an operational amplifier is connected to the neutral point N ₀ , and the inverting input terminal of the comparator CP ₂ is connected to the output terminal of the voltage dividing circuit 5, The first pulse generator MB ₁ consisting of a monostable multivibrator that sends the one-shot pulse signal to the output terminal of CP ₂ at the rising edge of the input signal and the _one- shot pulse signal at the falling edge of the input signal The second pulse generator MB ₂ consisting of a monostable multivibrator is connected to both input terminals of the pulse generators MB ₁ and MB ₂ and the output terminals Q of both pulse generators MB ₁ and MB ₂ are connected to the input terminal of the OR circuit OR ₁ . Connect to this OR circuit OR ₁
When switching the above-mentioned transistors Q _{u to} Q _z from the output end of, the malfunction due to the spike voltage generated in the induced voltage is prevented,
A synchronizing pulse signal synchronized with the rising and falling zero points of the neutral point voltage V _N0 is sent out. A DC blocking circuit 7 is provided between the non-inverting input terminal of the comparator CP ₂ of the synchronous pulse generating circuit 6 and the neutral point N ₀ of the motor 4 and has a capacitor C ₂
Insert the insert the bias resistor R ₁₀ between the input terminal of the comparator CP _2, the non-inverting input terminal of the comparator CP ₂ of the synchronizing pulse generating circuit 6, a DC contained in neutral point voltage V _N0 The output voltage V ₅ of the voltage dividing circuit 5 is sent out via the bias resistor R _10, and only the induced voltage is detected and output by the comparator CP ₂ . Reference numeral 8 is connected to the output terminal of the synchronous pulse generating circuit 6 so that a pulse signal is sent to the bases of the transistors Q _{u to} Q _z of the inverter circuit 3 via the drive circuit 9 when the motor 4 is started. It is a firing pulse generation circuit. This is because the input end of the NOR circuit NOR ₁ is connected to the output end of the OR circuit OR ₁ of the synchronizing pulse generating circuit 6 and the cathode of the diode D ₄ is connected to the output end of the NOR circuit NOR _1. Connect the connection point (point b) of the resistor R ₁₁ and capacitor C ₃ inserted in series between the constant voltage power supply V _C and circuit ground to the anode of the diode D ₄ , and connect this connection point (point b) to the notch circuit N. Through ₁ ,
Connected to the set input terminal S (input terminal of NA ₁ ) of the RS flip-flop circuit FF ₁ formed by the NAND circuits NA ₁ and NA ₂ ,
The output terminal Q of the flip-flop circuit FF ₁ (the output terminal of NA ₁ ) is connected to the input terminal of the NOR circuit NOR ₁ , and a resistor is connected between the output terminal Q and the circuit ground via a not circuit N _2.
Insert R ₁₂ and capacitor C ₄ in series, and connect the connection point (point e) between the resistor R ₁₂ and capacitor C _{4 to} the flip-flop circuit.
When the motor 4 is connected to the reset input terminal R (input terminal of NA ₂ ) of FF _{1 and} the motor 4 is stopped at the time of power-on or complete lock, the pulse signal for starting the motor 4 is supplied to the flip-flop circuit FF. The output terminal Q of ₁ is forcibly transmitted. Reference numeral 9 is an OR circuit OR ₂ connected to the output terminal of the OR circuit OR ₁ of the synchronizing pulse generating circuit 6 and the output terminal Q of the flip-flop circuit FF ₁ of the ignition pulse generating circuit 8, and is connected to its output terminal. In response to the application of the control power supply, the output terminal O ₀ sends out an “H” level output signal, and every time after that, the output terminal O ₁ → O ₂ →
A hexadecimal counter CU that sequentially outputs “H” level output signals in the order of O ₃ → O ₄ → O ₅ → O ₀ , and the above transistor
Has a Q _u to Q _z as many Orr circuit OR _u ~OR _z, Orr circuit
The counter CU outputs 0 ₀ and 0 ₁ are connected to the input terminals of OR _u , the output terminals O ₂ and O ₃ are connected to the input terminals of OR _v , and the output terminals O ₄ and O ₅ are connected to the input terminals of OR _w.
Outputs O ₃ and O ₄ are at the input of R _x and output O _{5 is} at the input of OR _y.
And O ₀ , the input terminal of OR _z is formed by a distributor DEV connecting output terminals O ₁ and O ₂ , respectively, and the OR circuits OR _{u to} OR _z
A base drive signal is sent from each output terminal of the transistors to the bases of the transistors Q _{u to} Q _z . 10 is
It is a constant voltage power supply circuit which is connected to the DC power supply 1 and sends a constant voltage power supply V _c to each circuit as a control power supply.

