DE1914562A1 - Circuit arrangement with a thyristor for controlling the speed of a single-phase electric motor - Google Patents

Description

Dr. F. Zumsfein - Dr. E. Assmann Dr. R. Koonicsberger

Dipl. Phys. R. Holzhauer 18290/68 Paienlanv / äüe

567O7 Munich 2, Bräuhaussiralje 4/111

JAUOMB SEWING MACHIEE CO. , Ltd., Tokyo / Japan

Circuit arrangement with a thyristor for regulating the speed of a single-phase electric motor.

The invention "relates to a circuit arrangement for regulating the speed of an electric motor using" a thyristor, in particular "the aim of the invention is to address a circuit arrangement for regulating the speed of a single-phase electric motor, in which the starting point of a ignition circuit is dependent
of the load-dependent. The engine speed is automatically changed ", from which a quantity for stabilizing the engine speed at a predetermined value is obtained.

Circuits for controlling the speed of motors using a thyristor are known. In known circuit arrangements of this type, however, the speed is one with a
AC power source connected single-phase motor by changing a continuity angle (continuity angle) of a symmetrical semicircle lying in the main circuit of the motor

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Conductor switching element of a main circuit thyristor controlled "or _. regulated. To change the continuity angle of the symmetrical .. see semiconductor elements of the main circuit thyristor is a additional ignition circuit provided, the phase input elements and a circuit for pulse generation, "in which a Resistance value of a variable resistor of the phase adjustment elements to change the single-phase voltage (or current) that occurs when the symmetrical is ignited Semiconductor switching element is generated in the pulse generator circuit. In the known arrangement, however, the speed of the Motor quite considerably unstable, in which the motor with a torque that changes greatly from time to time, such as for example in washing machines, is loaded, so that in effect an adequate speed control is not achieved.

It is the object of the invention to overcome the disadvantages of the known arrangements to eliminate. It is the main aim of the invention to gain stable speed control for a motor that is subjected to constantly changing loads. To achieve this, the motor supply is load-dependent automatically regulated .. The change in engine speed is recorded by a measuring generator and sent to an ignition circuit given, which is assigned to a main circuit thyristor. Through this the continuity angle of the main circuit thyristor is adjusted, and the speed change of the motor is compensated for. The continuity angle of the main circuit thyristor that is changes depending on the load, regulates the current supplied to the motor, so that its speed is kept at the predetermined value. In this way, a stabilized speed control can be obtained. It is also the aim of the invention to find the appropriate Structure of this stable speed monitoring device to specify. Here, according to the invention, the characteristic applied to the forward characteristic of a silicon diode in order to avoid fluctuations in a reference voltage as a function of load

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To prevent fluctuations in order to always obtain essentially the same reference voltage. The differential voltage is varied between the constant reference voltage and a control voltage that changes depending on the motor speed, which is used as a variable for constant and precise speed control of the motor.

1 .1 ·

Further details and advantages of the invention are given below with reference to the drawings "explained in more detail, for example.

Pig. 1 shows a "known circuit arrangement for speed control using a thyristor;

Pig. 2 shows the layout of the circuit according to the invention for speed control;

Pig. Figure 3 shows one versus that in Pig. 2 improved inventive Circuit arrangement for speed control;

Pig. 4 illustrates the relationship between a reference voltage appearing in the circuit arrangements in FIGS and a control voltage;

Pig. 5 serves to clarify the behavior of the im Circuit according to Pig. 3 used silicon diode.

In the known circuit arrangement according to Pig. 1 using of a thyristor in the main circuit 1 is a single-phase motor M connected to an AC power source. To monitor the speed of this motor, there is a symmetrical circuit in circuit 1 Semiconductor switching element SSS ,, as the main circuit thyristor and a secondary winding of a pulse transformer P.T. Parallel to the thyristor and the secondary winding of the pulse transformer the main circuit 1 is a phase adjustment circuit 2, the resistors R ^, Rp a variable resistor VR and a Reactance C. is formed. Hit this phase adjustment circle 2 is also connected to a circle 3 for pulse generation, the

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a symmetrical Ha.llDleitersch.alt el ement ^ .zur'Zündung, - - ". contains a primary winding of the pulse transformer PT and - as shown - a capacitor C _2. This forms an ignition circuit for the thyristor SSS _M. The engine M current supplied is regulated as a function of the continuity angle of the thyristor SSS ₁ U _1., Which is determined by the _,

^M jfzeugten .Single pulse s is determined by the switching element SSSm of the pulse generator or circuit ο / er-i ■. In brief, it can be said that the continuity angle of the thyristor SSS ^ can be regulated in a suitable manner by changing the signal phase in a certain angular range by means of a variable resistor VR. As with washing machines, for example, do not achieve sufficient speed control, since the change in torque changes the actually stabilized speed of the motor quite considerably.

