JPH0612960B2 - Motor speed controller with overcurrent coupling - Google Patents

Description

The present invention relates to a device for performing speed control by phase controlling the exciting current of an eddy current joint connected to a motor using a main thyristor.

There has been a speed control device for controlling the phase of an exciting current of an eddy current joint by a main thyristor, but the conventional one usually uses a phase shift circuit by a unijunction transistor UJT to simplify the circuit (for example, Japanese Patent Sho 54
-31163). This phase shift circuit outputs a gate pulse when the integrated value or the discharge amount reaches a certain amount by changing the time constant or the boundary condition at the time of charging / discharging by C and R. On the other hand, there is an inconvenience that a time delay occurs. When UJT is used, U
The output of the JT is further amplified by a gate pulse amplifier circuit to ignite the main thyristor. Conventionally, an auxiliary thyristor was used for this gate pulse amplifier circuit in addition to the main thyristor (see the above-mentioned publication). Conventionally, another auxiliary pulse transformer is used to ignite this auxiliary thyristor, but in this case, the number of pulse transformers increases and the operation becomes unstable. Further, there is also one that obtains the gate pulse of the main thyristor by discharging the pulse generating capacitor charged by the DC power source through the pulse transformer by the auxiliary thyristor. In this case, however, the pulse generating capacitor is necessary. There was an inconvenience that the score increased.

The present invention has been made in view of the above circumstances, and not only can improve the responsiveness to changes in the control input, but also can simplify the configuration of the gate pulse amplifier circuit and ensure reliable operation over a wide speed range. An object of the present invention is to provide a speed control device for a motor with an eddy current joint that operates stably.

According to the present invention, an object of the present invention is to control the excitation current of an eddy current joint in a phase by a main thyristor, and in a triangular wave generating circuit that outputs a triangular wave in synchronization with an AC power supply, a sum of a speed setting voltage and a speed feedback voltage. A proportional integration circuit that proportionally integrates and outputs a speed control voltage, a comparison circuit that outputs a rectangular wave by comparing the sum of the speed control voltage and a predetermined bias voltage with the triangular wave, and differentiates the rectangular wave. A gate pulse circuit for outputting a gate pulse from the pulse transformer by closing a transistor connected in series to the DC power supply and the pulse transformer, and an output voltage feedback for integrating the rectangular wave and negatively feeding it back to the proportional integrator circuit. And a speed of a motor with an eddy current coupling, characterized in that the main thyristor is ignited by the gate pulse. Control device, is achieved by.

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing output waveforms of respective parts thereof.
NR is a surge absorbing varistor, SCR is a main thyristor,
EC is an exciting coil of the eddy current joint, D ₁ is a free wheel diode, and these form a main circuit.

DC is a constant voltage circuit, which has a transformer T ₁ having an intermediate tap a, a diode bridge DB ₁ for full-wave rectifying the outputs of both ends of the transformer T ₁ , and a positive output end of the diode bridge DB ₁ and an intermediate portion. a smoothing integrated circuit IC capacitor C ₁ and the constant voltage present between the tap a, a smoothing capacitor C ₂ and the constant voltage diode D interposed between the negative output terminal of the diode yellowtail Tsuji DB ₁ and the intermediate tap a ₂ and.

A is a triangular wave generating circuit, which forms a Miller integrating circuit by an operational amplifier OP ₁ as an anti-phase amplifier and an integrating capacitor C ₃ interposed in its negative feedback loop, while the operational amplifier OP 1
_To the negative phase input terminal of ₁ , the one end of the transformer T ₁ is a diode D
The output voltage of the integrated circuit IC is applied while being connected via ₃ . As a result, the output terminal b of the operational amplifier OP ₁
As shown in FIG. 2, a triangular wave V (OP ₁ ) synchronized with the output V (AC) of the power supply AC is output to the.

B is a comparison circuit, which includes an operational amplifier OP ₂ as a comparator. The positive phase input terminal of this operational amplifier OP ₂ is the transformer T ₁
Of the operational amplifier OP ₁ and the output terminal C of the integrated circuit IC, respectively, through the resistors R ₁ and R ₂ .
The output voltage V (IC) of this integrated circuit IC also serves as a bias voltage. At the negative-phase input terminal d of the operational amplifier OP ² , a speed control voltage V _c, which is the output voltage V (OP ₃ ) of the proportional integration circuit E described later, is applied to the resistor R ₃ and the variable resistor VR _1.
Are superposed through. In order to make this speed control voltage V _c more negative than the intermediate tap a voltage, the proportional integration circuit E described later
Is configured.