Next, the operation will be described with reference to FIGS. 4 to 6.

(A) Startup at power-on Now, when the transistors Q _{u to} Q _z are all in the OFF state and the speed command is not given, and the power switch (not shown) is turned on, the DC power supply 1 is supplied, The constant voltage power supply circuit 10 supplies a constant voltage power supply V _c to each circuit as a control power supply. As a result, the power supply circuit 2 is connected to the comparator.
Since the output of CP ₁ becomes “H” level, the transistor Q ₂ turns on and the transistor Q ₁ does not deliver the output voltage V _s until it turns off. On the other hand by the supply of the control power supply, drive circuit 9, the output signal of the counter "H" level from the output terminal for example O ₀ of CU it is sent, and Orr circuit example OR _u distributor DEV
The “H” level output signal from OR _y is sent to the bases of the transistors Q _u and Q _y of the inverter circuit 3 as the base drive signal.
Since it has not received V _s , it does not turn on and motor 4 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 receiving this output detects the voltage V that has detected the error with the other input (OV). Output _EA1 . Error detector at this time EA ₁
Is the output voltage V _EA1 of the error detector and the output voltage V _EA2 of the error detector EA ₂ is V
_{Since EA1} <V _EA2 , the diode D ₂ is conducting (the diode D ₃ is non-conducting) and the comparator CP ₁ is
_{The EA1} and the sawtooth wave-shaped output signal of the pulse generator OSC are compared in level, and the output signal that is at the "H" level is sent while the output signal of the pulse generator OSC is at a level 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 off during this off period.
Is turned on, the capacitor C ₁ is charged through the chain yoke coil L, and the charging voltage is sent to the inverter circuit 3 as the output voltage V _s . On the other hand, the ignition pulse generating circuit 8 which receives the "L" level output signal from the synchronizing pulse generating circuit 6 by the supply of the control power supplies, the output signal of the note circuit N ₂ becomes "H" level C ₄ is C through resistor R ₁₂
It is charged for the time determined by the R time constant, the potential at point e rises to "H" level, and the output signal of NOR circuit NOR ₁ becomes "H" level, diode D ₄ becomes non-conductive, and capacitor C ₃ is charged through the resistor R _{11 for the} time period determined by the CR time constant, and the potential at the point b rises. This potential at the point b is the threshold hold level V _{th1 of the} note circuit N ₁ (Fig. 4b).
The output signal of the NOT circuit N ₁ is inverted to the "L" level (Fig. 4c), the flip-flop circuit FF ₁ is set by this inversion, and the output signal of the output terminal Q is set to the "H" level. It is inverted (output in FIG. 4). This is the drive circuit 9
The counter CU received through the OR circuit OR ₂ of the counter counts at the rising edge of the input signal and inverts the output signal of the output end, for example, O ₁ to “H” level (at this time, the output signal of the output end O ₀ becomes “L” "Inverts to the level. Fig. 4 O ₀ , O ₁ ). The distributor DEV which received this is a transistor whose OR circuit, for example OR _u and OR _z, uses the" H "level output signal as the base drive signal.
It is sent to Q _u and Q _z and turned on to energize the stator coils S _u and S _w of the motor 4. At this time, the ignition pulse generating circuit 8
Is the NOR circuit NOR _{1 when} the output signal of the output terminal Q of the flip-flop circuit FF ₁ is inverted to "H" level.
Output signal is inverted to "L" level, the diode D ₄ becomes conductive, and the capacitor C ₃ discharges its charge through the diode D ₄ so that the potential at the point b becomes a threshold hold.
Since it falls below the level, the output signal of the NOT circuit N ₁ is "H".
Invert to level (Fig. 4c). Further, the output signal of the NOT circuit N ₂ is inverted to the “L” level, and the capacitor C ₄ discharges the electric charge through the resistor R ₁₂ , so that the potential at the point e drops, and the potential at the point e that drops is the flip-flop circuit.
When the threshold level V _th2 of the NOR circuit NA ₂ of FF ₁ is reached (Fig. 4e), the flip-flop circuit FF ₁ is reset and the output signal at its output Q is inverted to "L" level, The output signal of the circuit 8 becomes "L" level through the circuit OR ₂ (output of FIG. 4). When the output signal of the flip-flop circuit FF ₁ is inverted to the "L" level, the firing pulse generation circuit 8 operates in the same manner as described above, and sends out a pulse signal (output of FIG. 4). The received drive circuit 9 switches the output signal of "H" level from the output terminals of OR _u to OR _z at the rising edge of the input signal to switch the transistors Q _{u to} Q _z of the inverter circuit 3 to, for example, Q _u → Q _y. → Q _v → Q _z →
The base drive signal is sent to control ON / OFF in the order of Q _w → Q _x .