With the one in Pig. 2, however, a substantially improved speed control can be achieved. A thyristor SSSjyp, an ignition switch element SSS _m , first and second resistors R. ,, R ₂ , a first and a second capacitor C .., C ₂ and a pulse transformer PT are arranged essentially in the same way and form the main circuit 1, the phase adjustment circuit 2 and the pulse generator circuit 3. With the circuit arrangement according to Pig. 2 also contains a double-ended linear slide 4, which consists of the diodes D ^, D ₂ , D, and D. and is connected to the main circuit 1 at terminal A and to the pulse generator circuit 4 at terminal B. In parallel with the DC voltage side of the rectifier 4, the collector-emitter lines of a transistor Tr and a further resistor R- are located between the terminals E and P. With the output terminal of the engine speed detecting generator PG and a predetermined point P of the resistor R ₄ is a

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Another variable resistor VB used for speed graduation. connected, which is connected via a tap and optionally via a resistor R ₅ to the base of the transistor Tr. To smooth the output voltage of the measuring generator PG, a third capacitor C ,, is parallel to the variable resistor YR, which is also connected to the DC voltage side of a second full-wave rectifier 5, which is formed by the diodes D ₁ -, Dg, D "and Dg. The third resistor R, between the base terminal of the transistor Tr and the resistor VR is used to set the feedback variable obtained from the change in the speed of the motor.

The circuit arrangement according to the invention as described above is, regulates the power supply of the motor M depending on the load. For example, the load torque of the motor M increases, so that its Speed is reduced, this speed change is detected by the measuring generator PG and fed back to the ignition circuit. This changes the continuity angle of the SSS ™ thyristor so that that the speed drop is compensated.

To further explain this process, as can be seen from the illustration, the continuity angle of the thyristor SSS ^ is regulated by changing the resistance value between points A and B, similarly to FIG . When the resistance value increases, the conicity angle of the thyristor SSS ™ is reduced, while when this resistance value decreases, the continuity angle is increased. In the circuit arrangement of this embodiment according to the invention, the resistance value between the terminals A and B is changed by changing the resistance of the collector-emitter path of the transistor Tr. As. known, the base current in this type of transistor is inversely proportional to the resistance of the collector-emitter path, so that when the base current changes automatically depending on load changes .der

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Continuity angle of the thyristor SSS ^ automatic, controlled or can be regulated. In the present EaIl, the Base current through the differential voltage between the reference voltage e, which is between the lower end of the resistor R ^ and the point P occurs and the control voltage e is regulated, which latter varies depending on the engine speed; changes and which is present at the variable resistor YR. In the In the present circuit arrangement, the base current is therefore automatically changed as a function of the load in order to reduce the angle of continuity of the thyristor to change, from which a variable current for the motor M results.

This means that the engine speed is always kept at a constant value. As can be seen from the circuit arrangement according to Pig. 2 results, a decrease in the resistance of the transistor Tr is followed by a drop in the reference voltage e. If the reference _{voltage e g changes} in the same ratio as the control voltage e, no feedback can take place. However, as illustrated in Pig. 4, the reference voltage follows a curve as shown in the dashed line, while the control voltage e in Depending on the speed ΪΓ of the motor den

shows the solid lower curve, feedback is possible. In other words, when the load torque increases and the speed decreases, the control voltage e decreases proportionally more than the reference voltage e, so that a sufficiently large feedback variable is obtained, since the decrease in the voltage e_ depends on the decrease in the resistance of the collector-emitter Distance depends when the base current increases as a result of a reduction in the voltage e. The appropriate selection of the resistance value of the resistor R-, which is parallel to the collector-emitter stretch? of the transistor Tr allows fine adjustment of the inclination of the increase in the reference _{voltage e g} as a function of the speed Ή of the motor according to P; Lg, .4, BQ that in effect so that the feedback or ^ M

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size is adjustable. About this resistance R. will also. the adjustment of the voltage e _{ß is} effected by limiting the voltage across the collector-emitter path of the transistor Tr by suitable selection of the point P ″.

The embodiment of the invention according to FIG. 2, which with the known Circuit arrangement according to Pig. 1 interacts can also be provided with a phase adjustment circuit. In this EaIl the reactance element in series with the input terminal of the first full-wave rectifier 4 (in Pig. 2 a capacitor C |) be an inductive element. ..

FIG. 3 shows a further embodiment of the circuit arrangement according to the invention with a motor, in which the basic circuit according to FIG. 2 is further improved. As mentioned, the internal resistance of the transistor Tr is generally regulated by the difference voltage between the voltage e, which changes as a function of the speed, and the reference voltage e. It is desirable that the reference voltage e is always constant regardless of the load. In the basic version of the circuit arrangement according to FIG. 2, however, the reduction in the resistance value of the collector-emitter path of the transistor Tr causes a voltage drop between the connection terminals G and D. depending on the stated resistance value. The course of the reference voltage e _o is for this case, as mentioned, in a dashed line in Pig. 4, and it can be seen that the greater the speed-dependent increase, the smaller the desired feedback amount. The embodiment according to FIG. 3. 3 improves this disadvantage. This circuit is designed in such a way that the reference voltage e changes only slightly when the voltage between the connection terminals G and D is changed. This is achieved in that between the terminals C and D of the circuit 6 in Pig. 2 an additional resistor R ₇ and at least more than one silicon diode D ₁₂ , D. ~ ...... are in series with one another, while the diodes