On the other hand, since the output impedance of the operational amplifier OP ₁ is substantially zero, a current flows from the point d to the operational amplifier OP ₁ through the resistor R _1, and the potential at the point d corresponds to the change of the triangular wave V (OP ₁ ). Change. When the potential at the point d becomes lower than the intermediate tap a potential, the output V (OP ₂ ) of the operational amplifier OP ₂ is inverted and V
(OP ₂ ) becomes a rectangular wave as shown in FIG. That is, the bias voltage V is applied to the negative phase input terminal d of the comparison circuit B.
(IC), speed control voltage V _c, and triangular wave V (OP ₁ ), the sum {V (IC) + V _c + V (OP ₁ )} is added, and when this sum becomes lower than the potential of the intermediate tap a, the rectangular wave V (O
P ₂ ) rises. In FIG. 2, the intermediate tap a
Is used as a reference (0 volt), and V (OP ₁ ) becomes a negative voltage triangular wave.

Since the bias voltage V (IC) is set to a positive voltage and the speed control voltage V _c is set to a negative value, if {V (IC) + V _c } becomes positive, the triangular wave V (OP ₁ ) moves to the positive voltage side. V (IC)
It is considered to move by + V _c }. As a result, the sum of the voltages {V (IC) + V _c + V (OP ₁ )} intersects 0 port, and the rectangular wave V (OP ₂ ) rises at this intersection. If the absolute value of the speed control voltage V _c increases, {V
It is considered that (IC) + V _c } decreases and the triangular wave V (OP ₁ ) decreases, so that the intersection with 0 volt advances. On the contrary, if the absolute value of V _c decreases, the intersection with 0 volt will be retarded.

C is a gate pulse circuit, and a pulse transformer PT and NPN connected in series between a capacitor C ₄ for differentiating the rectangular wave V (OP ₂ ) and a positive output terminal of the bridge DB ₁ and an intermediate tap a. And a transistor TR. The capacitor C ₄ is connected to the base of the transistor TR. Therefore, the transistor TR is closed in response to the rise of the rectangular wave V (OP ₂ ) and the pulse transformer PT
A current is supplied from the constant voltage circuit DC to the pulse transformer PT, and at this time, the gate pulse GP is output to the secondary side of the pulse transformer PT.
This gate pulse GP is input to the gate of the main thyristor SCR to fire the SCR. Therefore, the excitation coil E
A current corresponding to the shaded portion of V (AC) in FIG. 2 is supplied to C. That is, by changing the speed control voltage V _c input to the comparison circuit B, the rising phase of the rectangular wave V (OP ₂ ) changes, and the gate pulse G accordingly.
The phase of P can also be changed to control the exciting current of the exciting coil EC.

Next, a circuit for generating the speed control voltage V _c will be described.

The variable resistor VR ₂ is a speed setting device, and the speed setting voltage V _v changes by changing its resistance value. That is, when increasing the set speed, the resistor VR ₂ is adjusted so as to increase the speed set voltage V _v . This speed setting voltage V _v is a positive potential with respect to the intermediate tap a potential.

C ₅ is a time setting capacitor for cushion start, which converts a step change command of the speed setting voltage V _v into a tilt change command to suppress abrupt acceleration / deceleration of the motor.

D is a speed feedback circuit, which is a generator T for a speedometer that outputs an alternating current that changes in accordance with the rotation speed of the output shaft.
G, a diode bridge DB ₂ for full-wave rectifying the output of this generator TG, a smoothing capacitor C ₆ , a variable resistor VR ₃ for level adjustment, and the like. The speed feedback circuit D outputs a speed feedback back voltage V _f that increases or decreases in response to an increase or decrease in the output shaft rotation speed, and this speed feedback back voltage V _f is set to be negative with _{respect to} the potential of the intermediate tap a. .

E is a proportional-integral operation amplifier circuit (hereinafter referred to as PI circuit), which includes an operational amplifier OP ₃ as a negative-phase amplifier, a capacitor C ₇ and a resistor R ₄ connected in series to the negative feedback path thereof. The positive phase input terminal of the operational amplifier OP ₃ is connected to the intermediate tap a, while the speed setting voltage V _v and the speed feed back voltage V _f are applied in a superposed manner to the negative phase input terminal.
The speed setting voltage V _v is set higher than the speed feedback back voltage V _f , and as a result, the output voltage of the proportional-plus-integral operation circuit E, that is, the speed control voltage V _c becomes negative with respect to the intermediate tap a.