In this way, when the motor 4 is started, the pulse signal of the ignition pulse generating circuit 8 forcibly switches the transistor of the inverter circuit 3 to energize it. In this case, since the induced voltage is zero or very small, the stator coil S _u of the motor 4, S _v, the current flowing through the S _w is intends to become very large, this current Yotsute the current detector ID The detected output voltage is sent to the error detector EA ₂ of the chip power supply circuit 2,
The error detector EA ₂ outputs its output voltage V _EA2 when the input voltage is about to become higher than the other input voltage.
_From the output voltage V _{EA1 of 1} to V _EA1 > _EA2 , the diode D ₃ becomes conductive (D ₂ becomes non-conductive), and the error detector EA
Output ₂ is sent to the comparator CP ₁ in preference to the other, the comparator CP ₁ having received this by comparing the other input signal and the level, the pulse width of the "H" level of the output signal becomes wider As described above, since the ON period of the transistor Q ₂ is extended, the ON period of the transistor Q ₁ is shortened, and the output voltage V _s is reduced so that a current higher than a certain level does not flow. That is, it functions as an overcurrent limiter. The stator coil S _u, S _v, torque is generated in relation to the permanent magnet of the current and the rotor 4 _a flowing in S _w, the rotor 4 _a is turned to move to a predetermined position, the induced voltage is generated, medium The comparator CP ₂ of the synchronizing pulse generation circuit 6 which receives the neutral point voltage V _N0 of the sex point N ₀ via the DC blocking circuit 7 is the output voltage V ₅ (V _s /
2) and the level is compared, and an output signal that is at "H" level during the period of V _N0 > V ₅ is sent to the first and second pulse generators MB ₁ and MB ₂ . The pulse generator MB _{1 which} receives this generates a one-shot pulse signal having a constant pulse width T at the rising edge of the input and the pulse generator MB ₂ at the falling edge of the input, which is supplied to the OR circuit OR ₁ . An output signal obtained by taking the logical sum of both pulse signals from the output end is sent as a synchronizing pulse signal to the counter CU via the OR circuit OR ₂ of the drive circuit 9 (output of FIG. 4), and Iwayu synchronous operation is performed. enter. When the synchronous operation is started, the induced voltage also increases, the current decreases, the function as an overcurrent limiter is canceled, and the output voltage V _s corresponding to the speed command is sent to the inverter circuit 3 and the output voltage V _s becomes the above-mentioned output voltage V _s . The motor 4 rotates at an appropriate speed.