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parallel to resistor R ₄ - like from Pig. 3 are shown switched. These diodes D ₁₂ , D ^ ......, the resistor 7 and a further capacitor Cg, the puncture of which will be explained later, as well as the resistor R ₄ MIden a circle for the reference voltage. _{The voltage drop in the forward direction of the silicon diodes D 12} > - ⁰ 13 ······ is used to obtain the reference voltage e. As is known, the characteristic of a silicon diode runs in the forward direction as in the first quadrant of the graph according to Pig. 5, If, for example, the forward current i changes by a large value of ± 2 after i .., the forward voltage Ay changes only slightly. The circuit arrangement according to Pig. 3 makes use of this silicon diode characteristic. If, for example, the voltage between the terminals 0 and D changes so that a large change in diode current occurs ⁱⁿ silicon diodes D ₁₂ to D ^, the reference voltage e remains essentially corebant due to the diode structure. The diodes D ₁₂ to D ₁₄ thus also prevent load-dependent fluctuations in the reference _{voltage e s} ". Small voltage fluctuations in the voltage e due to the voltage drop Δ ν according to Pig. 5 nevertheless occur. In order to eliminate these fluctuations, the effects of the fluctuations Δ ν occur the reference voltage e _{Q is} prevented with the aid of the aforementioned capacitor Cg, ie smoothing takes place.

This means that the small fluctuations in the voltage e_ are

effect on the speed control of the motor.

Although according to Pig. 3 the resistor R _{4 is} parallel to the diodes D ₁₂ , D ₁₅ , and the contact P is provided for resistance variation on the resistor R ₄ , the variable resistor VR can also be connected directly to the connection point between the resistor R ^ and the diode D ₁₂ be connected. The diodes D ₅ to D ₁₀ in Pig. 3 form a full-wave rectifier for the output signals from the measuring generator PG. On the DC voltage side of this rectifier there are smoothing and com-

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pensati ons elements, which consist of the diode D ^, the resistors Rg, R "and the capacitors C * and C.; The resistor R connected to the base of the transistor Tr is used to set the feedback variable, while the capacitor C ₁ - suppresses unwanted oscillations.

As mentioned, according to the invention, the phase of the ignition circuit, i.e. the starting phase, automatically depending on load changes changed so that the speed of the motor is stabilized at any load torque. The speed control lets improve significantly with the circuit arrangement according to the invention. Since the reference voltage is also essentially is kept constant, regardless of load changes, the feedback is also significantly improved.

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Claims (5)

19U562 - ίο - Patent claims Circuit arrangement for regulating the speed of a single-phase electric motor using a thyristor, characterized in that between the terminals of an alternating voltage C [UeIIe the series connection of a reactance (C.) and one through diodes (D ^, D ₂ , D ,, D.) formed full-wave rectifier with input terminals (A and B) is that parallel to the DC voltage terminals (E, P) of the full-wave rectifier, the collector-emitter path of a transistor (Tr) and a reference voltage circuit, which has a resistor (R ^) and two input terminals (C, D) has that between the base terminal of the transistor (Tr) and the output terminal of the reference voltage circuit there is a variable resistance for speed division, which is connected to an output terminal of a measuring generator that detects the engine speed, whereby the base current of the transistor XTr ) as a function of the differential voltage between a partial voltage (e _g ) of the reference voltage circuit and one at the ve variable resistance lying rope tension (e) of the measuring generator is variable. 2. Circuit arrangement according to claim 1, characterized in that that in the main circuit (1) feeding the motor, the series connection of a symmetrical semiconductor switching element (SSSjyr), a secondary winding of a pulse transformer (PT) and the motor, and that in parallel with this series circuit, the two-way rectifier and reactance (C.) existing Series connection is connected. 3. Circuit arrangement according to claim 1 and 2, characterized in that that parallel to the series connection of two-way 909841/1094 -IT- Rectifier waäf reactance (C ^) two series-connected resistors (R ₁ and R ₂ ) lie, and that one made of a symmetrical Harb.leiterscha.ltelement (SSS ₁ ) intended for ignition, a primary winding of the pulse transformer (PT) and one Capacitance (G ₂ ) "existing series connection at the connection point of the resistors (R ₁ , R ₂ ) and at the input terminal (B) of the full-wave rectifier connected to the reactance (C.) is tapped. -mn ^ r ^^ ■■■ · ■■■ - 4. Circuit arrangement according to claim 1, characterized in that the resistor (R /) of the reference voltage circuit has a ■ certain point (P) at which the reference voltage (e_) can be tapped. 5. Circuit arrangement according to claims 1 and 4> characterized in that a 'resistor (R ₇ ) in series with a number of diodes (IL ₂ J D ..,., ..) between the DC voltage connection terminals of the full-wave rectifier ( D is ₁ to D.) so that the forward voltage drop of the diodes (D 'j _2, ···· D.J2) as R _e ference voltage (s) is usable. 909-841 / 1094