If the negative-phase input terminal potential of the operational amplifier OP ₃ suddenly changes due to a sudden load change or abrupt change of the speed potentiometer VR ₂ , the charging / discharging current freely flows to the capacitor C ₇ instantaneously, so the operational amplifier OP ₃ gain Is small, and at the time of settling, no current flows through this capacitor C ₇ , so the gain becomes large. As a result, it is possible to improve the stability against sudden changes such as load. In FIG. 1, VR ₄ is a variable resistor for bias adjustment at the negative phase input terminal of the operational amplifier OP ₃ , VR ₅ is a variable resistor for gain adjustment, and D ₃ is a zener diode as an output limiter.

F is an output voltage feedback circuit, and a capacitor C ₈
Together with an operational amplifier OP ₄ forming an integrator, and a variable resistor VR ₆
Through this operational amplifier OP ₄ output terminal and the operational amplifier OP ₃
A capacitor C ₉ and a resistor R ₅ connected in series with the negative-phase input terminal of a resistor R ₆ and a resistor R ₆ connected in parallel with this capacitor C ₉
With. The positive phase input terminal of the operational amplifier OP ₄ is connected to the intermediate tap a, while the rectangular wave V (OP ₂ ) output from the comparison circuit B is input to the negative phase input terminal. Therefore, the negative integrated voltage V (OP ₄ ) is output to the output terminal of the operational amplifier OP ₄ as shown in FIG. 2, but the area occupied by the waveform of this voltage V (OP ₄ ) (hatched portion). Is considered to be approximately proportional to the exciting current supplied to the exciting coil EC (corresponding to the shaded portion of the power supply voltage V (AC)). This integrated voltage V (O
P ₄ ) is formed of a capacitor C ₉ and resistors R ₅ and R ₆ and is negatively fed back to the proportional-integral operating circuit E through a filter. In this way, the output voltage feedback circuit F has a function of decreasing and increasing the gain of the entire circuit in accordance with the increase and decrease of the exciting current of the main circuit, and further stabilizing the operating characteristics.

In FIG. ₁ , the negative output terminal of the bridge DB ₁ and P
The resistor R ₇ connected between the operational amplifier OP _{3 and the} negative phase input terminal of the I circuit E is a resistor R ₇ when the set speed of the speed setter VR ₂ is zero.
The input terminal of the operational amplifier OP ₂ , that is, the potential at the point d is set to zero, and it is determined that the gate pulse GP is not output at this time.

Next, the operation of this embodiment will be described. First, at the time of startup, when the speed set by the speed setting VR ₂ is zero, the speed setting voltage V _v (> 0) is almost zero, the speed feedback voltage V _f (<0) is also zero, and the output of the PI circuit E is The absolute value of the speed control voltage V _c (<0) is also small and almost zero. Therefore, the voltage at point d {V (IC) + V _c +
In V (OP ₁ )}, the triangular wave V (OP ₁ ) is the bias voltage V
The waveform shown by α in FIG. 2 is obtained by raising only (IC) to the positive voltage side. The bias voltage V (IC) is set so that the waveform α at this time does not intersect with 0 volt. Therefore, at this time, the potential at the point d is always positive, and the gate pulse GP is not output. Therefore, no current flows through the motor.

When the set speed is increased and the speed set voltage V _v is increased, the absolute value of the speed control voltage V _c (<0) is increased, and V (IC)
The value of + V _v decreases. Therefore, the triangular wave V (OP ₁ ) descends and crosses 0 volt as indicated by β in FIG. When the waveform β crosses 0 volt, the output of the comparison circuit B suddenly rises, the differential output thereof causes the transistor TR to be closed, and the pulse transformer PT generates the gate pulse GP. SC by this gate pulse GP
R is ignited, and thereafter, the exciting current of the motor flows until the voltage of the power supply AC becomes negative, and the rotation of the output shaft rises. In this way, if the speed setting voltage V _v rises, the triangular wave V (OP ₁ )
Decreases, the gate pulse GP advances, and the motor current increases. On the contrary, when the speed setting voltage V _v decreases, the gate pulse GP retards and the motor current decreases.