In this way, the ignition pulse generating circuit 8 forcibly generates a pulse signal, and by this switching the transistors Q _{u to} Q _z of the inverter circuit 3 to energize, the motor can be easily started, and the ignition can be performed. The pulse generator circuit 8 has its resistance R
By selecting the CR time constant of ₁₁ and the capacitor C ₃ , the pulse signal can be generated at a frequency corresponding to the speed at the time of starting the motor 4 that is suitable for the load (hereinafter referred to as the starting frequency).

Then, when the motor 4 enters the synchronous operation, the synchronous pulse generation circuit 6 detects the induced voltage generated at the neutral point N ₀ of the stator coils S _u , S _v , S _w and outputs the synchronous pulse signal to the drive circuit 9. Since it is sent (output in FIG. 4), the potential at point b (charging voltage of the capacitor C ₃ ) of the ignition pulse generating circuit 8 is the not circuit N ₁
The discharge is performed without reaching the _threshold level V _th1 of the flip-flop circuit FF ₁ , and the flip-flop circuit FF ₁ is not set, and the compulsory generation of the pulse signal by the ignition pulse generation circuit 8 is blocked. In other words, when the motor 4 enters the synchronous operation, the switching of the transistors Q _{u to} Q _z of the inverter circuit 3 is switched from the pulse signal forcibly sent by the ignition pulse generating circuit 8 to the synchronous pulse signal of the synchronous pulse generating circuit 6. Is automatically switched to.

(A) Steady operation The output voltage V _s corresponding to the above speed command is applied from the power supply circuit 2 to the stator coils S _u , S _v , and S _w of the motor 4 via the inverter circuit 3 to generate this voltage V s. _The motor 4 is driven at a speed commensurate with _s , and the so-called steady operation is started.

To further explain the operation during the steady operation, the base drive signal of the drive circuit 9 causes the transistors Q _{u to} Q _z of the inverter circuit 3 to be sequentially switched.
Since the commutation noise of the transistor is heavy on the neutral point voltage V _N0 , the commutation noise causes the comparator CP ₂ of the synchronous pulse generation circuit 6 to operate and send an output signal.
That is, as shown in the input of CP ₂ in FIG. 5, the spike voltage V _SP due to the switching of the transistors Q _{u to} Q _z is superimposed on the neutral point voltage V _N0 , which is the output voltage V ₅ of the voltage dividing circuit ₅ . This is because the levels are crossed, and a pulse generated in a period W after detection of necessary detection points g and h is unnecessary, and it is necessary to mask this so as to prevent malfunction. Therefore, in the present invention, the first and second pulse generators MB ₁ and MB ₂ which send out the one-shot pulse signal with a constant pulse width to the output terminal of the comparator CP ₂ at the rising and falling edges of the input, respectively.
, And the first pulse generator MB ₁ for the positive half-wave W period of the neutral point voltage V _N0 , and the second pulse generator for the negative half-wave W period. in vessels MB _2, it is generated by respectively polymerizing the pulse signal Wanshiyotsuto, the MB ₁ and MB ₂
As shown in the output of FIG. 5 by setting the cooking sum of the pulse signal of the above, the rising timing of the output signal is the same as the zero point of the neutral point voltage V _N0 and the transistor Q _u ~. The sync pulse generating circuit 6 sends a pulse signal in synchronization with the induced voltage by preventing a malfunction due to a spike voltage generated when Q _z is switched (output of 6 in FIGS. 5 and 6). The counter of the drive circuit 9 that receives this
Each time the CU counts on the rising edge of its input, its output O ₀
The output signals of "H" level are sequentially output from ~ O ₅ (Fig. 6, O ₀
~ O ₅ ), the distributor DEV receiving this sequentially sends out pace drive signals from the output terminals of the OR circuits OR _{u to} OR _{z according} to the combination of the input signals (Fig. 6, OR _{u to} OR _z ). For this reason, the transistors Q _{u to} Q _z are turned on, for example, in the order of Q _u → Q _z → Q _v → Q _x → Q _w → Q _{y at} an appropriate time for a 120 ° energization period (Fig. 6, Q _{u to} Q _z ).
The input voltage V _s is supplied to the motor 4 as three-phase AC power to drive it.

(B) Variable Speed Control Next, in the steady operation state, the speed of the motor 4 is changed by changing the speed command (output voltage) of a speed setting circuit (not shown). That is, by changing the speed command to a voltage corresponding to the speed at which deceleration or acceleration is desired, the voltage is sent from the collector of the transistor Q _2.
By controlling the ON period of Yotsute transistor Q ₁ that changing the PWM signal, increase the output voltage V _s of Chiyotsupa power supply circuit 2 (acceleration) or drop (deceleration) is, the motor 4 stator coil S _u, S _v, the detected by connexion to the comparator CP ₂ of the synchronizing pulse generating circuit 6 an induced voltage generated in the neutral point N ₀ of S _w, and sends respectively rise and fall of the output signal of the comparator CP ₂ The pulse signals of the first and second pulse generators MB ₁ and MB ₂ are sent to the drive circuit 9 as a synchronizing pulse signal via the OR circuit OR ₁ and the pace drive signal of these signals causes the transistors Q _{u to} Q of the inverter circuit 3 to be transmitted. _{z is made} to conduct at a proper time, and the inverter circuit 3 converts the input voltage V _s into a three-phase AC voltage and supplies it to the motor 4, so that the speed of the motor 4 is tracked in synchronization with the rotation speed of the motor 4. Variable control.
Moreover, since the above-mentioned induced voltage is detected every 1/6 cycle (60 °) to follow the rotation speed of the motor 4, the output voltage V _s and load torque of the chip power supply circuit 2 are matched without causing step-out. The motor 4 is rotated at the number of rotations.

In this case, even by sudden change of the output voltage V _s of Chiyotsupa power supply circuit 2 rapidly changing the speed command, the synchronization the pulse generating circuit 6 is adapted to detect only the induced voltage, the output voltage V _s There is no possibility of erroneously detecting the change of the above as a change of the induced voltage, and the speed of the motor 4 can be variably controlled without causing the step out.

(D) At the time of overload When a load torque that locks the rotation of the motor 4 is applied and the current is about to increase, the output voltage V _EA2 of the error detector EA ₂ of the chip power supply circuit 2 becomes the error detector 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 When the signal is sent to the base of the transistor Q ₁ , the output voltage V _s of the chip power supply circuit 2 is lowered in preference to the speed command, and the current is suppressed.

The drop of the output voltage V _s causes the synchronization pulse signal of the synchronization pulse generation circuit 6 to be synchronized with the firing pulse generation circuit 8
If it becomes longer than the cycle of the pulse signal of, the transistors Q _{u to} Q _z of the inverter circuit 3 are sequentially switched through the drive circuit 9 by the pulse signal of the ignition pulse generating circuit 8, so that Even if the motor 4 is locked by the load torque and stopped by switching the stator coil without continuing energization, there will be no inconvenience if the stator coil of a specific phase is overheated.
When only a specific transistor is overheated, no inconvenience occurs.

Moreover, if the load torque that causes the locking is released, the operation is performed in the same manner as at the time of starting, and the synchronous operation is automatically started.

<Effects of the Present Invention> The present invention has the following effects.

(B) The sync pulse generator is connected to the output of the comparator connected to the neutral point of the star-connected stator coil and the output of the voltage divider that divides the input voltage of the inverter circuit in half. , The first and second pulse generators that generate one-shot pulse signals at the rising edge and the falling edge of the input are arranged in parallel, and the output of the logical sum of the pulse signals of both pulse generators is used as the synchronization pulse signal. Since it is designed to be sent out,
The sync pulse signal can be masked even if a spike voltage is generated in the induced voltage when switching the transistor energization, preventing false detection due to the spike voltage and rising the signal at the same time as the zero point of the induced voltage. can do. Moreover, since the transistor of the inverter circuit is sequentially energized by the synchronizing pulse signal, it is possible to always rotate in synchronism and step out to a low speed rotation where the induced voltage cannot be detected. It is possible to perform the synchronous operation without using the synchronous motor, and it is possible to freely control the variable speed over a wide range from low speed to high speed even though the motor is a synchronous motor.