The rotation of the output shaft is detected by the speedometer generator TG, and the absolute value of the speed feedback voltage V _f (<0) increases. Therefore, the input voltage of the operational amplifier OP ₃ is lowered to the speed control voltage V
The absolute value of _c (<0) also decreases, and as a result, the triangular wave V (OP ₁ ) rises, and the phase at which the potential at point d becomes zero is delayed. That reduces the exciting current, the rotation of the output shaft in a balanced rate determined by the speed setting voltage V _v and speed feedback voltage V _f is stabilized. In reality, the cushion start capacitor C ₅ , the PI operational amplifier E, the output voltage feedback circuit F, etc. cause the output shaft to change smoothly and reach the equilibrium speed quickly and become stable. At this time, the output of the comparison circuit B suddenly rises, the differential output thereof causes the transistor TR to be closed, and the pulse transformer PT generates the gate pulse GP. The gate pulse GP ignites the SCR, and thereafter, an exciting current flows until the voltage of the power supply AC becomes negative, and the rotation of the output shaft increases. The rotation of the output shaft is detected by the speedometer generator TG, and the absolute value of the speed feedback voltage V _f increases. Therefore, the input voltage of the operational amplifier OP ₃ decreases and the absolute value of the speed control voltage V _c also decreases, and as a result, the phase at which the potential at the point d becomes zero is delayed. That is, the exciting current is reduced, and the rotation of the output shaft is stabilized at the equilibrium speed determined by the speed setting voltage V _v and the speed feedback voltage V _f . Actually, the output shaft changes smoothly due to the action of the cushion start capacitor C ₅ , the PI operation amplifier E, the output voltage feedback circuit F, etc., and reaches the equilibrium speed quickly and becomes stable.

As described above, according to the present invention, the sum of the speed control voltage and the predetermined bias voltage is compared with the triangular wave synchronized with the power supply by the comparison circuit, and the transistor is activated by the rising or falling of the rectangular wave output by the comparison circuit. Since the circuit is closed and a pulse transformer connected in series with this transistor is supplied with current from a DC power source to generate a gate pulse,
The operation is an instantaneous operation type, and the responsiveness is remarkably improved as compared with the conventional device that changes the time constant during charging / discharging by C and R. Particularly, in this embodiment, the triangular wave generation circuit and the comparison circuit are composed of operational amplifiers, so that the response is further improved.

In addition, since the transistor is closed by differentiating the rectangular wave output from the comparison circuit, the gate pulse circuit does not require a measure for extinguishing the auxiliary thyristor unlike the conventional device, and the circuit configuration can be simplified. Furthermore, since a voltage is directly applied to the pulse transformer from a DC power source, a sufficient current is always supplied to the primary side of the pulse transformer,
A gate pulse having a sufficient gate current is surely output. Therefore, the reliability of the device is improved.

Further, the speed control voltage is obtained by a proportional integrator circuit that proportionally integrates the sum of the speed setting voltage and the speed feedback voltage, and the rectangular wave is integrated to be negatively fed back to the input terminal of the proportional integrator circuit. The gain of the entire circuit can be changed appropriately in accordance with the change of, and the operating characteristics are further stabilized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing output waveforms of respective parts thereof. EC ... Exciting coil, SCR ... Main thyristor, AC ...
... AC power supply, DC ... constant voltage circuit, A ... triangular wave generation circuit, B ... comparison circuit, C ... gate pulse circuit, E ...
Proportional integrator circuit, F ... Output voltage feedback circuit, V
(OP ₁₎ ...... triangular waveform, V (OP ₂₎ ...... rectangular wave, TR ...... transistor, T ₂ ...... pulse transformer, GP ...... gate pulse.

Claims (1)

[Claims] 1. A phase control of an exciting current of an eddy current joint by a main thyristor, wherein a triangular wave generating circuit for outputting a triangular wave in synchronism with an AC power supply, and a sum of a speed setting voltage and a speed feedback voltage are proportionally integrated. A proportional integrator circuit that outputs a speed control voltage, a comparison circuit that outputs a rectangular wave by comparing the sum of the speed control voltage and a predetermined bias voltage with the triangular wave, and a DC power source that differentiates the rectangular wave. And a gate pulse circuit that outputs a gate pulse from the pulse transformer by closing a transistor connected in series to the pulse transformer, and an output voltage feedback circuit that integrates the rectangular wave and negatively feeds it back to the proportional integration circuit. A speed control device for a motor with an eddy current joint, wherein a main thyristor is ignited by the gate pulse.