(B) Further, the variable speed control of the motor can be made to follow the rotation speed of the motor simply by changing the voltage applied to the inverter circuit, and the synchronization pulse generation circuit induces the follow-up to the rotation speed of the motor. Voltage 1/6 cycle (60
Since it will be detected every time, the followability can be further improved even for sudden changes in the load, and synchronization can be achieved without step out, and the drive frequency is automatically adjusted according to the load conditions of the motor. Can be driven automatically.

(C) Further, an ignition pulse generating circuit for transmitting a pulse signal by a flip-flop circuit which repeats set-reset with a time limit is provided at the output end of the synchronizing pulse generating circuit. Since either of the two pulse signals of the synchronous pulse generation circuit is used to sequentially switch the transistors through the drive circuit, the ignition pulse generation circuit can start the motor that adapts the pulse signal to the load by selecting the time limit. It can be generated at a starting frequency corresponding to the speed at the time, and even if the motor does not rotate, the energized phases are sequentially switched and repeated, so the motor can be easily started even at heavy load start, In the event of a load, the cycle of the sync pulse signal from the sync pulse generator will be the cycle of the pulse signal from the ignition pulse generator. Ri transistor by also pulse signal of the firing pulse generating circuit comprising such a situation occurs long can continue sequential energization switching.

(D) In addition, even if the motor is locked, the transistors in the inverter circuit can be switched to energize sequentially, so energization of the coil of a specific phase or a specific transistor continues. It does not cause overheating of the coil, does not damage the transistor by heat, and prevents the motor from being oversized for heat dissipation or by lowering the motor output. it can.

(E) Moreover, unlike a brushless motor having a position detecting element, there is no need to house and arrange a printed circuit board for the position detecting element in the motor body, and there is no need to suppress heat generation of semiconductor components used in the device. The heat dissipating means is not necessary, and the motor can be downsized, the reliability can be further improved, and the cost can be reduced.

[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 a motor U-
It is an equivalent circuit diagram at the time of V-phase conduction. FIG. 4 is a time chart for explaining the operation at the time of starting of FIG. 1, FIG. 5 is a time chart for explaining the operation of the synchronizing pulse generating circuit of FIG. 1, and FIG. 6 is for the steady state of FIG. 3 is a time chart for explaining the operation in FIG. 1: DC power supply, 2: Chip power supply circuit, 3: Inverter circuit, 4: Synchronous motor, 5: Voltage dividing circuit, 6: Synchronous pulse generation circuit, 8: Firing pulse generation circuit, 9: Drive circuit, MB ₁ : First pulse generator, MB ₂ : Second pulse generator,

Claims (1)

[Claims] 1. A chopper power supply circuit connected to a DC power supply so as to change and output an output voltage according to a speed command, and an inverter circuit in which a plurality of transistors are connected in a three-phase bridge form to the output terminal thereof. , It is provided between the input terminals of the above-mentioned inverter circuit and the synchronous motor, to which the star-connected stator coils are connected, respectively.
One-shot pulse signals are generated at the rising and falling edges of the input, respectively, at the voltage divider circuit that divides the voltage into 2 and outputs it, and at the output terminal of the comparator that is connected from the output terminal of this and the neutral point of the stator coil. A first and a second pulse generator are provided side by side, and the pulse signals of both pulse generators are sent out as a synchronization pulse signal via an OR circuit, and an output terminal thereof. From the pulse signal of the both pulse generation circuits, which is connected to the ignition pulse generation circuit, the pulse signal being transmitted by a flip-flop circuit that repeats set-reset with a time limit when the motor is started. A speed control device for a synchronous motor, characterized in that either one of the transistors is sequentially energized to be switched over by a driving circuit.